ST Regulator

[NoSpark]

Anyone add an AVR to their ST. I've found AVRs that wire in series with the Z windings to the rectifier and AVRs that eliminate the Z windings altogether, advantages/disadvantages? I need to get the voltage under control so I can finally hook this thing up to my home and not just my garage. I also need to get a 10 ohm rheostat either way.

[TimSR2]

Hmm. Mine ( PS ST5) runs at 250v @62 hz, down to 230 @ 58 hz. Why mess with that? Any voltage problem I have had is due to overloading a leg or under revving the prime mover. KIS (S)

[NoSpark]

I get a nonloaded voltage of over 270v @ 61hz, that's a problem I think.

[TimSR2]

I guess I am just lucky. What brand name is your head? I bought mine from PowerSolutions. Do you have a  western style bridge rectifier instead of the chinese diode bridge?  I converted mine to a 25a600v bridge rectifier  before putting it in service.

I'd definitely use the old school, tried and true, tapped resistor method before going to an AVR.

Tim

[NoSpark]

Brand-UDE
Western style rectifier (unknown V/A)
Metal fan
Sealed bearings
60Hz only

I never planned to use an AVR, its just a recent thought. At least if the AVR dies I can put it back "Old School".

[NoSpark]

How about a rheostat with a knob so that the voltage could be adjusted in real time?

[oiler]

How about a rheostat with a knob so that the voltage could be adjusted in real time?

I'm looking for one too, but i've had no luck so far.

Does anybody have an idea where to find one?

[Ronmar]

How about a rheostat with a knob so that the voltage could be adjusted in real time?

I'm looking for one too, but i've had no luck so far.

Does anybody have an idea where to find one?

Rheostats that large are getting harder to find. With the ammount of field current in use on a ST-5, that can be quite a bit of heat the rheostat needs to dissipate...

[NoSpark]

Here's one, but its for testing. May not tolerate being hooked up for long lengths of time. 0-28 ohms. Very tempting though. How about electric range rheostats, I wonder what the resistances of those are.

http://cgi.ebay.com/ebaymotors/Heyer-Ind-Marquette-Field-Rheostat-31456-Test-Tool_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem518c651b1dQQitemZ350247787293QQptZMotorsQ5fAutomotiveQ5fTools

Ron, you have an AVR, whats your opinion on them?

[TimSR2]

Gen heads  typically use  a tapped wire wound, tubular, ceramic coated high power resistor instead of a rheostat. About 8 inches long and an inch and a half around.  If this cannot be sourced a fixed resistor of the same value can be used and a strip ground off the side and tap added. The tap need consist of nothing more than a wire  and a hose clamp.  Go to any  ham radio swap meet and you will probably find some.  I have a pile of them, what value are you looking for?

Tim

[bschwartz]

I'd look at something more like this:
http://cgi.ebay.com/ebaymotors/Ohmite-100-Watt-16-Ohm-Rheostat_W0QQitemZ400069818615QQcmdZViewItemQQptZMotors_Aviation_Parts_Gear?hash=item5d2604f8f7&_trksid=p4506.m20.l1116

[Ronmar]

Here's one, but its for testing. May not tolerate being hooked up for long lengths of time. 0-28 ohms. Very tempting though. How about electric range rheostats, I wonder what the resistances of those are.

http://cgi.ebay.com/ebaymotors/Heyer-Ind-Marquette-Field-Rheostat-31456-Test-Tool_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem518c651b1dQQitemZ350247787293QQptZMotorsQ5fAutomotiveQ5fTools

Ron, you have an AVR, whats your opinion on them?

The electric range controls are not really a rheostat.  They are more along the lines of an adjustable thermal snap switch that cycles the burner on and off to maintain a relatively stable temperature output based on their cycle rate.  It is kind of fun to watch the kill-a-watt frequency yoyo when we use the range elements while on generator power:)

I have an AVR for testing, but I don't use it in practice.  The simple harmonic excitation/regulation works quite nicely for me.  The AVR does cut down on flicker from the single cylinder slow speed mover though.  One of the things that happens when a large load comes on to a harmonically excited set is that the voltage droops slightly along with the RPM untll the engine catches up.  This kind of softens the blow on the engine.  The same surge load on an AVR is more radical on the engine as the AVR maintains output voltage, so the mechanical load felt by the engine comes on quicker/steeper.  I noticed more puffs of black smoke and larger frequency excursions under load changes with the AVR connected.  Nothing serious in my opinion, just an observation.  Things seem a little smoother on the harmonic.  I think it is a good match for the slow speed listeroid mover.

As for the overvoltage ST head, the first question I would ask is since these simple generator heads are so sensitive to RPM, are you sure of your frequency?  If you were off by a cycle or two high, you could easilly see the voltages you are seeing.  If the freq is accurate, you may be able to divert some of that field energy instead of sending it thru the brushes to the rotor.  A series of small low wattage lights wired in parallel across the field circuit could be used to consume some of that energy and lower the field, and resultant output voltage a little.  Basically turn some of the excess energy into light and heat like the resistor would turn it into heat.  The bulb wattage would determine how much energy they would consume.  Using several small bulbs would also provide redundancy so one bulb burning out would not cause a sudden large overvoltage condition on the generator output.

[NoSpark]

 

Here's one, but its for testing. May not tolerate being hooked up for long lengths of time. 0-28 ohms. Very tempting though. How about electric range rheostats, I wonder what the resistances of those are.

http://cgi.ebay.com/ebaymotors/Heyer-Ind-Marquette-Field-Rheostat-31456-Test-Tool_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQhashZitem518c651b1dQQitemZ350247787293QQptZMotorsQ5fAutomotiveQ5fTools

Ron, you have an AVR, whats your opinion on them?

The electric range controls are not really a rheostat.  They are more along the lines of an adjustable thermal snap switch that cycles the burner on and off to maintain a relatively stable temperature output based on their cycle rate.  It is kind of fun to watch the kill-a-watt frequency yoyo when we use the range elements while on generator power:)

  I can't believe I wrote "electric range rheostats", I don't know what I was thinking, to many late nights I guess.    I'm quite aware of how an electric range cycling switch works.

Frequency is measured with Kill a Watt and  DVOM. My Kill-a-Watt actually reads 5 or 6 volts lower than actual but the frequency is accurate. I tried a ceramic automotive blower resistor measuring just under 5 ohms and got the voltage under 130 volts unloaded but loading just one leg makes the other leg go real high. It almost seems like I need a real light 240v load to equalize things. Maybe a 240v to 120v transformer. The bulb idea is interesting.

[NoSpark]

I was reviewing my posts on Listerengine forum from a year ago. I was getting 119v volts a year ago, how would this be possible? I did pull the generator apart last spring to paint and go through it. I soldered all the crimped connections at that time also.

[Ronmar]

How much does the voltage drop with a light load?  If it settles in to a more normal voltage when lightly loaded, I would suggest a new bridge rectifyer.  If one of the diodes were shorted, you could be putting some more pulsed energy inthere that is inflating the output voltage, but without the energy to support a load at that raised voltage.

As a test, you can get a 50V 25A bridge at radio shack for $3.29.  It's voltage rating is a little low for long term operation, but it should work as an inexpensive test...