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Topics - vwbeamer

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Generators / Variable speed Generators. good idea?
« on: October 08, 2007, 05:59:19 AM »

Great forum. I have an idea to throw out and see how other feel about it.

I have a chance to get an Isuzu 1.8l diesel engine and transmission for $100 bucks. It comes from a 82 model rear wheel drive US spec Isuzu I-Mark.
I want to make a 25K gen set using a ST head. My calculation say i will need about 45-50hp.

Problem is to make enough Hp to drive a 25 k gen set, the motor must turn more then 1800 rpm. It's rated at 52 hp at 5000rpm, kind of high for a diesel.
I believe it makes about 75ft-lbs of torque at 2000 rpm. I can't really find much info on the motor. But based on what I've read, about 12-15 k gen head is the most I can use if the engine is direct coupled and ran at 1800rpm.

If i increase the engine rpm by using a belt and two pulleys, I have problems also. If the Gen set is lightly loaded, I will lose economy by running the motor at high rpm. I'm also worried that the engine will wet load when delivering low demands. plus i will not get full power unless I run the engine at rpm all the time. This of course is going to make more noise and shorten engine life.

My thought was to keep the transmission. For light loads, I could use 4th or 5th gear to reduce engine rpm.
When the full 25k is needed, I could use 2nd or 3rd gear to increase engine rpm.

The problem then of course becames the governor because most are designed to regulate engine rpm., then I found an electronic governor, that regulates the engine speed based on output frequency. It keeps the gen head turning at 60 hz, regardless of engine speed.

"The FROG is a generator governor and a 'generator output display panel' in the same module. It regulates the frequency of the generator by adjusting the engine speed. This controller will automatically maintain a steady speed regardless of the engine or generator load."

I was looking at model #FRA103-A00. There is a PDF file you can download with specs and instructions.

Will allow me to direct couple gen set, no need for belts to get the proper ratio I need
Will allow me to run engine at 1800 rpm or lower rpm for light loads, improving economy.
Will save money for custom pulleys to fit Isuzu engine and st head..

Some disadvantages-
Parasitic Power loss in Transmission
Longer, more complex package
Must manually shift gears to match load.( wonder if an automatic tranny will work better?)
Cost of the frog

Do you think this is a workable plan?

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