Wiring field coils on a dc motor

[giselle]

I have a d.c. motor with field coils F1, F2, F3 and F4. Normally for the lower voltage connection, I would connect in series i.e. F2 to F3 and supply on F1 and F4. For higher voltage, I would connect in parallel, F1 to F3 and F2 to F4 with supply connected. What would happen if for the higher voltage i.e. series connection, F2 was connected to F4 with supply on F1 and F3? Would that affect the electric field orientation and the performance of the motor?

 

[Skogsgurra]

I think that you are mistaken. Connect in series for the higher voltage and parallel for the lower voltage.

Never make the field windings work opposite each other. Connect + to F1, F2 to F3, F4 to -.


Gunnar Englund

http://www.gke.org

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

 

[giselle]

oops - thanks for the correction - i didn't re-read before i posted

 

[aolalde]

Following the wiring instructions should keep the proper polarity. North, South, North, South etc. And certainly connected as Skogsgurra recommended.

Reversing half of the main pole polarities ( becoming all north or all South) will cause a big problem especially for motors, they could develop a flashover around the commutator.

 

[waross]

With the fields cancelling there will be no back EMF. Current will be very high and torque will be non-existent.
If the motor has interpoles to aid commutation, the motor may develop torque as a series motor. An unloaded motor may explode due to excessive speed.
Usually the current will be more than high enough to trip the breakers or fuse the fuses long before this happens.
This is probably not an issue with a static drive, but was quite possible with the older installations where DC motors were supplied from a common DC bus with lots of capacity.
respectfully