DIYbanter - View Single Post - shock in electrical panel learned something new

Ralph Mowery

In article , says...

If others are deciphering the picture, the fuses are not installed an go
in the open space toward the middle. The fuses are long because they are
for 480V.

You were doing well up to this point. The fuses are not long because of
480 volts. They are long as when they open up there is a long enough
path that an arc can not form and keep current flowing.

Most of the motor contactors are designed to have a way of 'blowing
out' the arc when the contacts open as opposed to some similar looking
relays (contactors) that are designed for resistance only loads.

In the same type of motor starter, many contactors will have a
transformer across 2 legs before the contactor that converts the 480 to
120 volts and the coil will be 120 volts. That is usually for long runs
to switches. The fuses for that transformer are not long at all.