I want to use a 3 cyl. Geo (automobile) engine to power a AC generator. The engine mounts, cooling/exhaust, alternator drive , etc. are no problem but how do you get the engine to respond (more gas) to load changes? Is there a commercial source for governor's that will work on automobile type engines? Thanks...
Just find a BIG relay and run all the power through the coil... Hook the pulling side of the relay to you gov... You will need to play with some springs untill you get it just right... You might need to rewind the coil with a few turns of heavy wire... Or you could just use an amp over the wire coil...
Uh, that'll be trying to regulate *current* not voltage.
You need something a little more sophisticated than just pulling the throttle closed with an electromagnet sensing output voltage. You need more loop gain than you can get with just that.
Just my .02, but I bet Don Foreman could design a controller for you in his sleep...
You are sure right about Don. I'm constantly amazed at the circuits he designs for me to use on big, diesel driven generators. If Don was to advise on how to solve this problem, you'd do well to try his suggestions. There arent adequet words of admiration in my vocabulary to describe Don.
Jerry (who knows some complicated ways to maintain constant (kinda) RPM with varying load)
There are two pieces to this problem. The RPM for an AC generator needs to be kept constant in order for the frequency to be correct. It does not have to be perfect unless you are running clocks or audio gear like tape decks or turntables, but it needs to be close. An RPM governer will handle the throttle, but you also need a voltage regulator to deal with the load changes.
Is this true? I thought voltage was a function of the guage and number of windings in the field. As long as the RPM is held constant the frequency and voltage remain the same. This is from the bottom of my memory that has been, in part, erased! Can anyone else shed any light one way or the other? Rick
As *I* read the original post, Jon wanted only to maintain constant RPM as additional loads are applied.. That can easily (but not simply) with a big solenoid to pull the throttle. But, if there is a need to maintain constant RPM *and* voltage while the load is varied, both a RPM control *and* a voltage regulator will be needed. I submit that Jeff Wisnia's suggestion is a good one ie get a Don Foreman.
For an AC generator you need to control the RPM to either 1800 or 3600 rpm +/- about 1.5% to 3% (which corresponds to +/- 1hz or +/-2 Hz. the generator should have enough internal control to hold the voltage within reason.
One issue on the GEO engine is that most alternators run either 1800 or
Rick, As you mentioned in your post, voltage is dependent on the number of windings and gauge. The reason that gauge is important is because it controls the resistance of the wire. That resistance is going to drop varying amounts of voltage as the current load varies, changing the output voltage accordingly.
I had an ancient military surplus AC generator that ran on a 4 cylinder Jeep engine. Somewhere before I got it, the voltage regulator got disconnected and a large variable resistor drove the field windings directly. The output voltage would change by 20 or 30 volts from the unloaded to fully loaded state.
Jerry, I agree that Jon was just asking about a throttle control that would respond to the load. I tossed in the voltage regulator suggestion because I think that there is more required. If Jon is running a pretty constant load, that is tolerant of voltage variations, he could probably get by without a voltage regulator. I would not suggest it though.
I'm sure you are right about both the RPM needed and the speed the GEO will run at. I am curious about how standard the alternators are with reguard to their number of poles. I now understand that these alternators are most commonly built to produce 60 Hz at either 1800 or 3600 RPM. Is that right?? And, why dont Geos like to run at either 1800 or 3600 RPM? I would have guessed that the 1800 RPM alternators were intended to be driven by diesels and the 3600 RPMs driven by gas engines. I'm not disputing your information. I'm looking for education.
Are there packaged cruise controls in aut stores anymore ? Seems like I wanted one like my father-in-law got - an after market add-on. Had to be in the Mid 60's maybe afterwards.
On 26 Jul 2004 01:48:03 GMT, snipped-for-privacy@aol.comCANSPAM (Rhbuxton) vaguely proposed a theory ......and in reply I say!:
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Not necessarily. The genset will have internal resistance. So as you vary the load at constant RPM, without a voltage regulator, the voltage would vary quite a bit. You need to generate more than you need, then cut it down using a regulator of some sort, so you can work withon that range and still get proper volts.
However, it depends on usage. IMO. Many small->medium (up to 10KVA) portable gensets are unregualted, or they certainly used to be. They simply relied on a mechanical throttel control, centrif based.
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Most small generators maintain a moderate control of speed by a simple vane that is activated by the fan and balanced between 2 springs . As the load increases, the rpms drop, as does the wind speed from the fan, one spring increases the throttle. Overspeed is lessened by the vane and other spring and load adjusting lever causing a decrease of throttle. At proper speed, the wind vane and springs balance to an adjustable load position. High to low to idle. Not precision, but better n nuttin. A voltage sensing electromagnetic solenoid replacing the load adjustment to the decreasing balance spring would offer somewhat more accuracy. (Lower air speed or lower voltage would allow for more throttle, if the magnet travel leads the vane, better load control.) This is all a balancing act, vane movement, throttle movement, spring tension and load adjustment. So unless you have lots of time to experiment, search for an alternative.
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