[kluppy]

Hi everyone, quick question on what the resistance of a servo motor should be. The motors i have are Sanyo Denki brand. Specs are 75 volts, 350 watts and 5.5 amps. So, simple ohms law tells me that the resistance of the motors should be about 13.6 ohms? I measured the two motors on my turret punch ( while the motors were disconnected) and one is 15 ohms and the other is 2 ohms. I tried blowing all the dust and such out of the 2 ohm motor but the resistance did not increase. So, assuming it was faulty (considering the resistance), i sent it to a motor rewinder who was recommended to me but they said it was fine, cleaned it out properly, recoated the windings and sent it back. So now i am horribly confused, is anyone able to tell me what resistance i should expect? is 2 ohms right and it's actually the 15 ohm motor that might be faulty?

any assistance would be greatly appreciated.

[Al_The_Man]

1st, you do not mention the technology of the motor?
Stepper, DC, BLDC, AC etc.
In any case, very low resistance is normal as a servo motor does not present a purely resistive load when in motion so simple ohms law does not apply to a static resistance test.
Inductance comes into play as well as back EMF.
The control of a servo motor generally involves a drive of some kind, which provides a controlled rate of acceleration etc by monitoring current.
Placing full voltage across a stationary servo motor would incur an initial extremely high current until the inductive effect and back EMF occurs.
Stepper motors are a slightly different case as it is normal to maintain a constant rated current at all times.
Al.

[TRMMEX]

Did you check the winding resistance in all three phases? did the values be the same between U-V, U-W, V-W? Are both motors same part number?
Low resistance values are common in servomotors depending on power. What is the problem you are getting on your machine?