PD Pump Low Speed Operation Motor Stall
PD Pump Low Speed Operation Motor Stall
(OP)
We have a PD Pump that we are just commissioning. The pump is intended to boost pressure for a Meg line from 14 MPa to approx 17 MPa. The turndown is supposed to be 10-1. The Variable Speed Drive has been programmed for 6-60Hz operation. The high pressure to provide suction to the pump is not available so 140 kPa was used. At 60Hz, approx 6000 kPa was generated. At 20Hz, approx 2000 kPa was generated. At 6 Hz, the motor stalls and no output pressure achieved.
My question is:
Is this an adequate test or should we expect at a higher suction pressure, it will be "easier" for the motor to pump and therefore not stall?
Thanks
My question is:
Is this an adequate test or should we expect at a higher suction pressure, it will be "easier" for the motor to pump and therefore not stall?
Thanks





RE: PD Pump Low Speed Operation Motor Stall
RE: PD Pump Low Speed Operation Motor Stall
I expect the field windings are not producing enough magnetism to provide the required linear torque demand.
With most of the standard VSDs that I have used, 5:1 is about it and the torque collapses.
However if you really need it, by using rotary encoder feedback and a fixed speed cooling fan on the motor, I have got better than 20:1 (on a belt feeder, if you are wondering). The rotary encoder measures the angular response of the output shaft and adjusts the driving frequency/current accordingly.
An outfit called PDL used to be really good at wide range frequency control.
If you have purchased the motor and VSD separately, you are in for an argument with the suppliers.
Good luck
Steve
RE: PD Pump Low Speed Operation Motor Stall
"Venditori de oleum-vipera non vigere excordis populi"
RE: PD Pump Low Speed Operation Motor Stall
RE: PD Pump Low Speed Operation Motor Stall
RE: PD Pump Low Speed Operation Motor Stall
Another idea maybe putting a small by-pass pipe from the pump outlet to the feed tank (with a throttle valve to fine tune). This will force the pump-motor to run a higher frequency while the pump is producing the same pressure/flow.
C.
RE: PD Pump Low Speed Operation Motor Stall
Do you have a manufacturer of this rotary encoder?
Thanks !
CARF
RE: PD Pump Low Speed Operation Motor Stall
I think you can get through PDL (Schneider) and also SEW (gearmotor manufacturers). From memory, there are several different types and selection is important; especially ensuring suitable interface with the VSD to close the loop.
If you have no luck, gert back to me and I will look more thoroughly.
Cheers
Steve