Hi peteeng,
Fu******king Oath its a problem!!! How do you suppose a coil in a car works. A current is feed through a coil and then when the points open, ie the current is suddenly open circuited
the voltage spike is sufficient to throw a multi-kilovolt spark at the spark plug when its under compression. That is how Kettering ignition works.
When the coil current of the electromagnetic brake is suddenly open circuited the voltage spike could literally be kilovolts and there will be an arc between the opening contacts.
Lenz's Law:
V=L.dI/dt
So effectively an open circuit causes a very large if not infinite rate of change of current, and therefore even with a low inductance the voltage will be high....kilovolt high!
Craig