Bridgeport Circuit Questions

Hi Norm.. Not sure what the 48/50v AC is used for but I'll take a look... I'm sure you've worked out the horizontal feed motor is powered from 110V (or 115V if for our American colleges) the motors rated at 370W if my memory correct. I was going to change the transformer just accommodate the feed motor plus a bit for the 110V control circuit.

If you're going the inverter route then a lot of the control harness will become obsolete - if your use to motor cycle wiring there nothing as complicated than that. Just the fast feed and motor feed speed needs a thought.

This style of control cabinet is too shallow to accommodate the inverter so it's planned to section the cabinet and weilding in a 50 mm or so to give me the depth. I was going to replace the entire control cabinet but the quality and the gauge of metal used is far superior than othe electrical enclosure I'm use to.

hope this helps... I'm in Reading if you need any other assistance.

John

I think that you will find that the 50 volts is for a low voltage light on the machine. 50 volt lights used to be common on machines.

Les.

Norm

No official detailed colour coded wiring diagrams were ever produced. Mine has numbered and lettered sleeves on most wires which is sufficent help although some have fallen off and / or got lost during previous servicing.

Putting the inverter in the cabinet may protect it but also makes it impossible to read frequency display on the box so you need a remote readout if you want to know what speed you have set.

Messing around altering wiring is a bad idea and more work than it sounds. Half new / half old non standard set-up is asking for headaches if it goes wrong. Probably the major issue that pushed me to the whole shop plug'n play system. Easiest way is to switch the transformer input to 220 /240 volts for the long feed system and run the spindle motor direct off the VFD. Or just junk the whole cabinet and give the feed unit its own small box and transformer. A compact VFD unit can be made to sit very nicely on the left hand side of the head. Fitted one in that manner for friend John on his J head equipped round ram Bridgeport, unfortunately no pictures. Separate motor supply looses the spindle-feed-pump interlocking but the Americans generally never had this and go along OK. Alternatively you could probably use the contractors as pure switches to control the VFD via its remote input ports after slipping the power wiring out of the way and running suitable signal rated cables.

Clive.

Thanks guys. Yes, I took the bulb out and it is 50v, so that answers that one!

Clive, thanks for confirming there are no other diagrams. I also have some numbered sleeves on cables but they seem only to have been numbered one end (?!) - it was probably done for assembly confirmation I suppose.

I think that the VFD must be outside the cabinet because the fans pull quite a bit of air through them, and up highish away from swarf! I will use the VFD extension/dongle to control the motor but I want to use the Bridgeport front switch box to power up the system, enable me to switch on/off the long drive feed, and I have an emergency stop by my knee to switch off everything. I'll sort it out, it will be fun to wire nicely.

Does anyone know what gives if the long drive motor comes up against a firm stop, or the table lock is on (which has happened once or twice)? I'm assuming there is a slip clutch in the drive motor somewhere, or does it just stall?

Norm

Norm

I think it just stalls if against a really firm stop. Mine has enough oomph to overcome the X axis lock. So far I've not been careless enough to run it into a really solid stop. I tend to use the stops on the rod connected to the forward-neutral-reverse selector lever as a safety net.

When investigating fitting a stand alone VFD pretty sure I decided that taking the power feed through the old spindle motor contractor would be a minimum modifications method of keeping the standard emergency stop set-up and electrical interlocking. Keeping the standard box and switches on the knee too. Probably with a new overload unit. Never got as far as properly looking into the wiring needed to retain interlocking of spindle, pump and feed system but don't recall thinking it unduly difficult. If you drop the interlock wiring is trivial.

I still have the nice Siemens VFD I found for the Bridgeport tucked away at the back of a shelf.

Clive.

Norm, your choice, obviously, but I would second Clive's words about keeping the wiring changes to a minimum. I have a circa 1986 BP with the 154-D control box, and it was a doddle to install the Genesis 2HP VFD down at bottom-rear inside the box. IIRC the wiring changes were trivial (I've probably got my notes somewhere), and I just mounted a small box underneath the DRO display with a pot and a fwd/rev toggle switch. All the main controls (emergency, x-feed, pump, etc) remain unaltered. The main BP motor switch remains permanently in the normal position, and I just flip the toggle switch on my speed-control box whenever I engage the low gear.

Roger