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Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

Purposely running a 3600rpm generator at lower speed


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  #11  
Old 11-03-2018, 09:57:57 AM
DustyBar DustyBar is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

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Originally Posted by Thaumaturge View Post
Watts = Volts x Amps. If 120 = 1000W then 112 = ~877W)
Doc
Actually it will be something less than 877 I think. From the rated wattage you can calculate the heater's resistance. Then apply that resistance to the lower voltage and I'm pretty sure it will be less than 877. Sorry I'm not sure of the formula but from experience I've seen that. Not that it matters...just a note that is the way it works.
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Old 11-03-2018, 12:08:24 PM
Fred M. Fred M. is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

I think the problem with running the generator slow, is that the power available may be proportional to the square of the speed. If this is correct, running a 1000 Watt generator at half speed, you would only have 250 Watts available.

For a specific load, you could probably find an ideal speed, so power available is equal to the demand.

Fred
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Old 11-03-2018, 02:35:43 PM
gnucklehead gnucklehead is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

Dropping to 3200RPM shouldn't be a problem for the engine.. what voltage comes out of it depends on the type of voltage regulation.

This is the perfect use for a smaller generator, say 3HP Briggs or Tecumseh, or dinky 80cc Champion, just stick to a 4-stroke.. cheap, lightweight, quiet, expendable.. For teeny-weeny engines, 3600RPM really isn't that big of a problem
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Old 11-03-2018, 03:04:17 PM
Andrew Mackey Andrew Mackey is offline
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Unhappy Re: Purposely running a 3600rpm generator at lower speed

Engine cooling should not be a problem at lower speeds,, nor should be oiling. Starting an air cooled splash engine in cold weather is. You will need to use a 5W-30 or even a 0W-20 if extremely cold, to prevent bearing starvation. SAE 30 will not work in a splash system under 40F. Certainly, running the gen end at lower speeds will cause cooling issues, especially if loaded. As noted, running at lower speeds will lower voltage and available amps. The heater will not put out the rated heat either, with the reduced power. In that case, reducing speed of the engine is self defeating - the block will not be heated as needed, and the gen set will not do as designed - make enough power to make the heater work as designed.
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Old 11-07-2018, 10:46:44 PM
turtmaster turtmaster is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

If the voltage is a bit too low at 3200rpm, why not use a ~24v ac step down transformer wired in "boost" configuration.
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Old 11-07-2018, 11:02:05 PM
Newoldstock Newoldstock is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

Just make sure there are no motors involved.

Years back I remember the parking lot at Pamour mine had big warning signs not to use a car heater only plug in your block heater.
But up in the near north there was always someone trying to run a 60hz interior car heater on 25 cycle and things would go wrong and burn up
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  #17  
Old 01-09-2019, 04:23:32 PM
csareb csareb is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

You can definitely safety idle it down to 3000 rpm for a resistance load like a heater. The exact same engine is used on generators sold for 50hz countries and those run at 3000rpm for 40hz. Granted the generator head is wired different for 240v 220v etc but the engine is identical. You will have low voltage at 50hz but the engine will be fine.
I wouldn't go lower than that for cooling and oiling reasons
Set governor for 50.0hz with. A 1500w heater connected. That way it will have headroom to run his 1000w heater without getting under 50hz or 3000rpm
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Old 01-10-2019, 05:18:53 AM
M.Canute M.Canute is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

Quote:
Originally Posted by Andrew Mackey View Post
Engine cooling should not be a problem at lower speeds,, nor should be oiling. Starting an air cooled splash engine in cold weather is. You will need to use a 5W-30 or even a 0W-20 if extremely cold, to prevent bearing starvation. SAE 30 will not work in a splash system under 40F. Certainly, running the gen end at lower speeds will cause cooling issues, especially if loaded. As noted, running at lower speeds will lower voltage and available amps. The heater will not put out the rated heat either, with the reduced power. In that case, reducing speed of the engine is self defeating - the block will not be heated as needed, and the gen set will not do as designed - make enough power to make the heater work as designed.
You are certainly correct about what oil viscosity to use.

Years ago I had a small Toro Snow Hound snow blower and one not too cold winter day I decided I should do an oil change on it so after using it for a half hour I whipped it inside my shop and pulled the drain plug. I was expecting hot oil but to my surprise it was just lukewarm and you know how cool it had to be to feel lukewarm after I'd been outside blowing snow! This was a replacement B&S engine designed for operating in the summer months so it had the normal type of cooling fins you'd expect to see on a small air cooled engine, but because they were designed to cool an engine on a hot summer day, they actually over cooled the engine on a cool winter day. Long story short, I think you won't have to worry about a generator engine overheating in the winter time but you might have to worry about it over cooling!
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  #19  
Old 01-11-2019, 12:30:04 AM
ulgydog56 ulgydog56 is online now
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Default Re: Purposely running a 3600rpm generator at lower speed

don' forget the dynamo they are also rated to turn at designed speed, you can burn it out running it at lower speed, stay within spec, that's how it was engineered...….
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  #20  
Old 01-11-2019, 01:03:09 AM
Vanman Vanman is offline
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Default Re: Purposely running a 3600rpm generator at lower speed

If it has no AVR it can be run at any slower speed you like. Too slow and it won't build up though. 1800 rpm would probably be too slow, but I'd bet it would work beautifully at ~2400 rpm.
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