Posted: 11/6/2013 11:01:06 AM EDT
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After reading ARJedi's great thread about his champion 4698 generator (here) I pulled the trigger and bought one. I wanted a backup generator to my bigger generac XG7000, and had my eye on this little champion for a while. I'm thinking that I can run it during off-hours to save a bit of gas (such as overnight when the heat needs to stay on, etc).
(some background...we lost power here on long island for two extended periods in the last 3 years...once after Hurricane Irene, and again after Sandy. I think we were out for a cumulative period of about 18 days). I brought the generator home from a tractor supply near my InLaws, and broke it in with a low load for 5 hours. Then, I decided to try plugging it into my house transfer panel. While I was running around cycling loads on and off, I connected a meter to an outlet and noticed that the voltage on one of the 240 legs of the the Champion dropped as the overall demand approached 3000-3500 watts (one leg dropped to around 105 volts, the other held close to 120). I posted a question regarding this in AR Jedi's above thread, and called Champion as well. The general consensus was everyone through my results weren't too bad or outside of the norm. Being obsessive compulsive, and wanting to expose my 10 year old to some basic electrical theories and wiring, I purchased two volt/amp meters and a frequency meter. I wired a L14-30 male plug up to two 12 gauge lines that terminated in junction boxes with outlets, with the hot on each monitored by the amp meter: 
I ran the generator for a bit, and made sure the meters were working (they were...I double checked everything with a separate meter): 
The above readings are a little odd, but I know that generators tend to give a better output under load. I put equal 1500 watt loads (heaters) on each leg. This is what I got: 
Not bad at all. Not a high load, but the voltage is great and better than it was with no-load or when it was plugged into my house. I tried to load down only one leg (recreating what could happen when it's plugged into the house), and that's when things got a bit odd: 
That low voltage concerns me, and looks very similar to the scenario that I ran into when it was connected to my house. As you can see, the actual load is only 900 watts (the heater was on high, so it should have been closer to 1500) which is only about 50% of that leg's ability. So...my question to the more electrically experienced ARFCommers=is this a normal result, or would I need to worry about connecting this to my house? |
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101.8 Hz would bother me more than anything else. The thing is that to get that high of a frequency would require over speeding the motor by a lot and it would probably kill the motor. So I do not believe the reading.
That low voltage concerns me, and looks very similar to the scenario that I ran into when it was connected to my house. As you can see, the actual load is only 900 watts (the heater was on high, so it should have been closer to 1500) which is only about 50% of that leg's ability. A 1500 W heater rated at 125 V run at 101 V would put out about 980 W in a perfect world. It is not that far off. |
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101.8 Hz would bother me more than anything else. The thing is that to get that high of a frequency would require over speeding the motor by a lot and it would probably kill the motor. So I do not believe the reading. The odd thing is the generator's motor is turning at about 3700 rpm (at no load), which should equate to 61-62 Hz. I used a separate tester, and got the same reading at no load. Once a load is applied (however small it may be), the frequency jumps right to the correct number. |
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The odd thing is the generator's motor is turning at about 3700 rpm (at no load), which should equate to 61-62 Hz. I used a separate tester, and got the same reading at no load. Once a load is applied (however small it may be), the frequency jumps right to the correct number. Quoted:
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101.8 Hz would bother me more than anything else. The thing is that to get that high of a frequency would require over speeding the motor by a lot and it would probably kill the motor. So I do not believe the reading. The odd thing is the generator's motor is turning at about 3700 rpm (at no load), which should equate to 61-62 Hz. I used a separate tester, and got the same reading at no load. Once a load is applied (however small it may be), the frequency jumps right to the correct number. As others may have mentioned, harmonics, etc in unloaded sources and inexpensive meters may cause unusual readings. |
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I'm certainly not one of the experts, but until they get here I'll give you my $.02. I think those numbers are suspect. When you got the ~100Hz reading, then plugged in a load, did the tone/pitch of the generator change significantly? I think the frequency of the electricity produced by any direct coupled generator is directly related to the engine's RPM's. If my math is right, to get 100Hz you're engine would have to have been running at 6000 rpm's -- and I think you'd notice that! Also, you're 900W load should've in theory been 7.5A @ 120V. 100V seems really low to me. A resistive load like a heater might not care, but I'd be worried about plugging my refrigerator into it if that's how it reacted. Did you try plugging it into the other leg and see what happened to the numbers? What happened when you plugged both in -- did the voltage balance back out? What other meter did you use to verify the results? If you have a kill-a-watt, it'll also provide the same info per device. you could use it to verify your new meter's data. |
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I think those numbers are suspect. When you got the ~100Hz reading, then plugged in a load, did the tone/pitch of the generator change significantly? I think the frequency of the electricity produced by any direct coupled generator is directly related to the engine's RPM's. If my math is right, to get 100Hz you're engine would have to have been running at 6000 rpm's -- and I think you'd notice that! Quoted:
I think those numbers are suspect. When you got the ~100Hz reading, then plugged in a load, did the tone/pitch of the generator change significantly? I think the frequency of the electricity produced by any direct coupled generator is directly related to the engine's RPM's. If my math is right, to get 100Hz you're engine would have to have been running at 6000 rpm's -- and I think you'd notice that! I have an hour meter and tach on the generator (after market install). The engine was running at 3700 rpm, when I was getting the 100mhz reading. I tend to agree EXPY37's above post...the meters aren't reading the no-load frequency correctly. Quoted:
What other meter did you use to verify the results? If you have a kill-a-watt, it'll also provide the same info per device. you could use it to verify your new meter's data. I have a pretty nice digital auto-ranging multimeter. I have no reason to doubt that one's readings. |
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Also, you're 900W load should've in theory been 7.5A @ 120V. 100V seems really low to me. A resistive load like a heater might not care, but I'd be worried about plugging my refrigerator into it if that's how it reacted. Did you try plugging it into the other leg and see what happened to the numbers? What happened when you plugged both in -- did the voltage balance back out? When I put a load on the other leg, everything seemed to balance again. Skibane broke down the schematics of this generator for me (on ARJedi's thread) and found that the AVR is only on one leg. That's probably why the one side holds voltage while the other sags. I ran out of time (and space heaters) today, but my next test will be to bring the load a little higher and see what happens with the readings. |
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I'm in the midst at the moment, ackshully, of wiring a 6kw light tower with 2 120 windings thru an auto transformer to eliminate exactly what you are dealing with.
Unbalanced loading on the two phases. Won't run a medium 120 vac compressor, but now, boom, no sweat! My posts detail what you're running into vis-Ã -vis running a heavy load on one of the 'phases'. Combining 2 phases at 240 into the transformer and having the benefit of the total power avail out of the genny at 120 vac. I can't find it right now and have to get back on the job, maybe someone saw it. |
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When I put a load on the other leg, everything seemed to balance again. Skibane broke down the schematics of this generator for me (on ARJedi's thread) and found that the AVR is only on one leg. That's probably why the one side holds voltage while the other sags. i don't think that is the case. the AVR module is using a portion of one leg (the center to the tap) of the AC output as the input part of the feedback control loop. as the AC output voltage decreases with greater load, or increases with less load, the AVR module adjusts the excitation voltage accordingly. the output voltage of the main windings (plural) is a function of the applied field and excitation voltages. the AVR is not simply managing the voltage on one leg of the split phase system. all of the above is just hypothesis. i design optical telecom gear for a living, not AC power generators. 
ar-jedi 
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there is a switch on this model generator to parallel the two main windings -- and the result is 120Vac only at twice the split phase 240Vac current. ar-jedi Quoted:
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Unbalanced loading on the two phases. there is a switch on this model generator to parallel the two main windings -- and the result is 120Vac only at twice the split phase 240Vac current. ar-jedi I went through every link you had posted in the other thread regarding converting the RVoutput to L14-30. Unfortunately, I'm too chicken to try making that work with this generator and my 240 volt transfer switch 
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I went through every link you had posted in the other thread regarding converting the RVoutput to L14-30. Unfortunately, I'm too chicken to try making that work with this generator and my 240 volt transfer switch Quoted:
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Unbalanced loading on the two phases. there is a switch on this model generator to parallel the two main windings -- and the result is 120Vac only at twice the split phase 240Vac current. ar-jedi I went through every link you had posted in the other thread regarding converting the RVoutput to L14-30. Unfortunately, I'm too chicken to try making that work with this generator and my 240 volt transfer switch Now there's something you need to do something abt! 
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there is a switch on this model generator to parallel the two main windings -- and the result is 120Vac only at twice the split phase 240Vac current. ar-jedi Quoted:
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Unbalanced loading on the two phases. there is a switch on this model generator to parallel the two main windings -- and the result is 120Vac only at twice the split phase 240Vac current. ar-jedi Very aware of this on your genny. |