Hi Guys, Can anybody guide me how

[kitha]

Hi Guys,
Can anybody guide me how to calculate the feeder and branch circuit protective devices and cables as per IEC or brtitsh methods. Where are the publications of locked rotor amps, temperature derating factors for cables can be found in the net? I am familiar with NEC/Canadian stds only. As an example I can ask you guys the following:

10 hp motors=02 nos(Direct online start)
60 hp motors=01 nos (star delta start)

what are the sizes of branch circuit condusctors, main feeder and their protective devices(time delay circuit breakers)

voltage is 400, 3ph/230-1ph

Thanks in advance for guidance.

 

[jbartos]

Suggestion: Visit

http://domino.automation.rockwell.c...3a02b803eb852569600079ff36/$FILE/193-2_10.pdf

http://domino.automation.rockwell.com/Applications/kb/kb.nsf/WEB_V_IECSTARTERS

http://www.cbi.co.za/papers/20/Motor.pdf

etc. for more info.

 

[19gabi50]

EDSA and ABB DOCWIN programs are applicable.

 

[neps3]

Kitha

You have talked about main feeder and branch conductors. Are you talking about the main feeder from the transformer and the cable to the motors.

1.The motor manufacturer should give you the locked rotor current. Rule of thumb is DOL about upto seven times.
2.You have to co-ordinate the fuse with the starting current and the short circuit current.
3.The motor overload is set approximately 105% of FLC.
4.The fuse is for short circuit protection of the cable.
5.Upstream protection should be descriminated with the sub-circuit protective devices.

If you need more info please give a full description of your system.