Control Sequence; The Method Of Manual Resetting - Hitachi CA47TLA-D2PE3 Manual

2-1．CONTROL SEQUENCE
The compressor is protected by OCR (overcurrent relay for compressor motor) and
a DT (discharge gas thermostat).
These safety devices are automatically reset.
Therefore, all control circuits should be designed to guard against harmful on-off restarting by
the installation of the automatic reset safety device.
A typical control circuit for the scroll compressors is shown in Clause 2 "Basic Electrical Wiring
Diagram (for 3 phase)."

2-2. THE METHOD OF MANUAL RESETTING

After the compressor stops due to the activation of the protection device, the compressor will be
reset automatically and start operation.
When the protection device is activated, it is necessary to investigate the causes of activation,
and if there are abnormalities, it is necessary to improve the causes before restarting.
When electric power is supplied to the control circuit, and each electric phase is correctly
connected to the compressor, turn off the reverse phase relay (RPR). At this time, when the
push button switch (PB1) is depressed, the control circuit is energized and the magnetic
contactor (CMC) connects the compressor to the power source. Even if PB1 is released, CMC
will maintain the connection until the supply of electric power shuts down.
But, when OCR (overcurrent relay for compressor motor) or DT (discharge gas thermostat) is
cut out, CMC is causing the contact to open and disconnecting the compressor from the power
source.
Even if OCR (overcurrent relay for compressor motor) or DT (discharge gas thermostat) is
automatically reset, the compressor will not be connected to the power source because CMC
is still open.
Therefore, the push button switch (PB1) should be depressed again manually for connecting
CMC and operating the compressor.
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