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When using a full voltage bypass contactor (not end of start/shorting), do you have to isolate the input of the soft starter from the main power before connecting power through the bypass contactor?

Published date: 20 May 2019

Issue:
When using a full voltage bypass contactor (not end of start/shorting), do you have to isolate the input of the soft starter from the main power before connecting power through the bypass contactor?

Product Line:
Altistart 22  with a optional bypass contactor.

Environment:
All units equipped with a full voltage bypass.

Cause:
Customer is installing a full voltage bypass contactor, not part of an enclosed system built by Schneider.

Resolution:
When a full voltage bypass is being used with an Altistart ATS22 product, an isolation contactor should be used to disconnect the input voltage of the soft starter from the L1 L2 L3 to ensure that power is not fed back into the input of the soft starter when the bypass contactor is pulled.   This Isolation contactor should be electrically and/or mechanically interlocked with the bypass contactor to ensure that only one can be closed at any given time.  Please note that you will need to install a bypass contactor overload with this too. See the example drawing below.  Note that a run command from Hand or Auto is still necessary for the system to run in bypass.


 

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