Motor Inrush Current

As a worst case you can take the dc resistance of the wiring in your motor coils.

There is no way to tell for absolute sure on any particular motor without asking the motor manufacturer, because a lot depends upon the construction of the motor itself. There are accepted "rules-of-thumb" which you already cited, but that is about as close as you can get without a lot more information. I suggest you read this paper:

http://www.lmphotonics.com/m_control.htm

Or this one:

http://www.thomasblairpe.com/paper3.pdf

Then pay particular attention to the "AC motor equivalent circuit" section to get a better understanding.

There is some good data here.

Inrush current = starting current = lock rotor current =

1000*hp*(kVA/hp)

--------------------

1.732*V

note :

*Where kVA/hp is Locked Rotor Code Letter refer to NEMA table 430-7(b) which is attached on the motor name plate as KVA Code for Siemen's motor.

*This is Approximate calculation only, the result is near 6 to 8 times In.

You may try.

cheers

The starting current as per IEC or BS should be 6 times the rated current with tolerance .There is a 20% tolerance on Starting current .So maximum can be 7.2 times.Many manufacturers face problems in limiting starting current particularly in 2 pole machines.In such cases the published figure in the catalogue subject to 20% is the max value of starting current.The published values in some cases may be high and when rreferred to rated current may workout to 8 times rated current value.

Look on the nameplate. There you will find a NEMA code (not to be confused with the insulation class) NEMA has established code letters which give you the starting kVA/hp for the motor. Once you have the code letter it is a simple matter to use the appropriate formula. Multiply the hp by the kva/hp factor (since the code gives you a range use the high end value) to get kva then just use basic electrical formulas to get A from kVA (formula depends on motor configuration 3 phase? single phase...) The NEMA standard as I recall is NEMA MG1

ASSuming he is in North America where NEMA motors apply...

I have seen motor manufacturer'sdata says its 5.5 some where 6, some where 5 etc.

Motor manufacturers will be happy to have 6+20%.Except on 8pole and above without special designs it is difficult and expensive to limit starting current 5.5 PU on 2,4 and 6P