US 2014/0111125 A1 · Traction Motor Retarding Flux Reference

Abstract

A traction motor system calculates motor flux by generating a real time effective resistance of a resistance grid calculated from motor torque and measured voltage on a DC link. Calculating effective resistance avoids solely relying on DC link voltage, which can be influenced by conditions such as wheel slip and drop out of one or more resistance grids. The effective resistance calculation is based on nominal motor values using known power levels and conditions. From these nominal values and the effective resistance, various scaling factors based on actual motor power can be generated and used to adjust a nominal flux reference to more accurately reflect actual motor flux. The scaling factors include power and torque scaling factors and a resistance scaling factor that is active during conditions such as wheel slip.

Claims20

Dependent claims

A method of adjusting electrical power application in a motor control system using an AC motor driven by an inverter bank that is coupled to a resistive grid during retard operation, the method comprising:

calculating a braking factor as a ratio of a nominal power DC voltage vs. a nominal brake DC voltage;
calculating a resistance scale factor as a ratio of measured grid resistance vs. a base grid resistance;
determining that motor operation is in one of a constant power region or a constant torque region;
multiplying a DC link voltage, the braking factor, the resistance scale factor and one of a power scale factor when in a constant power region or a torque scale factor when in a constant torque region to generate an adjusted flux estimate;
and
setting inverter operation to adjust motor torque based on the adjusted flux estimate, wherein the power scale factor is a function of a measured torque times mechanical frequency vs. a characteristic torque times a corner point mechanical frequency and the torque scale factor is a function of the measured torque vs. the characteristic torque.

3 more elements

An alternating current (AC) motor system adapted to adjust motor flux based on motor power, a direct current (DC) link voltage and an effective resistance at an inverter used to drive the AC motor, the system comprising:

an AC generator;
a rectifier that converts an output of the generator to DC power;
a DC link coupled to the rectifier;
a resistive grid selectively coupled to the DC link;
a plurality of AC motors;
a plurality of inverters, each of the plurality of inverters electrically coupling the DC link to a respective one AC motor of the plurality of AC motors;
a controller coupled to the DC link, the resistive grid, and each of the plurality of inverters, the controller including:
a processor;
and
a memory storing instructions that when executed on the processor cause the controller to:
calculate an estimated flux based at least in part on an effective resistance of the grid at each inverter of the plurality of inverters, the effective resistance calculated from actual torque, actual motor rotation frequency, the DC link voltage and a base resistance constant;
and
adjust a setting for each inverter of the plurality of inverters that controls a torque of the AC motor associated with each inverter.

10 more elements

Dependencies are inferred from the claim text.

Traction Motor Retarding Flux Reference

Life of this patent

Traction Motor Retarding Flux Reference

Life of this patent

Abstract

Claims20