remagnetizing an alternator 1

[hjherby]

Hello new on here, I m a marine engineer and deal with diesel engins ,steelwork ,etc.And now a friend has asked me to remagnetize his hydraulic turbine generator,it was left standing for a long time and now will not produce any power.
We are looking for 220volts @ 50 Hz a unhelpfull local electrical engineer told him " just put 6volts DC to it "
where?
howlong for?
I dont want to go down the hole and start flashing my car battery around in the dark!!!!!!!!!!!!!!

I will be very gratefull for any advice

 

[waross]

Down the hole?? Are you sure that it's turning?
There may be more than one type of PM alternator. If you have internal diodes possibly nothing will happen when you connect the six volt battery. The next thing to do will be to reverse the polarity. THEN the internal diodes will fry.
The old automotive generators sometimes needed a "flash" to establish some residual magnetism before they would generate. Time was that the residual magnetism in automotive alternators was not sufficient for them to bootstrap them selves. They needed some voltage to the field (controlled by the voltage regulator) before they would generate.
Neither of them had permanent magnets.
Permanent magnets tend to be, well, PERMANENT.
Lawn mowers, outboard motors and chain saws may sit for years without loosing the magnetism in the permanent magnets in the magnetos or in the charging circuits or starters if so equipped. I recently started up a riding mower that had been sitting for about 6 or 7 years. No problem with the magnetism in either the magneto or the starter.
That's the first answer, but we need a lot more information before guessing at the second answer.
Got any ratings?
A diagram?
A make and model number?

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

 

[hjherby]

Thankyou for your reply
Yes it is turning and the water flow is good.I have a photo of the connections on top of the alternator I will post it tomorrow night(04/02/09).
hopefully with some ratings etc........

herby

 

[wbd]

I have several old hydro turbines with Basler SSE type static exciters with no field flashing. When we do lose the fields, we will flash the field using a 12 volt car battery.

My units are 2300V, 800 kW, 60hz units.

 

[waross]

If you have an AVR be very careful flashing the field. The magic smoke in AVRs is often blue.

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

 

[powerwagon75]

Never flash an excitor field without having diode polarity protection on your battery leads.

Its preferred to flash a field without the AVR in-circuit; but if it is the diodes are definitely required, or as waross said............

eric

 

[hjherby]

Sorry everybody
I went to look at the machine today and listend to the long and complicated story of how and why it has not run for three years.
But it did not quite ad up so I started it just to see what would hapen.
Sparks flew from the printed circuit on top,so we dried that then under load the drive belt sliped and tried to come off,so we tightened it and realined the alternator.
It is now producing 10 Amps and runnig smoothly.

Thankyou for all the help.

 

[waross]

Thanks for the update.

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

 

[edison123]

LPS to the OP for caring to report back.