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.