MOTOR NO LOAD 1

[streeta]

Does anyone have a list of what the No load current is for motors. from 15kw upto 250kw??
Or what is the normal % you would use to work it out?

 

[eemotor]

What type of a motor is this for? DC, AC induction, AC synchronous, 1 or 3 phase?

 

[Marke]

Hello streeta

Generally, there are trends in open shaft motor current, and there are also exceptions.
Trends.
1) Very small motors can have an open shaft current in excess of 60% rated current. As the motor size is increased, this current reduces to as low as 20% on very large motors. For motors in the 15KW size, I would expect the average open shaft current to be in the order of 35 - 40%.
2) As the motor speed is reduced (increasing poles) the open shaft current increases. A large 2 pole motor may be in the order of 20% while an equivilent 6 pole motor may be in the order of 30%
3) High efficiency motors generally have a lower open shaft current than low efficiency motors.
Exceptions.
1) Motors that are intentionally overfluxed to reduce size, will have a higher open shaft current. Submersible pumps fall into this category. The increased flux will increase the iron loss, but the motor is fluid cooled so this is not an issue.
Best regards,

Mark Empson

http://www.lmphotonics.com