4NC5 – overload?

_oleksandr_

Hi,
Could you explain to me
what kind of overload has a current transformer 4NC5222-2CE20 (CLASS 1 200A/5A, 5VA).
For example, I have motor 45kW/400V/81A, starting current 6xInominar (6x81=486A, during 10sec),
what current will be on the secondary winding of the current transformer 4NC5222-2CE20 during starting motor?
(486A/200)*5=12.15A? 

Starting or peak current of motor would be 486 A but it would not be same for 10 sec i.e. during accelration time. As motor starts acclerating the current starts droping. Please refer Current transformer for low voltage  & 4NC5_en.pdf documents. The overcurrent limiting factor is expressed as FS & a factor, in this case it is FS5. So overload factor of CT is based on short circuit current & not on the inrush current of load. Please also refer Ith & Idyn values of CT in documents for more information.

HTH.