On Sat, 30 Jan 2021 22:51:34 -0600, Snag wrote:

On 1/24/2021 12:06 AM, Clare Snyder wrote:
On Sat, 23 Jan 2021 05:51:09 -0800 (PST), "
wrote:

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
A series wound motor has no "speed" contril - it ha torque control and
it has infinite torge at zero RPM, going to zero torque at infinite
RPM - in theory. When the counter EMF reaches the supply voltage the
torque is zero. There is no speed "regulation" - it slows sown with
load - USELESS for a machine tool.

A shuint motor has very strong speed regulation
To control series motor speed requires a feedback loop to control the
voltage in response to speed (inverse to load)


OK , this verifies something I thought I remembered from when I was a
boy about series motors . I was considering using this motor to power a
5" jointer/planer partly because it's size would anchor the base with
it's mass . The last thing I need is a runaway jointer ... so if I do
use it I'll be leaving it hooked shunt and on 110V .

Unloaded series-connected universal motors have no upper speed limit,
at least in theory.

A runaway is likely to overspeed the jointer knife assembly, which may
proceed to burst from centrifugal force - this would be dangerous to
man and machine.

Joe Gwinn