Voltage rating on electric motor name plate

[(unknown)]

Hello,

I am a totally new in Electrical field. I have some queries regarding voltage ratings mentioned on name plate of electric motors as below,

1.    In some motors voltage rating is mentioned as 1ph, 220-240V 50hz  OR

      1ph 208-230V 60hz.  Now in this case if I want to measure RPM of motor, at    what Voltage I should measure it?

2.    Some motors are suitable for both 50 & 60hz supply. ( Fractional HP motors used in air conditioners) In this case the voltage rating is 1 ph 208-230V 50/60HZ.

     Now in such motors at what voltage RPM should be measured? It should be      different for 50hz & 60hz supply?

3.    In some multi speed fractional HP motors it is observed that RPM is less in 60hz comparative to 50hz supply. However theoretically it should be more in 60hz.

     Pl.explain.

Regards,

Prasanna

[tecker]

   220 is usually residential voltage and 208 is two poles of a three phase 208 comercial drop . the motors should work fine at either voltage and give the same rpm give or take 10% .look on the  plate it should give the rpm rating there also .

[(unknown)]

Hello,

Thanks a lot. RPM is specified on name plate. I want to confirm it by fixing the motor in actual unit.

Pl. explain other points also.

Thanks once again.

Prasanna

[laskey]

What he is saying is that the motor will perform approximately within specs at the voltage and frequency range listed.  The motor will run slightly faster at the top of the range and slightly slower at the bottom of the range.  

What was this for... and air conditioning unit... so long as the motor has the required horse power output and makes "about" the right number of RPMs it really doesn't matter.

Cya,

Chris