On Friday, January 22, 2021 at 8:52:32 PM UTC-5, Snag wrote:
It's an old motor , 3/4 hp . And it's a universal motor , with a flat
disc commutator and brushes that can be rotated to reverse motor
rotation . I was looking at it today and saw on the tag that it can be
operated on 110 or 220 volts ... Currently it's wired with the armature
and field windings in parallel , I believe that's called shunt . I was
operating it on 110 volts on my lathe (until I got a smaller unit , this
thing is huge) . I have a project that I might use it on , but I'd like
to go 220V . Am I correct in assuming that hooking the windings in
series will convert it to 220 ? Since this motor is a universal motor ,
is it speed controllable by varying the voltage ?
--
Snag
Illegitimi non
carborundum

I am not a expert on motors or even reasonably knowledgeable about motors. But it seems to me that if the field and armature are in series and the voltage is close to being the same for the field and armature then it should be fine for 220 volts . And you should be able to check whether the voltages are roughly equal with 110 or 220 applied. And if you apply 110 volts with the field and armature in series, it should be obvious that the speed is controllable by varying the voltage.

Dan