I know that many manufacturers keep this information somewhat closely guarded, but let's say I pick up any old AC servo from eBay. Ignoring the encoder, how would I go about measuring the electrical parameters needed to run it on a generic servo drive 3rd party AC servo drive which allows manual entry of motor data? Some of this info is easy to find, but some very much not so. I've always resorted to begging for this data, and I can usually get it, but I've never considered actually trying to measure it. I've bolded the items I find hard to locate and would be good to know how to measure. This is a 3 phase synchronous permanent magnet AC servo motor with AC sinusoidal or trapezoidal commutation.
From my servo drives, here is the list of required data to run a motor:
From my servo drives, here is the list of required data to run a motor:
- Rated Power (W) <- Usually advertised
- Torque Constant (N*m/A_rms)
- Rated Torque (N*m) <- Usually advertised
- Peak Torque (N*m) <- Usually advertised
- Inertia (Kg*m^2)
- Poles Per Revolution (n)
- Winding Resistance (Ohms)
- Winding Inductance (H)
- Inductive Time Constant (ms)
- Rated Voltage (Volts) <- Usually advertised
- Rated Speed (RPM) <- Usually advertised
- Maximum Speed (RPM) <- Usually advertised
- Continuous Current (A) <- Sometimes advertised
- Peak Current (A) <- Sometimes advertised
- Damping Coefficient (N*m/(Rad/s))
- Voltage Constant (V_rms/k_RPM)
- Overload Limit (%)
<- 300% seems typical - Max Acceleration (Rev/s^2)
- Thermal Model Parameters: <- I'll usually copy from similarly sized and shaped motors with known values
- Rth-we (C/W)
- Cth-we (W*s/C)
- Rth-wa (C/W)
- Cth-wa (W*s/C)
- Flux Saturation Curve (% Nominal Inductance from 1/8 to full speed in 8 steps) <-Small motors are usually 1.0 for all values
- Commutation Angle (Electrical degrees) <-measure Back EMF with an Oscope while running the motor slowly and following the encoder signals
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