220v 15Kw ST generator head, voltage regulator ideas??

You should be able to lower the resistance (indicated in the schematic) to boost the output voltage, but the generator may actually be designed for 110 VAC (rather than 120), and it might not be able to be pushed much higher.

A simple solution is a boost transformer, which is simply a 120 VAC to

12 VAC transformer on the output. For 10 KW you only need a 1 KW transformer, something like 12 VAC at 80 amps. You might find one in an old welder or battery charger.

Paul

[...] The generator waveform is very good quality. Usually the cheaper the alternator, the worse the waveform. You can't do anything about the waveshape. It's 'engineered in', fixed by the physical coil structure and mettalics used. Measuring the motor inductance can be a futile excercise. Inductance varies widely depending on rotor angular position and for a reasonable L-deg graph has to measured with voltages and currents near to those in normal operation. Increase/reduction of output voltage can be by manual/auto adjustment of an external power supply, feeding AC or DC to the control winding rectifier. You'd only need a couple of amps at a few volts. Can allow 110V machines to run below 90Vac or upto 150Vac. (4Amp 'Variacs' are handy for this) These smaller alternators usually have noticable leakage inductance, so a few uF of power factor compensation caps wouldn't go amiss. john

Well, I noticed that the Stator voltage spikes seem to correspond to the noise in the output waveform. Any idea why I see such strange spikes when I put the O-Scope across the stator brushes (after the voltage rectifier?)

Actually, I was thinking about measure the inductance of the generator's stator winding. The hope being to help clean up the output voltage of the generator

True, currently the generator has a "Z" winding that feeds a simple rectifier that provides power to the stator. The only way I could increase the generator's output voltage would be to increase the voltage of the "Z" winding. A small step up transformer could work I guess.

My first hope was I could clean up the existing voltage regulation 'system' as I only need the generator to output another 10Vac (or so)..

Thanks

Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

Can you put a suitable AC capacitor between 2 poles to inhibit these spikes?

i

I don't have much experience with generators, but I have some ideas:

(1) The stator voltage could be increased and smoothed by adding a capacitor to the output of the bridge rectifier.

(2) The bridge rectifier may not be of the best quality, and may have some problems not detected by an ordinary forward conduction tester. Replace it with a high efficiency bridge with at least 600 V breakdown and 20 amps or more. Probably less than $5.

(3) The 15 Hz modulation is probably due to insuffient flywheel effect, or oscillation in your coupling bushing. If you removed or modified the original flywheel/pulley, make sure your new one has at least as much inertial mass.

(4) Your initial tests showed adequate voltage (243 V at 28 amps), but now you report only 111 VAC with it connected to the house. It is important to have a balnced load on both sides of the 240 VAC which is fed to the house. If you have only one phase connected, or if there is greatly different load on the two phases, you might get low voltage and distortion problems.

Paul

...

Sounds like your generator is getting dragged down by your HVAC, and the UPS is going into brownout.

Try not to run the air conditioner from your emergency power, maybe?

Good Luck! Rich

In article , James Lerch wrote: [snip]

These low power alternators all seem to use "harmonic excitation", which seems to be claimed as having self-regulation in some way.

What is "harmonic excitation"?

Is there any way to leave the main excitation loop as it is and add-in a controlled amount of extra field current, either from a crude closed-loop AVR, or simply in proportion to the load current?

--
Tony Williams.

That's on my to do list, I just wasn't sure how the Z winding would react, nor how much capcitance to put across the stator..

Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

I can give you a cap to try...

i

Thought so, I'll throw a few mF across it as see what happens

I actually have a few I salvaged out of a large SMPS, I'll give it a try and see if anything changes.

Well, I built it from scratch, so it is what it is.. One crazy Idea I had was to attempt to build an active voltage regulator, one that was smart enough to compensate for the reduction in angular velocity between power strokes. Sensing when to try and compensate for this, and how much to compensate might be interesting :)

Indeed, my load tests were into ideal loads (220v resistance heaters, a pottery kiln). The load on the house is a different story. However, Maybe adding some trim capacitors to the offensive inductive loads will help... (When running off the grid, I've been lead to believe residential customers don't' care about power factor, but when running off the genset, is power factor something to consider?)

Thanks

Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

Damn fine question, one that google doesn't seem to want to help me with :)

Not knowing how the system attempts to self regulate, I was (and am) a little conerned with adding capacitance across the stator. Perhaps I shoud incorporate a fuse into the stator power circuit before I start screwing around with it...

Probably, I've got an AVR based development board I plan on incorporating into the generator. The first job for this system will be to monitor for critical events and shut the system down in case of emergency. (low oil, high temp, etc). Once I get that part working, the next goal was to develop an assist system to help the mechanical govenor keep the engine RPM in check.

After all that's figured out, an active voltage regulator sounds like an interesting project...

Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

The diesel engine still has plenty of power left in it, and the engine RPM is accurate under the load of the HVAC. It is just the crude self regulation that isn't perfect. Considering how incredibly simple and crude the system is, I find it amazing it works as well as it does. If it wasn't for the UPS, I probably wouldn't even worry about it.

If only it were so simple!! {shrug}

James Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

Well, the variable resitor isn't included with the generator head when purchased. It would only be added as an option if the voltage were to HIGH...

I'm thinking that some Chinese company figured out that the generator would run with out the resistor if "X" amount of copper windings were removed. In doing so they saved the cost of the resistor and probably several feet of copper wire..

I guess you get what you pay for, but honesty I'm pretty happy with it so far (all things considered).

Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

Thanks Ig, but I probably have a few here :)

I have this real bad problem about refusing to throw away all the scrap SMPS I replace at work. They seem to be full of "candy" for tinkerig with electronic stuff. Heat sinks, fans, rectifiers, mosfets, etc.... :) My Induction heater was made from mostly SMPS parts!

Take Care, James Lerch

(My telescope construction, Testing, and Coating site) (My 11.2Kw generator project) Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

Yeah. I had a similar experience with UPSes. I made a phase converter out of an old Ferrups UPS (with a beautiful enclosure, big sliding tray etc).

this phase converter is now my big workhorse.

i