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 ?
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Answer Posted / a.kossay
FIRST OF ALL THIS MOTOR MUST HAVE A SOFT STARTER BECAUSE
STARTING THIS MOTOR WILL DRAW A HUGE AMOUNT OF INRUSH
CURRENT + HUGE AMOUNT OF STARTING CURRENT, SO YOU HAVE TO
USE SOFT STARTER , AND YOU HAVE TO USE SMART RELAY BECAUSE
STARTING AND INRUSH CURRENT CONATINS A HUGE AMOUNT OF
HARMONIC CONTENTS SPECIALLY THIRD HARMONIC SO THIS SMART
RELAY WILL DETECT THE VALUE OF THE THIRD HARMONIC COMPONENT
AND IF IT EXCEEDS ITS VALUE IT WILL TRIP
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