Re: [CAD_CAM_EDM_DRO] CNC mill DC motor field wiring

skykotechnologies wrote:

>I finally got around to installing a 5HP 4 quadrant regenerative
>drive (from KB) on my shizuoka B3V mill. I didn't really know the
>specs on the motor, except that it is a 5HP DC motor, so I figured it
>was probably 180V armature, 200V field. The old broken spindle
>driver was labled 3.7KW DC motor speed control model 1-4064 by Sanyo
>Denki Co.
>
>Anyway, it works just fine, except I don't know if it is rotating as
>fast as it was designed. The field resistance is about 116 ohms, so
>I figured it had to be 200V. Would it hurt things to run it at
>100V? I guess it is going to give reduced torque and double? the
>speed, which might be too much for the bearings.
>
>

Very roughly, that is correct. You can assume some saturation at rated
field current, and also
the field would run cooler, and therefore the copper resistance would
drop, so
half voltage would probably give you about 60% of the actual field
strength at 200 V.

>Any idea what the designed max rpm on this mill is? The old fanuc
>control panel had an analog spindle speed meter that has about
>3500rpm and 740rpm as the max meter movement. That makes sense as
>the mill has a geared head with a 5 or 6 to 1 ratio (haven't actually
>bothered to measure the ratio yet). I would estimate the motor is
>spinning much slower than 3500...perhaps 1800 or so.
>
>

You should be able to put a mark on the motor and crank the the spindle
around one turn
and see how many times the motor rotates in each gear.

>I just got a 240VAC 9.5 amp autotransformer at an auction, so I
>guess I could easily build a variable field voltage generator with
>the addition of a small bridge rectifier....
>
>

Yes, that should work.

Jon