Series field nomenclature

[GopelT]

Hi all,
I am connecting a compound DC motor and have run into series field markings that are new to me. Armature is marked A and AA, Shunt field is marked F1 and F2 and Series field is marked X and XX. I want to connect cumulative and I believe that my jumper connection should be AA to X or A to X depending on rotation. Anybody run into this style of marking? The motor was made in Birmingham, England about 30 years ago and is on a Bronx bar straightener. Thanks in advance.

 

[Skogsgurra]

A Bronx straightener - I have only seen them with Siemens DC motors. In such a motor, the connection usually is PLUS->E, F->HA, HB->MINUS. The HA and HB are connections to the interpole windings, which in turn connect to main armature A and B. PLUS->J and MINUS->K.

It is very probable (almost sure about it) that a similar method is used on your motor. I would connect like this:

PLUS->X, XX->A, AA->MINUS. PLUS->F1, MINUS->F2. That would make the motor speed load dependent so that load between upper and lower roll can be adjusted and stays stable.

The main thing is that series field and armature have the same polarity. So, if you want to run CCW, you connect XX->AA, A->MINUS. Leave all other connections.

It is possible that the peckerhead is laid out so it is easier to put series winding after armature. Keeping armature polarity and series winding polarity the same is the important thing.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[edison123]

Gunnar,

You said

Keeping armature polarity and series winding polarity the same is the important thing.

But You meant

Keeping shunt winding polarity and series winding polarity the same is the important thing.

Right ?

 

[GopelT]

Thanks Skogsgurra and Edison123,
The peckerhead is laid out for jumper connections and it will be easy to connect. Edison, for the load dependant speed regulation Skugsgurra is right. The armature and series field must maintain polarity. I see I flip flopped them in the original question. I'll try your connection suggestion and see how it performs under load. If the speed increases under load then I know that the armature and series field are opposite polarity. Thanks again.
Jim.

 

[Skogsgurra]

Yes, edison. Of course. The two fields shall work in same direction. Armature current goes either way, depending if the motor is motoring or braking. In a straightener, one of the motors is always braking.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[edison123]

Jim

By braking, if you mean plugging, yes, you always reverse the armature supply and never the shunt field supply in a compound motor. The series field (which is different from interpoles) should always have the same shunt field polarity. The series field is wound in the same pole brick that contains the shunt field.