On Tue, 06 Jan 2004 23:25:07 GMT, "Rick Legge"
wrote:

On first pass it worked real well but after
two or three 2 second cycles it burned up the coil.

Magnetising ?

The coil came from a
It's a 115 Vdc circuit with a bridge rectifier to energize dc to mag

Doh ! No wonder it failed. Try to find a design from someone who has
something resembling a clue.


You don't need a constant field to make a magnetiser, you need a
unidirectional field. So long as it retains the same polarity, a
pulsed field is OK.

A solenoid winding (relay, transformer or motor) is a reactive load,
which means that it has a higher impedance at AC than at DC. For AC,
even at 50Hz, this impedance limits the current. Run it on DC though
and it's the same as sticking a fairly short length of copper wire
straight across the supply - no wonder it burned out !

Most decent magnetisers are pulsed, using a capacitor bank. Real ones
also monitor the winding temperature, or else limit the duty cycle.

--
Smert' spamionam