Asynchronous Motor Characterization at Standstill

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Solution Overview

Problem

Existing methods for determining the electromagnetic characteristics of asynchronous motors are often inaccurate, require motor rotation, and can cause damage due to high current injection, and are slow, making it difficult to obtain precise control and data at standstill.

Innovation Solution

A method involving applying a voltage pulse to the motor system, taking samples of the current pulse, and using a non-linear curve fitting algorithm, such as the Levenberg-Marquardt algorithm, to determine transient inductance, and injecting signals at varying frequencies to determine magnetizing inductance and flux, allowing for precise characterization without motor rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If large currents are injected into the motor to mitigate nonlinearities and explore magnetic saturation, then measurement precision is improved, but the motor and inverter are damaged due to heat generation

Engineering Contradiction:

Improvemeasurement precisionVSAvoidheat generation

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic voltage pulses at different frequencies to the motor windings instead of continuous large currents. This periodic excitation allows measurement of electromagnetic characteristics through frequency response analysis, achieving precise characterization without sustained high current that causes overheating

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the frequency parameter of the applied voltage signal to extract different electromagnetic characteristics. By analyzing the motor's response at multiple frequencies, the system determines inductance, resistance, and saturation characteristics without requiring large amplitude currents that generate excessive heat

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the motor rotates to determine electrical and magnetic properties, then measurement precision is improved, but the system becomes more complex and control becomes difficult when the motor is installed

Engineering Contradiction:

Improvemeasurement precisionVSAvoidease of operation

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent enables the motor to self-characterize while at standstill by measuring its electrical response to applied voltage pulses. The system extracts electromagnetic parameters directly from the motor's own current response without requiring external rotation mechanisms or complex test rigs, making the process simple and applicable to installed motors

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces mechanical rotation with electrical excitation for characterization. Instead of physically rotating the motor to measure properties, the system applies voltage pulses and analyzes the electrical response, substituting a mechanical test method with an electrical one that is simpler and non-intrusive

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Quantity of substance

If existing methods are used to obtain motor characteristics, then data can be obtained, but the process is slow and not efficient

Engineering Contradiction:

ImprovedataVSAvoidproductivity

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The patent uses periodic voltage pulses at multiple frequencies to rapidly extract electromagnetic characteristics. By analyzing the frequency response, the system obtains complete motor parameters in a single test sequence rather than requiring multiple separate measurements, significantly improving characterization speed

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent employs feedback through real-time measurement of current response to applied voltage pulses. The system continuously monitors the motor's electrical response and uses this feedback to calculate electromagnetic parameters, enabling rapid and accurate characterization without iterative mechanical testing

Inventive Principle:

Principle #23Feedback

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 accurate and efficient determination of electromagnetic characteristics, reducing the risk of damage and improving control precision by allowing characterization at standstill, while minimizing heat generation and avoiding nonlinearities.

Implementation Method 1

applying a voltage pulse to the motor system; taking a plurality of samples of a rising portion of a current pulse generated in response to the voltage pulse

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10241152B2Automated motor adaptation

Publication Date: 2019.03.26 DANFOSS POWER ELECTRONICS AS

AI summary

A method of determining electromagnetic characteristics of an asynchronous motor system is described. A motor system model is presented including a stator resistance, a transient inductance, a magnetizing inductance and a rotor resistance. A DC sequence is used to determine the stator resistance, a voltage pulse is used to determine the transient inductance, a binary injection frequency search algorithm is used to determine the magnetizing inductance, and an AC sine wave at slip frequency with DC offset is used to determine the rotor resistance.