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PM ALTERNATOR AC OUTPUT

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Fri Apr 20, 2007 10:48 pm Post subject: PM ALTERNATOR AC OUTPUT

Hi,,

I have only 0.2V AC output from the stator of my single phase PM alternator when the battery is disconnected. Is this correct?

Is there any way to get full regulated DC output from a PM alternator if the battery is isolated from it?

Thanks,

Peter H

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klehman(at)albedo.net
Guest

Posted: Sat Apr 21, 2007 4:21 am Post subject: PM ALTERNATOR AC OUTPUT

Hi Peter



I get over a 100 vac from mine like that depending on engine speed. It 

isn't going to charge at all unless you have something like almost 20vac 

going into the regulator rectifier. Are you sure you aren't measuring 

with a DC meter?



Yes some of those units will operate with just a large capacitor and no 

battery but I would hesitate to try that without a load connected unless 

you know your combination of parts will do that.



Ken

Peter H wrote:



 	  Quote: 	
		  



Hi,,

I have only 0.2V AC output from the stator of my single phase PM alternator when the battery is disconnected. Is this correct?

Is there any way to get full regulated DC output from a PM alternator if the battery is isolated from it?

Thanks,

Peter H

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sat Apr 21, 2007 10:59 pm Post subject: PM ALTERNATOR AC OUTPUT

Hi Ken,

Thanks for that. Today I checked it again and got a reading of 46VAC at idle

, then zero, then 0.2VAC and I think my multimeter is faulty. Then I found a

loose connection B+ to the regulator, fixed and it all works fine. I am

still puzzled because I saw 16V charge just before the system stopped in

flight and the alternator CB did not open. Ken I am interested in your

comment about the use of a capacitor. Is it connected across the two AC

leads? And what value? Have you got a reference I could follow up ?

Thanks,

Peter



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Gilles.Thesee(at)ac-greno
Guest

Posted: Sun Apr 22, 2007 1:45 am Post subject: PM ALTERNATOR AC OUTPUT

Peter Harris a écrit :

 	  Quote: 	
		   



 Hi Ken,

 Thanks for that. Today I checked it again and got a reading of 46VAC at idle

 , then zero, then 0.2VAC and I think my multimeter is faulty. Then I found a

 loose connection B+ to the regulator, fixed and it all works fine. I am

 still puzzled because I saw 16V charge just before the system stopped in

 flight and the alternator CB did not open. Ken I am interested in your

 comment about the use of a capacitor. Is it connected across the two AC

 leads? And what value? Have you got a reference I could follow up ?

   


	


Peter,



You'll find the Z16 figure in Bob's Appendix Z most useful for your 

application.

It applies to PM alternator engines such as the Rotax 91X but should 

work just fine with a Jabiru.



Re the alternator CB you are referring to, this is a CURRENT related 

device, and it won't react to an over VOLTAGE event. A CB or fuse is 

intended to protect the wires from overheating.



Regards,

Gilles Thesee

http://contrails.free.fr

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klehman(at)albedo.net
Guest

Posted: Sun Apr 22, 2007 4:05 am Post subject: PM ALTERNATOR AC OUTPUT

Peter



If your meter has shorted diodes or is not switched to AC you can get 

very inconsistant readings much like you saw although it sounds like 

your problemt was just a loose connection.



Yes Gilles pointed you in the right direction for the capacitor. I think 

Bob recommends at least 1,000 mfd per amp of alternator capacity so 

typically 20,000 mfd. That seems to work fine with the B&C and the rotax 

regulators I think but I don't know about others.  I immediately 

destroyed a John Deere regulator which was connected to a completely 

dead battery (my mistake) but no capacitor. I only had about an amp of 

other loads connected at startup as the battery was not taking any 

current (which happens for awhile with a completly dead AGM battery). So 

I conclude that with my particular setup, I'd want a capacitor and also 

some way of keeping  a reasonable load connected at all times to help 

keep the voltage reasonable.  It seems that my regulator can not handle 

starting up with no load connected which might be the case if you were 

expecting the alternator to close a battery contactor to connect it to 

the load. Or maybe I would have been fine with a capacitor.  In most 

cases I do think these units would continue to run just fine if the 

battery disconnected in flight.



Ken



Peter Harris wrote:



[quote]



Hi Ken,

Thanks for that. Today I checked it again and got a reading of 46VAC at idle

, then zero, then 0.2VAC and I think my multimeter is faulty. Then I found a

loose connection B+ to the regulator, fixed and it all works fine. I am

still puzzled because I saw 16V charge just before the system stopped in

flight and the alternator CB did not open. Ken I am interested in your

comment about the use of a capacitor. Is it connected across the two AC

leads? And what value? Have you got a reference I could follow up ?

Thanks,

Peter



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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sun Apr 22, 2007 4:52 pm Post subject: PM ALTERNATOR AC OUTPUT

Thanks Gilles and Ken.

I am still a bit puzzled that I saw 16V before the alternator went off line,

the CB did not pop and all I have done is recheck the CB connections and the

master switch all of which seemed OK, but now B+ to the alternator is OK and

it is working again.

I understand your comment about the CB Gilles but have no explanation why

the alternator went off line.

The 16V must suggest a regulator fault which has now disappeared. ! I can

only try another flight.

Thanks for the insight.

Peter 

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sun Apr 22, 2007 8:52 pm Post subject: PM ALTERNATOR AC OUTPUT

Gilles,

Is the OVM crowbar sold ready made or in a DIY kit?

Thanks

Peter



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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sun Apr 22, 2007 10:19 pm Post subject: PM ALTERNATOR AC OUTPUT

Gilles

Apologies I have found B and C and ordered the OVM. How essential do you

consider the alternator relay? And where to buy as I did not see at B&C ?

Thanks for your trouble,

Peter H



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nuckollsr(at)cox.net
Guest

Posted: Mon Apr 23, 2007 6:43 am Post subject: PM ALTERNATOR AC OUTPUT

At 04:13 PM 4/23/2007 +1000, you wrote:



 	  Quote: 	
		  

<peterjfharris(at)bigpond.com>



Gilles

Apologies I have found B and C and ordered the OVM. How essential do you

consider the alternator relay? And where to buy as I did not see at B&C ?

Thanks for your trouble,


	


   The S704-1 IS a B&C part number. They offer the ov crowbar

   ov module, capacitor, relay and installation hardware at:



http://www.bandc.biz/PmOVdesc.html



   Bob. . .

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