I don't know much about permanent magnet alternators, but am surprised at the very un- "sine" like shape of the output waveform, on a single phase motorbike type I'm working on. It's very "peaky", with first gently sloping excursions but that then become steep spikes, like nothing in the text books. Is this normal, or am I doing something silly with the CRO? By comparison, a 240V-18V transformer I tried has the classic sinewave shape.
Sine-ish wave?
Sep 24, 2012
6 Replies
"Jordan"
** Simple alternators do not produce a sine wave emf - more often it looks like a flattened off sine wave with a wiggle near each zero crossing.Where the wave is used to produce DC, this flattened shape is an advantage.
Imagine if it were a good square wave, then rectification would give you pure DC.
.... Phil
Yes, in fact alternators don't 'naturally' generate sinewaves, you have to work hard at the design of the machine geometry in order to get a reasonable one. With large power station machines, the shaping and alignment of the pole pieces is very precise, on littlies like auto gensets it's not so important.
Mine seems to have the opposite extreme, with relatively little "area under the curve". Could be it's just not a high quality design. Interesting to hear about sinewaves not happening naturally. Thanks.
"Jordan"
** Sure you got that scope DC coupled ?... Phil
I tried every possible setting on the CRO, not knowing much about them! I'll confirm DC coupling, thanks.
That waveform is not unprecidented, I've seen similar waveforms discussed for bicycyle PM generators.
?? 100% natural
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required