Re: [CAD_CAM_EDM_DRO] Bridgeport 440 volts to 220 volts.

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