Does the brushed DC motor and Permanent magnet Dc motor need position feedback in the control system

I can just imagine it getting up and walking across the room. Same thing happens if the triac goes S/C. Washing machines don't have quite the same level of monitoring and interlocking as machine tools though.

Here's the drives cabinet of that lathe of about 1978 vintage. Top left is the spindle drive, IIRC 7hp 0-320V DC out. Lots of hardware trimpots and status indicators on the front. LEDs include overspeed, underspeed, overcurrent, AC supply out of range, tach error, motor temp, heatsink temp, field loss etc.

Field loss on a wound-field shunt motor is another problem that can cause massive overspeed. In the good old days of rheostatic starters for brush motors, the hold coil was often series-fed from the end of the shunt field, so that the starter would release if the field circuit opened up.

To the right of the spindle drive are the DC axis drives. They don't look very chunky but they are quite capable of eating their 32A 400V supply fuses without harm, if something goes disastrously wrong that stalls the axis motors, like an endstop overrun.

oracle said:

Ever had one of these "Run away" or overspeed due to a loss of tacho feedback?

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yes and laughed my arse off when the conveyor flung the cooling pies against the wall
the manager was sh!tting kittens until he found the emergency shutdown button)

back to the original post I agree that the question should have been thought out properly before asking.