Suppose we using 3 phase motor of 440 v means what range of C.T. is require for measuring current, the rating of motor is 1HP

1 HP = 735.5 W
Voltage = 440 V
3 Phases
Current = 735.5/ (1.732x440) = 0.96 amp
We don’t require a CT, because the main purpose of CT is to step down the current, so that the ammeters or relays would work (ammeters and relays work at low level of current). If we get more current like 200 amp or so then need to use CT (200/5) to step down the current and it would feed in to Relays, ammeters etc..
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