Series Field DC Motor

I have a DC motor with Terminals A1, A2, S1, S2, F1, F2. My DC drive is a DC powerflex from Allen Bradley 4 Quadrants. Normal connection for this kind of motor (compound) is (+)A1,A2-S1,S2(-) @500 VDC and (+)F1,F2(-) @300 VDC. I can not use series field with 4 quadrants, I do not have contactors to invert A1,A2 so I do not want to use S1 and S2 coil.
My question is S1, S2 are to be shorted out or just leave them isolated and disconnected ?

Leave the series field disconnected, and open. Tape up the ends. You should be fine.

Lessee if I understand.
you want to reverse this motor and (operate in all 4 quadrant)
BUT do not have enough contacts to enable reversing the motor configured as compound.

I suppose you could remove the series field to simplify switching
BUT you are going to lose a lot of torque as a result. I would approach this very carefully since motor may not have enough torque to drive the load, stall and burnout.

Dan Bentler

Thanks rdrast and leitmotif, I left S1 and S2 disconnected and my problems went away, I´m reversing the motor thru the drive. No contactors are used.

But, widelto, you should note leifmotif's comment. With no series field to add to the field intensity, this motor will always be short of nameplate torque and hp. And, you will find that the shaft speed will be somewhat higher for every armature voltage. In fact, at 500V on the armature and 300V on the field, the shaft speed will be at least 20% higher than nameplate and maybe as much as 50% higher.

If you have encoder feedback, your drive max speed parameter will still prevent overspeed but it will take less than 500V to reach nameplate speed.

As long as your machine doesn't need the full torque and hp, you will be fine. If it does, and in both directions, then you have the wrong motor. Either that or you will have to add the contactors to reverse A1 and A2 without reversing the S leads.

This is an often-overlooked characteristic of compound wound motors. They are not symetrical. Usually they are applied to unidirectional loads like extruders only.

DickDV tks for your comment, I´m aware of leitmotif´s advice, I know I will lose some startup torque but I have no choice, they do not want to spend more money on contactors, so i will reverse motor direction from drive. I´m using a 1024 PPR encoder as feedback. And DickDV series field was in series with armature not with field. If you see my initial comment S1-S2 coil is in series with armature.
Tks.

Yes, widelto, the series field is in series with the armature but MAGNETICALLY it adds to the shunt field to create a field that strengthens as the load increases. That is because the series and shunt fields are wound over the top of each other. The loss of torque will occur at all speeds, not just at starting but, it seems that your machine is ok without it so there is no problem. And the encoder will control speed properly.