1. compound dc motor series winding wire gauge and turns+ 2. starting with smaller wiring

Thread Starter


Joined Jan 30, 2022
I have 2 real newbie questions = stupid.

I have constructed hobby serial dc motor oldest historical type.

3 armature poles, power supply 20 v drill battery, no electronics, resistors, thermistors, centrifugial switch.

Wires: armature 18 gauge about 30 rounds of wire/tooth and stator 12 gauge wire 11 rounds/ pole (2 of these)
To my surprise it did not shortcircuit the battery or did not burn wires but did develop, of course, too fast speed to start burn commutator (a kind of runaway I think).

I think to change it to the compound type motor not running away.
Would anybody have a very rough feasible idea about suitable series field wire gauge and number of rounds to this device specification?
I have an idea to get more torque not burning wires or shortcircuiting battery and implement it : 9 gauge stator winding, 12 gauge armature winding + some serial winding to be compound motor and use 40v li-ion battery.
Now start up current is huge destroying battery or burning wires.

A theoretical question (probably stupid):

If we have not control electronics or centrifugial switch can we do as follows ?
We build up a full motor with smaller gauge wire everywhere and start it but on top of this winding is everywhere heavy winding and we connect it when speed is fast deloping enough back emf, so we have two full windings in the same motor and good torque and efficiency in the end.

I figure out that this embedded thin wire high resistance motor do not destroy battery and can be such that it do not burn wires either.

The question is really theoretical. Everybody can say: why to do that odd thing, use centrifugal switch or soft starter!


Joined Jan 23, 2018
The motor you are describing, that has a commutator, is called a "universal" motor. For that variety of motor the maximum speed is usually limited by the lad and friction, and so they can spin very fast.
So with heavy wire and I quite high voltage and current it is entirely reasonable that there was over-speed and burning up.

There is an incredibly vast amount of information available about motors, including the universal type , and it willprovide enough information to give you actual insight about the motors that interest you.