Paul Keinanen wrote:

Also if a toroid mains transformer is used, the transformer start-up
current can be huge for a large (say 1 kVA) transformer, which could
harm the house wiring or burn the fuses in the main distribution
panel.

Depending at what mains cycle phase angle the transformer was
previously disconnected and on what phase angle it is reconnected to
the mains, the start-up peak can be insignificant or the current can
be huge, which is limited just by the copper resistance of the
primary.

This might be a good time to mention that light bulbs, which I've seen
recommended here as a test load, have a resistance when cold that's only
about a tenth their resistance when hot. So you'll get some pretty
awesome current when you first connect one. A supply with foldback
current limiting probably won't light one at all unless the voltage is
raised slowly.

Roy Lewallen, W7EL