Electric Automation Forum
Forum » General Discussion » Why it's 50 or 60 Hz, not 85 or 25hz
Topics: Why it's 50 or 60 Hz, not 85 or 25hz on General Discussion
Start by
Usaid Javaid
09-17-2013 07:47 AM

Why it's 50 or 60 Hz, not 85 or 25hz

what is the logic /reason behind 50 or 60 Hz? Why not we go for Say 85 or  29 Hz i.e. for any random frequency?
09-17-2013 10:43 AM
Top #2
Tony Cutner BSc CEng MIET
09-17-2013 10:43 AM
Early mechanical machinery would only rotate slowly- in fact 25 Hz was initially used. Then 50 Hz/ 3000 rpm, and the latest machines 3600 rpm/ 60 Hz.
It also has an influence on the iron losses efficiency- the higher the frequency the less losses, like aircraft use 400 Hz to get the transformer weight down.
09-17-2013 01:28 PM
Top #3
Chandra Sekhar Nuli
09-17-2013 01:28 PM
Higher frequency corresponds to higher iron losses.
Pulsating torques (from motors) can be avoided at higher operating frequencies.
Of course, lesser flux densities require less magnetic core material in transformers.
09-17-2013 03:44 PM
Top #4
Tony Cutner BSc CEng MIET
09-17-2013 03:44 PM
Chandra is right, higher frequency , more losses. My poor selection of English. However in aircraft the "cost" is in the flying that weight around. . So using a higher frequency allows less iron to be used, so less weight, (400 Hz transformer is 8 times lighter than a 50 Hz version) less fuel burn, but more electrical losses are acceptable in that cost /advantage balance ratio we all engineer to.
Reply to Thread