Polarizing generator

[kazek]

Hi.i have RK-28 Johnson 40 hp electromatic with generator.ammeter gauge is not showing discharge or charge.is that means that generator needs to be polarized.what are the steps of that .how to test charging components.thanks

 

[Cap'n Chaos]

Re: Polarizing generator

If you were to take the belt off and spin the generator (with a high speed drill) you should be able to detect an output voltage on a multimeter.

I've tested car alternators and generators using this method...it's very "shadetree mechanic" but it tells you what you need to know.

 

[kazek]

Re: Polarizing generator

Sounds simple,I will try that.i just finished putting generator back after disassembly.brushes are in good condition and points are working.when I connect field terminal to + 12v and ground to housing,generator spins.slowly but spins.is that normal???

 

[boobie]

Re: Polarizing generator

Put the 12v + to the armature terminal once and ground the field to the hsg and see what happens.

 

[Joe Reeves]

Re: Polarizing generator

A quick test........ Ground the field terminal. Connect a voltmeter between the Armature terminal and the generator ground. Hold the generator pulley up against a wire brush of a grind wheel. That'll show the actual output voltage.

No, the wire brush won't damage the pulley.

 

[F_R]

Re: Polarizing generator

The proper way to bench test a generator:
Ground the field terminal (the smaller one) to generator body
Ground the generator to battery (-)
Connect armature terminal (the larger one) to battery (+)

Generator should run slowly like a motor. If it does, it is working.

This operation polarizes the generator at the same time.

 

[kazek]

Re: Polarizing generator

Thanks for replies.generator turns out to be fine,as per most tests.sorry joe i don't have wire brush,I used drill @ 2800 and with analog multimeter set to high(30v) connected to battery i got steady 12.5v.no mater if i turned GEN or not.ammeter did not record anything eather.does it mean that my regulator is bad or RPM are too low on drill and its time to invest in wire brush and try again.why ammeter -20 + 20 amps would not move?

 

[Don Hansen]

Re: Polarizing generator

Sounds simple,I will try that.i just finished putting generator back after disassembly.brushes are in good condition and points are working.when I connect field terminal to + 12v and ground to housing,generator spins.slowly but spins.is that normal???

I've seen setups where the generator was also the starter. Even though it was designed to be that way it made a lousy starter. Too weak.

DLH

 

[F_R]

Re: Polarizing generator

Thanks for replies.generator turns out to be fine,as per most tests.sorry joe i don't have wire brush,I used drill @ 2800 and with analog multimeter set to high(30v) connected to battery i got steady 12.5v.no mater if i turned GEN or not.ammeter did not record anything eather.does it mean that my regulator is bad or RPM are too low on drill and its time to invest in wire brush and try again.why ammeter -20 + 20 amps would not move?

You need to understand the system. That is a DC generator system, and they do not charge at idle. In fact, the motor needs to be running at least 1500 RPM or better to develop enough generator output to close the cut-out relay in the voltage regulator. Because of the belt pulley size ratio, the generator is turning much faster than the motor flywheel. What I'm saying is that a drill is nowhere near fast enough to close the relay and charge the battery. Once it is running fast enough, the regulator limits the voltage to about 14V and the current output to 10 amps. So......the ammeter should read 10 amps if the battery is discharged enough to need it. Otherwise the amps will be whatever the battery and regulator agree it should be at the moment, 10 amps maximum.

Before somebody comments on the 10 amps, remember most newer motors with standard alternators only put out 5 or 6 amps. But thei will charge a bit at idle.

 

[kazek]

Re: Polarizing generator

Point taken.i will keep that in mind.thank you