I may be able to obtain a very small 2-pole 240 vac contactor I need rated
for 50 Hz only.
If I install it in N. America, what's the implication? Is the hold-in
magnetism less than if it were 60 Hz? Just noisy?
Yes, the hold-in force will be proportionally less. If the
coil impedance was due entirely to the inductance, it would
be 50/60ths of the force. However, part of the current limiting
is done by the coil resistance, and that won't change so the
reduction in hold-in force will actually be less than this.
The pull-in force before the magnetic core is closed also
depend on the impedance and resistance, but the impedance
will be lower, and thus the pull-in force will be reduced by
even less.
The pull-in force usually has to overcome a faily weak return
spring. The hold-in force has to overcome a stronger contact
pressure spring. Providing both these conditions are still met,
you should be OK. Ideally, you should check that you have a
reasonable working margin by testing the coil at lower
voltage. If you don't, then the contactor might fail to
close properly on minimum supply conditions which could cause
it to burn out.
I would not expect it to be more noisy if it closes properly.
Noise would be an indication that is isn't closing properly.
Of course, you void all waranties and certifications by
operating it outside of it's specified ratings. The
manufacturers advice should be sought, but unless you are
buying lots of them, they probably won't commit other than
to say it's at your own risk.
