[bassguitarist1985]

The SX460 is an inexpensive AVR, often used as a replacement for when the DPE is fried. It uses the main windings as the DPE instead. While this could work, it will reduce the output capacity of the generator. DPR or displaced phase excitation windings are 90⁰ out of phase with the main winding. So when the spinning rotor pole comes across the DPE to be charged, the AVR has a full charge to the rotor to pass to the main winding. This creates a positive feedback loop allowing the generator to "self excite." Without the DPE the positive feedback loop is lost, and relies on extra large capacitance in the AVR to compensate. I myself have not retrofitted a generator with this AVR, but what I mentioned before is accurate.

Cheers!

 

[zz28zz]

A while back I was investigating different types of excitation methods looking for the one that would be best at starting a deep well pump. Main thing I remember was that if the AVR is powered from the main output windings, it won't have as good of a start-up capacity for large elec motors. Reasoning was that the output winding voltage drops when a large elec motor is started, the field winding need lots more current at that moment but since the output drops and the AVR is powered from the output, it makes starting a large elec motor more difficult. If the AVR is powered from it's own source (DPE) it doesn't have the voltage drop problem.

 

[bassguitarist1985]

A while back I was investigating different types of excitation methods looking for the one that would be best at starting a deep well pump. Main thing I remember was that if the AVR is powered from the main output windings, it won't have as good of a start-up capacity for large elec motors. Reasoning was that the output winding voltage drops when a large elec motor is started, the field winding need lots more current at that moment but since the output drops and the AVR is powered from the output, it make starting a large elec more more difficult. If the AVR is powered from it's own source (DPE) it doesn't have the voltage drop problem.

Correct because of the DPE being 90⁰ offset from the main windings. Power the AVR with the main windings 0⁰ in phase source/load, now you rely on extra large capacitors on the AVR, which are no match for the large oil filled hard start cap on the pump.

 

[Corded]

Brushed or brushless makes little difference
It’s the power and voltage rating of the board that matter.
Worst case he needs about 5 amps and let’s say 90 volts
A lot of boards can do that.
I know the Stamford clone boards can be had real cheap on aliexpress.
There may be other choices

searching for something that’s universal and aftermarket might be an option

 

[Corded]

I haven't seen a design in which this AVR was used with a brushed generator like the Powermate.

this will blow your mind
It’s an Onan AVR from the 60s
Doesn’t have any tubes or transistors
Just a control transformer, a handful of diodes and resistors and a class B amplifier made mag amps.

that is elegant

 

[Corded]

Deleted by Corded

 

[tabora]

A lack of an edit function sure makes posting here on a phone difficult for old fat fingered people mr moderator…..

Click the three vertical dots in the upper right corner of your post and select Edit.

 

[Corded]

So much for my fat fingered excuses lol

 

[Corded]

So I did some digging and generac has 3 to 5.5 a ranges for the breakers on these things.
I haven’t look at any winding data for this kind of stuff in 30 years so my memory is fuzzy.
As I recall the winding is not simply 90 deg electrical out of phase but laid out in small coil groups in order to increase excitation, kind of like a current transformer off the main winding.

if 12 volts is inducing 50 volts on the primary windings it’s a safe assumption the maximum excitation voltage is around 50 on the field.
This is inline with what I might expect….

So any aftermarket avr that can be fed off the main should work within that range
Likely your going to need someway to flash the field on it each time you start the plant.

Is that worth the trouble?

 

[toomuchfun]

...DPR or displaced phase excitation windings are 90⁰ out of phase with the main winding. So when the spinning rotor pole comes across the DPE to be charged, the AVR has a full charge to the rotor to pass to the main winding. This creates a positive feedback loop allowing the generator to "self excite." Without the DPE the positive feedback loop is lost, and relies on extra large capacitance in the AVR to compensate. I myself have not retrofitted a generator with this AVR, but what I mentioned before is accurate.

Yes, I completely get what you are saying. I actually took the time to read your (extremely detailed) write up on youtube (a little late, but better late than never) and as soon as I got to the part about the 90 degree phase difference it made sense as to the reasoning. That said, what I have now is a boat anchor because the stator isn't made anymore, and used ones are more than replacement generators (same goes for having it rewound), so if I can turn it into a 3.5 kw generator (or whatever) it'll be better than nothing. Especially since the motor runs really well and has very low hours.

...FWIW, it's for brushless systems. I haven't seen a design in which this AVR was used with a brushed generator like the Powermate.

Yes, I got that it's for a brushless system, but I appreciate you pointing it out. Seems to me (with my admittedly little knowledge) that there's a good chance it'll work for driving the brushes as long as the max specs of 4 Amps and 90 Volts (less worried about the voltage) are sufficient. I don't have a variable PS around or I would have tried to see what voltage and current are needed to run it at 120/240 V under load. I guess I can use two car batteries for 24 Volts to see where that gets me, but it's far from variable. I do know that 12 VDC gets me to 49 Volts with a current of only around a quarter amp (but this was at less than half the output voltage through a 120V 40W light bulb, I'm certain things will change radically once it's at spec and under load). Not sure if the 4 A max current will be enough, guess we'll see.

What I'm more worried about is how to start it because apparently it requires a residual voltage of at least 5 Volts and I don't believe I have that (unless it's stored in the AVR itself). I guess I can just apply a DC source to the brushes but I'm assuming I'll want to use diodes, or some sort of protection circuit to not damage anything once the generator and AVR circuit start producing voltage.

EDIT:
So for some reason I didn't see the last six posts when I (thought I) refreshed the page, so I'll post my belated responses here:

Worst case he needs about 5 amps and let’s say 90 volts
A lot of boards can do that.

This is what I was thinking about. I ordered a SX460 to test out. It's only 4 Amps, guess we'll see if it's enough. Glad to hear it's doable though.

So any aftermarket avr that can be fed off the main should work within that range
Likely your going to need someway to flash the field on it each time you start the plant.

Is that worth the trouble?

Yes, because I can turn it into an emergency generator only used a few times per year, better than a boat anchor. How do you suggest flashing with the SX460 connected? Do you think I need circuit protection for when the generator starts producing voltage, or just be real quick about it?

 

[toomuchfun]

I'm getting things ready for the SX460 as it should arrive in a few days. I added a small sealed 12 VDC, 7Ah battery, connected a momentary push button switch, as well as a diode inline to the positive brush. Negative is always connected (from battery to brush). The whole setup is very lightweight and will be simple to flash as needed.

My question now is, after I install the SX460, should I leave the 130 mfd capacitor in place (the diode bridge module will be removed). I'm assuming so as it's across the field winding, but figured it best to ask.

 

[Corded]

I'm getting things ready for the SX460 as it should arrive in a few days. I added a small sealed 12 VDC, 7Ah battery, connected a momentary push button switch, as well as a diode inline to the positive brush. Negative is always connected (from battery to brush). The whole setup is very lightweight and will be simple to flash as needed.

My question now is, after I install the SX460, should I leave the 130 mfd capacitor in place (the diode bridge module will be removed). I'm assuming so as it's across the field winding, but figured it best to ask.

Removed all the existing stuff
The board does not need anything like that

 

[toomuchfun]

Removed all the existing stuff
The board does not need anything like that

Ok, thanks. I'm glad I asked because I would have kept it in place.

 

[toomuchfun]

Thought I should provide an update here. It took a very long to receive the AVR module, then, by the time I got back into the project, I forgot that I hadn't removed the capacitor (which I last wrote about). It fired right up and the voltage was super stable and perfect. However, even under no load, the DPE winding began glowing orange. Not sure what was going on, it looked to be in good physical shape, but I figured it must have been shorted to something somewhere (which brings up the old question of did the bridge rectifier module go out first or was it damaged by the winding). That said, I pulled the stator from the generator, cut, then physically removed the entire DPE winding from the stator.

While everything was apart I also removed the aforementioned capacitor and after it was all put back together, it worked perfectly and was producing proper voltage. I spoke with a local small engine place and was told that I should dip or coat the stator to prevent further problems, so I pulled it apart again and had them do it. Hopefully all is now well, and will stay that way for some time.

A couple quick additional notes...
1) Output voltage seemed smoother when I (accidentally) left the OEM capacitor in place across the field terminals. It still works very well without it (way better than the OEM, non-AVR, setup), but the receptacle output voltage continuously bounces around (just tenths of a volt to 1 volt), whereas, when it was in place, it was more stable and there was less bouncing back and forth.

2) We speculated that I would need to flash the field, but, for whatever reason I don't need to flash it. It automatically detects that the generator has started and begins sending voltage to the brushes. Nice!