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 ?