Hitachi RAF-35NH5 Service Manual page 270

. Overload control ciricuit (OVL control circuit)
¥ Overload control is to decrease the speed of the compressor and reduce the load when the load on the air conditioner
increases to an overload state, in order to protect the compressor, electronic components and power breaker.
¥ Overloads are judgement by comparing the DC current level and set value.
¥ Fig. 5-1 shows the overload control system configuration and Fig. 5-2 is a characteristic diagram of overload judgement
values. There are two judgement methods-external judgement which mompares the externally set value with the DC
current value regardless of the rotation speed and internal judgement which compares the set value that according to the
rotation speed programmed in the micro computer software with the DC current value.
Translation
To power module
negative terminal
(R503)
Detection
resistor
Primary
CT
0V
0V
Voltage amp.
circuit
(Internal judgement)
DC voltage
RC filter circuit
Fig. 5-1 Overload Control System Configuration
Judgement value according to the rotation speed
(internal judgement value)
Rotation speed
AX-6N00 micro computer
Judgement OVL
with respect to
externally set
value
Judgement OVL
A/D
according to the rotation
convarter
speed
Selects data according
A/D
to the rotation speed and
convarter
DC voltage.
A/D
OVL start current data
convarter
External judgement value
Fig. 5-2
- 300 -
Motor control
process