Electrical Question

I have a Rockwell Mill wiith the power table feed. The original feed controller is history. I purchased a controller from Beel Industries. The problem is the field of the motor is 60VDC and the Beel product puts out

90VDC. Instant short when voltage applied. If I back the input voltage down to ~60 VAC with a Variac all is well. No short or blown fuses, speed control works fine.

I would like to eliminate the variac.

How is the best way to do it?

I've considered a step down transformer (220-110) hooked to 110. I don't know how the controller will like 60v in as far as power output (with the variac the motor was running free, no load) Or even if this will work at all.

A separate transformer for the field once I figure the current requirements with it's own bridge rectifier and then the controller run on 110 separately.

I've even thought about having the field rewound to 90v.

Other ideas?????

Reply to
Clif Holland
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Clif, I have the same mill and had the same problem. The ancient SCR control was toast and crap to start with. I bought a Minarik (Dart is the same) full wave torgue feedback drive from Surplus Center that fits in the housing perfectly AND they had a new

90V DC permag motor that was the same physical size (just had to make a new mounting ring plate). After repairing the front bearing support, it's way better than new now. About $50 total spent. RichD
Reply to

I'd look for a 110-60 transformer with the correct power requirement.


Reply to
Grant Erwin

Your KA5IPF sig suggests that you're able to build elex. A 66% dutycycle PWM would do the job nicely with a 555, a MOSFET, a snubbing diode and some minor bits and bobs to power the elex from 90 volts. Email me if you'd like a schematic, say what the field current requirement at 60 volts is. I'll offer a more-than-sufficient MOSFET and snubber free if you want to go that route, I have more than I'll ever use. Warning: these parts are not RohS compliant. If you use tin-lead solder in assy of your elex then the point is moot.

That said, RichD's solution sounds like a good one for $50.

Reply to
Don Foreman

Yep! I would purchase a 110/24 volt transformer with sufficient current capacity on the 24 volt side to handle the current for your motor. Connect the primary of the transformer to 110 VAC and then connect the 24-volt secondary so that it "bucks" the 90 volts from your controller. The result will be plenty close enough to 60 volts.

i just solved a nasty problem with a 208 volt UPS (fed from 230 volts) the same way. There are several companies who will happily sell you a special 'buck/boost" transformer, but in your case I think a simple,cheap 24 volt unit will do the job nicely.

Vaughn WB4UHB

Reply to
Vaughn Simon

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