In article , DoN. Nichols says...

And another question is what kind of load is planned? Assuming
that he really *did* mean 220V single phase to something like a
reversible lathe motor, then he will need all three sets of contacts (on
a typical drum switch) to be able to start the motor in either
direction.

One can do this with three contacts as long as the motor is a
120/240 volt motor, because of the peculiarity that when those
are wired for the higher voltage, the start winding is tied
to the *center* *tap* of the run windings (which are in series
when wired for 240) and can thus be reversed with a single
contact, as shown in this diagram:

http://www.metalworking.com/DropBox/_2001_retired_files/wire.jpg

There is an associated text file with that,

http://www.metalworking.com/DropBox/_2001_retired_files/wire.txt

I think that reversing a single-voltage 240 volt motor would
in principle require four contacts.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================