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Poles in Motor

Poles in Motor

Poles in Motor

So we have an existing motor rated 220/440VAC,3Phase,60Hz,2‐poles then we'll be buying a pump for this but what they can offer are pumps compatible only with a 4-poles bec. the capacity we provided is only suitable for 4-poles, now will there be a problem with that?

RE: Poles in Motor

I would think that the capacity of the pump would be dependent on the HP/Speed of the motor, not whether it was 2-pole versus 4-pole. How is the motor connected to the pump? Is a direct flange mount or is by a coupling or perhaps even a belt & pulley drive?

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Poles in Motor

Here it goes:
The capacity of pump we are looking for should be 320lpm at 11m head.. actually the end user bought first the motor for this w/c is rated 1.5KW H‐line Cooling Pump, 220/440VAC, 60Hz, 2‐poles, 3Phase. Now what suppliers can offer to us is always @1750rpm selection w/c means there’s no pump that can accommodate given duty parameter at 2 pole speed with existing respective motor KW rating. It is not yet connected Sir because we're still looking for suitable pump.

RE: Poles in Motor


2-pole motor runs at just shy of 3000 rpm in the 50Hz world, or just shy of 3600 rpm in the 60Hz world. A 4-pole machine would run at just shy of 1500 rpm or 1800 rpm respectively. Pole count and speed are inherently linked.

New motor time. At that size it shouldn't be particularly expensive.

RE: Poles in Motor

You could always use a belt & pulley system and reduce the pump input speed to the desired value.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Poles in Motor

Two choices;
1> Scotty's suggestion is a good one. Buy a new motor.
However, if you have not yet bought the pump, it may be cheaper and easier to buy a pump and motor combination that will serve your needs and sell the existing motor. (E-bay?)
2> Belt drive a pump from the existing motor as per John's suggestion.

"Why not the best?"
Jimmy Carter

RE: Poles in Motor

belt drive on a unit of this size is crazy, in terms of being mechanically sound and useful. As Waross said above - do it the right way, source a pump/motor unit -- easy and an efficient solution.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Poles in Motor

I think that the amount of time you have spent posting this question has already surpassed the cost of buying the correct motor.

Ask the vendors if they have a 2 pole / 3600 rpm selection that will work.
Find the pump that does the job you want, and buy the correct motor for it. 1.5kW, that's what, $500 if you splurge?

RE: Poles in Motor

This is really in the pump section, but FYI, if you really want to do the wrong thing and mate a 3600rpm motor to a 1780 rpm pump be aware that the pump will take it, but for a centrifugal pump the following applies:

flow will increase in proportion to speed ( double)
head will increase in proportion to speed ^2 (i.e quadruple)
power demand from the pump will increase in proportion to speed ^3 ( x 8)

So your original pump will need to be very small (160l/min at 3m head)and will probably not like being run at double the speed.....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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