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Generator/Voltage Reg.

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emu21(at)sbcglobal.net
Guest

Posted: Wed Jul 01, 2009 6:03 am Post subject: Generator/Voltage Reg.

Gang,

 Occationally(maybe between 5 and 10 flts) after eng. start the generator wouldn't

 come on line. Just ran the throttle up and back thru 1,000RPM a time or two and  then gen.

 would come and all was fine. So during the conditional insp. checked brushes and

 found one a little more worn than the others so got new ones from Doug and now gen.

 won't come on line at all. We flashed field and gen is putting out voltage at gen. but

 not coming on line. Did continuity check of all wires seems fine. My system does

 not have std. voltage reg. but a Zener Diode for regulation. Does anyone else have this set up? Any ideas what to check next? 

 Thanks,

 Ron Kalemba

 [quote][b]

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mark.bitterlich(at)navy.m
Guest

Posted: Wed Jul 01, 2009 10:37 am Post subject: Generator/Voltage Reg.

What kind of airplane?  If Russian, then suspect your DNP-200 relay is going south.  



Mark Bittelich



P.s.  When you say the generator is not coming on line, how are you verifying that?   



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emu21(at)sbcglobal.net
Guest

Posted: Wed Jul 01, 2009 6:12 pm Post subject: Generator/Voltage Reg.

Mark,

 Sorry, its a CJ6 with The Housai 285HP. Verifying by gen. light staying on and 

 the volt/ammeter. Talked to Doug again today and I do have a solid state regulator.

 but don't know how to check if its good.

 Thanks,

 Ron



--- On Wed, 7/1/09, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil> wrote:



 [quote]

From: Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil>

Subject: RE: Generator/Voltage Reg.

To: yak-list(at)matronics.com

Date: Wednesday, July 1, 2009, 1:30 PM



 What kind of airplane?  If Russian, then suspect your DNP-200 relay is going south.  



Mark Bittelich



P.s.  When you say the generator is not coming on line, how are you verifying that?   



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k7wx(at)earthlink.net
Guest

Posted: Wed Jul 01, 2009 7:57 pm Post subject: Generator/Voltage Reg.

Ron,



I have never worked on a CJ generator, but I've flashed other  

generators when the output is lost. You probably already thought of  

this, but it's important to remove the positive and negative exciter  

field leads from the voltage regulator beforehand. If this is not  

done, the flashing procedure may damage the regulator.



I would check the regulator to make sure that it's OK.



Warren



On Jul 1, 2009, at 7:11 PM, Ronald Kalemba wrote:



[quote] Mark,

 Sorry, its a CJ6 with The Housai 285HP. Verifying by gen. light  

 staying on and

 the volt/ammeter. Talked to Doug again today and I do have a solid  

 state regulator.

 but don't know how to check if its good.

 Thanks,

 Ron



 --- On Wed, 7/1/09, Bitterlich, Mark G CIV Det Cherry Point, MALS-14  

 64E <mark.bitterlich(at)navy.mil> wrote:



 From: Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil 

 >

 Subject: RE: Generator/Voltage Reg.

 To: yak-list(at)matronics.com

 Date: Wednesday, July 1, 2009, 1:30 PM



 What kind of airplane?  If Russian, then suspect your DNP-200 relay  

 is going south.



 Mark Bittelich



 P.s.  When you say the generator is not coming on line, how are you  

 verifying that?



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mark.bitterlich(at)navy.m
Guest

Posted: Thu Jul 02, 2009 7:35 am Post subject: Generator/Voltage Reg.

I really know nothing about CJ's.  Doug/Dennis/others are the experts.  



That said, with any generator, by design it has to have a reverse

polarity relay somewhere.  That's because at low RPM, the generator can

not put out more voltage than the battery.  When that happens, battery

voltage flows back into the generator, and can achieve a very dramatic

current flow.  In order to prevent this, as the engine slows down to

idle, and current just starts to flow "backwards" (towards the generator

instead OUT of it), a system of some sort senses this, and opens a relay

to prevent it from happening.  



The generator light is normally an indicator of the status of this

relay.  As in: OPEN or CLOSED.  When open, the light is on. 



To close this relay requires that the generator is putting out as much

or more than the battery, if a battery is installed.  If a battery is

NOT installed, it will typically close around 22 volts or so (on a 28

VDC system), and will power the aircraft on it's own.  Not all systems

do this of course, but these aircraft do, and I think that includes the

CJ.    



The voltage regulator controls the generator to put out a steady and

consistent voltage.  It is not very easy to take out and CHECK, but it

IS very easy to see if it is working or not.  Simply connect a voltmeter

on the generator plus and minus contacts, then being very careful, start

the engine.  As you raise engine RPM up past 40% or so, you should see

the voltage on your voltmeter come up and stabilize at around 27.5 to

28.5 volts.  As you run the engine up and down from say 55% to 80% the

voltage on the meter should stay pretty darn stable.  If it does, your

voltage regulator is working.  If it does not, then your voltage

regulator is not working.  By not working... I mean that typically one

of two things will happen.  Either you will have no voltage at all, or

the voltage will rise and fall evenly with engine RPM and up around 80%

you could see a voltage as high as 35 volts or so.  It is also possible

to have a bad voltage regulator and still have voltage out of the

generator.  When this happens, poor regulation is normally noticed.  Be

aware that SOME voltage out of the generator may not be ENOUGH voltage

out of the generator to close the reverse polarity relay, so make darn

sure the voltage goes up to at least 27-28 volts.  



If there is NO voltage there is another set of testing procedures that I

see no need to go into, since you say you do have voltage.  



I assume there is nothing but a discharge on the amp meter, and you are

showing nothing but battery voltage on the voltmeter.  This is indeed a

solid sign that the generator is not being connected to the main bus of

the electrical system.  



Again, if the battery voltage is solid and stable as you vary engine RPM

above 50% or so, then you need to track down where the main contactor

relay is for your aircraft ... Doug?  Dennis?   I don't know where it

is, or even what it looks like.  On the YAK's and older Sukes, it is the

DNP-200 relay and it has the MAIN contactor relay, the reverse polarity

relay and two other control relays inside of it.  In any case, that is

the device, whatever it is called on your aircraft, that you need to go

find.  A strong possibility is that in some way or another, the gen

light is connected to it, either directly or indirectly.  Be careful

messing with it when you find it.  If you close it somehow and the

engine is at low RPM or not running, then there will be a very high

current flow from the battery to the generator.  Your fuse or circuit

breaker should protect you from a disaster, but it is still not a good

idea to be careless with this thing.  Disconnect your battery when

messing with it, so you will be safe.  



 



Mark Bitterlich 



  



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