A special dynamometer for testing small motors

Transfer function and parameter evaluation for D-C servomotors

“…Several unique test methods are presented for determining the moment of inertia of the motor and its load without the necessity of adding tachometers which, in the case of small motors, might greatly alter their operating characteristics. and in general R/L»f/J; therefore, the first factor reduces to (6) s s+ JR (7) The second factor in the denominator of equation 6 is determined by the dif- CONSTANT…”

“…A very satisfactory technique that can be employed when there is no tachometer is to set a stroboscope on the 60-cyc]e line frequency and to adjust the magnitude of the impressed voltage E until a revolving disk mounted on the motor shaft appears stationary. A plot of E-IR versus 6) will yield a straight line the slope of which is K". This method produces a very accurate evaluation of K fJ, as it is not necessary to rely on the stroboscope frequency calibration.…”