5 Kw Gen set identification

[Keith_J]

I will give that a try. What is that capacitors function,and where would be a good place to look for a replacement.

Thanks

The capacitor stores a charge. More importantly, it functions like a shock absorber in an automotive suspension.

The module takes alternating current, changes it to direct current through a series of diodes but it still is a bit "choppy". The capacitor smooths this out to drive the exciter circuit which provides the field current that creates the rotating magnetic field necessary to generate power.

When there isn't a load on the generator, it doesn't take a strong magnetic field strength to create 120 volts AC. So the exciter current is minimal. But when there is a maximum load on the generator, the magnetic field must be large enough to maintain 120 volts AC. So a proportional increase in exciter current is needed.

Yes, there are aftermarket brushless exciter voltage regulators on the market. But you have to know the design current of the exciter system. So you would have to measure the exciter current and voltage as it is now. If you had a variable voltage power supply, you could connect this to the exciter coil and run the generator engine, varying the power supply voltage until you got 120 volts output.

Or you could go to Allied Electronics and cross reference the big blue capacitor, probably a $6 part. then replace it. Note, this is a polarized capacitor so be sure to reinstall it correctly.

 

[PeterD]

Just so one doesn't get one's hopes up too high, though capacitors fail frequently, it is entirely possible that the problem with the unit/regulator is not that capacitor, but is something else such as a pass transistor.

 

[Isaac-1]

I just noticed you are just outside Phoenix, as chance would have it I have to fly out there in 2 or 3 weeks for a business meeting, if you don't have things working by then I could bring some test equipment (variable AC power supply, multimeter with capacitor tester, Megger insulation tester, DC clamp meter, etc.) in my luggage and try to help out a bit while there measuring things for a best guess replacement AVR, although I will only have a few free hours.

Ike

 

[RWG421]

That would be wonderful. I would hate to impose on you though, and wonder if I could pay you for your diagnostics.

I will try the capacitor fix myself first.

So is the sole purpose of the module to excite the Field, and is that voltage static. (To achieve 120 volts)

(I mean static once 3600 rpm is reached.)

Is the excitation current not affected by load unless motor bogs and rpms are decreased?

 

[Keith_J]

That would be wonderful. I would hate to impose on you though, and wonder if I could pay you for your diagnostics.

I will try the capacitor fix myself first.

So is the sole purpose of the module to excite the Field, and is that voltage static. (To achieve 120 volts)

(I mean static once 3600 rpm is reached.)

Is the excitation current not affected by load unless motor bogs and rpms are decreased?

No. Exciter current is proportional to load but is varied to keep output voltage constant.

If that regulator is toast, this one will work:http://www.power-tronics.com/PDF Compressed/XR500D.pdf

Made in Texas. Yeah, that just happened

 

[RWG421]

Would this replace the whole module, or just one part?

 

[Isaac-1]

It would replace the whole module, but it is best to measure the field resistance before buying any AVR to make sure the output is in range, a much cheaper option may be getting a chineese clone of the Stamford Newage SX460 available on ebay for $60-$75. Again best to check field resistance first, although a lot of people have had good luck using the SX460 clones (genuine SX460's cost about $300), on the MEP-016 and MEP-017 families. Connection is fairly simple, just 4 wires required (optional 2 more for remote adjustment) the F1 and F2 exciter leads and 120V or 240V (selectable) input/reference.

Ike

p.s. This is not meaning to say anything bad about Power Tronics they do make some very good aftermarket AVR's just they can be pricey

 

[RWG421]

When I unpot the module is it best to melt it out with a heat gun??? or pick it out?

 

[Isaac-1]

pick it out, for now you only need to get enough out to get to the leads on the big capacitor, and possibly to read the markings on it.

Ike

 

[PeterD]

If soft/rubbery (RTV) picking is the only way. If it is black, relatively hard, then heat is the only way (and that stuff is nasty/messy.)

I'm going to guess it is softer, so picking it is best. As mentioned, you only have to get at that big cap first, and you need to be able to read the values on it. Both the capacitance value, and the voltage. Note if it says VDC, or VAC. Sometimes there are non-polarized (VAC) capacitors in these things and putting in a polarized (VDC) will cause the capacitor to fail quickly with some rather spectacular results!

Also realize that today's cheap Chinese capacitors are overrated, so if the one in the unit says 150 VDC, I'd recommend replacing it with one that says 200 or 250 VDC... Seems they (the off-shore makers) are over optimistic about their voltage ratings!