CT burden resistor calculation

Other Hardware General Electronics
21

kamelryttarn:
Large electric motors can generate very high currents when starting up. I have absolutely no idea HOW large these can be but assuming 2 time normal running current (normal running current being 30A RMS) startup current can reach 60A RMS or 85A peak.

Factor of 20 is much more likely. A large 24V DC motor with ~ 1 kW rating will have winding resistance
of a few 10's of milliohms. Theoretical stall current ~ 1000A. Such current would destroy the motor
brushes (unless its built like a car starter motor) - such a motor would normally carry about 50A, peak
150A or so.

Large motors require current-limited motor drivers because the full stall currents will totally destroy
things, which means they need to sense current and limit drive to keep current within safe limits, including
when actively braking.

22

I find solution for IT characteristic. this sample example given here. need c code

assume Overload current = 10A(user defined setting)

Over load current trip time =10s(user defined setting)

if curve 2C is selected

calculation are as below The relay should turn on 30% over load trip time i.e 13A
Trip_Time over_current
10 10
9 10.3
8 10.6
7 10.9
6 11.2
5 11.5
4 11.8
3 12.1
2 12.4
1 12.7
0 13

in code if the Nominal current exceeds overload current these are trip timing for relay. The timing and current will change as per user defined setting. can some one guide me C code.