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Liam McDuffie
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Problems with an induction Generator

Marathon Electric 5kw induction Generator. 240 V, Single phase with synchronous speed of 1200 rpm

It appears that when connected, the Induction Gen is acting as a Motor. Regardless of the available power to increase the RPM’s higher to generate power, the motor is throttling that down to maintain the 1200 RPM sync speed.

Marathon believes if the connection is taking place at an RPM lower than the slip value (about 1180), then the Induction Gen is being energized as a Motor. If we test this by manually connecting the Generator load above the synchronous speed of 1200, the Gen should energize as a Generator.

So we tested multiple startup procedures with the manual cut in above 1200 RPM to see if we get a steady Gen. and the ability to run at 1250 to make power. The result was that we had the rpms up to 1350~1400 and when we cut in the gen, it immediately brought the rpms down to 1200 and stayed at sync speed – as a motor, and not generating power.

The drive train runs like silk when disconnected from the grid. When connected, the Gen holds the RPM’s @ 1200 and the drive train surges as the Gen (motor) is fighting the drive train to hold RPM’s down.

There does not appear to be any mechanical reason for this. The Gen has run at as a 5kw Gen in the past.

The previous owner has said that the Grid is holding the RPM’s back but that has to be complete bullshit.

Any electrical/engineering types have an idea of what could be wrong that is preventing the generation of power?

Here is the Hydro


Where This dam


Puts water down this Flume


Which turns the 16ft overshot wheel


Which drives the chain to the gearbox


Which turns the Generator


Which feeds power to the grid

 
                    
Posts: 238
Location: AR ~ozark mountain range~zone7a
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Have you tried 'flashing the field'? You might google 'flashing the field', but this article I found seems fairly accurate: http://www.dieselduck.info/machine/03%20electricity/flashing_generator.htm

Your powerhouse is really nice, do you use it for anything else other than electric generation...like sawmill?~~~ just curious.

james beam
 
Bill Bradbury
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Location: Richmond, Utah
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Hello i am or is it Mr. Xanadu?
Are you connecting to a live grid? If so how are you synchronizing outputs?
I haven't done this in quite some time, but it sounds like the gen/grid frequencies are not synchronized.

I love your set up!
 
Liam McDuffie
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Hello Gents,

That Flashing info I have sent to my Son in law the engineer. He'll look at that. Noting else is connected in the way of other equipment. This was designed strictly to generate grid-tied electricity.

In that regard, it is tied to the grid and the previous owner advises to run the Gen rpm at min 1230 rpm with an overspeed safety at 1270 that will auto shut down the flume gate. There are other safetys, underspeed, over-voltage, ect.
 
Bill Bradbury
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Location: Richmond, Utah
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The thing with AC is you must synchronize the wave forms of the gen to the grid or the grid will synch them for you as a motor. It looks like you have an electronic gadget to perform this task, I would look at that and see if it is wired up and operating properly, or if there is a synch function that you use before throwing the cut-in switch.
 
Barry Fitzgerald
Posts: 43
Location: Welland, Ontario, Canada
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I think induction generators are a problem, I would prefer a synchronous permanent magnet type. The only application I have come across using an induction set up was a hoist, it ran as a motor to raise the load and a generator to lower a heavy load. It worked within it's limits but it was 3 phase and if you exceeded the limits on lowering it would run away. I imagine a single phase unit like you have would be a lot worse.
 
Liam McDuffie
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Problem solved - we added more water and voile' got the HP and the generating power @ 4.5KW straight to the grid. That means flashboards on the dam.

The induction generator is best for our needs. The tach has a high and low RPM safety setting that automatically disconnects power and shuts down the water flow and stops the wheel. Similar safeties are in place for over & under voltage and over & under amps.
 
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