Service
Operation & Maintenance Manual 57
Power Panel
On the left side of the power panel, terminal blocks for main power connection are prepared. The field supplied 400VAC
main power lines and neutral line for control power are connected to these terminal blocks.
There are three magnetic contactors for the wye-delta starting of the compressor and OCR (Over Current Relay) for the
compressor. For wye-delta starting, there are three magnetic contactors installed inside of the power panel.
By the wye-delta starter, the starting inrush current is reduced by 1/3 of direct starting method. The line voltage(VL) of
the both of wye and delta winding configuration is 400VAC, but the phase voltages(VP) of the wye winding configuration
is reduced by 1/3 of the delta winding configuration. Additionally, the line current (IL) is also reduced by 1/3 of the delta
winding configuration. Consequently, the current of the wye winding configuration is reduced by 1/3 of delta winding
configuration. Using the principle, the compressor starts with the wye winding configuration. And the winding configura-
tion is changed into delta configuration after few seconds for the normal operation of the compressor.
Fig. 35
Main Power
Compressor
Wye-delta
Starter
Compressor
OCR
