Regarding plug reversing, I recently rewired an older BP head. I was surprised
to see considerable evidence of arcing near the contacts in the drum switch. I
figured that plug reversing it was the reason - a LOT of current flows, and
motors with all their inductance do NOT like current changes. So regardless of
what you do with your phase convertor, I strongly suggest that you not plug
reverse anything using a drum switch unless that switch is extremely heavily built.

I know of no value in adding rotary mass. The armature of an idler motor is
already quite a bit of rotary mass.

GWE

Christopher Tidy wrote:

Hi all,

I'm trying to figure out if there is any benefit in adding a flywheel to
a rotary phase convertor. I've heard varying opinions on the subject.
Having thought about it myself, I've reached the following conclusions:

(i) The sag in voltage on the third line is caused by the fact that it
is not connected directly to the supply. The flywheel doesn't change
this. Nor will it change the steady speed at which the rotor turns, so
unless it has some averaging effect on a cycle-by-cycle basis which I
haven't considered, it won't affect the quality of the three phase
output when the convertor is running in a steady state.

(ii) It might be an advantage when trying to plug reverse the load
motor. As far as I can see (on the most simplistic level), the motor
with the most kinetic energy will win.

I can't seem to find any used flywheels to fit my motor, but I can get a
brand new flywheel for £40. I'm not sure if it is worth it in order to
satisfy my scientific curiousity. If I get a different motor, I can get
a flywheel for next to nothing, but that will involve lots of effort,
bartering and deals in order to get a motor which isn't quite so cool.

Any opinions and arguments? Thoughts would be appreciated...

Best wishes,

Chris