Hitachi RAC-50YH7, Service Manual, Page: 64 / 103

– 73 –
Fig. 3-5
●
Since current flows at point B only when U+ transistor and V– transistor is ON, the current waveform at
point B becomes intermittent waveform as shown in Fig. 3-3. Since current at point B is approximately
proportional to the input current of the air conditioner, input current is controlled by using DC current (Id)
detection resistor.
<Reference>
If power module is detective, self diagnosis lamps on the control P.W.B. may indicate as shown below:
From results of power module simple inspection (inspection mode when operated with compressor lead
disconnected), LD310 blinks four times about 2 seconds later: Unit has not entered the normal operation.
Fig. 3-4 System Power module circuit (U+ is OFF, V– is ON)
Self-diagnosis
Self-diagnosis lamp
and mode
lp (peak current cut)
LD301
Abnormal low speed
rotation
LD301
Switching incomplete
LD301
Blinks 2
times
Blinks 3
times
Blinks 4
times
Table 3-1
+
U
U
V
W
—
U
+
V
—
V
+
W
—
W
_
+
System Power Module
320-360V
R24
DC current (Id)
detection resistor
A
U coil
DC compressor
motor
V coil
W coil
B
SMOOTHING
CAPACITORS
SYSTEM POWER
MODULE (SPM2)
LD301
LD302
LD303
LD304
SERVICE SWITCH
MAIN P.W.B.
POWER P.W.B.