"Mr Macaw" wrote in message news
On Fri, 13 May 2016 06:44:02 +0100, Rod Speed
wrote:



"Mr Macaw" wrote in message
news
On Sun, 08 May 2016 23:03:48 +0100, Fredxxx wrote:

On 08/05/2016 15:23, Mr Macaw wrote:
My jigsaw started sparking and throwing out smoke, so I took it to
bits,
found a shorted coil in the motor, and disconnected it. But it's
still
doing this (sew video). Is there anything that can be done, or does
it
go in the bucket?

https://www.dropbox.com/s/75z1zyve3jajgg7/Saw.AVI?dl=0

Consider the armature approximating a rotating transformer.

One segment that has a short is like shorting a winding in a
transformer.

Either get a new armature, or get a new jigsaw. I would favour the
latter.

Couldn't I short a winding 180 degrees round from the already shorted
one?

You could, but you'd still get that arcing.

Why?

Because that is how those motors work.

Changing 12 coils in series to 11 coils in series doesn't change much
surely?

It isn't 11 coils in series. A much smaller number is electrically connected
at a particular
time and the arcing is due to the fact that the one coil is a sort
currently.