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Comparing voltage regulation....
It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? Just curious about the two different strategies. -- EA |
Comparing voltage regulation....
"Existential Angst" wrote in message ... It seems that a genset regulates voltages by keeping the rpm constant. How No, rpm regulates frequency...if the alternator is placed under a heavy electrical load then it is necessary to supply more shaft horsepower if close frequency regulation is desired.. Output voltage is controlled by varying the strength of the rotor magnetic field (unless it's a permanent magnet machine) is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? http://en.wikipedia.org/wiki/Voltage...cal_regulators Just curious about the two different strategies. -- EA |
Comparing voltage regulation....
On Thu, 11 Oct 2012 22:01:59 -0700, PrecisionmachinisT wrote:
"Existential Angst" wrote in message ... It seems that a genset regulates voltages by keeping the rpm constant. How No, rpm regulates frequency...if the alternator is placed under a heavy electrical load then it is necessary to supply more shaft horsepower if close frequency regulation is desired.. Output voltage is controlled by varying the strength of the rotor magnetic field (unless it's a permanent magnet machine) Yup. And everything is different if it's an inverter gen-set. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Comparing voltage regulation....
On Fri, 12 Oct 2012 00:22:18 -0400, Existential Angst wrote:
It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? Just curious about the two different strategies. A not-inverter style genset regulates voltage by varying the current in the field windings. An inverter genset just makes rough DC, and cleans it up with an inverter. Car alternators have regulators that vary the current in the field winding. Old car regulators did this with three relays (no, I can't remember what each one did -- but each one had a purpose). New car regulators have little black things filled with magic smoke: if the smoke comes out, the regulator don' work no more. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Comparing voltage regulation....
"Existential Angst" wrote in message ... It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? Just curious about the two different strategies. -- EA Car alternators have terrible voltage regulation by themselves; they depend on the battery to hold the voltage steady. If the battery connection momentarily shakes loose this can happen: http://en.wikipedia.org/wiki/Load_dump It's the same process that generates high voltage in a magneto or ignition coil. In the mid 70's I built a load dump simulator for GM, to test the Seville fuel injection computer. After a couple of pulses the solder connecting the heavy wire to the Zener protection diode melted, the wire popped off and the module fried before we could shut off the machine. I think they switched to side terminal batteries as a result. |
Comparing voltage regulation....
"Existential Angst" wrote in message
... It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. EA I have two Coleman generators that use the internal engine governor to regulate speed and voltage. I have to set the no-load voltage to about 135V to get 115V near full load. Usually I adjust the voltage for light loads indoors with a Variac. |
Comparing voltage regulation....
Jim Wilkins wrote:
"Existential Angst" wrote in message ... It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. EA I have two Coleman generators that use the internal engine governor to regulate speed and voltage. I have to set the no-load voltage to about 135V to get 115V near full load. Usually I adjust the voltage for light loads indoors with a Variac. This summer I had a pretty spectacular variac fire. Here in Chicago the utility company has been increasing the line voltage all over as they replace the 80 year overhead wires and transformers. Line voltage for me is now about 126 at off peak times and still over 120 if everybody is cranking the AC. I was curious as to how much this affected power use of stuff like window AC units, so I was running one off a standard 1.4kVA Staco autotransfomer. Days later I smell electrical fire smoke. Semiconductors, PCBs and phenolic insulation all burn with that horrible smell. Sure enough, the variac is glowing orange inside with spewing smoke and on fire. Of course the fuse never blew, but they don't sense fire. It seems the brush loosened up or started to arc/turns shorted/something as that's where the problems stared. The non 1970s versions of these things are made with a glass filled plastic base, including the mounting feet. This deformed, but did not ignite. So watch out with these things, they can get a hot spot for no really good reason and burn up. I always evercise the graphite brush by doing a few full range turns before use, but it din't matter this time. Except for the shipping cost, it would be fun to send it back to Staco and ask for a repair quote. |
Comparing voltage regulation....
On 2012-10-12, Existential Angst wrote:
It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. I doubt that they get anywhere close to 1%. :-) The ones which I have seen have an electromagnet powered from the generated power which draws the carb closed Too much power, it closes the carb a bit to slow down the motor. One major disadvantage to this is is you have anything which cares about the power line frequency (electro-mechanical clocks, old phonographs or reel-to-reel tape recorders) they will show problems (losing/gaining time, incorrect and widely varying pitch, etc.) In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? Well ... first off, the battery acts as a *very* large capacitor, so short term variations are absorbed by this. The frequency does not matter, as it is immediately rectified and turned into DC anyway. In the old regulators, there were relays which sensed current (very heavy wires wound around the core) and voltage (a lot more turns of much finer wire) which adjusted the amount of current fed to the rotor, which has an electro-magnet coil around the shaft, with two cups of interleaving fingers on either side, making pole pieces to generate voltage and current in the stator (frame) windings. The current into the rotor is on a pair of "slip rings" to get the current into the moving part. So -- it simply turns up and down the magnetic field strength on the rotor, to keep the battery at near the proper voltage. (Oh yes, the "proper" voltage is a function of temperature too, so at least some of the relays are fighting a bimetal thermostat to adjust the voltage for the environment in the engine compartment. Just curious about the two different strategies. Two totally different applications. The genset has to produce AC voltage, and ideally cares about the frequency. The alternator only cares about the DC voltage fed to the battery to maintain the charge -- and about not putting *too* much current into the battery, which will boil it dry of electrolyte rather quickly. The generators which preceded the alternators were controlled similarly to the alternators -- except that the voltage was generated in the rotor and rectified by the commutator, and the control voltage was put into the stationary field pieces on the frame. Enjoy, DoN. -- Remove oil spill source from e-mail Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Comparing voltage regulation....
On Fri, 12 Oct 2012 00:53:05 -0500, Tim Wescott
wrote: On Fri, 12 Oct 2012 00:22:18 -0400, Existential Angst wrote: It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? Even older cars (model A) used a single relay (cutout) mounted on top of the generator Just curious about the two different strategies. A not-inverter style genset regulates voltage by varying the current in the field windings. An inverter genset just makes rough DC, and cleans it up with an inverter. Car alternators have regulators that vary the current in the field winding. Old car regulators did this with three relays (no, I can't remember what each one did -- but each one had a purpose). New car regulators have little black things filled with magic smoke: if the smoke comes out, the regulator don' work no more. --- Gerry :-)} London,Canada |
Comparing voltage regulation....
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Comparing voltage regulation....
On Sat, 13 Oct 2012 15:33:33 +1100, John G
wrote: presented the following explanation : On Fri, 12 Oct 2012 00:53:05 -0500, Tim Wescott wrote: On Fri, 12 Oct 2012 00:22:18 -0400, Existential Angst wrote: It seems that a genset regulates voltages by keeping the rpm constant. How is this accomplished? I gather there is some kind of linkage to the carburetor, but it sure seems odd that this can yield 1% regulation.... RPC's can't maintain 1% regulation. In contrast, the rpm of a car alternator varies wildly, but the voltage is kept relatively constant. How was this done before solid state, visavis solid-state? Even older cars (model A) used a single relay (cutout) mounted on top of the generator If you want to go that far back. The single relay was the cut-out to stop the battery dischargeing thru the generator when the engine was stopped and the voltage was adjusted by moving the brush assembly around the commutator.. It's been a while - 50+ years - since I drove a model A but I seem to recall that the electrical system worked quite well. Of course there weren't the loads then that there are today. --- Gerry :-)} London,Canada |
Comparing voltage regulation....
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