Motor Protection 51 Settings

[kobavr]

Hi,

How can we set motor 51 protections low set, high set or IDMT?

 

[rcw retired EE]

Use inverse time overcurrent for overload protection and an instantaneous overcurrent for short circuit protection. Set the curve to match the motor overload curve. Usually set pickup at 115%-125% of Full Load Amps (FLA) with the time dial adjusted to trip on Locked Rotor Current faster than the allowable hot stall time and slower than the motor/load's acceleration time.

Set instantaneous above the motor inrush current.

You will need the motor thermal limit curves to properly set the relay.

 

[purplepete]

And check that the contactor can open on short-circuit current if it's ever called so to do.