HAI,HOW TO SET THERMAL OVERLOAD RELAY FOR DOL STATRTER
FEEDER AT START AND RUNNING?
Answer Posted / fairos
First, for thermal overload relay has no meaning in term of setting it while on running or starting. It purely based on rated current of the motor.
when you look at the nameplate of the motor there should be a data that mention "duty" which normally either 1, 1.1 or 1.2 in value. If the duty is 1 then you can only set the overload relay at 100% of the rated current. If duty is 1.1 then the motor is allowed to operated at 10% higher than it rated current hence you can set your relay at 110% of rated.
Generally people would set at 10-15% higher than rated current. But sometimes being conservative is okay, which you can set the relay below the rated current. This can be done as long as it is not tripping unnecessarily.
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