AN1857 Freescale Semiconductor / Motorola, AN1857 Datasheet - Page 32

• Manufacturer Part Number: AN1857
• Description: A 3-Phase ac Induction Motor Control System Based on the MC68HC908MR32
• Manufacturer: Freescale Semiconductor / Motorola

Freescale Semiconductor, Inc.
Application Note
voltage is calculated. The PWM generation process calculates a system
of 3-phase voltages of the required amplitude and frequency that
includes dead-time. The 3-phase PWM motor control signals are then
output to the power stage.
The dc bus voltage and dc bus current are measured during the control
process. They are used for overvoltage and overcurrent protection of the
drive. The overvoltage protection is performed by software while the
overcurrent fault signal utilizes a fault input of the microcontroller.
If any of the aforementioned faults occur, the motor control PWM outputs
are disabled to protect the drive. The system fault state also is displayed.
These faults, depending on the operating mode of the system, are output
to the LEDs on the controller and/or the PC terminal connected to the
control board.
The design of the system requires the system software to take some
values from the user interface and sensors, processes them, and
generates 3-phase PWM signals for motor control.
The control algorithm for a close loop ac drive is described in
Figure
20.
It consists of processes described in following subsections. Special
attention is given to the subroutine’s 3-phase PWM calculation and volts
per hertz control algorithm. Also, initialization of the microcontroller is
described.
AN1857
32
MOTOROLA
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