Lister St 2 Cylinder Diesel Engine For A Generator

samthedog

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I have been considering getting a backup power supply for a while. I currently have a Yanmar diesel generator which is a great machine, however it runs at 3600 RPM, which I think results in a machine that is not a long-term power solution.

I have the chance to buy a Lister 18 HP 2 cylinder diesel engine. I would like to make this the powerplant for a larger generator. The benefit is that the engine's RPM under normal use is 1500 so I would imagine this engine would have a longer service life than my Yanmar.

Anyway, here is the engine here:

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I can likely score it for about 500 USD (the exchange rate is TERRIBLE right now for us in Norway). Anyway, has anyone ever done this kind of project? I think it would be worthwhile since these engines get about 20 000 hours between in-frame rebuilds so realistically this should last me the rest of my life as a back-up. The engine is located near a small fresh water lake so it has not seen salt use and seems too be in pretty good shape.

Opinions are welcome.

Paul.

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mike837go

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There is a reason gensets run at 3,600 rpm. That yields a 60 HZ sine wave output.

You'll need to work the gearing (belts) on a 1,500 rpm engine to get the alternator spinning at 3,600 rpm.

Or connect your Diesel to a 120 or 150 amp truck alternator. Connect the alternator to a 12V deep cycle battery. Then power your shop/home from an inverter.

You're power plant will be much quieter when converting Diesel fuel to electricity. But will be really quiet during those times you don't need to run the engine and just use power from the batteries.

I built a much smaller a rig (3hp gas engine, 30A alternator, 2kw inverter) for my RV for when we camp without hookups.
 

samthedog

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What do you plan on using for a power end?

I plan on using a 1450 RPM 50 HZ 10kW 3 phase motor. This matches nicely with the 1500 RPM of the diesel motor.

There is a reason gensets run at 3,600 rpm. That yields a 60 HZ sine wave output.

You'll need to work the gearing (belts) on a 1,500 rpm engine to get the alternator spinning at 3,600 rpm.

Or connect your Diesel to a 120 or 150 amp truck alternator. Connect the alternator to a 12V deep cycle battery. Then power your shop/home from an inverter.

You're power plant will be much quieter when converting Diesel fuel to electricity. But will be really quiet during those times you don't need to run the engine and just use power from the batteries.

I built a much smaller a rig (3hp gas engine, 30A alternator, 2kw inverter) for my RV for when we camp without hookups.

What about connecting directly to a 1450 RPM 3 phase motor? This would allow me to draw both 3 and single phase and the alternator would be spinning at the correct RPM. I can pick up a1450 RPM 10 kW motor for about $150 that I could connect directly to the engine or put a clutch between them. Power here runs at 50 HZ so this seems like it would work however electrickery is not my strong suite.

Paul.
 

mike837go

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I plan on using a 1450 RPM 50 HZ 10kW 3 phase motor. This matches nicely with the 1500 RPM of the diesel motor.
What about connecting directly to a 1450 RPM 3 phase motor? This would allow me to draw both 3 and single phase and the alternator would be spinning at the correct RPM. I can pick up a1450 RPM 10 kW motor for about $150 that I could connect directly to the engine or put a clutch between them. Power here runs at 50 HZ so this seems like it would work however electrickery is not my strong suite.
Paul.

I've never tried to convert a motor to an alternator. However, I have found that spinning a permanent magnet DC motor will produce DC power.

Now to some reality and let the more knowledgeable folks chime in.

In order to generate electrical power, you have to have a wire moving through a magnetic field (generator) or a magnetic field move past a wire (alternator). Just spinning a field wound motor will generally not produce significant amounts of electricity. You need to pump some serious quantities of DC into the fields while spinning the armature at the correct speed to produce the proper frequency of AC.

If my understanding of 3-phase motors is correct (and I'm pretty sure it isn't) you'll have to totally separate the fields from the brushes and include some heavy-duty rectifiers...
 

RJSakowski

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A 150 amp automotive alternator will provide less than 15 amps at 120 v.a.c. It is fine for low power applications but not really suitable for whole house backup. Also a typical 12v. deep cycle battery has a storage capacity of about 1 kwh. Some high end batteries will double that capacity but at much higher cost. One the other hand, a sine wave inverter can provide clean, well regulated frequency stable power for sensitive equipment.
 

samthedog

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The motor I would use as the generator would be a 3 phase, AC motor. I wouldn't use DC for this application.

Paul.
 

mike837go

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A 150 amp automotive alternator will provide less than 15 amps at 120 v.a.c. It is fine for low power applications but not really suitable for whole house backup. Also a typical 12v. deep cycle battery has a storage capacity of about 1 kwh. Some high end batteries will double that capacity but at much higher cost. One the other hand, a sine wave inverter can provide clean, well regulated frequency stable power for sensitive equipment.

You are absolutely correct about the momentary capacity of this set up. Your main limitation is how much inverter you can afford. With the engine running and the battery charged you could go as high as 2kw for a several minutes.

What I described would run a refrigerator, some lights and a TV for when the power grid goes out. You won't live 'normally' but it'll keep the food fresh, get the news and you'll have lights when the sun goes down. Out in the field, it'll cover one person's use of power tools.


The motor I would use as the generator would be a 3 phase, AC motor. I wouldn't use DC for this application.
Paul.

Even though an alternator produces AC power, internally it needs DC in the fields to produce the magnetic field.

If you disassemble your existing genset, you will find the output of the stationary windings (the "stator") is connected to a rectifier that sends DC into the rotating armature (the "rotor") via a pair of brushes and slip rings. By spinning the stable magnetic field within the stator, AC is induced at the frequency the rotor is spun at. There may be an adjustable voltage regulator associated with the rectifier. By varying the voltage in the rotor, the AC output voltage can be adjusted. The throttle (governor) is adjusted to get the correct frequency.

(Unless you have a brushless design, then there will be a large capacitor connected to 1/2 the output of the stator, an extra winding on the rotor and a rectifier between the two sets of windings on the rotor. Frequency is still engine speed dependent, but the output voltage is controlled by the size of the capacitor.)
 

JimDawson

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I may be missing something here, but how the heck do you turn a 3 phase motor into an alternator? You have to generate the magnetic field some way and a standard armature has no windings to create the field. Alternators have a wound rotor that a DC current is applied to, thus generating the magnetic field.

You could use a permanent magnet or wound field DC motor and an inverter. A brushless DC motor will output 3 phase also, they have a permanent magnet rotor.

.
.
 

mike837go

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I may be missing something here, but how the heck do you turn a 3 phase motor into an alternator? You have to generate the magnetic field some way and a standard armature has no windings to create the field. Alternators have a wound rotor that a DC current is applied to, thus generating the magnetic field.

You could use a permanent magnet or wound field DC motor and an inverter. A brushless DC motor will output 3 phase also, they have a permanent magnet rotor.
.

You're not missing anything. My knowledge of 3-phase motors falls somewhere between "not much" and "zero". A shunt-wound single phase motor can be modified into a very inefficient generator if you want to bother...

I am, however, quite familiar with how generators and alternators work. And what it takes to fix them when they don't.

Technically, an automotive alternator produces very high frequency 3-phase AC. 6 diodes turns that into something close enough to DC to charge the battery, operate the lights and run all of the electronics.
 
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