2 pole motor replaced 4 pole motor

[Trevor]

Dear Members,

 

I had a watermaker on a motor vessel repaired including the replacement of the A C Motor. 

About 1 HP 240 volt.

The contractor charged me lots of extras for additional work: Resizing pulleys because the pump was going too fast, seals kept failing, the inverter would not start the motor etc.  The new motor was a 2 pole motor.  I believe and am seeking to prove, that the motor should have been a 4 pole,

 

How can we identify from the windings of the old corroded motor that it is in fact 4 pole ?

Can a qualified member confirm that those failures mentioned are the sympoms expected of a motor driving the unit at 2980 RPM instead of the 1480 of the 4 pole?

 

Please assist if posible.

 

[toma....@atce.com]

Trevor,

The 2 pole motor turns 2 x faster than the 4-pole motor, so the pump
going to fast, pulleys, etc are understandable and possible. Seals
falling may be also possible. But the fact that the inverter does not
start the motor should not be an issue. Each motor, regardless of the
number of poles, at the same power rating (HP/kW) is designed to fall
withing a range of efficiency/power factor, therefore the currents
should be within a close range between them (assuming the voltage and
number of phases was the same).
Under normal circumstances the outside diameter of a motor with more
poles is larger by comparison with a motor of the same rating but with
less poles. Looking at the opened motor (stator), try to follow the
winding, starting at one terminal. If for a coil the span (distance
between the 2 legs) is around 50% of the diameter, the motor has 2
poles, if it extend over approx 25%, you have 4 poles, a.s.o.