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Voltage Regulation

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TXYak

Joined: 02 Aug 2008
Posts: 14

Posted: Thu Feb 26, 2009 7:05 am Post subject: Voltage Regulation

Question regarding Voltage Regulation in a Yak 52.



First, this is a project airplane and has not been flown yet in the US.  I have gotten it running, but have no voltage regulation.  When I first started it, I had the Gen Fail light at low RPM...as I increased power (at) 40% the light went out(started charging)  Around 45% the Gen Fail light would come back on and pop the overvoltage breaker.  I connected a voltmeter to the DMR-200 as I ran it even if I adjusted the regulation screw...I got no change in voltage.  Volts increase with throttle until 45%RPM and kicks Gen offline at (at)30.5 volts.  I have tried another voltage regulator(it had been sitting for 6-7 years unused) got the same symptoms.  



Can anyone recommend more places to look, as most of you have a better understanding of this electrical system than I do.  My level of frustration is tempting me to go with a B & C alternator/regulator.  Any advice for or against.  If there is a problem in the system somewhere elsse...I don't want to start frying B & C's.



Thanks,



Chris Keating

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mark.bitterlich(at)navy.m
Guest

Posted: Thu Feb 26, 2009 4:34 pm Post subject: Voltage Regulation

Your problem is... As you have said, ....is clearly a voltage regulation

issue.  Your generator is working fine, but is not regulating what-so-ever.

In this mode of operation, the voltage will increase as the speed of the

generator increases.  Your over-voltage protection is merely doing it's job

which is a good thing.  



Nothing wrong with B&C products.  If ease of getting parts and weight is an

issue, go that route!  I would not advise the small PMG 10 amp model unless

you seriously think you need it.  The bigger 35/45 amp model is the best

investment. 



As for fixing yours... Since you tried a new voltage regulator, I suspect

that is not the problem.  So it's bound to be a wiring problem.  OR.. And

this is the first thing I would check... You have a bad voltage control

potentiometer in the cockpit.  Rule of thumb.  In electrical systems, things

that fail first usually either move, or are something that human hands mess

with!  You need to get a meter and someone who knows how to use it.  Ring

out the wiring from the voltage regulator back to the voltage control

resistor in the cockpit and read through it to see if it is working

correctly.  



If that checks OK, then check the wiring from the voltage regulator BACK to

the generator (the middle wire on the generator terminal board).  



Really.... Going into each and every wire would be too difficult over the

internet and with the written word.  There should be a fairly good diagram

pasted to the cover that goes over the electrical panel .. I hope you know

where that is.  



If you give up, there is nothing really in the aircraft that will end up

damaging a new B&C system.  Most of what is in there is just BY-PASSED and

removed.  The over-voltage device, the bucking transformer, the regulator,

the main contactor relay... All come out.  You just end up connecting the

output voltage of the new system directly to the output bus bar of the main

contactor relay.  



Mark Bitterlich

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gill.g(at)gpimail.com
Guest

Posted: Fri Feb 27, 2009 9:57 am Post subject: Voltage Regulation

This maybe generator related.  I would check the generator brushes and

springs. Make sure brushes are clean, move easily and are seated and brush

springs are properly installed.



Gill 



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mark.bitterlich(at)navy.m
Guest

Posted: Fri Feb 27, 2009 12:53 pm Post subject: Voltage Regulation

Gill, with respect... If the generator puts out voltage, and the gen

light goes out when the engine RPM is increased past 40%, and then the

over-voltage circuit breaker pops at 30-31 volts, this is not a brush or

spring problem.  



If the brushes or springs are completely bad, (either / or) you will

have no voltage at all out of the generator.  If a spring is weak, you

will have intermittant voltage.  I.E.: It will be turning on and off

rapidly.  



Brushes and springs push against the commutator windings taking the AC

output of the windings and essentially giving you a DC output.  Thus the

brushes and springs are critical to the generator putting out any output

AT ALL.  



This is a regulation problem dealing with the probable loss of field

current from the voltage regulator.  



For a complete understanding of the theory involved here, you might want

to check out this site.  



http://www.rowand.net/Shop/Tech/AlternatorGeneratorTheory.htm



Mark Bitterlich 



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gill.g(at)gpimail.com
Guest

Posted: Fri Feb 27, 2009 1:34 pm Post subject: Voltage Regulation

Mark,



The problem originally described was that the generator light went off at

the normal point and then came on with increasing RPM, this suggests that

brushes may not be making solid contact and should be easily checked as

previously suggested.  I am not there so the mic (mechanic in command) will

have to decide.



Gill



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TXYak

Joined: 02 Aug 2008
Posts: 14

Posted: Fri Feb 27, 2009 5:11 pm Post subject: Re: Voltage Regulation

Thanks for the replies.  I'll follow up on Monday or Tuesday after I get back in town.



Chris Keating

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TXYak

Joined: 02 Aug 2008
Posts: 14

Posted: Tue Mar 17, 2009 5:46 am Post subject: Re: Voltage Regulation

Well, I finally gave up on the Russian system after chasing wires and trying 3 different voltage regulators.  I installed the 35 amp B & C alternator and regulator.  Thanks to Mark Bitterlich for the technical advice.  He made it an easy installation.  Was able to remove 42 lbs. and replace it with 6.5 lbs.



Chris Keating

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yakplt(at)yahoo.com
Guest

Posted: Tue Mar 17, 2009 3:47 pm Post subject: Voltage Regulation

Thanks Chris, that was nice to say.  

  

 Mark Bitterlich

 

 

 

   From: TXYak <CKeating(at)peoplepc.com>

To: yak-list(at)matronics.com

Sent: Tuesday, March 17, 2009 9:47:00 AM

Subject: Re: Voltage Regulation



--> Yak-List message posted by: "TXYak" <CKeating(at)peoplepc.com (CKeating(at)peoplepc.com)>



Well, I finally gave up on the Russian system after chasing wires and trying 3 different voltage regulators.  I installed the 35 amp B & C alternator and regulator.  Thanks to Mark Bitterlich for the technical advice.  He made it an easy installation.  Was able to remove 42 lbs. and replace it with 6.5 lbs.



Chris Keating





Read this topic online  here:



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