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self excited self powered generator? Answered

I have a portable generator (tiger diesel generator's alternator of 220v 750 watt rated power output) connected to a 1 hp ac induction motor using a pulley-belt system. The rpm of both the alternator of the portable generator and the ac induction motor is 2800 rpm so the size of the pulleys that i used are almost the same. Initially when i bought the generator i tested the output with a digital multi-meter and it checked right.(working powered by the diesel combustion engine). But i have coupled it with the ac induction motor i can only draw out 12 v ac at around 1 amp. I tested this from the same out put plug of the original generator. so I'm wandering what went wrong. Any one have an insight to this I would be grateful for your comments!

5 Replies

Toga_Dan (author)2017-09-08

so you made what amounts to a mechanical Transformer?

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rickharris (author)2017-09-01

firstly. 750 watts is about 1 Hp (746watt/hp to be exact)

so your motor is underpowered to give you 750 watts.

In fact I doubt if you check it is reaching full RPM which is where you problem starts.

Your diesel engine will have been perhaps 4 or 5 Hp.

Essentially to get 750 watts out you have to put in more than 750 watts because the generator may only be 50% to 80% efficient.

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iceng (author)rickharris2017-09-01


Where should our young electricians learn these things if one day the will be asked to contribute to society in a meaningfull way !??

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rickharris (author)iceng2017-09-02

Ideally in some kind of technical school.

It would help a lot if youngsters who would like to learn more read as much as they can, there is a wealth of information on the web by individuals and by universities.

Read and more important chew at it until understanding arrives. Your then in a much better place to experiment.

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Downunder35m (author)rickharris2017-09-02

You need more nergy to feed than what you get out, and that only works if the RPM's are correct.
If you have both 12V and 220V output then the 220V will only work if:
1. The generator has enough speed.
2. There is a load present (many simple generators won't output without a small load).
3. The generator does not need an external voltage to exite the windinds inside.
It would pay off to check the generator for these things...

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