Yes,a single phase AC motor should be connect through a O/L relay.There are single phase O/L relays are available in market how ever a three phase relay can be used.Out of three terminals one terminal to be connect for neutral and remaining two terminals to be conect in series (incoming terminal of one phase - Out going of the same phase terminal -again from out going of the phase 1 to incoming og phase-2 and final out going will be from 2nd phase out going terminal). it will protect the motor from O/C and other faults like E/F and S/C etc.
BS7671:2001 states that motors over 0.37kW need an overload device.
More recent specs may vary - I don't have the latest edition to hand - and as I don't know where in the world you are, I can't comment on your local regs.
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Some small 1 phase motors have a thermal OL device built-in to the motor. If the nameplate says "Internally Protected" or something along those lines, then it has that feature. If not, assume it does not and use an external OL relay. If all you have available is an IEC type 3 phase OL relay, make sure you read the instructions for it regarding looping the wiring back through to ensure that current is flowing through all 3 legs, otherwise it may give you nuisance trips.
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motor
Re: motor
