"N_Cook" wrote in
:

Wild_Bill wrote in message
...
I don't know about the semiconductors, but the loop of wire may be a
braking
"resistor".
Battery powered power tools with permanent magnet fields sometimes
have a loop of wire to dump the spinning motor current into, when the
trigger is released. This causes the cutting blade, in a saw for
example, to stop sooner than just letting the armature to coast to a
stop.

You may know a procedure for testing the LRA locked rotor amperage of
the motor, which may be a useful indicator for selecting the
semiconductors.

Metal current feedback circuit "resistors" that I've seen in DC motor
drives
and treadmill drive circuits sometimes look like strips of bare
sheetmetal,
or just a half-circle of very heavy gage copper wire.
I guess the type of material used will depend upon the circuit
designer's background and material/part cost.

--
Cheers,
WB
.............


"N_Cook" wrote in message
...
The 2 paralelled output TO220 thyristors had their identities
ground off before insertion. 200W, 12V motor so 17 amp so would
they be say 30V
8amp,
10amp or 15 amp rating each? No fuse in the control anywhere but
there
is
a
main relay and more electronics than just for controlling speed so
could there be an overload sensing cct that drops out the relay ?
While at it there is an off board loop of copper coloured wire,
perhaps microbore copper
tube could that be a 20 or 500 amp fuse or just a dropper element
for overload sensing ?




Taking a closer look it is probably solid 1.7mm copper wire in a loop
above the board of about 1 inch diameter. It is in the supply line to
the power devices (maybe powfets rather than thyristors) not the power
to the electronics. But operation is via rotary pot with switch so
have to go throu gh minimum revs (pulses) before switching off. So
still a mystery, no way a fuse , the cross section of the tracks, wide
yes, must be less than 1.7mm solid wire. Incidently now all in working
order on the bench, not reassembled yet onto the caddy a G Caddy TEDC
12201 that I find no www ref to




maybe it's a current probe test point?
a loop you can hook a current probe over,without breaking the circuit.

--
Jim Yanik
jyanik
at
localnet
dot com