Voltage leak to chassis from 48v series motor

[Golfdog]

Its a 1997 DS series cart that suddenly gave up the ghost. It appears that the speed controller has gone but the issue I am grappling with is that the motor is leaking voltage to the chassis. I disconnected motor terminals A2 S2 and S1 and left A1 connected to the B+ on the controller. With a multimeter (-) probe on controller B- and the (+) probe on the chassis I get 15v. When I disconnect the A1 on the motor and do the same probe there is 0v. I stripped the motor, blew out the inners with compressed air to get rid of the carbon dust and put in new terminal insulators. A continuity test of all four terminals to the motor housing shows no continuity. I test ran the motor connecting it directly to 2 batteries and it ran fine. The 15v leak is still there, anyone have any ideas on what to do next.

[Stevec3201]

Originally Posted by Golfdog

Its a 1997 DS series cart that suddenly gave up the ghost. It appears that the speed controller has gone but the issue I am grappling with is that the motor is leaking voltage to the chassis. I disconnected motor terminals A2 S2 and S1 and left A1 connected to the B+ on the controller. With a multimeter (-) probe on controller B- and the (+) probe on the chassis I get 15v. When I disconnect the A1 on the motor and do the same probe there is 0v. I stripped the motor, blew out the inners with compressed air to get rid of the carbon dust and put in new terminal insulators. A continuity test of all four terminals to the motor housing shows no continuity. I test ran the motor connecting it directly to 2 batteries and it ran fine. The 15v leak is still there, anyone have any ideas on what to do next.

Do you think it's possible the voltage leak is going through the motor to the axle and then to the frame? Just a thought for you to consider...

[ForBruce]

as the windings of a motor age it is possible ( although not always the case ) for the insulation on the windingsto break down and short to the case.

When i test a commercial 3-phase motor a standard VOM (volt ohm meter ) will not always pick up the short due to the high resistance of the short and the battey voltage of the "VOM" at only 1 1/2 or 3-volts

an insulation breakdown meter will test at a higher voltage typically 500 with almost no amperage to do damage. This will definetly give you an answer

I suspect that at only 3 volts no short shows but as you increase to 48 volts
it is enough to leak to ground.

[Golfdog]

Originally Posted by ForBruce

as the windings of a motor age it is possible ( although not always the case ) for the insulation on the windingsto break down and short to the case.

When i test a commercial 3-phase motor a standard VOM (volt ohm meter ) will not always pick up the short due to the high resistance of the short and the battey voltage of the "VOM" at only 1 1/2 or 3-volts

an insulation breakdown meter will test at a higher voltage typically 500 with almost no amperage to do damage. This will definetly give you an answer

I suspect that at only 3 volts no short shows but as you increase to 48 volts
it is enough to leak to ground.

You are spot on. I took the motor to a Motor Rewinding firm and he tested it with his instrument and it showed the leak . He said that an ohm meter would not pick it up. He is going to clean out the motor and bake it in an oven and hopefully by Friday I will hear that its sorted. The carbon dust etc. can create a path for the current. Tks for the input

[ForBruce]

Originally Posted by Golfdog

You are spot on. I took the motor to a Motor Rewinding firm and he tested it with his instrument and it showed the leak . He said that an ohm meter would not pick it up. He is going to clean out the motor and bake it in an oven and hopefully by Friday I will hear that its sorted. The carbon dust etc. can create a path for the current. Tks for the input

He is dead right about the carbon dust....and once it creates a short..that trace will continue to conduct even if the dust is blown away.

I had ajob where the "BAKEaLITE" insulator became a full conductor. It got wet ..a spark was generated ...and the heat of the spark caused a carbon trace.....and the insulator became a conductor....

good luck on the motor..... it would be more reliable to just have the motor rewound and get it over with rather than just cleaning and baking with epoxy

this way you won't have to remove the motor twice....

And you don't risk damaging the controller as the short progresses