Abstract: The temperature (25, 33, 43) of solid state switching devices in variable speed motor drives (11, 18), such as elevator motor drives, are utilized to reduce the load on the drive, by reducing the switching frequency (50) or the commanded load (110). The choice between the preferred non-switching zero state and an alternative zero state is determined (60) by temperature (28, 34, 56) of the switched transistor's anti-parallel diode. The rate of recognizing reduced temperatures is limited (33, 34) to avoid motor speed and/or load variations. The temperature may either be measured (24, 27) or determined (70) from models utilizing manufacturer product specification and normalized thermal transient response from the transistor/diode package to a heat sink.

Abstract: A self-commissioning controller 7 for a field-oriented elevator motor controller 14 includes calculating an integral gain K.sub.I, a proportional gain Kp, and an overall gain (Gc) for the motor controller; obtaining initial values of a rotor time constant .tau..sub.R, magnetizing current Id, and motor torque constant K.sub.T for the motor controller 14, and obtaining a value of a motor transient inductance L.sigma.; calculating final values for said rotor time constant .tau..sub.R and magnetizing current Id, using said transient inductance L.sigma.; and calculating a system inertia J* parameter for speed loop compensation 16 within the motor controller 14. The controller 7 may also include calculating the initial values for .tau..sub.R, Id, and K.sub.T *, and performing self-commissioning automatically upon receiving a command from a service tool 80.

Abstract: An elevator controller 7 is provided with logic 48 which automatically calculates a motor time constant (.tau..sub.R) for a field-oriented current regulator/motor drive 20 by running the elevator up and down while computing an average of a sign-adjusted error signal DXD.sub.ERR for the up/down run and while varying .tau..sub.R and determining the value of .tau..sub.R at which the average of DXD.sub.ERR for the up and down runs equals zero within a predetermined tolerance. Alternatively, instead of computing the average of DXD.sub.ERR, a single elevator run may be used to determine the value of .tau..sub.R at which DXD.sub.ERR equals zero within a predetermined tolerance.