Hitachi RAF-25FX8 Service Manual page 106

• IPM drive circuit
The inverter driving device (IGBT) and the drive circuit are built in the IPM. The IPM receives the
signal from the microcomputer and convert it to 0 – 15 V signal to drive the IGBT.
When the unit operates at low speed, a chopper signal is emitted from the microcomputer as shown
in Fig. 4-6. (0 to 5 V)
The signal is converted to 0 – 15 V at inside the IPM and transmitted to the gate of the transistor
(IGBT) in each phase to drive the IGBT.
When abnormal peak current was detected while the inverter is driving, the IPM outputs the Fail
signal immediately from the pin
In this step, the Q501 is turned on and the input signal of the upper arm is also shut off through the
D501 and D502, so that all signals to the IGBT are shut off. This signal is also distributed to
microcomputer (pin
time.
When the peak current is detected, the IPM keeps the lower arm off for about 4ms. and the drive
signal into stand-by state. 3 minutes after this state, the microcomputer outputs the drive signal and
restarts the operation.
and forces the lower arm transistor to shut off at the same time.
29
) as a Lo signal to stop the drive signal and blink the self diagnosis lamp as two
17
5V
0V
15V
0V
Fig. 4-6
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