Confused

Driving a Cryogenic pump motor, the motor rating plate states that the Nominal Voltage is 400V, 6090 RPM and 101,5 Hz.

It also states that the motor may run between 62 and 110 Hz with a speed of 3700 to . I think 6900 Rpm... not too sure on the actual value.

I programmed the nominal rated frequency and RPM into the drive and the motor just kept on shuting down within seconds of starting .... the only fault it indicated was overbraking..... Im lost... since over braking should not apply at start up...
I played around with the settings and set the rated motor frequency at 62 Hz and the RPM at 3700 .....and it works well no problems at all....

I am still confused as to why it would not work with the correct name plate settings. Can anyone shed some light...

zero load motor current

How would I determine the correct current that a motor would draw if it ran without a load ??

Motor starters

Please advise on why some motors are limited to several starts per hour....

Is it due to fear of Overheating the windings due to high inrush current or is it ti prevent mechanical damage to motor and or pumps.

PFC Tripping problem

Hi all

;c;
We have 360KVAr 400 Volt PFC Bank 6 steps, controled by a 6 step Varlogic controller.

The Problem that we are having is that the Circuit breaker supplying this bank trips (due to differencial current) everytime two or three substantial loads are shutdown. We have a torroid coil that feeds a Differencial relay.
This is the first time that I have seen a Differencial relay protecting a capacitor bank. Is this correct ??

What would happen to the current being drawn by the capacitors when the Power factor goes into leading as opposed to lagging ?

would this shift in current cause an imbalance in the phases causing the relay to trip ??

thanks to all
porky