4QD controller for field wound motors

[Brian Baker 2Participant @brianbaker2]

Greetings,

Hope someone can help with my problem.

I am involved in the modernisation of a 1980's of a large 71/4 electric loco. It has two high quality, barely used 24v DC motors each one about 1 KW, and each driving one bogie. It is controlled by a sealed box built into the body that cannot be opened without major dismantling, which we will have to do because the "Box" which used to click , now is getting hot & not working. It only gave two speed control forwards & reverse. The motors are unreachable, but have 4 wires to each, and I take this to be that they are field wound motors, 2 wires to field coils, and 2 to the rotor coils.

Another loco in the fleet has 2 wire motors and we easily converted this with a suitable 4QD controller, and it works well, and we would like to do the same to the poorly one. $QD have little information, but say "it can be done".

Any ideas how this might be done?

Could I rig an uncontrolled, supply to the field coils, and use the 4QD to feed the rotor coils, and do I need to limit the current in the field coils?

Any suggestions would be much appreciated.

Regards

Brian

[Brian Baker 2Participant @brianbaker2]

[duncan webster 1Participant @duncanwebster1]

Any info on motor plate? It is likely that you just connect the field across the supply and feed the armature from the 4QD, but without motor details this might release a lot of magic smoke. With a field wound motor various other possibilities arise, you can make it go faster by weakening the field. Don't do it too much or the rotor will lock, been there done that with a dynamo converted to a motor. You don't actually need the full capability of a 4QD as reversing can be done via the field, but using the 4QD is probably the simplest. Have you tried contacting 4QD or Parkside electronics direct

[Brian Baker 2Participant @brianbaker2]

Hi Duncan,

I will give them a call.

I will try to try to get a look at the motors next Sunday, but they and the controller are buried inside the body with no obvious access.

many thanks

regards

Brian

[Author]

Posts