Machine Question No.11 - 50HZ or 60HZ

#1
Sat, November 8, 2008 - 19:54
On a 3 phases system the frequency variation is normally within limits, which according to IEC 60034-1 is +/- 2%. The reason for keeping the frequency variation low is that it is not influenced by any condition outside the generating point, and at the generating point, it is maintained constant through automatic speed regulation of the prime mover (frequency is directly proportional to the speed).But in this case you want use one equipment in other system, so you must consider some problems.

The effect of frequency variation is discussed below:

- Speed
Since the speed is proportional to frequency, it is affected the most and in turn influences the performance of the driven equipment in the same proportion as its relation to the speed.

- Slip
The motor adjusts its speed according to the frequency and therefore there is no change in the slip.

- Motor output and torque
The torque of the motor would approximately vary inversely as the square of the frequency.
The power will also be affected, being a multiple of T.N, i.e. by roughly l/f

-Effect on power factor
The no-load losses will slightly decrease or increase with an increase or decrease in the supply frequency since
L= k. B2 . f2
where the cumulative effect of flux density is in the square proportion and that of frequency f .
With an increase in frequency, therefore, the core losses decrease slightly and vice versa. The efficiency improves slightly and so does the power factor at higher frequencies and vice versa.

#2
Sat, February 12th, 2011 - 12:43
supply voltage also has to be changed.pl recall the emf equation