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3-Phase AC Induction Motor Drive with Dead Time Distortion Correction Using the MC68HC908MR32
Designer Reference Manual
M68HC08
Microcontrollers
DRM019/D Rev. 0, 03/2003
MOTOROLA.COM/SEMICONDUCTORS
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3-Phase AC Induction Motor Drive with Dead Time Distortion Correction Reference Design
Designer Reference Manual -- Rev 0
by: Radim Visinka, Ph.D. Motorola Czech Systems Laboratories Roznov pod Radhostem, Czech Republic
DRM019 -- Rev 0 MOTOROLA
Designer Reference Manual 3
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Revision history
To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify you have the latest information available, refer to: http://www.motorola.com/semiconductors The following revision history table summarizes changes contained in this document. For your convenience, the page number designators have been linked to the appropriate location.
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Revision history
Date January 2003 Revision Level 1 Initial version Description Page Number(s) N/A
Designer Reference Manual 4
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
List of Sections
Section 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Section 2. System Description. . . . . . . . . . . . . . . . . . . . . 15
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Section 3. Hardware Design. . . . . . . . . . . . . . . . . . . . . . . 27 Section 4. Software Design . . . . . . . . . . . . . . . . . . . . . . . 37 Section 5. System Setup . . . . . . . . . . . . . . . . . . . . . . . . . 49 Appendix A. References. . . . . . . . . . . . . . . . . . . . . . . . . . 61 Appendix B. Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
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List of Sections
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Table of Contents
Section 1. Introduction
1.1 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Application Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Benefits of the Solution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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1.2 1.3
Section 2. System Description
2.1 2.2 2.3 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 System Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Dead Time Distortion Correction . . . . . . . . . . . . . . . . . . . . . . . 18
Section 3. Hardware Design
3.1 3.2 3.3 3.4 3.5 3.6 3.7 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 MC68HC908MR32 Control Board . . . . . . . . . . . . . . . . . . . . . . 29 3-Phase AC BLDC High Voltage Power Stage. . . . . . . . . . . . . 31 Optoisolation Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Motor-Brake Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Hardware Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Section 4. Software Design
4.1 4.2 4.3
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Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Data Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Designer Reference Manual 7
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Table of Contents
4.4 Algorithm of Dead Time Distortion Correction . . . . . . . . . . . . . 43
Section 5. System Setup
5.1 5.2 5.3 5.4 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Jumper Settings of Controller Board. . . . . . . . . . . . . . . . . . . . .51 Required Software Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Building the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Executing the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Controlling the Application with PC Master Software . . . . . . . . 57
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5.5 5.6 5.7 5.8
Appendix A. References Appendix B. Glossary
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List of Figures
Figure 2-1 2-2 2-3 2-4 2-5 3-1 3-2 3-3 4-1 4-2 4-3 4-4 5-1 5-2 5-3 5-4 5-5 5-6 Title Page
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System Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Volt per Hertz Ramp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Dead Time Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Topology of Current Polarity Sensing . . . . . . . . . . . . . . . . . . . . 21 Proposed Current Threshold for Correction Toggling. . . . . . . . 24 Hardware Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 MC68HC908MR32 Control Board . . . . . . . . . . . . . . . . . . . . . . 30 3-Phase AC High Voltage Power Stage . . . . . . . . . . . . . . . . . . 32 Data Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3-Phase Sine Waves with Amplitude of 50% . . . . . . . . . . . . . . 40 mcgen3PhWaveSine Data Explanation - Phase A . . . . . . . . . . 41 Dead Time Correction State Machine. . . . . . . . . . . . . . . . . . . . 45 Setup of the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 MC68HC908MR32 Jumper Reference. . . . . . . . . . . . . . . . . . . 52 Execute Make Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Control Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 USER LEDs, PWM LEDs, and RESET . . . . . . . . . . . . . . . . . . 55 PC Master Software Control Window . . . . . . . . . . . . . . . . . . . . 58
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List of Figures
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Designer Reference Manual 10
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List of Tables
Table 2-1 2-2 2-3 3-1 3-2 3-3 3-4 4-1 4-2 4-3 5-1 5-2 5-3 Title Page
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PWM values loaded into registers PVAL1-6 . . . . . . . . . . . . . . 22 PWM Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Sensing of the Current Polarity and Magnitude for Ph. 1 . . . . 25 Electrical Characteristics of Control Board . . . . . . . . . . . . . . . 30 Electrical Characteristics of Power Stage . . . . . . . . . . . . . . . . 33 Electrical Characteristics of Optoisolation Board. . . . . . . . . . . 34 Motor - Brake Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . 35 State Machine Flag Registers dtStateFlagsAB . . . . . . . . . . . . 46 State Machine Flag Registers dtStateFlagsC . . . . . . . . . . . . . 46 dtCorrect_s Structure Elements. . . . . . . . . . . . . . . . . . . . . . . . 47 MC68HC908MR32EVM Jumper Settings . . . . . . . . . . . . . . . . 52 Motor Application States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Dead Time Distortion Correction . . . . . . . . . . . . . . . . . . . . . . . 57
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List of Tables
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Designer Reference Manual 12
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Section 1. Introduction
1.1 Contents
1.2 Application Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Benefits of the Solution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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1.3
1.2 Application Functionality
This Reference Design describes the design of a 3-phase AC induction motor drive with dead time distortion correction. It is based on Motorola's MC68HC908MR32 microcontroller which is dedicated for motor control applications. The system is designed as a motor drive system for medium power three-phase AC induction motors and is targeted for applications in both industrial and appliance fields (e.g. washing machines, compressors, air conditioning units, pumps or simple industrial drives). The reference design incorporates both hardware and software parts of the system including hardware schematics with a bill of material, and a software listing.
1.3 Benefits of the Solution
The design of very low cost variable speed 3-phase motor AC control drives has become a prime focus point for the appliance designers and semiconductor suppliers. Replacing variable speed universal motors by maintenance-free, low noise asynchronous (induction) motors is a trend that supposes total system costs being equivalent. Six-transistor inverter is the most used topology for AC motor drives. The dead time must be inserted between the turning off of one transistor in the inverter half bridge and turning on of the complementary transistor.
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Introduction
The dead time causes distortion to the generated voltage, and thus a non-sinusoidal phase current. This distortion causes distortion of the motor performance. It is especially apparent in low speeds, when the dead time is comparable with the PWM pulse width. Also, the longer the dead time, the higher the influence it has over the motor performance. Dead time distortion can be corrected by properly modulating the power stage control signals. The advantages of dead time distortion correction are: * * * * Smoother running motors Less torque ripple Quieter motors More efficient operation (less harmonic losses).
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Designer Reference Manual 14
DRM019 -- Rev 0 Introduction For More Information On This Product, Go to: www.freescale.com MOTOROLA
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Section 2. System Description
2.1 Contents
2.2 System Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Dead Time Distortion Correction . . . . . . . . . . . . . . . . . . . . . . . 18
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2.3
2.2 System Concept
The application is designed to drive a 3-phase AC motor in an open speed loop mode with dead time distortion correction (see Figure 2-1). The desired speed is set-up in the user interface. The desired frequency and amplitude of the motor voltage sine wave is calculated according to the desired speed using Volt-per-Hertz table. The sine wave generator generates the PWM values for all three phases of the AC bridge inverter according to the selected type of dead time distortion correction algorithm. The system incorporates the following hardware blocks: * * * * power supply rectifier, three-phase inverter including optoisolation, feedback sensors: DC-Bus voltage, DC-Bus current, temperature, polarity of phase currents, microcontroller MC68HC908MR32.
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System Description
3-phase AC Power Stage
Line AC
AC
ACM
DC DC Bus Voltage DC Bus Current Temperature Polarity of Phase Currents I sense
LOAD
MC68HC908MR32
PWM's
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Fault Protection Desired Sine Frequency Sine PWM Generation Desired Sine Amplitude Desired Correction of PWM's
START STOP DOWN UP PC Control
V/Hz Ramp Req. Speed Speed Ramp Desired Speed
Dead Time Correction State Machine
Dead Time Correction - Disabled - Partial - Full
SCI
Figure 2-1. System Block Diagram The drive is designed as a "Volt-per-Hertz" drive. It means that the control algorithm keeps constant magnetizing current (flux) of the motor by varying the stator voltage with frequency. The commonly used Volt-per-Hertz ramp of a 3-phase AC induction motor illustrates Figure 2-2.
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System Description System Concept
Phase Voltage 100%
Base Point
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Boost Voltage
Boost Frequency
Base Frequency
Frequency (rpm)
Figure 2-2. Volt per Hertz Ramp The Volt per Hertz ramp is defined by following parameters: * * Base Point - defined by Base Frequency (usually 50Hz or 60Hz) Boost - Defined by Boost Voltage and Boost Frequency
The ramp profile is set to the specific motor and can be easily changed to accommodate different ones.
The dead time distortion correction algorithms provide a correction of the PWM values with respect to the actual polarity of the phase currents. The current polarity is evaluated by sensing the phase voltage during the dead time and is carried out by the on-chip circuitry of the 908MR32 microcontroller. Two types of dead time distortion correction algorithms are implemented - partial, and full correction. The partial correction algorithm detects just the current polarity and the correction is done almost entirely by the on-chip PWM hardware. On the other hand, the full correction algorithm also detects the magnitude of the phase currents (low/high), and implements advanced s/w which improves the correction results. The user has the choice of selecting either of the correction algorithms. The type of dead time distortion correction is indicated by a yellow LED on 908MR32 controller board.
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System Description
The PWM frequency can be changed at any time during the motor operation to one of the following values: - 4kHz - 8kHz - 16kHz - 32kHz The drive incorporates fault protection, so in the case of DC-Bus over-current, DC-Bus over-voltage, or DC-Bus under-voltage faults, internal fault logic is asserted and the application enters a fault state. This state can be exited only if the fault disappears and it is acknowledged, by toggling the START/STOP switch through the STOP state. The application states are displayed by green LED on 908MR32 control board. The application can operate in two modes: 1. Manual Operating Mode The drive is controlled by the START/STOP switch. The direction of the motor rotation is set by the FWD/REV switch. The motor speed is set by the SPEED potentiometer. 2. PC Master Software (Remote) Operating Mode The drive is controlled remotely from a PC through the serial communications interface (SCI) communication channel of the MCU device via an RS-232 physical interface. The drive is enabled by the START/STOP switch, which can be used to safely stop the application at any time.
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2.3 Dead Time Distortion Correction
Six-transistor inverter is the most used topology for AC motor drives. The dead time must be inserted between the turning off of one transistor in the inverter half bridge and turning on of the complementary transistor. The dead time causes distortion to the generated voltage, and thus a non-sinusoidal phase current.
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System Description Dead Time Distortion Correction
In order to achieve a sinusoidal phase current, and thus limit the harmonic losses, noise, and torque ripple, the dead time distortion correction needs to be implemented. The on-chip Pulse-Width-Modulation (PWM) module, of the MC68HC908MRxx family of Motorola microcontrollers, contains the patented hardware block that simplifies the task. The dead time correction is based on the evaluation of the phase current polarity of the respective phase, and proper counter-modulation of the dead-time distortion. The basic situation is shown in Figure 2-3. The desired load voltage is affected by the dead time. During dead time, load inductance defines the voltage needed to keep inductive current flowing through diodes. So full positive or full negative voltage is applied to the phase, according to the phase current polarity. For positive current (i+), the actual voltage pulses are shortened by dead time, for negative phase current the voltage pulses are lengthened by dead time.
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Desired load voltage
deadtime
TON
+U/2
PWM to top transistor
i+
iPWM to bottom transistor
TON - 2xdeadtime
Actual load voltage (for i+)
TON + 2xdeadtime
- U/2
Actual load voltage (for i-)
Dave Wilson
Figure 2-3. Dead Time Distortion
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System Description
To achieve distortion correction, one of two different correction factors must be added to the desired PWM value, depending on whether the top or bottom transistor is controlling the output voltage during the dead time. When the voltage pulse is shortened due to dead time, the control PWM signal is extended by dead time, so the actual voltage pulse matches the desired voltage. Vice versa, when the voltage pulse is lenghtened due to dead time, the control PWM signal is shortened by dead time, so again the actual voltage pulse matches the desired voltage. Therefore the actual signal equals the desired one, and the generated phase current is sinusoidal. The dead time distortion correction utilizes phase current sensing. The on-chip PWM module of MC68HC908MRxx microcontrollers contains the block that enables them to evaluate the polarity and the size of the phase current without the need of an expensive current sensor. It is based on the sampling and evaluation of the phase voltage level during the dead time. The zero voltage during dead time reflects a positive phase current, the full DC-Bus voltage during dead time reflects a negative phase current. So comparing the phase voltage with the half DC-Bus voltage enables an evaluation of the current polarity. The topology is illustrated in Figure 2-4. The output of the comparator is connected to the current polarity sensing input of the MC68HC908MR32 microcontroller. The microcontroller contains the hardware that samples the current sensing inputs during dead time. It enables evaluation of the current polarity and also the region of low currents.
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Designer Reference Manual 20
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System Description Dead Time Distortion Correction
+U
+U
/2 + ISx
PWM0
i+
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iPWM1
Figure 2-4. Topology of Current Polarity Sensing During PWM reload ISR, the desired PWM values for all three phases are calculated as: * * * PWM1 for phase 1 PWM2 for phase 2 PWM3 for phase 3
The values loaded into the individual PVAL registers of the separate phases are shown in Table 2-1. Since AC motor control utilizes center-aligned PWM modulation, only half of the dead time needs to be added to / substracted from the desired PWM duty cycle to achieve the distortion correction. Without dead time correction, the even PVAL registers are loaded with the required PWM value, but the odd PVAL registers are not used. When dead time correction is used, the even PVAL registers are loaded with the desired PWM plus half of the dead time (PWMx+DT/2), while the odd PVAL registers are loaded with the desired PWM minus half of the dead time (PWMx-DT/2).
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System Description
Table 2-1. PWM values loaded into registers PVAL1-6
Phase PVAL register PVAL1 PVAL2 PVAL3 PVAL4 PVAL5 PVAL6 Required values in PVAL without dead time correction PWM1 PWM2 PWM3 Required values in PVAL with dead time correction PWM1 + DT/2 PWM1 - DT/2 PWM2 + DT/2 PWM2 - DT/2 PWM3 + DT/2 PWM3 - DT/2 Actual values loaded into PVAL registers PWM1 + DEADTM/2/PWM_PRESC PWM1 DEADTM/2/PWM_PRESC PWM2 + DEADTM/2/PWM_PRESC PWM2 DEADTM/2/PWM_PRESC PWM3 + DEADTM/2/PWM_PRESC PWM3 DEADTM/2/PWM_PRESC
Phase 1
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Phase 2
Phase 3
When calculating the values to be loaded into the PVAL registers, the MRxx's Dead Time register can be used. The dead-time register (DEADTM) holds an 8-bit value which specifies the number of CPU clock cycles to be used for the dead-time, when complementary PWM mode is selected. Dead-time is not affected by changes to the prescaler value. On the other hand, the PVAL values are affected by the prescaler of the PWM counter. Therefore the value stored into the dead time register needs to be scalled by the PWM prescaler (PWM_PRESC in Table 2-1). The PWM Control Register 2 (PCTL2) contains the PWM generator prescaler. The buffered read/write bits, PRSC0 and PRSC1, select the PWM prescaler according to Table 2-2.
Table 2-2. PWM Prescaler
Prescaler bits PRSC0 and PRSC1 00 01 10 11 PWM Frequency fOP fOP/2 fOP/4 fOP/8 Prescaler PWM_PRESC 1 2 4 8
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System Description Dead Time Distortion Correction
The on-chip PWM module of MC68HC908MRxx microcontrollers enables them to perform two types of dead time distortion correction: * * Partial correction Full correction
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Partial dead time distortion correction is based only on polarity detection of phase current. The hardware, sensing the current polarity according to Figure 2-4, needs to be implemented. The software is responsible for calculating both compensated PWM values and placing them in an odd/even PWM register pair according to Table 2-1. The distortion correction is fully implemented by the on-chip PWM module according to the following scheme: * If the current sensed at the motor for that PWM pair is positive (voltage on current pin ISx is low), the odd PWM value is used for the PWM pair. Likewise, if the current sensed at the motor for that PWM pair is negative (voltage on current pin ISx is high), the even PWM value is used.
*
For partial correction, the on-chip dead time correction block is set in the automated mode - current sense correction bits ISENS1:ISENS0 of PWM Control Register 0 (PCTL1) are set to 10). The disadvantage of the partial correction is that some dead time distortion still exist - the current is flattened out at the zero crossings.
Full dead time distortion correction (implemented in dtCorrectFull algorithm) improves the partial dead time correction by sensing not only the polarity, but also the magnitude of the actual phase current. In the full dead time correction method, the threshold, where the correction values should be toggled is not in the zero level, but slightly advanced. The threshold is illustrated in Figure 2-5. Toggling of the correction offset needs to occur before the current has a chance to
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System Description
flatten out at a current zero-crossing. So, the current sense scheme must sense that the current waveform is approaching the zero-crossing.
Current with Correction Disabled
Falling threshold
High Positive Magnitude Low Magnitude
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Rising threshold
High Negative Magnitude
Dave Wilson
Figure 2-5. Proposed Current Threshold for Correction Toggling To achieve the full distortion correction, again one of two different correction factors must be added to the desired PWM value, depending on whether the top or bottom transistor is controlling the output voltage during the dead time. The software is responsible for calculating both compensated PWM values and placing them in an odd/even PWM register pair. Then the s/w needs to determine which PWM value is to be used, according to the following scheme: * If the current sensed at the motor for that PWM pair is positive and of high magnitude, or negative and of small magnitude in a trend approaching zero crossing, the odd PWM value is used for the PWM pair. Likewise, if the current sensed at the motor for that PWM pair is negative, or positive and of small magnitude in a trend approaching zero crossing, the even PWM value is used.
*
The MR32 contains a hardware circuitry that enables it to sense the current polarity together with the magnitude. The current polarity and magnitude is sensed using the DT-DT6 of FTACK register in '908MR32
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System Description Dead Time Distortion Correction
microcontroller. For Phase 1, the bits DT1 and DT2 are used as shown in Table 2-3. Table 2-3. Sensing of the Current Polarity and Magnitude for Ph. 1
DT1 0 1 0 DT2 0 1 1 Current Condition of Phase 1 high magnitude I+ high magnitude Ilow magnitude, either polarity
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For phase 2, bits DT3 and DT4 are used. For phase 3, bits DT5 and DT6 are used. As was stated the determination of the correct PVAL used for the PWM generation is done purely by software. The on-chip dead time correction block is set in the manual mode - current sense correction bits ISENS1:ISENS0 of PWM Control Register 0 (PCTL1) are set to 00 or 01.
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System Description
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Section 3. Hardware Design
3.1 Contents
3.2 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 MC68HC908MR32 Control Board . . . . . . . . . . . . . . . . . . . . . . 29 3-Phase AC BLDC High Voltage Power Stage. . . . . . . . . . . . . 31 Optoisolation Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Motor-Brake Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Hardware Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
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3.3 3.4 3.5 3.6 3.7
3.2 System Configuration
The application is designed to drive the 3-phase AC motor. It consists of the following modules (see Figure 3-1): * * * * MC68HC908MR32 Control Board 3-phase AC/BLDC High Voltage Power Stage Optoisolation Board 3-phase AC Induction Motor
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Designer Reference Manual 27
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Hardware Design
Red White Black
White
Red
Black
28
+12VDC
GND
Designer Reference Manual
U2
40w flat ribbon cable
U3
JP1.1 JP1.2
40w flat ribbon cable
U1
Controller Board
L
J11.1 J11.2
N
J14
J1
PE
3ph AC/BLDC High Voltage Power Stage
Optoisolation Board
ECOPT
J2
J1
MC68HC908MR32
100 - 240VAC 49 - 61 Hz
J13.1 J13.2 J13.3
MB1
AM40V
SG40N
J5
Motor-Brake
ECOPTHIVACBLDC
Figure 3-1. Hardware Configuration
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ECMTRHIVAC
Not Connected
Not Connected
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Hardware Design MC68HC908MR32 Control Board
3.3 MC68HC908MR32 Control Board
Motorola's embedded motion control series MR32 motor control board is designed to provide control signals for 3-phase AC induction, 3-phase brushless DC (BLDC), and 3-phase switched reluctance (SR) motors. In combination with one of the embedded motion control series power stages, and an optoisolation board, it provides a software development platform that allows algorithms to be written and tested without the need to design and build hardware. With software supplied on the CD-ROM, the control board supports a wide variety of algorithms for AC induction, SR, and BLDC motors. User control inputs are accepted from START/STOP, FWD/REV switches, and a SPEED potentiometer located on the control board. Alternately, motor commands can be entered via a PC and transmitted over a serial cable to DB-9 connector. Output connections and power stage feedback signals are grouped together on 40-pin ribbon cable connector. Motor feedback signals can be connected to Hall sensor/encoder connector. Power is supplied through the 40-pin ribbon cable from the optoisolation board or low-voltage power stage. The control board is designed to run in two configurations. It can be connected to an M68EM08MR32 emulator via an M68CBL08A impedance matched ribbon cable, or it can operate using the daughter board. The M68EM08MR32 emulator board may be used in either an MMDS05/08 or MMEVS05/08 emulation system. Figure 3-2 shows a block diagram of the board's circuitry.
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Hardware Design
TERMINAL I/F
OPTOISOLATED RS-232 I/F
FORWARD/REVERSE SWITCH START/STOP SWITCH
SPEED POT
TACHOMETER INPUT HALL EFFECT INPUTS (3)
EMULATOR/ PROCESSOR CONNECTOR
CONFIG. JUMPERS
RESET SWITCH (2) OPTION SWITCHES
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dc POWER 12 Vdc
REGULATED POWER SUPPLY
PWM LEDs (6) OPTO/POWER DRIVER I/O CONNECTOR 40-PIN RIBBON CONNECTOR
OVERCURRENT/ OVERVOLTAGE INPUTS
CURRENT/TEMP SENSE INPUTS PWM (6) OUTPUTS
BACK EMF INPUTS MISC. POWER AND CONTROL I/O
Figure 3-2. MC68HC908MR32 Control Board The electrical characteristics in Table 3-1 apply to operation at 25C. Table 3-1. Electrical Characteristics of Control Board
Characteristics DC power supply voltage Quiescent current Min logic 1 input voltage (MR32) Max logic 0 input voltage (MR32) Propagation delay (Hall sensor/encoder input) Analog input range RS-232 connection speed PWM sink current IPK Symbol Vdc ICC VIH VIL tdly VIn Min 10.8* -- 2.0 -- -- 0 -- -- Typ 12* 80 -- -- -- -- -- -- Max 16.5* -- -- 0.8 500 5.0 9600 20 Units V mA V V ns V Baud mA
* When operated and powered separately from other Embedded Motion Control tool set products
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Hardware Design 3-Phase AC BLDC High Voltage Power Stage
3.4 3-Phase AC BLDC High Voltage Power Stage
Motorola's embedded motion control series high-voltage (HV) AC power stage is a 180-watt (one-fourth horsepower), 3-phase power stage that will operate off of DC input voltages from 140 to 230 volts and AC line voltages from 100 to 240 volts. In combination with one of the embedded motion control series control boards and an optoisolation board, it provides a software development platform that allows algorithms to be written and tested without the need to design and build a power stage. It supports a wide variety of algorithms for both AC induction and brushless DC (BLDC) motors. Input connections are made via 40-pin ribbon cable connector J14. Power connections to the motor are made on output connector J13. Phase A, phase B, and phase C are labeled Ph_A, Ph_B, and Ph_C on the board. Power requirements are met with a single external 140- to 230-volt DC power supply or an AC line voltage. Either input is supplied through connector J11. Current measuring circuitry is set up for 2.93 amps full scale. Both bus and phase leg currents are measured. A cycle-by-cycle over-current trip point is set at 2.69 amps. The high-voltage AC power stage has both a printed circuit board and a power substrate. The printed circuit board contains IGBT gate drive circuits, analog signal conditioning, low-voltage power supplies, power factor control circuitry, and some of the large, passive, power components. All of the power electronics, which need to dissipate heat, are mounted on the power substrate. This substrate includes the power IGBTs, brake resistors, current sensing resistors, a power factor correction MOSFET, and temperature sensing diodes. Figure 3-3 shows a block diagram.
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Hardware Design
HV POWER INPUT
SWITCH MODE POWER SUPPLY
PFC CONTROL dc BUS BRAKE
SIGNALS TO/FROM CONTROL BOARD
3-PHASE IGBT POWER MODULE GATE DRIVERS PHASE CURRENT PHASE VOLTAGE BUS CURRENT BUS VOLTAGE MONITOR BOARD ID BLOCK ZERO CROSS BACK-EMF SENSE 3-PHASE AC TO MOTOR
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Figure 3-3. 3-Phase AC High Voltage Power Stage The electrical characteristics in Table 3-2 apply to operation at 25C with a 160-Vdc power supply voltage.
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Hardware Design Optoisolation Board
Table 3-2. Electrical Characteristics of Power Stage
Characteristics DC input voltage AC input voltage Quiescent current Min logic 1 input voltage Max logic 0 input voltage Symbol Vdc Vac ICC VIH VIL RIn VOut ISense VBus IPK PBK PBK(Pk) Pdiss Min 140 100 -- 2.0 -- -- 0 -- -- -- -- -- -- Typ 160 208 70 -- -- 10 k -- 563 8.09 -- -- -- -- Max 230 240 -- -- 0.8 -- 3.3 -- -- 2.8 50 100 85 V mV/A mV/V A W W W Units V V mA V V
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Input resistance Analog output range Bus current sense voltage Bus voltage sense voltage Peak output current Brake resistor dissipation (continuous) Brake resistor dissipation (15 sec pk) Total power dissipation
3.5 Optoisolation Board
Motorola's embedded motion control series optoisolation board links signals from a controller to a high-voltage power stage. The board isolates the controller, and peripherals that may be attached to the controller, from dangerous voltages that are present on the power stage. The optoisolation board's galvanic isolation barrier also isolates control signals from high noise in the power stage and provides a noise-robust systems architecture. Signal translation is virtually one-for-one. Gate drive signals are passed from controller to power stage via high-speed, high dV/dt, digital optocouplers. Analog feedback signals are passed back through HCNR201 high-linearity analog optocouplers. Delay times are typically
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Hardware Design
250 ns for digital signals, and 2 s for analog signals. Grounds are separated by the optocouplers' galvanic isolation barrier. Both input and output connections are made via 40-pin ribbon cable connectors. The pin assignments for both connectors are the same. For example, signal PWM_AT appears on pin 1 of the input connector and also on pin 1 of the output connector. In addition to the usual motor control signals, an MC68HC705JJ7CDW serves as a serial link, which allows controller software to identify the power board.
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Power requirements for controller side circuitry are met with a single external 12-Vdc power supply. Power for power stage side circuitry is supplied from the power stage through the 40-pin output connector. The electrical characteristics in Table 3-3 apply to operation at 25C, and a 12-Vdc power supply voltage.
Table 3-3. Electrical Characteristics of Optoisolation Board
Characteristic Power Supply Voltage Quiescent Current Min Logic 1 Input Voltage Max Logic 0 Input Voltage Analog Input Range Input Resistance Analog Output Range Digital Delay Time Analog Delay Time Symbol Vdc ICC VIH VIL VIn RIn VOut tDDLY tADLY Min 10 70(1) 2.0 -- 0 -- 0 -- -- Typ 12 200(2) -- -- -- 10 -- 0.25 2 Max 30 500(3) -- 0.8 3.3 -- 3.3 -- -- Units V mA V V V k V s s DC/DC converter HCT logic HCT logic Notes
1. Power supply powers optoisolation board only. 2. Current consumption of optoisolation board plus DSP EVM board (powered from this power supply) 3. Maximum current handled by DC/DC converters
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Hardware Design Motor-Brake Specifications
3.6 Motor-Brake Specifications
The AC induction motor-brake set incorporates a 3-phase AC induction motor and attached BLDC motor brake. The AC induction motor has four poles. The incremental position encoder is coupled to the motor shaft, and position Hall sensors are mounted between motor and brake. They allow sensing of the position if required by the control algorithm. Detailed motor-brake specifications are listed in Table 3-4. In a target application a customer specific motor is used.
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Table 3-4. Motor - Brake Specifications
Set Manufactured Motor Specification: EM Brno, Czech Republic eMotor Type: Pole-Number: Nominal Speed: Nominal Voltage: Nominal Current: Brake Specification: Brake Type: Nominal Voltage: Nominal Current: Pole-Number: Nominal Speed: Position Encoder Type: Pulses per Revolution: AM40V 3-Phase AC Induction Motor 4 1300 rpm 3 x 200 V 0.88 A SG40N 3-Phase BLDC Motor 3 x 27 V 2.6 A 6 1500 rpm Baumer Electric BHK 16.05A 1024-12-5 1024
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Hardware Design 3.7 Hardware Documentation
All the system parts are supplied and documented according to the following references: * U1 - MC68HC908MR32 Control Board: - supplied as: ECCTR908MR32 - described in: Motorola Embedded Motion Control MC68HC908MR32 Control Board User's Manual MEMCMR32CBUM/D * U2 - 3-ph AC/BLDC High Voltage Power Stage - supplied in kit with Optoisolation Board as: ECOPTHIVACBLDC - described in: Motorola Embedded Motion Control 3-Phase AC BLDC High-Voltage Power Stage User's Manual MEMC3PBLDCPSUM/D * U3 - Optoisolation Board - supplied with 3-ph AC/BLDC High Voltage Power Stage as: ECOPTHIVACBLDC - or supplied alone as: ECOPT - optoisolation board - described in: Motorola Embedded Motion Optoisolation Board User's Manual MEMCOBUM/D * MB1 Motor-Brake AM40V + SG40N - supplied as: ECMTRHIVAC Detailed descriptions of individual boards can be found in comprehensive User's Manuals belonging to each board. The manuals are available on the Motorola web. The User's Manual incorporates the schematic of the board, description of individual function blocks and a bill of materials. An individual board can be ordered from Motorola as a standard product.
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Section 4. Software Design
4.1 Contents
4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Data Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Algorithm of Dead Time Distortion Correction . . . . . . . . . . . . . 43
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4.3 4.4
4.2 Introduction
This section describes the design of the software blocks of the drive. The software will be described in terms of * * Software Data Flow Algorithm Dead Time Distortion Correction
4.3 Data Flow
The requirements of the drive dictate that software takes some values from the user interface and sensors, processes them and generates 3-phase PWM signals for motor control. The control algorithm of closed loop AC drive is described in Figure 4-1. It consists of processes described in the following sub-sections. The dead time distortion correction algorithm is described separately in the successive section.
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Software Design
SCI Communication
Switches
A/D converters omega_reqPCM_mech
Process PC Master Software Control
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Process Speed Command dtCorrectOption Process Status Control Current Polarity Sensing
u_dc_bus
omega_reqOMP_mech
Process Dead Time Distortion Correction
Process Acceleration/Deceleration Ramp appFaultStatus omega_reqRMP_mech Process Fault Control pDtCorrectApp
Process V/Hz Ramp
OV Fault
OC Fault u_ramp phase_increment
Process PWM Generation
PVAL1,2
PVAL3,4
PVAL5,6
Figure 4-1. Data Flow
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Software Design Data Flow
4.3.1 Speed Command & Status Control In the Manual Operating Mode, the required speed is set by speed potentiometer and switches (start/stop, forward/reverse). In the PC Master Software (Remote) Operating Mode, the required speed is set by PC. In the process, the input parameters are evaluated and the speed command is calculated accordingly. Also the DC-Bus voltage is measured. The application fault status is analyzed and the state of the drive is set. The status LED's are controlled according to the system state.
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4.3.2 Acceleration/Deceleration Ramp The process calculates the new speed command based on the required speed according to the acceleration / deceleration ramp.
4.3.3 V/Hz Ramp This process provides voltage calculation according to V/Hz ramp. The input of this process is the generated inverter frequency omega_req_RMP_mech. The outputs of this process are the output sine wave parameters required by PWM generation process: the table increment phase_increment that corresponds to the frequency omega_req_RMP_mech and is used to roll through the wave table in order to generate the output inverter frequency, and the corresponding amplitude of the generated inverter voltage u_ramp.
4.3.4 Process PWM Generation This process generates a system of three phase sinewaves shifted 120o each other. The function mcgen3PhWaveSine is used for the sine wave calculation. The mcgen3PhWaveSine function calculates an immediate value of the three-phase sinusoidal system from given amplitude and actual phase pointer: *
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Phase A -- sPhaseVoltage.PhaseA
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Software Design
* * Phase B -- sPhaseVoltage.PhaseB Phase C -- sPhaseVoltage.PhaseC
The individual waves are shifted 120 each other. The shape of the generated waveforms depends on the data stored in the sine table. In motor control applications, data usually describes a pure sinewave or a sinewave with addition of the third harmonic component. Figure 4-2 shows the duty cycles generated by the mcgen3PhWaveSine function when amplitude is 50%.
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1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 DutyCycle.PhaseA 0.1 0.0 DutyCycle.PhaseB DutyCycle.PhaseC
Figure 4-2. 3-Phase Sine Waves with Amplitude of 50% The calculation is based on the wave table stored in FLASH memory of the microcontroller. The table describes either a pure sinewave or a sinewave with the third harmonic addition. The second case is often preferred because it allows one to generate the first harmonic sine voltage equal to the input AC line voltage. The format of the stored wave table data is from #0x0000 (for ZERO Voltage) up to 0x7fff (for the 100% Voltage). Thus the proper data scaling is secured (see Figure 4-3).
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Software Design Data Flow
It is important to note that 50% PWM (or 50% of PWM Modulus loaded to the corresponding PVAL registers) corresponds to the ZERO phase voltage. But in the wave table, the ZERO phase voltage corresponds to the number #0x0000. Therefore the fetched wave value from the table must be added to the 50% PWM Modulation for quadrant 1 and 2 or substracted from the 50% PWM Modulation for quadrant 3 and 4. Thus the correct PWM value is loaded.
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0x7fff 0x7fff
ActualPhase(n) Actual Phase (n)
PhaseIncrement Phase Increment
amplitude = 100% Amplitude = 100%
ActualPhase(n-1) Actual Phase (n-1)
0x4000 0x4000
(DutyCycle.PhaseA) (DutyCycle.PhaseA)
0x0000 0x0000
0x8000 = -180 0x8000 = -180 o
amplitude Amplitude
00
0x7fff = 180 0x7fff = 180 o
Figure 4-3. mcgen3PhWaveSine Data Explanation - Phase A The output parameters of the process are: * * * PWM value for phase A: PVAL1 register PWM value for phase B: PVAL3 register PWM value for phase C: PVAL5 register
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Software Design
In case of dead time distortion correction, the corrected PVAL values PVAL1-6 are calculated and used for the PWM generation according to the detected phase current polarity. The process can be described by following points: * * * Wave pointer for phase A is updated by the table increment. Based on the wave pointer, the PWM values for all three phases are calculated. PWM values are rescaled according to the PWM modulo (PWM frequency) and loaded into PVAL1, 3, 5 registers. Registers PVAL2, 4, 6 are loaded automatically because of complementary PWM mode selected during the PWM module initialisation. In case of dead time distortion correction, the corrected values PVAL1-6 are calculated and used for PWM generation according to the detected phase current polarity.
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*
The process is accessed regularly in the rate given by the set PWM frequency and the selected PWM interrupt prescaler.
4.3.5 PC Master Software Control The process provides SCI communication with PC using PC master software service routines. These routines are fully independent on the motor control tasks. They enable for example to set the desired speed, the PWM frequency and the type of dead time distortion correction.
4.3.6 Fault Control This process is responsible for fault handling. The software accommodates three fault events: DC-Bus over-current, DC-Bus over-voltage and DC-Bus under-voltage. DC-Bus Over-current: In case of DC-Bus over-current, the external hardware provides a rising edge on the DC-Bus over-current fault input of the microcontroller. This signal disables all motor control PWM outputs (PWM1 - PWM6) and sets the application fault status.
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Software Design Algorithm of Dead Time Distortion Correction
DC-Bus Over-voltage: In case of DC-Bus over-voltage, the external hardware provides a rising edge on the DC-Bus over-voltage fault input of the microcontroller. This signal disables all motor montrol PWM outputs (PWM1 - PWM6) and sets the application fault status. DC-Bus Under-voltage: The sensed DC-Bus voltage is compared with the limit within the software. In case of DC-Bus under-voltage, all motor control PWM outputs (PWM1 - PWM6) are disabled and the application fault status is set.
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If any of the faults occurs, the application status is changed into the Fault Status.
4.3.7 Dead Time Distortion Correction The process defines the value registers to be used for PWM generation according to the type of dead time distortion correction and the state of the immediate phase current polarity. * If no dead time correction is required, the PVAL1,3,5 are used, the complementary PVAL values are calculated by on-chip PWM peripheral automatically. If partial dead time correction is required, the PVAL value is selected by on-chip PWM peripheral automatically according to the phase current polarity sensing If full dead time correction is required, the process selects the desired PVAL registers according to the dead time distortion correction state machine.
*
*
In the following section the dead time distortion correction algorithm is described in detail.
4.4 Algorithm of Dead Time Distortion Correction
The algorithm dtCorrectFull calculates the IPOL bits defining the PVAL registers to be used for MC68HC908MR32 PWM generation for full dead time correction. The IPOL bits are determined according to the phase
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Software Design
current polarity detection bits DT1-6, actual sine wave pointer, and the actual state of the algorithm state machine. The algorithm state machine samples the actual state of the phase current, and selects appropriate PVAL registers to be used for PWM generation. The state machine, implemented in the dtCorrectFull algorithm, is illustrated in Figure 4-4. When the algorithm is enabled, the state machine is entered from initial state 0. It is waiting till the high magnitude of positive current is detected (State 1, confirmed by State 2), then the algorithm enters the state machine (State 3). The state machine is performed in circle 3-4-5-6-3. As soon as the low magnitude of negative current is detected, the IPOL is changed to 1, requesting the even-numbered PWM registers to be used for PWM generation, the actual value of the wave pointer is recorded (C), and State 4 is entered. State 4 is preserved for 80 electrical degrees, until a high negative current can be expected. Then State 5 is entered. As soon as the low magnitude of positive current is detected, the IPOL is changed to 0, requesting the odd-numbered PWM registers to be used for PWM generation, the actual value of the wave pointer is recorded (C), and State 6 is entered. State 6 is preserved for 80 electrical degrees, until a high positive current can be expected. Then State 3 is entered and the state machine loop is repeated. In this way, it is ensured that the required IPOL changes when a small amplitude of respective current is detected by the hardware. Please note, that the wave pointer is recorded into the algorithm variable PointA, PointB, or PointC, in the moment when the respective phase current crosses the low current threshold.
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Software Design Algorithm of Dead Time Distortion Correction
INITIAL STATE
Algorithm enabled
0 1
00 00 00
Initial recognition of positive current
2
00
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High positive current
X0/0
Waits for high positive current
3
X1/1
Low negative current
4
Change IPOL (current treshold crossing) Waits for high negative current
|-C|>80o / 0
|-C|>80o/1
6
Low positive current
0X/0
5
High negative current
1X/1
STATE TRANSITION KEY: DT1 DT2 / IPOL REGISTERS CONTROL THE OUTPUT IPOL = 0: ODD-NUMBERED PWM REGISTER CONTROLS OUTPUT ODD NUMBERED REGISTERS CONTROL THE OUTPUT IPOL = 1: EVEN-NUMBERED PWM REGISTER CONTROLS OUTPUT EVEN NUMBERED
Figure 4-4. Dead Time Correction State Machine Such a state machine is independently implemented for each phase (A, B, C). The algorithm contains 2 flag variables, determining actual state of the state machine for individual phases. Flag variable dtStateFlagsAB determines state of the state machine for phases A & B, dtStateFlagsC determines state of the state machine for phase C. The meaning of individual bits of dtStateFlagsAB is listed in Table 4-1. The meaning of individual bits of dtStateFlagsC is listed in Table 4-2.
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Table 4-1. State Machine Flag Registers dtStateFlagsAB
phase bits bit0 - lock bit1 bit2 bit3 bit4 - lock bit5 bit6 bit7 0 0 State 1 0 1 2 1 0 0 1 0 0 3 1 1 0 1 1 0 4 1 0 1 1 0 1 5 1 1 1 1 1 1 6
phase A
phase B
0 0
0 1
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Table 4-2. State Machine Flag Registers dtStateFlagsC
phase bits bit0 - lock bit1 bit2 bit3 bit4 bit5 bit6 bit7 0 0 State 1 0 1 2 1 0 0 x x x x 3 1 1 0 x x x x 4 1 0 1 x x x x 5 1 1 1 x x x x 6
phase C
reserved
x x x x
x x x x
NOTE:
Detailed explanation of the dead time distortion correction can be found in a comprehensive application note of Motorola, AN1728 "Making Low-Distortion Motor Waveforms with the MC68HC708MP16" by David Wilson. Note, that MC68HC708MP16 is the predecessor of MC68HC908MRxx family and contains identical on-chip PWM block.
Algorithm Data Structure: Algorithm data structure is defined in dtCorrect.h header file. See Table 4-3.
typedef struct { UByte dtBits; UByte ipolBits; type_uBits dtStateFlagsAB; type_uBits dtStateFlagsC; Designer Reference Manual 46 Software Design For More Information On This Product, Go to: www.freescale.com DRM019 -- Rev 0 MOTOROLA
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Software Design Algorithm of Dead Time Distortion Correction
SByte pointA; SByte pointB; SByte pointC; SByte pointerA; } dtCorrect_s;
Table 4-3. dtCorrect_s Structure Elements
Variable Explanation INPUT: actual status of the dead time bits DT1-6, format | x | x |DT6|DT5| |DT4|DT3|DT2|DT1| fits to FTACK of `MR32 OUTPUT: ipolBits - new top/bottom correction bits IPOL1-3, format | x | x | x |IPOL1| |IPOL2|IPOL3| x | x | fits to PCTL2 of `MR32 internal dead-time correction flags for phases AB internal dead-time correction flags for phase C internal capture of the pointer for phase A internal capture of the pointer for phase B internal capture of the pointer for phase C INPUT: actual pointer of the generated wave phase A
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dtBits
ipolBits dtStateFlagsAB dtStateFlagsC pointA pointB pointC pointerA
The dead time correction algorithm dtCorrectFull adds the correction factor to originally calculated sine wave. It is necessary to ensure that the calculated PWM duty cycles do not exceed the PWM modulus. The dtCorrectInit function must be called before starting any call to the dtCorrectFull function, to ensure proper functionality.
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Section 5. System Setup
5.1 Contents
5.2 Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Jumper Settings of Controller Board. . . . . . . . . . . . . . . . . . . . .51 Required Software Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Building the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Executing the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Controlling the Application with PC Master Software . . . . . . . . 57
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5.3 5.4 5.5 5.6 5.7 5.8
5.2 Hardware Setup
Figure 5-1 illustrates the hardware setup of the application. It incorporates the following modules: * * * * MC68HC908MR32 Control Board 3-phase AC/BLDC High Voltage Power Stage Optoisolation Board 3-phase AC Induction Motor
The correct phase order (phase A, phase B, phase C) for the shown AC induction motor is: * * * Phase A -- red wire Phase B -- white wire Phase C -- black wire
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System Setup
If you view the motor looking into the shaft end, and the phase order is phase A, B, C, the motor shaft should rotate in a clockwise direction (i.e., positive direction, positive speed).
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Figure 5-1. Setup of the Application
5.3 Warning
This application operates in an environment that includes dangerous voltages and rotating machinery. Be aware, that the application power stage and optoisolation board are not electrically isolated from the mains voltage - they are live with risk of electric shock when touched.
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System Setup Jumper Settings of Controller Board
An isolation transformer should be used when operating off an AC power line. If an isolation transformer is not used, power stage grounds and oscilloscope grounds are at different potentials, unless the oscilloscope is floating. Note, that probe grounds and, therefore, the case of a floated oscilloscope are subjected to dangerous voltages. The user should be aware, that: * Before moving scope probes, making connections, etc., it is generally advisable to power down the high-voltage supply. To avoid inadvertent touching live parts, use plastic covers. When high voltage is applied, using only one hand for operating the test setup minimizes the possibility of electrical shock. Operation in lab setups that have grounded tables and/or chairs should be avoided. Wearing safety glasses, avoiding ties and jewelry, using shields, and operation by a personnel trained in high-voltage lab techniques is also advisable. Power transistors, the PFC coil, and the motor can reach temperatures hot enough to cause burns. When powering down; due to storage in the bus capacitors, dangerous voltages are present until the power-on LED is off.
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* * * *
* *
5.4 Jumper Settings of Controller Board
The MC68HC908MR32 control board jumper settings shown in Figure 5-2 and Table 5-1 are required to execute the 3-phase AC motor control application with dead time distortion correction. For a detailed description of the jumper settings, refer to the MC68HC908MR32 Control Board User's Manual (Motorola document order number MEMCMR32CBUM/D).
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Designer Reference Manual 51
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System Setup
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JP5 JP4 JP3 JP2 JP1
Figure 5-2. MC68HC908MR32 Jumper Reference
Table 5-1. MC68HC908MR32EVM Jumper Settings
Jumper Group JP1 JP2 JP3 JP4 JP5 JP7 Comment Tachometer input selected Encoder input selected Back EMF signals selected Power factor correction -- zero cross signal selected Power factor correction -- PWM signal selected Power Supply connected to jack J3 Connections No connection 1-2 No connection No connection No connection 1-2
5.5 Required Software Tools
The application requires the following software development tools:
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System Setup Building the Application
* *
Metrowerks1CodeWarrior(R)2 for MC68HC08 microcontrollers version 1.2 or later. PC master software version 1.2.0.11 or later
5.6 Building the Application
To build this application, open the 3ph_acim_dt_correct.mcp project file and execute the Make command; see Figure 5-3. This command will build and link the motor control application along with all needed Metrowerks libraries.
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Figure 5-3. Execute Make Command
5.7 Executing the Application
To execute the motor control application, in the pull-down menu choose the Project/Debug command in the CodeWarrior(R) IDE, followed by the Run command.
1. Metrowerks(R) and the Metrowerks logo are registered trademarks of Metrowerks, Inc., a wholly owned subsidiary of Motorola, Inc. 2. CodeWarrior(R) is a registered trademark of Metrowerks, Inc., a wholly owned subsidiary of Motorola, Inc.
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Designer Reference Manual 53
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System Setup
If the MMDS target is selected, CodeWarrior will automatically download to the MMDS05/08 emulator. The application can operate in two modes: 1. Manual Operating Mode The drive is controlled by the START/STOP switch (SW3). The direction of the motor rotation is set by the FWD/REV switch (SW4). The motor speed is set by the SPEED potentiometer (P1). Refer to Figure 5-4 for this description.
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Speed Speed potentiometer Potentiometer
Fault POT Fault POT Over-Voltage Over-Voltage
Forward / Reverse Forward / Reverse Switch SW4 switch SW4
Fault POT POT Over-Current Over-Current
Start / Stop Start Stop Switch SW3 switch SW3
Figure 5-4. Control Elements
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System Setup Executing the Application
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Figure 5-5. USER LEDs, PWM LEDs, and RESET 2. PC Master Software (Remote) Operating Mode The drive is controlled remotely from a PC through the serial communications interface (SCI) communication channel of the MCU device via an RS-232 physical interface. The drive is enabled by the START/STOP switch, which can be used to safely stop the application at any time. Setting the required speed of the motor is the supported control action. The application states are displayed with on-board LEDs. Refer to Figure 5-5 for the LED positions. If the application runs and motor spinning is disabled (i.e., the system is ready), the green status LED will blink. When motor rotation is enabled, the green status LED will be on, and the actual state of the pulse-width modulator (PWM) outputs are indicated with PWM output LEDs, labeled PWM1 - PWM6. If DC-Bus over-current / DC-Bus over-voltage occurs, or if the wrong system board is identified, the green status LED will start to flash quickly and the PC master software will signal the identified fault. This state can be exited only with the application reset.
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System Setup
Refer to Table 5-2 for a description of the application states and their corresponding LED indications. Table 5-2. Motor Application States
Application State Stopped Running Fault Motor State Stopped Spinning Stopped Green LED State Blinking at a frequency of 2Hz On Blinking at a frequency of 8Hz
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Once the application is running: * * * Move the START/STOP switch (SW3) from STOP to START Select the direction of rotation by the FWD/REV switch (SW4) Set the required speed by the SPEED potentiometer
If successful, the 3-phase AC induction motor will be spinning.
NOTE:
If the START/STOP switch is set to the START position when the application starts, toggle the switch between the STOP and START positions to enable motor spinning. This is a protection feature preventing the motor to start spinning when the application is executed from CodeWarrior. You should also see a lighted green LED indicating the application is running. If the application is stopped, the green LED will blink at a 2-Hz frequency. When the application is started, the type of dead time distortion correction and desired PWM frequency can be selected using the PC master software control page. The phase voltage and motor current can be observed using the oscilloscope, and the efficiency of dead time distortion correction can be evaluated. The type of dead time distortion correction is indicated by a yellow LED on MR32 controller board. When the dead time distortion correction is disabled, the yellow LED is turned off. When partial correction is selected, the LED flashes with 2Hz frequency. With full correction, the LED is turned on (refer to Table 5-3).
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System Setup Controlling the Application with PC Master Software
Table 5-3. Dead Time Distortion Correction
Distortion Correction Disabled Partial (h/w) Full (s/w) Off Blinking at a frequency of 2Hz On Yellow LED State
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5.8 Controlling the Application with PC Master Software
Project file for the PC master software is located in: ..\pcmaster\3ph_acim_dt_correct.pmp Start the PC master software application window and choose the appropriate PC master software project. Figure 5-6 shows the PC master software control window for 3ph_acim_dt_correct.pmp. The type of dead time distortion correction (no/partial/full), and the PWM frequency (4kHz/8kHz/16kHz/32kHz) can be selected in the variables pane, as shown in Figure 5-6.
NOTE:
The desired dead time can be set in application configuration file appconfig.h, where all on-chip modules of the 68HC908MR32 microcontroller are initialized.
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Designer Reference Manual 57
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System Setup
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Select no / partial / full dead time distortion correction
Figure 5-6. PC Master Software Control Window The PC master software displays the following information: * * * * * required and actual speed of the motor phase voltage amplitude (related to given DC-Bus voltage) application mode -- START/STOP DC-Bus voltage fault status
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System Setup Controlling the Application with PC Master Software
The PC master software allows the user to * set the PWM frequency (the frequency can be changed at any time during the motor operation): - 4 kHz - 8 kHz - 16 kHz - 32 kHz
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*
select dead time distortion correction (the selection can be done at any time during the motor operation): - no - partial - full
The PWM frequency and type of dead time distortion correction can be selected in both the manual and the PC master modes, using the PC master software. It is possible to use the oscilloscope to display the phase currents and voltages for dead time distortion evaluation.
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System Setup
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Designer Reference Manual -- 3-ph. ACIM Drive with DTC
Appendix A. References
1. Motorola, Inc. (2001). 68HC908MR32 User's Manual, MC68HC908MR32/D
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2. Motorola, Inc. (2000). Motorola Embedded Motion Control MC68HC908MR32 Control Board User's Manual, MEMCMR32CBUM/D 3. Motorola, Inc. (2000). Motorola Embedded Motion Control 3-Phase AC BLDC High-Voltage Power Stage User's Manual, MEMC3PBLDCPSUM/D 4. Motorola, Inc. (2000). Motorola Embedded Motion Optoisolation Board User's Manual, MEMCOBUM/D 5. Motorola, Inc. (1997). Making Low-Distortion Motor Waveforms with the MC68HC708MP16, AN1728
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References
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Designer Reference Manual -- DRM019
Appendix B. Glossary
AC -- Alternating Current ACIM -- AC Induction Motor
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ADC -- Analogue-to-Digital Converter BLDC -- brushless DC motor DC -- Direct Current DT -- see "Dead Time (DT)" DTC -- Dead Time Correction, see "Dead Time (DT)" Dead Time (DT) -- short time that must be inserted between the turning off of one transistor in the inverter half bridge and turning on of the complementary transistor due to the limited switching speed of the transistors. duty cycle -- A ratio of the amount of time the signal is on versus the time it is off. Duty cycle is usually represented by a percentage. interrupt -- A temporary break in the sequential execution of a program to respond to signals from peripheral devices by executing a subroutine. input/output (I/O) -- Input/output interfaces between a computer system and the external world. A CPU reads an input to sense the level of an external signal and writes to an output to change the level on an external signal. logic 1 -- A voltage level approximately equal to the input power voltage (VDD). logic 0 -- A voltage level approximately equal to the ground voltage (VSS).
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Glossary
MC68HC08 -- A Motorola family of 8-bit MCUs MCU -- Microcontroller Unit. A complete computer system, including a CPU, memory, a clock oscillator, and input/output (I/O) on a single integrated circuit. MR32 (908MR32, MC68HC908MR32) -- See "MC68HC08" phase-locked loop (PLL) -- A clock generator circuit in which a voltage controlled oscillator produces an oscillation which is synchronized to a reference signal. PVAL -- PWM value register of motor control PWM module of MC68HC908MR32 microcontroller. It defines the duty cycle of generated PWM signal. PWM -- Pulse Width Modulation reset -- To force a device to the known condition. SCI -- See "serial communications interface module (SCI)" serial communications interface module (SCI) -- A module that supports asynchronous communication. serial peripheral interface module (SPI) -- A module that supports synchronous communication. software -- Instructions and data that control the operation of a microcontroller. software interrupt (SWI) -- An instruction that causes an interrupt and its associated vector fetch. SPI -- See "serial peripheral interface module (SPI)" SR -- switched reluctance motor timer -- A module used to relate events in a system to a point in time.
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Designer Reference Manual 64
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HOW TO REACH US: USA/EUROPE/LOCATIONS NOT LISTED: Motorola Literature Distribution; P.O. Box 5405, Denver, Colorado 80217 1-303-675-2140 or 1-800-441-2447 JAPAN: Motorola Japan Ltd.; SPS, Technical Information Center, 3-20-1, Minami-Azabu Minato-ku, Tokyo 106-8573 Japan 81-3-3440-3569 ASIA/PACIFIC:
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Information in this document is provided solely to enable system and software implementers to use Motorola products. There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters which may be provided in Motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. Motorola does not convey any license under its patent rights nor the rights of others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part.
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