Diesel engine gen-set control

splog

I married a small 12hp diesel to an ST gen head and am now left with the problem of
a governor. I am not sure whether I should be trying to build one based on frequency or voltage or even that it should or could be done with a stamp, BS2PX- has been suggested.
There are quite a few circuits out there for controlling motors up to quite a few amps but not much in the way of input circuitry.

Has anybody had any experience with this or know of which channel there is a/are posting/s on this subject. I have tried the search engine here but its a bit sucky, returns all kinds of stuff not searched for, so if there is anything pertaining to my needs it's probably missed it.

Jonathan

splog,

Shouldn't be too hard. Of course, that's from a guy who doesn't have to do it :-0

Seems like I would start by measuring freq. and voltage, and see which is most linear. You could also put a tach on the motor and try that.

I assume you want to govern the speed to load. So adding a current sensor might be a good idea. Allegro make some nice Halll effect sensors in a variety of current ratings. They are easy to interface with a stamp using an ADC or with the resolution you need, you might be able to use RCTIME.

I'm not sure about how to do this, but I would want a spring loaded fuel rack controller for the govoner, so if the Stamp failed, the motor would be pulled into the idle/off position by the spring. You could use a servo/spring set up for this maybe.

I wouldn't think you need a 2px. Seems like a slower Stamp should be fine.

Jonathan

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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

Bruce Bates

Splog -

I don't have any specific suggestions for you, but I'll teach everyone a little trick which I've found invaluable over the years. All you need to have to accomplish this is a (say) regular 60 watt light bulb, an ordinary pigtail socket with wires on it, and a few feet of insulated wire.

Here's how you can set the frequency of your generator to the mains line frequency, to within less than 1/2 a percent. Take the lamp and screw it in the socket. Twist and tape or wire-nut one piece of the insulated wire to one of the wires on the lamp socket. Take the other end of that same wire, and run it to the HOT terminal of the generator while it is OFF. Take a second piece of wire and attach it to the other side of the pigtail socket, twisted and taped, or wire-nutted as before.

Now you have to start being careful as from here on in, a SHOCK HAZARD EXISTS! Place the lamp in a safe place where it can't fall and break and make sure the taped ends of the pigtail socket aren't touching anything, including each other. Determine by use of a voltmeter or any other convenient means, which is the HOT side of your nearest 110 volt receptacle.

Now you can fire up the generator and let it warm up at idle. Once it's warmed up, run the wire with the still exposed end, over to the HOT side of the 110 volt receptacle, and plug it in carefully. If you have to have someone else hold in in do so, but remember to warn them about the possible shock hazard.

If your connections are sound the lamp will be FLICKERING. The generator output and the mains are out of phase relationship, and thus are out of frequency respective to one another. Raise the speed of the generator slowly by use of the idle speed screw, until the flickering STOPS and if you have a 60 cycle mains frequency the output of the generator will be now be very, very close to that. The same can be said for 50 cycle mains, and a 50 cycle generator.

Regards,

Bruce Bates

SPENCE

Splog,
as far as i know, power generators are always governed by frequency. Then you have to control the voltage by other means.

Some loads require accurate generation frequency while others might let you get by with 5 to 10% variation.. Get a vibbrating reed frequency meter as a standard check. Many generators have those built in.

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73
spence
k4kep

stamptrol

Splog,

I expect an engine as big as 12hp will already have a govenor to control its speed ( ie frequency). Your work will be to regulate voltage as the load swings.
Depending on the field controls of the generator, this will range from easy to a real pain. The process is, of course, simple in theory: measure the voltage periodically and adjust the field to raise or lower the output voltage.

Do you have any schematics of the generator?

Regards

Jim Richey

I put together a similar machine to power our home during blackouts.Diesel/10kw.The generator unit turns at 3600rpm,producing 60hz current@240/120 volts.You know that it is turning the correct rpm by measuring the voltage.It is not necessary to govern it in any way because subjecting the generator to a heavy load has no effect on the ability of the diesel to maintain it's setting.I have logged around 150 hours of use without problems.

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Thanks, Parallax!

splog

Thanks to all that answered my cry for help.
Sorry but I suppose I was not too clear about my quest.


Governor
The engine does not have any type of governor on it, it will have to be controlled using a small gear motor to drive the throttle shaft cw or ccw in order to keep the engine running at a speed (approx 1800rpm) that will result in the generator head delivering 250vac at 60Hz.

Generator
The generator is a standard four pole ST-12 type. In my case it’s a 12Kw I know I can get at least 5Kw out of it.

Frequency
My VOM has a freq. Meter built in for this and anyway generally speaking when the generator is putting out the right voltage the freq. Is very close to 60hz.

Spring on the throttle
This is a good idea but I think that if I use a gear motor the spring might not be able to pull the shaft back down.

My aim

To have something, either voltage comparator or frq. Detector (perhaps a Schmitt trigger) that generates an output to a motor driver (H bridge or such) that turns an engine throttle shaft until the output from the generator matches a set reference equivalent to 250vac or 60Hz whichever will be the simplest..to null out the input.

What I don’t want to do

Re-invent the wheel. I have scoured the net and found a few already made electronic governors for sale but they all cost more money to buy than I have spent on the gen-set to-date, including welding rods and mistakes. There are plenty of motor driver circuits out there including Stamps but no actual examples of input circuits.

SPENCE

Splog,
have you thought about useing a stepper motor with threaded rod thru a anchor nut to push or pull the throtle.

73
spence
k4kep

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73
spence
k4kep