1. Using overload relay: The control contact of the relay should be connected in series with the control circuit. The NEC in general requires the maximum size overload device be set to open at 115% or 125% of the motor’s full-load current rating, depending upon the service factor and/or temperature rise of the motor.
There are however, exceptions. NEC Article 430.31
2. Using phase failure relay: connect a phase failure relay to the branch circuit conductors of the power line in the right sequence RST to UVW respectively. Connect the normally open terminal of the relay in series with the control circuit. Complete three phases on the power line will turn on the phase failure relay and absent of any one phase or wrongly sequenced phases will turn the relay off.
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