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post #1 of 26 (permalink) Old 01-29-2019, 11:09 AM Thread Starter
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Voltage fluxterations with new generator

Hi guys. I have just bought my first generator, not a expensive one though, Bohler 6500W-e 2800watt. I have only used it for about 20 mins and its only had a light load connected to it so far. But I have noticed the voltage constantly changes, about 10-15 volts up and down where it should be at. Is this normal with portable petrol cheap generators? Thanks


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post #2 of 26 (permalink) Old 01-29-2019, 11:58 AM
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I assume you are generating 230V 50Hz power? Try it with a more substantial load, and also measure the voltage with a digital multi-meter if you have one. The analog meters in generators tend to bounce a bit due to the vibrations.

Also, is the speed of the engine fluctuating? Should be staying very close to 3000 RPM for 50Hz.

Last edited by tabora; 01-29-2019 at 12:10 PM.
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post #3 of 26 (permalink) Old 01-29-2019, 03:57 PM Thread Starter
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Originally Posted by tabora View Post
I assume you are generating 230V 50Hz power? Try it with a more substantial load, and also measure the voltage with a digital multi-meter if you have one. The analog meters in generators tend to bounce a bit due to the vibrations.

Also, is the speed of the engine fluctuating? Should be staying very close to 3000 RPM for 50Hz.
according to the specs its 220v and 50hz, but the labels on the plug socket say 230v and I think the engine speed is 3600rpm. The reason I bought the generator was home backup power for when I had power-cuts. I have all my stuff in my bedroom plugged in to a UPS (uninterrupted power supply), so when I have a powercut I only have to plug in 1 plug into the generator to get everything powered up, about 300-400watts in total. The UPS displays the voltage and hertz and thats what I am going by when I plug the generator into the UPS.. The needle slightly moves back and forth on the generator, but hardly anything. I guess if I didnt have the voltage readout on the UPS I wouldnt be worried at all.

Do you think it just needs to get broken in as I have only used it for about 20mins and had about a max load of about 400watts so far, but during a power-cut I'll be using it more then just to power my bedroom?
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post #4 of 26 (permalink) Old 01-29-2019, 04:12 PM Thread Starter
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Ah yeah the speed of the engine sounds constant not speeding up or slowing down at all.. I was quite impressed when I started it for the first time, all it took was a 1 second turn and hold with the key and it roared into life.. Not bad for a Chinese made generator hey?
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post #5 of 26 (permalink) Old 01-29-2019, 04:20 PM
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according to the specs its 220v and 50hz, but the labels on the plug socket say 230v and I think the engine speed is 3600rpm.
If you're generating 50Hz, the generator speed should be 3000 RPM.
Generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120
50Hz = 3000RPM * 2 Poles / 120
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about 300-400watts in total. The UPS displays the voltage and hertz and thats what I am going by when I plug the generator into the UPS.
That's a VERY light load. Try it with more like 1/2 the rated load and see if it settles down.
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Do you think it just needs to get broken in as I have only used it for about 20mins and had about a max load of about 400watts so far, but during a power-cut I'll be using it more then just to power my bedroom?
Yes, I would run it at least an hour with 1/2 load before trying to determine stability. You can use a bunch of light bulbs to get the load up there, and maybe a small motor like a hand saw or something similar that can be locked in the on position.
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post #6 of 26 (permalink) Old 01-29-2019, 04:49 PM Thread Starter
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I will get it going again the next half decent warmish day I get. and get more of a load plugged into it and see if that makes the voltage more stable, also I will get a light plugged into it aswel to see if the bulb flickers or dims at all..... Also if the generator is cold will that make the voltage not stable, as I havent used the generator longer then about 10mins at a time so far?

This is the spec

  • Maximum Output: 2800W/2.8kW/3.4KVA
  • Voltage Regulator: Automatic voltage regulator
  • Emergency Indicator: Auto breaker overload protection
  • Safety Measures: Low oil automatic shut down
  • Continuous Rated Output: 2600W/2.6kW
  • Rated Voltage: 220V
  • Fuel Tank Capacity: 11 Litres
  • Oil Capacity: 0.6L
  • Oil Type: 10W30 or 10W40
  • Engine Type: Single-Cylinder, 4-Stroke, Air-Cooled, OHV horizontal shaft
  • Engine Output: 8hp
  • Engine displacement: 210cc
  • Starting System: Recoil/Ignition/Electric
  • Continuous Operating Time: 10h
  • Noise Level: 66dB

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post #7 of 26 (permalink) Old 01-29-2019, 09:04 PM
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You said you think it's 3600RPM, but that your UPS also displays Hz. So, was it showing 50 Hz, or 60 Hz? It should be 50 Hz, assuming you're in Europe, or similar.

In my limited experience, the voltage shouldn't be unstable just due to the generator being cold. I never noticed that with mine (different brand), even with a small load. Like tabora said, adding a significant load, like a hair dryer, would be interesting, to see how it reacts.
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post #8 of 26 (permalink) Old 01-29-2019, 10:08 PM Thread Starter
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I dont want to put too much of a load on the generator with it being new, but I really hope the voltage fluctuations clear up on its own. But like I said if I hadnt of seen the digital voltage readout from the UPS I wouldn't of been concerned because the analog voltmeter barely moves on the generator.

The Hz is 50 and I think that goes up and down a bit aswel, I think I have seen it at a max of 52Hz, but I have been more concerned about the voltage.

A totally different question that I dont really understand as I am new to generators... I am guessing that 3000rpm is max speed for a generator and its running at that speed all the time. So where does the power come from when the load increases?

Last edited by speedy2019; 01-29-2019 at 10:48 PM.
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post #9 of 26 (permalink) Old 01-30-2019, 06:31 AM
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Yes, your generator should always be running at 3000 RPM, to produce 50 Hz electricity.

Horsepower = Torque times RPM.

As you put a larger load on the generator, it needs to produce more amps of current. The engine produces more torque (twisting the crankshaft harder), to meet this added demand. And even though the RPMs remain the same, the extra torque means that more power is being produced by the engine.

An analogy would be riding a bicycle, at a constant speed, in a particular gear. How hard you're pushing on the pedals is torque, and how fast the pedals are turning is your RPM.

On level ground, you don't have to push very hard on the pedals. So low torque, times a certain RPM = low power. But then you start to climb a hill, at the same speed. Now you have to push a lot harder on the pedals. So high torque, times the same certain RPM = high power that your legs are putting into the bike. But you're still going the same speed.
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post #10 of 26 (permalink) Old 01-30-2019, 07:53 AM Thread Starter
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Ah that makes sense, I see that you can by a 6hp engine that can power the same amount of watts as my 8hp can, but the 6hp will struggle more then a 8hp engine as the load increases to maintain the 3000rpm.

If I can, today I will get the generator going if its not too cold, as it takes me longer todo stuff because I am in a wheelchair...Thats the reason for the generator being outside my door and all plugged in and ready to go, with the extension lead through the door frame. So I just only have to remove the waterproof cover from the generator and start it up.

Anyway heres a picture of it with the waterproof cover removed, all ready and waiting to go
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File Type: jpg 1q0ego.jpg (113.7 KB, 3 views)

Last edited by speedy2019; 02-06-2019 at 12:29 PM.
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