High Current

[None]

Dear All,

 

We have recently hook up a condenser water pump to a VSD. During the testing, when the VSD hit around 40+ hz, high current alarm was prompt on the VSD. Initially we thought that the problem lies with the VSD, however after further testing by hooking up to another VSD to this pump, the same problem occur, hence we conclude that the fault lies with the pump.

 

Appreciate if any of you here can advise what might have cause the high current in the motor. For your info, the motor was sent for re-winding few months back due to some problems. Not sure if this might be related to the winding, as it could still run normally when not drive by the VSD.

 

Thanks

[marke]

Hello None

 

Welcome to the forum.

 

You may have a problem with the "hydraulics".

If the pump is designed to operate with a pressure differential of say 4 bar and you run it at zero bar, then the flow will be much higher and the energy consumed will be higher. Check the pump curves and compare them against the actual operating conditions.

 

Best regards,

Mark.

[None]

Hello None

 

Welcome to the forum.

 

You may have a problem with the "hydraulics".

If the pump is designed to operate with a pressure differential of say 4 bar and you run it at zero bar, then the flow will be much higher and the energy consumed will be higher. Check the pump curves and compare them against the actual operating conditions.

 

Best regards,

Mark.

 

 

Hi Mark,

 

Thanks for the reply. How do I check what is the pressure differential during the operating time. The Pump do come with a pressure gauge. However, it only shows the pressure and not the differential pressure which you mentioned here.

 

But, when the pump is running under soft starter, it could ramp up normally.

 

I presume that it could only be cause by the turbulence in the pipe. What do you think..?? Pls advise.

[yuri]

How do I check what is the pressure differential during the operating time. The Pump do come with a pressure gauge. However, it only shows the pressure and not the differential pressure which you mentioned here.

Hello None.

By closing the valve at the discharge you will increase the head pressure and so the head/suction ratio.

Does the current drawn by the motor, when it runs direct on line, not exceed the rated value mentioned on its plate ?

[marke]

Hello None

 

when the pump is running under soft starter, it could ramp up normally.

If the pump starts and runs normally with a soft starter, then it should start and run normally with a VFD.

 

It sounds as though the settings for the VFD are not correct for the motor. Check that the settings in the VFD for the connected motor reflect the actual motor ratings, especially the motor voltage and the motor frequency. If these settings are not correct, the V/Hz curve will be incorrect and this could cause the problems you describe.

 

Best regards,

Mark.