Transient inductance tuner for motor control

An inductance identifier for use with a three-phase field orientated motor controller which provides small q-axis command and feedback voltage signals and a initial inductance estimate and uses an inductance value for motor control, the identifier comprising:

• a comparitor for comparing the command and feedback voltage signals to derive an error signal:
• a proportional-integral regulator for increasing a magnitude of the error signal;
• and
• a summer for adding error signal and the initial inductance estimate;
• wherein the identifier operates during normal motor operation and further includes a switch which, when the error signal is essentially zero, maintains a constant correct value.

A method for deriving an inductance estimate for use with a three-phase field oriented motor controller which provides q-axis command and feedback voltage signals and an initial inductance estimate and uses and inductance value for motor control, the method comprising the steps of:

• comparing the command and feedback voltage signals to derive an error signal:
• passing the error signal through a proportional-integral regulator to increase the error magnitude;
• adding the error signal and the initial inductance estimate to provide a corrected value for use by the controller;
• wherein the method operates during normal motor operation and further includes the step of, when the error signal is essentially zero, maintaining a constant correct value and, wherein there are a plurality of correct values corresponding to different motor loads and each value is a function of motor load, the controller is capable of simulating different motor loads during the commissioning procedure by providing d and q-axis current command signals and the method includes the steps of correlating correct values and the q-axis current command signal and storing each value as a function of the q-axis current command signal.

A method for deriving a load dependent transient inductance table for use during normal motor operation for driving a three phase field oriented motor controller, the controller providing q-axis command and feedback voltage signals and an initial inductance estimate and including a memory, the controller using an inductance value for motor control, the inductance value being load dependent and the controller capable of simulating different loads during a commissioning procedure, the method comprising the steps of:

• (a) simulating a motor load by providing command signals to the motor;
• (b) comparing the command and feedback voltage signals to derive an error signal;
• (c) mathematically combining the error signal and the initial inductance estimate to provide a correct inductance value;
• (d) correlating the correct value with the instantaneous q-axis current command signal;
• (e) storing the correct value and q-axis current command signal in the memory;
• (f) changing the command signals to the motor to simulate a different load;
• and
• (g) repeating steps a through f until a plurality of correct values and q-axis current command signals have been correlated and stored in the memory.