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12. Electric expansion valve
The electric expansion valve is driven by DC 12V. Power is supplied to 1 or 2 phase winding to switch
G
magnetic pole of winding in order to control opening degree.
Relationship between power switching direction of phase and open/close direction is shown below.
G
When power is supplied, voltages at pins
when no power is supplied. When power is reset, initialization is performed for 10 or 20 seconds.
During initialization, measure all voltages at pins
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.
G
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.
Fig 12-1
to
of CN 15 and CN 16 are about 0.9V; they are about 12V
4
1
to
of CN15 and CN16 using tester. If there is any
4
1
Table 12-1
– 63 –
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