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RAM DBS II soft starter trips on phase loss at end of ramp.

Issue:
What causes the DBS II to trip on phase loss just as the bypass contactor pulls in?

Product Line:
RAM DBS and DBS II

Environment:
All

Cause:
Faulting Phase Loss

Resolution:
The DBS is always monitoring the amps in each phase.  After the DBS ramps the motor to full speed, the DBS sends control power to the bypass contactor coil to close it.  After a short delay, the DBS shuts down the SCRs.  Motor current should be maintained throughout this sequence. If current is interrupted, the DBS trips on Phase Loss.

Typical causes:
- Problem in the 120Vac control circuit to the bypass contactor coil.  Check circuit wiring and DBS contact closure between terminals 9-10.  Secure wiring or replace the control board set.
- Bypass contactor failure.  Check the coil, contact tips and mechanical action.  Replace the contactor.
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