Synchronous Motor Inductance Mapping With Square-Wave Excitation
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Solution Overview
Problem
Existing methods for establishing the inductance parameter model of a motor require a long measurement time, especially for higher current resolution, and can cause rotor vibration, affecting measurement accuracy.
Innovation Solution
A method for obtaining synchronous motor parameters that involves setting an operating current, applying a positive and negative fixed voltage to detect feedback current, generating a square wave voltage, and calculating inductance values based on the voltage and current, allowing for the rapid establishment of a parameter table of inductance versus current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inverter applies sine wave voltage and gradually increases current to measure inductance values at multiple current points, then the resolution of current points is higher and measurement precision is improved, but the measurement time increases significantly
Solution Approach 1:
The patent applies periodic square wave voltage instead of gradually increasing sine wave voltage. By using periodic square wave excitation at different duty cycles, the system can rapidly measure inductance at multiple current points without the time-consuming gradual ramp-up process, reducing measurement time from 300 seconds to a much shorter duration while maintaining measurement precision across 100 current points
Solution Approach 2:
The patent changes the voltage waveform from sine wave to square wave and modifies the excitation parameters by using different duty cycles (20%, 40%, 60%, 80%) to generate different current levels. This parameter change enables rapid acquisition of inductance values at multiple current points, achieving high current point resolution without proportionally increasing measurement time
2Measurement precision
If the inverter gradually increases the applied current to measure inductance at higher current points, then the current range is expanded and measurement precision is improved, but the rotor vibration increases and affects measurement accuracy
Solution Approach 1:
The patent uses periodic square wave voltage excitation with controlled duty cycles to generate current at different levels. This periodic excitation method allows the system to reach desired current points rapidly without the gradual increase that causes rotor vibration, thereby maintaining measurement accuracy while expanding the measurable current range
Solution Approach 2:
The patent skips the gradual current ramp-up process that causes rotor vibration. By directly applying square wave voltage at specific duty cycles, the system rushes through to the target current points quickly, minimizing the time during which rotor vibration could affect measurement accuracy while still achieving high current point resolution
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the inverter to establish the parameter table in a very short time, improving control performance and reducing current oscillation during motor control.
Implementation Method 1
calculating a first inductance value of the first axis based on the fixed frequency, a voltage value of the square wave voltage, and a current value of the axial current
Data Source
AI summary
A method of obtaining a parameter of a synchronous motor is disclosed and includes: setting an operating current of the motor; providing a positive fixed voltage to the motor and monitoring a feedback current from the motor; recording a triggering time for the feedback current to reach the operating current; providing a negative fixed voltage to the motor for the triggering time; obtaining a square-wave voltage with a fixed frequency based on the positive fixed voltage and the negative fixed voltage being provided; providing the square-wave voltage with the fixed frequency to one axis of the motor; transforming three-phase current from the motor into an axial current; computing an inductance value of this axis based on the fixed frequency, the square-wave voltage and the axial current; and, creating an inductance-current parameter table based on a plurality of the inductance values and the axial currents correspondingly.