Diesel generator fabrication

mianrehman60

New member
I am new to smokstak forum. Thanks for allowing me to become a member.
I need some guidance in fabricating a diesel generator. The generator is being put together in my farm garage. The prime mover is a used diesel toyota engine and the generator is 10 KW. Coupling is through a flexible universal joint. Question that I have is: should i use a additional rotating weight or the weight of the engine flywheel is adequate. Any help will be much appreciated. https://www.smokstak.com/forum/images/smilies/smile.gif
 

BTPost

Moderator
One question that might need some serious attention, if this was a vehicle Engine is, What are you going to do for a Governor? Vehicle Engines don't usually have a Constant Speed Governor, and that will be needed for a Genset Application...
 

mianrehman60

New member
appreciate response. I think you are correct. The response will be delayed. The added weight will make the system even worst as there is no governor to rev up the prime mover upon load. However this is crude setup only for light load i.e. lighting etc. which remains constant. The question arose when the fabricator wanted to add rotating weight to which i disagreed.
 

mianrehman60

New member
BT post Hi. You are correct vehicles engines are not designed to be used for such an application as there max HP is at a much higher RPM than what is required for generator application 1500 - 1800 RPM and the governor situation as you mentioned. However our is a crude set up for light load which more or less will stay constant. And the engine used is off a vehicle not the best option. The question arose as the fabricator wanted to add a rotating weight to which I had my reservations.
 

Vanman

Subscriber
A constant speed generator can only benefit from greater rotating mass. A governor will be required though, unless the load truly is nearly constant. Auto engines are just fine as generator engines, so long as they are run nice and slow for durability and the load requirements are within the engine’s hp capability at the particular speed and the timing and so forth is optimized for the speed. Lots of OEM generator set manufacturers have used auto engines throughout history and to this day.

Keith
 

Harvey Teal

Subscriber
Direct coupling may not be your best option. A belt drive will give you the flexibility to match the genhead to the engine’s best speed/torque.
 

mianrehman60

New member
Vanham, thanks for the reply. Trying to understand, a constant speed generator will be one with no switching load but a continuous load. While our load is a mixture of continuous and switching loads i.e. (lights, refrigeator & A/C), but why would a continuous/constant load benefit from a additional rotating mass. Is the built-in rotating mass of the system i.e. the armature of the generator and the flywheel of the prime mover not adequate ? Regarding the prime mover I have some reservation in using a vehicle engine as its optimal hp is produced at a higher RPM and where in gen application it is limited to 1500-1800 RPM using direct coupling. The other option is as Harvey Teal mentioned to use a belt drive where the prime mover RPM can be increased producing higher HP.
 

mianrehman60

New member
Harvey, Thanks for the info. While we have decided to direct couple the gen i agree that for optimum use of the vehicle engine a belt drive will be more efficient.
 

Birken Vogt

Email NOT Working
I think that 1800 RPM is a good choice for an automotive engine used in a generator application. We are trying to generate power, not win a race. My car runs about 1800 RPM all the time at cruising speed which is kind of what we want.
 

Vanman

Subscriber
Assuming you’re using a four pole ac generator and want 60 cycle current, it must run at 1800 rpm at all times, regardless of the load amount. The engine governor accomplishes this in large part, but it’s response time to changing load has limitations. The inertia of the rotating assembly smooths out sudden changes in load, giving time for the governor to respond, thus avoiding large changes in speed, and therefore frequency. If you’re running an A/C unit, you will need an engine governor, as the difference in load on the engine between A/C running, off, and starting will be substantial. I would imagine that the generator, engine, and it’s flywheel all together would be adequate, in conjunction with a good governor.
 

Tracy T

Subscriber
to put it in simple terms the added rotating weight is basically a flywheel storing enegery. look at a hit and miss engine same princapal. those flywheels cary the engine thru the load until the engine needs to fire again. they will smooth the transition between no load and load.
 
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