Run a series 1 MK2 Bridgeprt cnc on a converter

[colin1544]

Hello has nay one got any experience on running a Bridgeport series 1 Mk 11 CNC mill on a rotary three phase converter if so what size have you run it on and have you had problems or good results, or is it possible to seperate the control out using single phase to run the Heidenhain 155 control on single phase and the main spindle and coolant motors on an inverter I would be very interested in any comments. Thanks Colin

[acerocket]

My shop has 125V per line single phase and I hooked a Bridgeport Series I with Centroid controls (replaced Boss 3 controls) to a American Rotary Gentech 7.5 HP 3 phase convertor. So far it has worked just fine (about 3 months now). A few things I was told: Since my Centroid refit uses DC servos, I can get away with the 250V 3 phase. Also, it is possible to split off the computer and run it from 110 power, but I decided just to run it from the 3 phase since I don't program at the machine. It is a good idea to split off the computer in case you want to do intuitive or manual programming at the machine so you don't have to run the convertor all day. It is usually recomended to go at least twice the HP as your main motor (2 HP motor so a minimum 4 HP phase convertor for my machine) but I went with the 7.5 HP unit because of the 5% voltage balance up to 50% load. It does make a little noise but nothing intolerable. When running, I get 252V, 250V and 246V on the three phases.

I also run a Femco HL-25E Durga lathe (15 HP motor) with a seperate 30 HP convertor. However, for the lathe, it is not recommended to give the machine more than 230V (208V is the best) so I had to install a 24V buck/boost transformer in line before the convertor to cut the power to 232V 3 phase. When I run this machine, I get 232V, 231V and 221V on the three phases. Of course this convertor is a bit louder because of the larger 30 HP motor, but again, when the machine is running, you hardly notice the convertor.

A few things to be careful of are that you need to do if you use a convertor: follow the manufacturer's specs for wiring sizes when having your electrician install the convertor. My electrician thought he knew more than the Gentech people and he undersized the wires to the 30 HP convertor - so he had to buy me a new set of star capacitors, a new relay, and rewire the convertor back to the electrical panel after it blew up. Also, keep the convertors close to the electrical panel and the machine. They recommend no more than 10-15 ft from panel to convertor and convertor to machine.

Powerwise, they actually don't consume too much power when idling. I use 30-50 kWh a night to run my 4 2000 watt electric heaters, but can run both my machines all day with less than 15 kWh of power.

In case you want to check them out, here is where I got mine from: http://www.americanrotary.com/rotary...onverters.html

If you have any other questions, feel free to PM me.

[colin1544]

Hello again thanks for the reply but the series 1 boss 3 machine you have is different to a MK2 as the MK2 has a 5KW DC spindle drive and no gear change which is alot heftier than a 2 HP standard 3 phase motor, but I spoke to a local supplier Drives Direct and he can supply a 10HP digital drive that gives balanced voltage surge control and can run other machines as well and does not need a pilot motor, the problem is the price £1750.00 (3500.00$) have to see if I can clear some old gear out to pay for it.
Cheers Colin