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Generac Generators (SEARS, etc.)

Generac Voltage Regulator Reverse Engineered...


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  #41  
Old 02-27-2011, 12:48:54 AM
jimgrease jimgrease is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Kevin,

PM sent, I looked at the engine more closely today and it will need some work. Lots of buildup around the intake valve. Valves themselves don't look so good. However, the cylinder wall looks good so its worth cleaning up. Its an aluminum bore with a sleeve crank bearing, basic Briggs.

Also, I managed to simulate the VR21 Onan board today in LTspice. Still some bugs to work out, but it looks like the Onan regulator is filtered on its Zener regulator which only feeds the Op-Amp. Not sure yet if the Onan will synchronize its SCR firing pulses with the zero crossings like the generac does, but it's early in the analysis here.

Having some fun with this.
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  #42  
Old 03-20-2011, 12:01:14 PM
jimgrease jimgrease is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Just another quick update here.

I've decided to abandon the VR21 simulation work for now because I didn't really discover a compelling reason to use this circuit for my generator.

Instead, I've switched back to modifying the original Generac circuit. One thing I'd like to say now is that I'm not using the bridged-T or the twin-T filter on the feedback network. The bridged-T is too gradual in transitioning from the frequency selective portion to the straight attenuating portion. It defeats the main purpose of unloading the engine when RPMs fall off when larger loads are applied.

Simply said, it wont' unload the engine enough near the desired operating point.

So, I'm experimenting with a slightly more complicated design that is very similar to Kevin's suggestion earlier about using a second feedback network that isn't frequency selective. The knee point will be adjustable, and I'll try to add in some LEDs to allow easy tuning of this knee point.

Things are coming together, but it's still slow going. It's just not very high on my priority list at the moment.
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  #43  
Old 04-20-2011, 11:42:01 PM
jimgrease jimgrease is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Taxes, family emergencies, etc. Still working on the circuit when I have a spare moment.

In the meantime, I did see this in a recent searching episode:
http://www.autopartsource.com/lukesm...et/EET480W.pdf

Some day I might even have enough time to digest what was done with this particular regulator re-design. In the meantime, perhaps some other Smokstak readers would like to see it.
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  #44  
Old 04-21-2011, 09:05:19 AM
Kevin K Kevin K is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

I'm still around as well, and I'm still scouring Craig's list for a generator that uses a DPE winding, has a bad voltage regulator, and is cheap, that I can use as a test bed for this project.

I seem to remember coming across the PIC regulator project you linked to sometime in the past. The good news is the 16F88 is still in current production. Building on this circuit to add features such as voltage roll off with RPM would be easy. On the other hand, having programmed PIC's in assembler, they tend to be temperamental, and I would never trust the design without a thorough debug. I'll probably leave this one alone and go with the KISS principal.

Take a look at this forum where a gentleman in Australia has reverse engineered the voltage regulator for a small generator:
http://forum.allaboutcircuits.com/sh...ad.php?t=47606

Also, I'm attaching a schematic I found of a Honda EG1500 regulator.
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  #45  
Old 10-23-2012, 03:28:46 PM
tinkerman2012 tinkerman2012 is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

One would ASSUME the DPE winding produces a sine wave in phase with the output voltage, but this may not be the case. [/QUOTE]

I would assume that the Displaced Phase Excitation(DPE) winding produces a sine wave at some angle to the output voltage other than 0 or 180 degrees.
Keep up the good work.
Jack Hottel[/QUOTE]


Just jumping into this thread and I haven't studied fully yet so if someone has already commented I apologize. From my motor theory and rewind experinece, this generator I'm working on (Generac Magnaforce 6500 watt) has the DPE winding place at the 9 O'Clock position relative to the main winding which is place at 12 O'Clock ad 6 O'Clock. I've replaced the 6 O'Clock winding as it was burned. The rest of the winding was OK. The DPE winding would be out of phase by 90 degrees relative to the main winding. Someone correct me if I'm wrong.
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  #46  
Old 10-24-2012, 08:44:52 AM
tinkerman2012 tinkerman2012 is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Interesting part about Generac's DPE winding/excitation is that Coleman and Champion windings are placed in the same manner. Has Generac come up with a fancy marketing term. What is the significance or Displaced Phase Excitation? It all gets converted to DC current for powering the field winding. There is no phase angle with DC. I believe they use those slots in the core at 90 degrees position since they would be unused otherwise and placing the DPE winding in the same pysical position to the main would use up valuable space in the slots required for the main windings.

Just a thought.

Comments anyone?
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  #47  
Old 10-24-2012, 11:42:21 AM
len k len k is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Haven't given it much thought, but very likely a space issue. No room for them at main windings.
Also since current lags voltage by 90 degs in an (ideal) inductor , then current would be nearing a max as feild rotor pole passes main winding. Good for hi power output. Fluctuating field current not so good for clean non-distorted sine wave. I would think it wants a cap to smooth the DC to field.
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  #48  
Old 10-24-2012, 07:19:47 PM
tinkerman2012 tinkerman2012 is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Good point. With an SCR as the control I can see where it wouldn't fire until voltage started to build in the AC sine wave of the DPE winding. That would be plenty of time for the magnet field to build to create voltage in the main winding.
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  #49  
Old 06-12-2015, 09:02:08 PM
Graniteman57 Graniteman57 is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

I just picked up an 8000 watt generac generator with electric start, I fixed the starting system and got it to run but it runs like it is under a full load all the time and when I tried my electric drill it barely ran like it had low voltage. I am wondering if is the voltage regulator like I am reading here? Any suggestions?? Graniteman57
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Old 06-12-2015, 10:22:07 PM
pegasuspinto pegasuspinto is offline
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Default Re: Generac Voltage Regulator Reverse Engineered...

Running like a full load all the time sounds like shorted windings.

The purpose of the D in the DPE is to decouple the exciter current from the output. If the DPE was in phase with the main winding, a surge load would cause the main winding and the exciter winding to collapse at the same time. Taking it out of phase gives it some independence from the load on the output windings.
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