On Oct 16, 3:30 am, (DoN. Nichols) wrote:

O.K. Then this suggests to me that the best way to control a
large one like his (the rating of his breaker) is to replace the switch
with a solid-state relay, which maintains the "on" state until both the
control voltage is off, *and* the current through the load drops to
zero. This should minimize the spikes when switching on to half of
worst-case. (Even better would be if the turn-on control could be
zero-crossing as well.

Think about it a bit more. The flux is at a maximum at the zero
crossing of the current. So switching at the current zero crossing
would insure that the core is magnetized as much as possible. Turning
on at the voltage zero crossing would insure that the breaker would
trip half of the time.


Dan