Generator Voltage

[truk4u]

I didn't get any comments on this, so I'll try again..

When running on gen, if the loads get real high on one leg and voltage starts down into the teens, the other leg voltage climbs to about 130 volt. The Liberty does this and also my CC did. I talked to Powertech about this and they said that is normal. Just curious why this happens and if anyone else has the same thing happening.

[Jon Wehrenberg]

Tom,

I have zero knowledge about our generators so consider this nothing more than speculation.

Our generators appear to respond to loading. In other words the motor produces power proportional to the load. When no load is on the generator is is using only enough horsepower to maintain a given RPM. As the loads increase its fuel flow and horspower produced increases proportional to the demand.

It is generating power on two legs. If one is heavily loaded, the generator is responding by producing power to meet that demand, but since the other leg is lightly loaded excess power is available on the unused or lightly used leg.

My guess would be if you could load your batteries in a split system so one set is loaded and the other is not, you would see the same thing.

My single alternator charges house and chassis batteries. If we want to play when we get together at PSL I'll bet we find the voltage on the house side which I can easily load is lower than the chassis side. May not be a very good analogy, but i'll bet the results are the same.

Shouldn't you be worrying about your dipstick so you can explain to me how you can maintain a hermetically sealed refrigeration system? You dipstick.

[Kenneth Brewer]

I didn't get any comments on this, so I'll try again..

When running on gen, if the loads get real high on one leg and voltage starts down into the teens, the other leg voltage climbs to about 130 volt. The Liberty does this and also my CC did. I talked to Powertech about this and they said that is normal. Just curious why this happens and if anyone else has the same thing happening.


I didn't get any comments on this, so I'll try again..

When running on gen, if the loads get real high on one leg and voltage starts down into the teens, the other leg voltage climbs to about 130 volt. The Liberty does this and also my CC did. I talked to Powertech about this and they said that is normal. Just curious why this happens and if anyone else has the same thing happening.

Subject to immediate derision and dismissal, and while I cannot call myself an expert in any case, let me see if I can pretend to be one without getting caught). Please; this is a general explanation: In most cases, when we say 'legs' we are actually talking about phases, which is the case with most homes. These phases are separated, usually, into port and starboard sides in the case of RVs, so as to evenly load each phase (or leg). In a/the breaker box, similarly, there are 2 rows which happen to be the two phases separated as well. Where there is a need for 230 volts, a 230vac dryer, for example, or a 230V HVAC system, connection is made between phases (and the reason for the double breakers). Same as in a home.

It won't be possible to evenly load phases exactly, because appliances/outlets are already wired to one side/leg or the other anyway,
and it depends on what is turned on, besides. This is entirely and necessarily normal. The 'off' (or less) loaded phase or leg climbs because the field current is increased to maintain the load voltage on the loaded side, and that is why the 'off' or lightly loaded side/leg voltage climbs somewhat (how much depends on control sophistication, which equals money). Or I could be wrong.

I'm done on this one, too.

[JIM CHALOUPKA]

So Ken, have you ever noticed that imbalance on your bus?

I have also seen it at the mentioned 130v on my bus. I have a Kohler 20,000watt unit.

JIM

[Jerry Winchester]

Ken,

You sound like an expert to me and that's about 90% of what you need to be one on this board.

I like it. Opine some more.

JDUB

[dreamchasers]

I experienced the same situation with my 17.5 generator. I was able to obtain an electronic version (.pdf) of the service manual and Skiff posted it on the site under shared articles.

http://www.prevostownersgroup.com/users/BD83DEF1-CF1D-CEE2-5BF432431EE8B2E3/library/files/PTSMH%20-%2015-17.5-20%20OPERATORS%20MANUAL.pdf

Once the manual is opened (It is a big sucker, 5.37 Meg, so be patient when opening.)go to page 22, look under Voltage Connection, then second paragraph. Apparently, the control point is 240 volts and the two 120 volt levels will fluctuate to maintain this levels.

.................................................. ...........

Although the 120/240-volt connection may also be used when all loads requires only 110 volts, it should be pointed out that this connection, the 240-volts, is regulated and the lightly loaded phase, or line, will deliver a high line to neutral voltage and the heavily loaded phase will deliver a low line to neutral voltage. The heavily loaded line may have such a low voltage that air conditioning will have more difficulty in starting, and long starting lines may overload generator and trip circuit breakers.
.................................................. ..........



Hector

[truk4u]

I got your dipstick tweezer boy.:o

[Kenneth Brewer]

So Ken, have you ever noticed that imbalance on your bus?

I have also seen it at the mentioned 130v on my bus. I have a Kohler 20,000watt unit.

JIM

Yes, I think so. But the two sides never matched exactly anyway, and I wouldn't expect them to. Certainly it occurs when running off the inverters (batteries only, no gen or shore power). I see the voltage pulled down slightly when the water pump is running, or the compressor is on (big draw), wasn't watching when the wife is using the microwave because I stay away until the food is ready then.

We have the 20KW Kohler too.

[garyde]

On Generators, your nuetral wire, going back to the generator, is bonded to the chasis. That is your ground reference. When you have more load on one phase, the return path of voltage and current to the generator is thru the nuetral to chasis ground. There is no earth ground. So, the phase with less load has less current flowing back to ground, consequently higher voltage on that phase. Anyway, I believe its an imbalance of load issue with the fact of having no earth ground.

[Kenneth Brewer]

On Generators, your nuetral wire, going back to the generator, is bonded to the chasis. That is your ground reference. When you have more load on one phase, the return path of voltage and current to the generator is thru the nuetral to chasis ground. There is no earth ground. So, the phase with less load has less current flowing back to ground, consequently higher voltage on that phase. Anyway, I believe its an imbalance of load issue with the fact of having no earth ground.

I would respectfully disagree, for the reason that neutral is same for both sides, meaning the voltage reference is to the neutral: there is a true difference due to the second phase. In any parallel circuit, current flow through any parallel path is at the same voltage. The voltage does not change across loads connected in parallel, by definition. Nodes are nodes. In the case of phases, the voltage difference occurs because of (separately) generated volltage with respect to neutral, of each phase. The voltage at/on each phase is a function of field current, and connected load. Even if there existed a separate ground, it would be for both phases.

As an aside, in Europe, ungrounded systems are much more widely used and encountered for a number of reasons, but with the same result insofar as our discussion.

That's my unsolicited two cents, right or wrong. Thanks.

[jello_jeep]

Even if I disagreed with this, he said it way too intelligently for me to argue with !



I would respectfully disagree, for the reason that neutral is same for both sides, meaning the voltage reference is to the neutral: there is a true difference due to the second phase. In any parallel circuit, current flow through any parallel path is at the same voltage. The voltage does not change across loads connected in parallel, by definition. Nodes are nodes. In the case of phases, the voltage difference occurs because of (separately) generated volltage with respect to neutral, of each phase. The voltage at/on each phase is a function of field current, and connected load. Even if there existed a separate ground, it would be for both phases.

As an aside, in Europe, ungrounded systems are much more widely used and encountered for a number of reasons, but with the same result insofar as our discussion.

That's my unsolicited two cents, right or wrong. Thanks.

[truk4u]

NOW the Juice is flowing!:p