motor rpm

[candji]

Can somebody tell me what the 120 in motor rpm calculations is? rpm= 120xhz/#of poles

[cool runings]

Can somebody tell me what the 120 in motor rpm calculations is? rpm= 120xhz/#of poles

rpm??

RPM = Revs Per Min

coolrunnings

.

[candji]

yes,rev's per min

[Magoo]

the synchronys speed factor for 3 phase motors.

[Tayters]

Speed of rotation is:

Number of current reversals per minute / number of poles

For a 1 HZ cycle of a sine wave there will be 2 reversals, this will occur once a second. So to get it to minutes (remember we are after Revs per Minute) 2 x 60 = 120

Cheers,

Andy.

[Quality]

Speed of rotation is:

Number of current reversals per minute / number of poles

For a 1 HZ cycle of a sine wave there will be 2 reversals, this will occur once a second. So to get it to minutes (remember we are after Revs per Minute) 2 x 60 = 120

Cheers,

Andy.

could not have put it better myself

I call it 1 and 2 but it does not explain frequency
its 2 cycles 50 times per sec but 25 times 1 and 2

[nike123]

That number is constant in connection with seconds to minute conversion (as Tayters alredy explained).
If you using other formula with number of pairs of poles, that constant is 60 (seconds).
S = f60/p

where: S = rotor speed in rpm (revolutions per minute)
f = AC line frequency
n = number of pairs of poles

[nike123]

the synchronys speed factor for 3 phase motors.

It is same for 1 phase motors! If we use revolutions per second, that constant(factor) is not used.

[Yuri B.]

So, one who used "120" (60 sec multiplied by 2) was speaking about number of POLES in the formula,
if one prefers PAIRS of POLES, then just 60 would be used.