Using VFD as a phase convertor to run 3 phase pumps 9

[Wedoca]

Hi people ,

I recently have seen a Culter Hammer VFD been used as a phase convertor get gain 3 phase at an area where only single phase is avaliable. now ....the problem is that when every we run the pump the output frequency would only go up to around 50 hz.. and it gets worst when I try to run both pumps (its a dual pump station) at the same time (Frequency drops to around 45 hz) ..I have checked the VFD setting and its all correct .. I have consult with the VFD Manufactor tech. and he said its because the utility is not supplying enough power to this local station......can someone tell me if thats true ?? or is there any other possible explaination??? is there a solution???

 

[burnt2x]

If money is the main issue, (your principal doesn't want to spend more on this project) why don't you just set your VFD to an output frequency where your motor doesn't overheat? Keep the discharge valve fully-opened and watch the inverter amps while you up your frequency to a level where your motor is happy with!
Just a suggestion though, it's your call.

 

[Amotor]

I would suggest throttling the valve and allowing the motor to run at 60hz with a lighter load. But burnt is on the right track for a cost saving system.

I have some experience with a pump which the mechanical guys stroked out somehow. (it was a reciprocating pump). The control was calling for 7 l/s or something and the vfd had to throttle back to hold this flow. Running at low speed kept causing 'electrical' problems and we found the pump was now missmatched to the system.

Of course, its itching by brain to know why the 36A load.

 

[rasevskii]

For Wedoca:

Throttling the valve is probably not an option, as it is sewage and may clog. Also reducing the frequency as a permanent fix may cause too low velocity in the force main.

There are threads about force mains problems under the water and wastewater blog on eng-tips.

regards rasevskii