Thanks for the reply, waross
You are right - considering the starting current,a 300A breaker is marginal. I remember using a 300A breaker on a 110kW motor once, and it used to trip immediately because of the 1st cycle inrush current.
Unless I install a very large breaker, I may have to go with...
I am used to seeing a circuit breaker, or fuses, used with a contactor and overload relay in motor control circuits.
However, we've taken delivery of a feeder conveyor which uses a large circuit breaker to supply the two motors on the conveyor, with a contactor and overload relay for each...
Is there any standard recommending certain IP ratings for indoor switchboards (motor control centres)?
I know that for indoor boards IP41 is quite standard with board manufacturers.
Also, what proof can one ask of a manufacturer to satisfy oneself that his boards comply to his claimed IP rating?
DanDel,
The analog ammeters that are connected to the CT's are used for indication only, so the accuracy of the reading is not that important.
seanmx, A new CT will be installed after a month or two. I was wondering if it is ok to use the existing CT in the interim.
Can I 20/1 CT(probably 2.5VA, or maybe 5VA) be used for measuring current on a 380V motor with a FLC of 23A. I am not worried about accuracy, but rather whether the CT might fail in service. The only connected load consists of 2 ammeters, one situated about 100m away via 2,5mm^2 cable.
The CT...
