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?????

--

Clif Holland KA5IPF
www.avvid.com

Clif Holland wrote:

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?????


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

GWE

On 23 Mar 2006 21:51:31 -0800, wrote:

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

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.

"Clif Holland" wrote in message
news:RgLUf.15556$bu.7210@trnddc04...

Other ideas?????

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