Two-Pole Induction Motor: Effect of Frequency and Voltage

See the previous thread. http://cr4.globalspec.com/thread/33399

It has a very good information with an initiative of guru 'SB'.

- MS

You can see from the other linked information that the current rises significantly and you will likely see the motor fail if you apply 480V 50Hz. The losses increase in the motor alot so I guess this is a high risk strategy.

In any event, you will only be pumping at 5/6 speed so your system will be starved of flow / pressure, so why do this?

The easy answer at low cost (for 3HP application?) is to use a VFD, which you set for a 440V 60Hz wound motor. Normally, you would connect this via your normal supply, which is 400 / 415V in UK. if you have 480V, this is also OK, just remember to set the output as 440V / 60Hz. The 10% drop in voltage at full speed if you only have 400V is unlikely to have any detrimental effect.

If your supply can also be 230V-240V, you can also use a single phase input VFD and connect the motor in Delta if this is preferred, motor rated current would be √3 x your Star rated Current on the nameplate.