whit3rd wrote in message
...
On Sunday, May 19, 2013 12:58:34 AM UTC-7, N_Cook wrote:
800 watt toroidal transformer operating at say 400 watts. Secondaries
lead

to conventional bridge rectifier and smoothing caps for +/- rails. A
break

appears in the DC rails central 0V return to the transformer, could that

lead to a blown mains fuse, via inductive action?

Yes, kinda. The trick is, an intermittent contact can accidentally
rectify, and the primary (AC) current shoots through the saturated
transformer. It'll more likely pop the small device fuse than the
main breaker panel.

It'd have to be a LOT of DC on the secondary to cause saturation.

A bad connection could also generate heat at/near a fuse, and cause
it to fail by heating from outside, but that's less likely.


A good introduction to this (I did only once) testing a 12V relay. 2 wires
to the screw terminals of a power supply. Hold the relay at the pins , one
finger holding one wire to one pin and make and break the other contact with
another finger touching it. But that is high voltage , rather than high
current.