"Jim Adney" bravely wrote to "All" (11 Nov 04 20:57:04)
--- on the heady topic of " Detect shorted turns in motor windings..."

JA From: Jim Adney

JA On 11 Nov 2004 08:08:07 -0500 Sam Goldwasser
JA wrote:

Jim Adney writes:

On Tue, 9 Nov 2004 16:41:01 -0500 "Charles Schuler"
wrote:

Disassemble the motor and just take in the rotor, so that they don't
have to do any significant work.

IF, it's a wound rotor motor. Most ac rotors are of the squirrel cage
variety.

I was wondering about that. Wouldn't a squirrel cage motor still have
the same magnetic properties? I'm not sure, but I'd bet that such a
rotor would still pass the growler test, but it's hard to imagine a
squirrel cage rotor with a short in it, which, I believe is what the
OP asked about.

By definition, a squirrel cage rotor is all shorts.

JA Right, but so is a regular commutator rotor. The only difference, I
JA think, is that the squirrel cage rotor is wound with much more rugged
JA "wire."

The squirrel cage rotor is really a rotating transformer with a very
low resistance secondary. Any phase difference (slip) between the
applied field and the transformed field generates very high currents
in the range of 100's of amperes. To say the rotor is wound with much
more rugged wire is really an understatement. It is this high current
that causes a counter emf, applying a mechanical torque to the shaft,
and results in the desired motor action.

A*s*i*m*o*v

.... Electrical engineers deal with current events.