In article ,
says...


If it can be avoided, it is a bad idea to switch the DC input to
the coil. It is much better to feed the coil from a full wave
rectified AC supply and switch on the AC side as this is much kinder
to the contactor.

It would be worth looking at the existing generator's
controls. I wouldn't be surprised if the magnet is hard
wired to the output and the magnet turned on and off by
controlling the generator's field.

Ned Simmons