DC Motor with no name plate 2

[edison123]

I have just recd a very old DC Motor with no nameplate. The motor was shipped across continents from a scrapped plant. So no info is available from this old working location of this motor. Is there any way to know the rated voltage/speed/HP of this motor?

 

[jbartos]

Suggestion: It is not easy analysis to establish accurate parameters of unknown motor. Often, it must be done in a specialized laboratory with necessary equipment and conditions. If accurate parameters are not needed, then the governing variables are motor temperature, variable voltage input, adequate time interval for measurements and testing, and commutator brushes sparking.

 

[DougMSOE]

This may get you into the approximate rateing
1. Measure the shunt field resistance in ohms and the temperature of the winding. Yes the field winding may be shorted, but it is a start.
2. Measure the footprint of a commutator brush. Typically the amps/in^2 will be in the 50 to 70 amps/in^2. Reverse calculate the armature amps taking into consideration of the possible parallel brush holders.
3. Most DC motors are 125 or 250 DC. Rarely are there 550 or higher.
4. Measure the diameter of the shaft. Most old DC motors had a safety factor of at least 5, some as high as 12. You may assume a 1025 steel. Again reverse calculate for torque.
5. Operating RPM is tricky, but most 4 or more pole motors are less than 1800RPM. You may want to look at the commutator diameter as this is about the only clue to operating RPM.
GOOD LUCK!

 

[edison123]

Thx dougmsoe. That's a good start.

 

[jbartos]

Suggestion: The dc motor may be shunt, series, compound, universal or with separate field winding. If the motor is disassembled, the number of poles, motor winding connections, winding conductor sizes, etc. may be observed.
Universal motors tend to have larger diameter of the commutator. Also, they run on AC.
Physical dimensions can also be to some help. A visit of a motor repair shop may also be fruitful.