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JCHannum
09-30-2012, 08:53 PM
I have a couple of small, 1/20HP Bodine brush type motors. They are four lead motors. My confusion arises from the fact that they are marked 115VDC. All other markings are the normal 1725RPM, continuous duty, 40*C temp rise. They appear unused, but were take offs from some equipment or other. They are the once ubiquitous black Bodine motor, which is apparently no longer being manufactured.

I am guessing they are universal AC/DC motors but were marked DC for the OEM manufacturer. If this is the case, is the AC wiring the same as for DC?

MaxHeadRoom
09-30-2012, 08:57 PM
If they are Universal motors, they will have 2 wire feed and wound field, not P.M.
Bodine make DC P.M. principally, so it would pay to investigate further, also two may be a tach, although I have not seen many Bodine with Tach feedback?
Max.

JCHannum
09-30-2012, 10:21 PM
These are wound field. The four leads are taken outside the motor rather than connected internally. Two are field and two are to the brushes.

J Tiers
09-30-2012, 10:44 PM
A universal motor differs from a DC series motor in that it must have lower inductance. Such a motor could be universal, or not. In that case, 4 leads would allow reversing. They might also be regular shunt wound field, in which case they may be marked with a field rating.... or not if for an OEM.

The answer is found by using the ohmmeter. if the field winding is a high resistance, it is a DC shunt motor, at least externally. You would connect the field to the same voltage as the armature, typically, with or without some form of controller. That would account for the "DC" rating.

If the field winding is low resistance, it is likely to be a series field, and would be a DC series motor.

MaxHeadRoom
09-30-2012, 11:37 PM
These are wound field. The four leads are taken outside the motor rather than connected internally. Two are field and two are to the brushes.

You most likely can run them off of the common KB/Baldor SCR drives if you need variable speed, these have provision for field supply.
The 1725rpm would tend to indicate a shunt motor.
Max.

JCHannum
10-01-2012, 06:59 AM
Thanks for the answers. Do they translate to these are DC only motors? I would prefer AC, but I do have a DC control available. I am looking for a small motor to make a powered collet fixture for my T&C grinder and these were in my stash. One is a 10-1 gerahead that would be ideal for my purposes.

J Tiers
10-01-2012, 08:18 AM
Being MARKED DC, one would suppose so.

But measure the field resistance, and you will instantly know what's up.

A shunt (DC ONLY FOR SURE) motor will have a resistance allowing only about 10% of the rated current to flow in the field (maybe less) at rated volts.

A series field will have only about 10% voltage drop at rated current. Most series motors will be universal, but some may not be.

A series motor has such lousy speed regulation that it is generally a poor choice for machine tooling, despite use in hand tools.