We have 800KW motor operating at 6600Volt,50 Hz
supply.During 1st startup it tripped on overcurrent
trip.It's FLA is 88 Amps.The K factor of Thermal overloaaad
was set on .94 initially.then we set at 0.97 and then it
started fine.i dont understand why it tripped first?What
are the protections which comes in picture during starting ?

Answer Posted / ghani

It is right that starting current of this much big motor is
very high whihc varies as per data from 6 to 8 times, so if
the protection relay is of static or digital then there
must be a restraining setting for starting current with
time delay, so you can increas both values keeping the data
sheet of motor in view.

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