I was recently given an old Lima loco 12V motor to repair. The loco belongs to the CTSMEE and someone had removed one of the coils of the 3-pole motor which apparently had burned without too much damage.
When it was given to me for repair, one of the 3 coils were absent and the remains of the two brushes were melted into the top plate.
The transfer gears to the wheels are still OK and I started by cleaning up the two brush locating holes, made two new brushes from brush material, corrected one of the bent brush pressure springs and then proceeded to cleaning up the little 3-segment commutator disc.
The next step was to remove the remaining coils, measure the guage of the wire and count the number of turns for each coil and the direction of winding.
I had the same guage wire in stock and each coil has 425 winds.
I then got some schematic drawings off the 'net and concluded that these motors are 'delta'-wound with all three coils wound (by the looks of things) in the same direction - in this case anti-clockwise as I found with the two remaining coils.
I rewound the motor, following the 'net schematic and all attempts to get the motor to work has failed when connected to my power supply set at anything from 8 to 12Vdc.
There are no 'impediments' from the mechanism, the new rod-type brushes have even pressure on the commutator disc but nothing I tried works. And of course there's no shorting between the coils and the rotor's metal parts.
Yesterday, I took the little motor to the bloke who recently rewound my compressor's motor. The first thing he asked me was how I rewound the coils and I mentioned each coil had been rewound in the same anticlockwise direction. He informed me this was incorrect. The three coils should be wound anticlockwise, clockwise and anticlockwise.
He also looked at the polarity of the two ferrite magnets which was found to be correctly orientated.
I have now rewound the rotor as described (anticlockwise, clockwise and anticlockwise again) and still no go.
Any ideas what is wrong here?
mafioso
When it was given to me for repair, one of the 3 coils were absent and the remains of the two brushes were melted into the top plate.
The transfer gears to the wheels are still OK and I started by cleaning up the two brush locating holes, made two new brushes from brush material, corrected one of the bent brush pressure springs and then proceeded to cleaning up the little 3-segment commutator disc.
The next step was to remove the remaining coils, measure the guage of the wire and count the number of turns for each coil and the direction of winding.
I had the same guage wire in stock and each coil has 425 winds.
I then got some schematic drawings off the 'net and concluded that these motors are 'delta'-wound with all three coils wound (by the looks of things) in the same direction - in this case anti-clockwise as I found with the two remaining coils.
I rewound the motor, following the 'net schematic and all attempts to get the motor to work has failed when connected to my power supply set at anything from 8 to 12Vdc.
There are no 'impediments' from the mechanism, the new rod-type brushes have even pressure on the commutator disc but nothing I tried works. And of course there's no shorting between the coils and the rotor's metal parts.
Yesterday, I took the little motor to the bloke who recently rewound my compressor's motor. The first thing he asked me was how I rewound the coils and I mentioned each coil had been rewound in the same anticlockwise direction. He informed me this was incorrect. The three coils should be wound anticlockwise, clockwise and anticlockwise.
He also looked at the polarity of the two ferrite magnets which was found to be correctly orientated.
I have now rewound the rotor as described (anticlockwise, clockwise and anticlockwise again) and still no go.
Any ideas what is wrong here?
mafioso
