Speed increase by 6 pole to 4 pole
Speed increase by 6 pole to 4 pole
(OP)
We have a pump drive that is currently a 6 pole motor, to increase pump capacity it has been suggested that we change to a 4 pole motor(1200 -> 1800 rpm).
Is it really that simple?
What increase in current (starting and full load) can we expect?
Will the motor be the same frame size?
Thanks
AD90
Is it really that simple?
What increase in current (starting and full load) can we expect?
Will the motor be the same frame size?
Thanks
AD90





RE: Speed increase by 6 pole to 4 pole
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If we learn from our mistakes I'm getting a great education!
RE: Speed increase by 6 pole to 4 pole
It is a quite a small pd pump and we have confirmed that the piping is OK and that we will still have enough NPSH on the pump, and it was the pump OEM that suggested the motor change.
As for rating, does the rule for Centrif/Axial Pumps (BHP2=BHP1x(N2/N1)3)[That should be to the power of 3]apply? That makes the power requirement 3.375 times greater!
RE: Speed increase by 6 pole to 4 pole
For PD pump: Flow rate ~ N. A given system characteristic will obey DP ~ Flow-rate squared ~ N^2 for high velocity turbulent flow. Fluid horsepower ~ Flow rate * DP ~ N * N^2 = N3. That suggests the motor power draw is roughly proportional to speed squared ASSUMING:
1 - efficiency of pump does not change significanltly accross the range
2 - the fluid system does not change. * Often times the system has throttle valves or parallel paths that are switched in/out - changing these will have a BIG effect.
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RE: Speed increase by 6 pole to 4 pole
Keith Cress
kcress - http://www.flaminsystems.com
RE: Speed increase by 6 pole to 4 pole
depending on the HP/kW then the frame size could change, meaning a different flange and shaft size.
RE: Speed increase by 6 pole to 4 pole
4 pole @ 60 Hz is about 1800 RPM's & 50 Hz is about 1500 RPM's
6 ploe @ 60 Hz is about 1200 RPM's and 50 Hz is about 1000 RPM's
Chris
"In this house, we obey the laws of thermodynamics." Homer Simpson
RE: Speed increase by 6 pole to 4 pole
RE: Speed increase by 6 pole to 4 pole
The current motor is 3.6kW (4.8hp) and we run a 60Hz system
Thanks
ad90
RE: Speed increase by 6 pole to 4 pole
Yes, if the piping and pump has no mechanical restrictions, flow will vary proportional to cube of the rpm and power will also vary accordingly. You can contol some power by controlling the flow through valves.
Consider using a higher speed motor with a VFD so you can adjust speed with much more flexibility.
RE: Speed increase by 6 pole to 4 pole
RE: Speed increase by 6 pole to 4 pole