In Reply to: Re: Generator not charging on 6 V 49 8N posted by raven on June 05, 2013 at 10:01:20:
"So ,if the generator is polarized INCORRECTLY and....". When gen speed is increasing to the point that the cut out voltage coil pulls in relay & contacts close, then you have a generator putting out a positive and trying to force it into a negative battery.
A collision! Initially an abnormally high current. From here on, a bit of chance is involved & the same events will not likely occur each & every time. Best, is that the battery will immediately overpower the generator, generator will now be correctly polarized, the cut out points escape being burned/welded closed, wiring not damaged, and everyone lives happily ever after. Worse; cut out tried to close, cut out current coil sees reverse current, so cut out tries to open, then tries to close, tries to open, etc. as contacts chatter and arc until heat destroys them and if they end up welded closed and you walk away disgusted then the battery discharges into the generator and the current will be high in the low resistance armature & the heat may ruin the wiring/windings insulation (maybe not if lucky). Field is heated too, but much less, as resistance is perhaps 5X higher, thus 1/5 th the heat.
"Also, is there a procedure to check if the generator is polarized correctly?" On the bench, connect a voltmeter (set to low voltage range such as 1v) to the ARM of generator, jumper FIELD to gen ground. This will be much easier to see on analog voltmeter! Use hand to spin in normal direction of rotation and you will see minor deflection of meter. If battery on tractor is POS gnd, the generator needs NEG output. If voltmeter deflected NEG when you spun it, then it is correctly polarized.
"Seems like there is on;y a 25% chance on a two terminal generator to get it correct.
The FO-4 manual states connect to the battery terminal but does not indicate whether to use + or -. The procedure is based on a + grd."
Don't see 25%, but that isn't important. "Does not indicate = or -". It really ought to be obvious that you connect to the ungrounded battery terminal. Not a darn thing is going to happen if you connect a grounded generator to the grounded battery terminal!
"Believe the the manual polarization procedure on page 54 is based on the so called A type generator, battery & VR all connected and not bench polarized." Yes.
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