Generator regulation question

[dave313]

Hello all, I have a question about a brushless single phase AC generator.

I acquired an old light tower with a 240 vac 8 kw Dyna generator. The voltage "regulator" consisted of a tap off the windings thru a diode and then into the field stator winding. The stator resistance is about 3 ohms and I think it runs around 12 vdc or so.

I installed a SX-460 AVR with the appropriate series resistor to meet the minimum 15 ohm required by the regulator. The AVR puts out 4 amps continuous and 6 amps for 10 seconds.

The problem I have run into is that after a 4-5 kw load the field current seems to be maxing out around 4 amps and the regulator starts to current limit dropping the output voltage as the load increases.

My options are to get a larger AVR (some have a 4 ohm minimum and output 7-16 amps) or having the field stator rewound to get 10-15 ohms that most of these regulators seem to like.

Since I do not know what the max field current is on the stator, a larger AVR might burn out the field. Also if I rewind the stator I do not know what "surprises" may be in store for me.

Having little experience with this kind if generator I would appreciate any recommendations or advice you can offer.

Thank you

 

[iceworm]

"The field winding ends up providing around 12 vdc to the field stator.
That surprises me. It looks like the two windings are in series.

You're welcome, even though I really didn't add anything you didn't already know. Thanks for letting me look over your shoulder.

One of the reasons I'm interested is I have been contemplating a one-lung Listeroid, generator with heat recovery. Listeroid driven generators are not available in the US anymore, so I'll be building it up. Now if I could just find a 12pole, 4kw brushless generator end I could afford. Or, maybe a 5hp wound rotor, 8 pole, induction motor, that I could connect as a Double Fed Induction Alternator - Hey, It works during my electroshock therapy dreams.

I'm off to work for six weeks or so. I'll check in when I get back to see how it went.

ice

Harmless flakes working together can unleash an avalanche of destruction

 

[waross]

Hi ice. Belt drive is doable for 4 KW/5 HP.
That should make generator selection easier.
Another option is an agricultural, PTO drive generator. Typically 540 RPM in with gearing to spin the alternator at 1800 RPM.
These come up for sale fairly cheap at farm auctions. Most are more than 4 KW but as long as you keep the load within the capacity of the prime mover that should be no problem if the price is right.

Bill
--------------------
"Why not the best?"
Jimmy Carter