Re: Bridgeport 440 volts to 220 volts.

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