De-Rectifying Automobile Alternator

[edable]

Hi, Automobile Alternators produce AC currents which are converted to DC currents by a diode bridge known as the rectifier.The question is.

How does one remove the rectifier so the Alternator produces AC current only.
How can it be connected to a Transformer
Is there any adverse effect on the Alternator if the rectifier is removed.

 

[sophiecentaur]

Problem is that the alternator output is three phase - before the internal rectification - in order to get a good smooth DC out. If you really need single phase AC, you may need to use an inverter or a different design of alternator.

 

[edable]

So what you are saying is that I will still need to convert the three phase AC to DC before it can be utilised if the rectifier is removed right?

 

[sophiecentaur]

I'm saying that converting three phase to a single phase supply is not 'easy' and certainly not efficient. There would be no point in doing your own rectification of three AC outputs from the alternator - it does that very well on its own. I'm suggesting that you could achieve what you want with an inverter circuit which will provide a single phase output from the DC which your alternator gives you.

It really depends upon the sort of 12v(?) load you have which needs AC. If it's a mains operated device then buy an off the shelf DC - mains inverter. What is the actual problem that you need to solve?

 

[Averagesupernova]

Or, the OP could just choose only one phase and use it.

 

[sophiecentaur]

Oh yes, that's a good point. It would depend on how much power was needed but it could turn out to be the easiest solution.

 

[turbo]

Or run the DC through an inverter. Such beasties are pretty cheap (I bought one to run my telescope's AC drive off my SUV's battery), though the output is not a sine wave. Some equipment won't like the square wave-form.

 

[edable]

what am trying to do is upgrade the 12 or 24v current produced by the alternator to a 240V AC, without having to invert from DC to Ac first.Whawill be the best option.

 

[sophiecentaur]

You could take take the 3 phase AC off the alternator, use a transformer on one of the phases and give yourself 240V. Not a very satisfying solution, maybe, and, as I said before, it depends on how much actual power you want off the system. The alternator would have to run at 1/3 of its VA rating.

There is one more issue which you may need to consider. What do you intend to run the alternator from? Unless you regulate the speed of your engine, the frequency of the AC from the alternator will not remain at 50Hz. You obviously couldn't run the system in a vehicle on the move.

AC to DC (in the alternator), followed by an inverter would solve most of your problems - which is why it's usually done that way on RVs and Boats. I think you are swimming against the tide here which will only make sense under particular circumstances.