Hitachi RAW-35RHC, Руководство по обслуживанию

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4 Electrical checks of main parts
Outdoor unit
SMGB0135 rev.0 - 06/2020 41
4
4.1.6 Electric expansion valve circuit
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RED
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Electric
expansion
valve
Microcomputer
The electric expansion valve is driven by DC12V. Power is supplied to 1 or 2 phases of 4-phase winding to switch
magnetic pole of winding in order to control the opening degree.
Relationship between power switching direction of phase and open/close direction is shown below. When power is
supplied, voltages at pins 4 to 1 of CN15 are about 0.9V and 12V when no power is supplied.
When power is reset, initial operation is performed for 10 or 20 seconds. During initial operation, measure all voltages
at pin 4 to 1 of CN15 by using a multimeter. If there is any pin with voltage that has not changed from 0.9V or 12V,
expansion valve or micro computer is broken.
Figure below shows logic waveform when expansion valve is operating.
Drive status
CN15 pin
number
Connector
pin number
Wire
Operation mode
Valve close
Valve open
With expansion valve control, opening degree is adjusted to stabilize target temperature by detecting compressor head
temperature. The period of control is about once per 20 seconds and output a few pulse.