synchronous speed

[Flight987]

Hello,
I have a Ques. on a pratice test, that askest; What is the synchronous speed of a 460 volt, 60 hertz, 4 pole
moter? Curt Nobel

 

[rbalex]

The "raw" answer is 1800rpm.

Volts is irrelevant.

The "simple" formula for sync speed in rpm is: (60 x frequency)/(Poles/2)
so

(60x60)/(4/2)

3600/2

1800rpm

Its a bear factoring it all out.

 

[mbeatty]

From my school days, many years ago, I always remember this type of equation by simple abbreviations, as follow (Note: The last part of the equation is always the portion left out of the rest of the equation):

RIF: RPM = 120 X Frequency / Number of Ploes

PIF: Poles = 120 X Frequency / RPM

FPR: Frequency = Poles X RPM / 120

Works for me.

 

[zog]

We had a different one in the Navy, not suitable for posting here