Author Topic: AC AVR for 12V Alternator.  (Read 2122 times)

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george65

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AC AVR for 12V Alternator.
« on: December 18, 2016, 08:51:30 AM »

I was given a couple of brand new 240V Generator AVR's the other day. I'm wondering, can a vehicle alternator be modified to use these ?

Can't see the difference between the setup of an AC and vehicle generator and why the 12V generator couldn't run the higher Voltage.  The ones I have all do about a KW in 12V so can't see why they couldn't do the same in 240? The avr Controlls the same things in the 240V units as what is in a 12V alternator.  Is there any more to it than bypassing the Voltage controller and Rectifiers in the alt and wiring in the AVR?

Anyone tried this or have any hands on  experience with this sort of conversion?

SparWeb

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Re: AC AVR for 12V Alternator.
« Reply #1 on: December 18, 2016, 11:51:49 AM »
Hmmmm
I don't see these two items as compatible with each other.  Have you checked how fast the auto generator has to turn?
My other suspicion is that wiring designed to work at 12V is going to have trouble at 240VAC, particularly due to insulation breakdown.  Not necessarily the wiring you can see coming out of the unit...
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joestue

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Re: AC AVR for 12V Alternator.
« Reply #2 on: December 19, 2016, 01:36:18 AM »
The insulation could handle it but you might need 20,000 rpm to get that kind of voltage without rewinding it. Also the eddy current losses would be insane. And the frequency would probably be too high for the scr(s) to reliably trigger properly.
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george65

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Re: AC AVR for 12V Alternator.
« Reply #3 on: December 19, 2016, 07:35:53 AM »

The avr specs say they can feed the rotor up to 90V.
Normally they would be at 9-14V so I'm wondering if the alt would need to be turned overly fast given the higher level of excitation.

Chances of the frequency being on spec are a million to one but should be ok for resistive loads at least.

Are there any SCR's to worry about if the alt is converted to put out AC?

I don't see the insulation being much of a prob. the difference between isolation for 12V and 240 would probably be no different. Not like 240 is going to want to start jumping around and as far as I have seen, it's all lacquered copper and the same sort of connections in 12V alts as it is in 240 Gennys.

Bruce S

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Re: AC AVR for 12V Alternator.
« Reply #4 on: December 19, 2016, 08:56:57 AM »
george65;
Most car alts here in the USA are actually 110Vac rectified to 13Vdc. You can certainly remove the rectifier, run the alt at high-idle engine speeds (1500RPM) and get 110vac out. IF I remember , it's 3-phase too. I did this years ago , just to see if it could be done. Worked "OK" lit incandescent bulbs easy enough.

BUT with it being 3-phase you should be able to get 220Vac out easy enough.

 Go digging into the alt for the rectifier, find the 3 wires from the stator, put a  meter on it. 
Hope this helps
Bruce S
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george65

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Re: AC AVR for 12V Alternator.
« Reply #5 on: December 19, 2016, 12:12:07 PM »

That's what I thought and why I asked about this.  The car alts and the AC alts are so similar in construction. By Bypassing all the internal regulation and letting the AC avr take care of it, I can't see why it couldn't be done.

-I- can't see why it can't be done so really I'm asking others to point out what I have missed. It seems a bit too easy just to do this and with this sort of thing, I DO look gift horses in the mouth. So far the suggestions made seem like they can be over come or not too great a problem.
Might be just as easy to hook an alt up to an electric motor and the avr and see if any magic smoke comes out or a light bulb comes on either ac Powered or in my head as to what I was missing.

Bruce S

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Re: AC AVR for 12V Alternator.
« Reply #6 on: December 19, 2016, 03:04:55 PM »
I've seen some pretty spiffy setups, some with multiple meters to keep HZ on track with Voltage. Some with RPM monitors ,etc ,etc.
Most are merely 4-stroke lawnmowers with a smallish 12Vdc battery for field, a cheapo digital meter to show voltage a 20A light switch and a for USA 110Vac outlet.
Here's a that is good and basic , USA 110Vac but still very usable. IT has the standard disclaimer people put on these.

https://www.youtube.com/watch?v=QHRpA_xeFjM
 
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Bruce S
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