Sylvia Else Inscribed thus:

On 24/02/2011 10:25 PM, Andre Majorel wrote:
On 2011-02-16, kwamena wrote:

To be very sure you disconect the motor and test it on the mains at
a reduced voltage.

The BTB15-600C is hard to find but RS carry the BTB16-600C.
Swapping in a new triac made no difference, though.

So I tried exactly what you're suggesting : motor on a big 24 V
transformer. If the rotor is a certain angle (or 180° from it),
the motor doesn't start when power is applied.

When you reverse the phase on the stator (for reverse), you
still have a pair of diametrically opposed "dead spots" but
they're at an angle from the original ones.


That doesn't really sound right. Reversing the stator winding current
should reverse the force on the rotor, not change a zero force into a
non-zero force or vice versa.

I'd have to wonder whether one of the rotor windings has failed
open-cicuit. I think that could even account for the sparks. The
magnetic field for a winding that is becoming disconnected by the
brush action has to collapse because the broken winding that's being
connected cannot maintain the field.

Sylvia.

Sounds like OC segments on the comm...

--
Best Regards:
Baron.