Re: Bridgeport 440 volts to 220 volts.

Gary, what tye of CNC is this? Is it a BOSS 6 or older? If so, the
heater is in the large power enclosure on the rear of the machine. It
is separate from the contactor and mounted next to it in the upper
part of the enclosure. However, it's an old Sylvania part that is
hard/expensive to get. If you're not going to be running the machine
hard, just short the heater out until you retrofit the machine (you
will want to after you use the BOSS control).

I converted my BOSS 6 from 440V to 220V by changing the wiring on the
main stepper transformer and the 110V transformer. Don't worry about
the fuses unless your going to run the machine really hard. I have
not had any problems and did not change the fuses. If you don't short
the heater or change it, it will trip after running the spindle for
several minutes.

~petev

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cncgramps" <cncgramps@y...>
wrote:

> Jeff,
>
> Thanks for the reply.
> I am starting to think it might be easier to replace the switch.
> Mine has the high/low switch plus it has the emergency stop switch.
> Bridgeport manual says the heaters are in the switch box and are
> very hard to get at. I have looked and you can not see the typical
> coil type overload heaters.
>
> Thanks
>
> Gary
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "washcomp" <jeff@w...>

wrote:

> > Gary:
> >
> > The motor starter is sometimes called the contactor. It is
> > sometimes combined with a safety switch (combination starter).
> The
> > three things you look for:
> >
> > 1) The heaters (overloads) will be pretty ovbious to any
> > electrician with motor experience. If you contact the
> manufacturer
> > of the starter, they can help you locate the heaters. Depending
> on
> > the vintage of the starter, they may look like a losenge with a
> > number on them or may look like a spring. They will break the
> coil
> > circuit if they are overloaded.
> >
> > 2) Check the coil voltage of the starter. If your tool uses

high

> > voltage control, the coil may be 440v and have to be changed.
> >
> > 3) Check the current rating of the starter. The motor will draw
> > about twice as much current at the lower voltage. Since starters
> > are sized by current, if yours was marginal at 440 volts, you may
> > need to change the starter.
> >
> > Regards,
> > Jeff
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "cncgramps"
> <cncgramps@y...>
> > wrote:
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>
> > wrote:
> > > >
> > > >
> > > > cncgramps wrote:
> > > >
> > > > >I am about to hook up a Bridgeport Series 1 CNC that is

wired

> > for
> > > > >440. I have the manuals and it shows and tells how to change
> to
> > > 220
> > > > >which I need to do.
> > > > > The part that I am in question about is the overload

heaters

> > > that
> > > > >are in the switch. The manual says they are hard to get at
> and
> > > that
> > > > >they recommend getting a new switch wired for 220.
> > > > > I looked in the switch box and I can not see the typical
> > heaters.
> > > > >Has anyone ever changed those overload heaters out so as to
> be
> > > able
> > > > >to run on 220 volts?
> > > > >
> > > > >
> > > > You just have the little 2 x 2 x 4" drum reversing switch on
> the
> > > motor?
> > > > That has no heaters. The heaters would be in a device called
> > > a "motor
> > > > starter" and usually are mounted right on one of the
> > contactors.
> > > These
> > > > break the control circuit if the heaters get too hot,
> indicating
> > > the
> > > > motor is drawing too much current on at least one phase.

That

> > way,
> > > > they protect the motor from overload, single phase operation

or

> > > > internal shorts.
> > > >
> > > > If there are contactors in the motor box, one of them should
> have
> > > > heaters on it. They may be quite small, like little
> cartridges
> > > that
> > > > plug in. You will need to change them, as the current draw

on

> > 220
> > > > will be twice as high, and will cause the spindle to shut

down

> > very
> > > > easily.
> > > >
> > > > Jon
> > >
> > > No mine has a large box with a forward reverse "hi/low" switch
> > plus
> > > an emergency switch.
> > > The manual talks about the heaters being in the main switch

box

> > for
> > > the motor and being hard to get at. Thus the reason for
> replacing
> > > the switch.
> > >
> > > Gary