Induction Motor Constant Estimation With a Fixed Rotor

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Solution Overview

Problem

Existing methods for estimating the electrical constants of induction motors are inaccurate due to the use of concentration constant models, which do not accurately represent the distributed constants of real induction motors, and require excitation conditions that differ from actual operation.

Innovation Solution

A method that involves fixing the rotation axis of a three-phase induction motor and using an inverter to energize DC and three-phase AC currents, allowing for the measurement of electrical constants under conditions similar to actual operation without rotating or driving the motor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If mathematical model matching method is used to obtain electrical constants, then the measurement can be performed without rotating the motor, but the accuracy of electrical constant estimation deteriorates due to excitation conditions differing from actual operation

Engineering Contradiction:

Improvemeasurement operationVSAvoidelectrical constant estimation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The invention changes the excitation parameters (voltage, frequency, current) to match actual operating conditions. By applying excitation voltages at frequencies corresponding to actual motor operation and using the measured currents to calculate electrical constants, the method ensures accurate estimation while keeping the motor stationary.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the mechanical rotation requirement with an electrical excitation system. Instead of rotating the motor to measure electrical constants, the method uses controlled electrical excitation and current measurement to derive the constants, substituting mechanical action with electrical measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If excitation frequency is increased to obtain impedance difference for accurate measurement, then measurement accuracy improves, but the motor is excited under over-slip condition which is not possible in actual operation

Engineering Contradiction:

Improveelectrical constant measurement accuracyVSAvoidapplicability to actual operation

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The invention changes the excitation frequency parameter to match actual operating frequencies rather than using high frequencies for impedance differentiation. By measuring currents at multiple frequencies that correspond to real motor operation and using least squares fitting, the method achieves accurate electrical constant estimation under applicable operating conditions.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If automatic adjustment function is implemented before actual operation, then electrical constants can be set for motors with unknown constants, but the adjustment process requires motor rotation and driving

Engineering Contradiction:

Improvecapability to handle unknown electrical constantsVSAvoidoperation complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The invention replaces the mechanical rotation and driving process with an electrical excitation and measurement system. By applying controlled excitation voltages and measuring the resulting currents, the method automatically calculates electrical constants without requiring motor rotation, simplifying the adjustment process while maintaining adaptability to unknown motor parameters.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 highly accurate measurement of electrical constants, ensuring secure starting torque and a stable drive system for induction motors.

Implementation Method 1

the inverter controls the three-phase induction motor with the rotating shaft fixed by the fixing mechanism, energizes DC current and three-phase AC current

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250070700A1Drive unit for induction motor

Publication Date: 2025.02.27 HITACHI IND EQUIP SYST CO LTD

AI summary

The objective is to accurately estimate the electrical constants required for control of a three-phase induction motor for which the electrical constants are unknown. To achieve the above-mentioned purpose, a three-phase induction motor, a fixing mechanism that can fix the rotation axis of the three-phase induction motor, an inverter that drives the three-phase induction motor, a current detection means that detects the current of the three-phase induction motor, the current detection means for detecting the current of the three-phase induction motor and control the three-phase induction motor by using the inverter, wherein the inverter controls the three-phase induction motor with the rotating shaft fixed by the fixing mechanism, energizes DC current and three-phase AC current, and measures the electrical constant of the three-phase induction motor using the control voltage obtained as a result of the energization.