Breaker Selection Criteria for Motorized Load

you can calclate 100% correctly the size of protection device.But it depend your knowledge, and not our.

Thank you for your GA wareagle. Ray

You could try going to an electrical engineering school. You might try going to a seminar on the wiring standards for your location. You could even become an apprentice to a local electrician and learn while working. You could even try the large number of on-line university reference material available on the web and come back to us with a few pertinent questions.

But we have worked hard for the knowledge we've gained in one of the above paths. If we just handed you an accurate formula, no one here will know if you can use it properly or what it means.

→ British Standard 7671.

No. I will use only NEC.

an ugly's book sound like it could be your best friend. and if your wondering that is the books name: ugly's electrical reference

See this link

http://cr4.globalspec.com/comment/586920

If you are in the NEC world, you can select a MCP (a motor circuit protector) which will avoid the motor inrush but provide short circuit protection. A soild state thermal relay will be able to provide overload protection. With an isolation switch,and a contactor, the entire assembly is called a combination starter. Now if you are in the non-NEC world, the best bet will be a suitably selected MCCB, overload relay with an isolation switch. Best advice would be to contact your local MCC vendor, and give him the LV motor details. The nameplate rating, Locked rotor current etc will be required.