I bought a second hand woodworking lathe some months ago which came
with an ABB contactor switch (type A12-30-10). I didn't consider it
necessary to have a contactor and an 2kw electronic controller for the
lathe, so re-directed the starter for driving my circular saw. This
had a contactor in a home made box so there was an attraction in having
a pukka device.

I'd checked the new contactor's operation sometime back and was a bit
suspicious that it was a bit sluggish in pulling in. This is now
confirmed when connected to the 2kw motor for the saw. Sometimes it
will operate OK and the saw starts up fine, otherwise there is a lot of
chattering, sparking, chuntering from the saw motor and nothing
happens.

I jury rigged the original contactor to see if it is something to do
with the change of site and it operates fine - pulls in perfectly each
time.

This is a 240v single phase system.

Anyone any ideas before I go the the bother of fitting the old, and
operating, contactor into the 'new' starter box, and dumping the 'new'
one.

snip


One of the common arrangements in 3-phase "boxed" contactors, with
buttons on them, is to use a coil with a voltage around 400v, operated
across the incoming phases. Trying to use one of those on 230v would give
symptoms similar to those that you are getting. There is insufficient
magnetism to completely close the contacts and they burn up!

The A12-30-10 has 3 main poles and one normally open auxiliary. IIRC the
main poles are 1-2 3-4 5-6, the coil is A1-A2 and the auxiliary is 13-14
(although I may be wrong on some of those - the catalogue is at work).
They are sold in a range of coil voltages, and the voltage/frequency is
marked on the coil, visible through a window on one side of the contactor
IIRC. The A12 bit is the contactor rating. In this case it's 11A AC3
(motors inching & plugging). If you are tracing the wiring note that
there are A2 terminals at both top and bottom (internally linked) to make
wiring easier.

You have to have a means of disconnection (i.e. a contactor) with an
electronic controller because they don't isolate the motor so can't be
used with an emergency stop system safely. Some of the controllers
actually include their own contactor inside the housing.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.