During Start Current Control - Hitachi RAS-25CNH1 Service Manual

R229, R230, R231 detect the DC voltage at the power circuit. The micro computer receives a DC voltage
(210-300V) via HIC
when the DC voltage is high (low).
(Since the load level is indicated by the DC voltage multiplied by DC current, R229, R230, R231 are
provided to perform the same overload judgement even when the voltage varies.)
0
0
< During start current control >
It is required to maintain the start current (DC current) constant to smooth the start of the DC motor for
the compressor.
The RAC-25CNH11 uses software to control the start current.
The start current varies when the supply voltage varies. This control method copes with variations in the
voltages as follows.
(1) Turns on the power module's U + and V – transistors so the current flows to the motor windings as
shown in Fig. 8-9.
(2) Varies the turn-ON time of the W + transistor according to the DC voltage level and the start is
controlled so the start current is approx. 8A as shown in Fig. 8-10.
DC 260-290V
Detection
resistor
Chopper duty: high
8
6
4
2
0
and applies correction to the overload set value so the DC current is low (high)
64
DC current
U +
U -
Start
Amplification : low
DC voitage : low
DC current : high
Amplification : 8 times
DC current : 260v
Amplification : high
DC voltage : high
DC current : low
Rotation speed
Fig. 8-8
Power module
W +
V +
W -
V -
Fig. 8-9
DC voltage (start current)
Fig. 8-10
– 82 –
Compressor motor
U
V
W
DC voltage: low
DC voltage: 260V
DC voltage: high
Set value
Time