Permanent-Magnet Synchronous Motor Start-Up Current Control

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Solution Overview

Problem

Permanent-magnet type synchronous motors used in vehicle air conditioners face challenges in smooth start-up due to unknown rotor position at startup, leading to increased start-up failures and power consumption, especially in hybrid and electric vehicles where power source efficiency is critical.

Innovation Solution

A control device and method that sets a synchronous operation current based on a current limiting value determined by the inverter's temperature, with monitoring and updating during the rotation stabilizing period to prevent overcurrent and optimize motor loads, eliminating the need for sensor information from the motor or compressor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If constant current is applied without knowing compressor condition, then start-up control is simple, but start-up failure rate increases

Engineering Contradiction:

Improvestart-up control simplicityVSAvoidstart-up success rate

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control device determines an appropriate synchronous operation current value before actual start-up by applying a test current and measuring the back electromotive force. This preliminary action provides information about the compressor condition, enabling reliable start-up control without complex sensors or feedback mechanisms during the critical start-up phase.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If high current is applied to ensure start-up, then start-up success rate increases, but inverter damage risk increases

Engineering Contradiction:

Improvestart-up success rateVSAvoidinverter damage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control device dynamically adjusts the synchronous operation current based on real-time measurements of back electromotive force during a test period. By continuously monitoring the compressor's actual condition and adjusting the current accordingly, the system ensures reliable start-up while preventing excessive current that could damage the inverter.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control device measures the back electromotive force generated during a test current application period and uses this feedback information to determine the appropriate synchronous operation current. This feedback mechanism enables the system to adapt to actual compressor conditions, ensuring both reliable start-up and protection against inverter damage.

Inventive Principle:

Principle #23Feedback

3Use of energy by moving object

If synchronous operation current is updated during rotation stabilizing period, then power consumption is reduced, but control complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoidcontrol complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The control device updates the synchronous operation current in periodic stages: first during a test current application period to determine initial current, then during a rotation stabilizing period to optimize current based on measured back electromotive force. This periodic update approach reduces power consumption while maintaining manageable control complexity through structured, time-based control phases.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS8353172B2Control device, method, and program of permanent-magnet type synchronous motor

Publication Date: 2013.01.15 MITSUBISHI HEAVY IND LTD

AI summary

There is provided a control device of a permanent-magnet type synchronous motor that sets a synchronous operation current at start-up in response to a current limiting value determined from the temperature of an inverter that supplies three-phase power to the permanent-magnet type synchronous motor, that monitors an output voltage or an output current of the inverter during a rotation stabilizing period after start-up, and that updates the synchronous operation current using this output voltage or output current.