Hitachi RAM-18QH5E, Руководство по обслуживанию

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12. Electric expansion valve
Fig 12-1
●
The electric expansion valve is driven by DC 12V. Power is supplied to 1 or 2 phase winding to switch
magnetic pole of winding in order to control 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 CN 15 and CN 16 are about 0.9V; they are about 12V
when no power is supplied. When power is reset, initialization is performed for 10 or 20 seconds.
During initialization, measure all voltages at pins
4
to
1
of CN15 and CN16 using tester. If there is any
pin with voltage that has not changed from around 0.9V or 12V, expansion valve or microcomputer is
defective.
●
Fig 12-2 shows logic waveform when expansion valve is operating.
Table 12-1
With explosion valve control, opening degree is adjusted to stabilize target temperature, by detecting
temperature of compressor head.
The period of control is about once per 20 seconds, and output a few pulses.