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Chapter 4
Description of Operation
4-2
Figure 4.1
PWM Waveform
300V DC
Bus
0
400µs
Typical
The three-phase relationship between the reference signal and the timing
wave provide PWM pulses to the power transistor base drive. This base
drive switches the power transistors across the 300V DC bus, providing
current to the motor windings, thus causing the motor to turn. A resolver
attached to the motor provides a signal corresponding to the actual rotor
position of the motor. This signal is decoded to a signal representing rotor
position and is fed to the commutation logic along with the torque
command. In this way, the drive combines the desired position signal and
current reference with the decoded resolver signal to produce a reference
signal commanding the motor to speed up or slow down. See Figure 4.2.
Figure 4.2
Operation
Commutation
Current
Logic & Current
Reference
Loop Integrator
Position Decoder
400µs
Typical
400µs
Typical
PWM Generator
& Base Drive
Timing Signal
Generator
400µs
Typical
Time
Motor
Resolver
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