The Influence of Motor Parameter Deviations in Feedforward Field Orientation Drive Systems

Abstract
If the value of the time constant used in the slip calculator of a feedforward field orientation drive system deviates from the correct value, the decoupling of flux and torque is lost, and both steady-state and transient response is degraded. An analysis of detuned operation shows that the amount of performance degradation is strongly dependent on machine parameters. The large magnetizing inductance and low rotor resistance typically associated with larger, more efficient machines is shown to tend to amplify the effects of detuning compared to the relative insensitivity of small low-efficiency machines. It is also shown that for many applications the transient response effects of detuning can be handled by the outer control loops and that the major problem is maintaining the steady-state operating flux and current at reasonable levels.