AN1857 Freescale Semiconductor / Motorola, AN1857 Datasheet - Page 35

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

AN1857
MOTOROLA
During deceleration, the motor can work as a generator. In the generator
state, the dc bus capacitor is charged and its voltage can easily exceed
its maximum voltage. Therefore, the dc bus voltage is measured and
compared with a limit. In case of deceleration overvoltage, the
deceleration is interrupted and the motor runs with constant speed to
discharge the capacitor down to an acceptable limit. Deceleration can
then continue. During deceleration, depending on the input line voltage,
the PFC algorithm is either turned off or the dc bus voltage controlled by
the PFC is reduced to 340 volts.
The speed sensor process utilizes the MR32’s input capture interrupt
function. The circuit in
tachogenerator output. The input capture interrupt reads the time
between the rising edges of the speed sensor’s output and calculates
the actual motor speed V_tacho. A software filter of the speed
measurement can be incorporated in the process for better noise
immunity. In this case, the actual motor speed is calculated as an
average value of several measurements.
Freescale Semiconductor, Inc.
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V_command <> 0
V_command = 0
Start/Stop = 1
PWM enabled
v_pi_out = 0
MCS State
Run
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V_command <> 0
Figure 21. Drive State Diagram
Figure 5
V_command = 0
Start/Stop = 1
PWM disabled
PWM disabled
MCS State
MCS State
Stand-By
signal conditions the motor’s
Reset
Stop
Start/Stop = 0
Over Voltage
General Fault Recovery = 0
General Fault = 0
MCS State
Recovery
MCS State
disabled
disabled
Fault
PWM
PWM
Fault
Over Current
Application Note
Software
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