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Dave Martindale

(Michael Moroney) writes:

Yes the inability to go to the nearest WallyWorld and buy a 240V 4kW
cooker/microwave/whatever is a big problem. European appliance could be
got, but I'd worry about anything with a motor (50 Hz), clock (do their
electronic clocks operate off the line frequency like some in the US?),
microwaves (don't they use frequency-dependent constant voltage
transformers?).

A motor designed for 50 Hz would run fast on 60 Hz, which might
overload something like a fan motor. A clock would run fast. On the
other hand, more iron is needed for 50 Hz motors (at a given voltage
and number of turns), so the motor is actually overbuilt for 60 Hz
operation. Same goes for ordinary transformers.

I've taken a number of microwave ovens apart over the years, and none of
them used constant-voltage transformers. They do have a magnetic shunt
to give them somewhat of a constant *current* characteristic, and that
might reduce the magnetron current some when operated from 60 Hz.
The magnetron itself operates from half-wave rectified DC, so it
shouldn't care.

Some Panasonic microwave ovens use an inverter to generate the HV supply
for the tube. Feeding it 60 Hz instead of 50 Hz should not be a
problem; it will just reduce the ripple at the output of the initial
rectifier.

Dave