Power factor correction.

[hojo85]

I have a 6kv motor with a damage capacitor out of circuit. The motor is 375kw, with no resistance box nor a liquid starter. It drives a large impact crusher. NB: a hydraulic coupling is on the drive shaft. We generate our own power; every time we start this unit it trips other equiment on the plant. What can we do in the short term to prevent these trips and explain what the capacitor is doing in the circuit.

Thank You
hojo85

 

[jbartos]

Questions/Suggestions:
Has the motor starts been tripping other loads since the capacitor was damaged and removed from the circuit?
Is the hydraulic coupling working normally?
The capacitor connected in parallel with the motor terminals reduces the motor inrush current and the motor load current from the motor terminals upstream. It also improves power factor to the combined capacitor-motor load. Since the capacitor is removed, there might be larger voltage dips and drops negatively affecting other loads and the lower power factor.

 

[Shortstub]

What was capacitor's size?

 

[sykimk]

Motor starting requires lots of reactive power from power supply. Due to this reason, there are large voltage dips when motor starting, if reactive power supply is insufficient. I guess that your capacitor would supply reactive power to compensate required reactive power demand when motor starting. After start-up, it help improve power factor.

I am not sure which kinds of trips arose, but I guess that magnet contactor (MC) in motor starter could be released due to large voltage dips when motor starting although 375kW motor would be started. It is one of possible case, if MC is a inferior unit. If my assumption is correct, please check and test MC first.

If 375kW motor failed to start-up and its starting behavior trips other equipment, your present system does not provide the required reactive power when motor starting.
Therefore, I suggest you to increase opearating voltage of in-plant generator within its permissible operating region to supply more reactive power to your system for motor starting.

 

[jbartos]

Suggestion: Visit

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

etc. for more info

 

[brucecranene]

Suggest visit http"\\

http://www.wyesenergy.peachhost.com

if you don't know what size capacitor you need.

 

[tmahan]

as a short term solution is it possible to use a smaller "pony motor" to get the primary motor spinning? it sound like you could use the coupling to disengage the motor from the load.

If this is possible, it will greatly reduce the current demand once the 3kV voltage is applied to the primary motor