# Servo motor torque current calculation

#### Raghu6300

Joined Mar 23, 2024
1
HI ,
I am currently working with 3 phase AC servo motor and it is rated as 230VAC. I have the measurements of currents of the three phases - 1.2A, 0.8A, 0.8A respectively with load and rotating at 20 rpm. I want to calculate the torque using the relation Power = 2*pi*speed(rpm)*torque/60. for this i want to calculate the power the motor is consuming during the load.

can someone help me out in calculating the power of motor using the rated voltage and phase currents ?

#### MisterBill2

Joined Jan 23, 2018
19,045
There is a considerably more accurate and easier to use method for determining the torque fro a servo motor, which is to use the torque tables provided by the manufacturer for that specific model of motor. I learned about this in the first servomotor class I went to at the MOOG company training location.
And I offer a caution, which is that if it really is a three phase servomotor the current for each phase should be very close. Is it possible that one of those phase sources is also operating a brake release magnet?? Otherwise, all three phase currents should be similar.
OR, is it possible that what you have is a standard AC servomotor with sine and cosine phases connected like a three phase motor???

Joined Jul 18, 2013
28,779
Check manuf. spec sheet, most offer the torque curve specifications..
Torque for most servo motors is generally maximum at zero RPM, one simple method is the spring scale method.
Is this a PM rotor 3ph version?