On Dec 5, 1:07 am, m II wrote:
Bob wrote:
On Dec 4, 5:44 pm, wrote:
Yep, it is called a series motor.

Ever see a series only DC motor not connected to any mechanical load
get energized?

It is not pretty. Since there is no mechanical load, the current is
very low. Since the current is very low, the field is very week.
Since the field is very weak, the speed is very high, usually high
enough that you get to see what a commutator that has flown apart
looks like. On a 30-40 hp motor it is ugly. Trust me.

Bob

I've also heard of shunt motors disintegrating if the field failed. A
series motor, of course, would just stop.

mike

Pretty rare, because field loss circuits interrupt if the field
current goes below a set value, and a more common failure mechanism is
shorted turns due to insulation failure, and that would present as the
motor having reduced torque and generally be found. But, I'm sure it
has happened...

Bob