Sensorless Motor Startup Detection Using Velocity and Current Monitoring

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Solution Overview

Problem

Sensorless motors without sensors face challenges in determining normal start-up, especially when position estimation fails, leading to potential motor damage due to high currents and difficulties in distinguishing between normal and abnormal start-up conditions.

Innovation Solution

An apparatus and method that include an elapsed time determination unit, motor velocity determination unit, and current value determination unit to assess whether a sensorless motor has reached a predetermined velocity and current levels after a predetermined time, allowing for normal start-up determination regardless of position estimation accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the operating level of the overcurrent protection circuit is lowered below a predetermined value to protect the motor, then the motor protection is improved, but the power device operation is stopped even when current flowing in the motor is normal

Engineering Contradiction:

Improvemotor protectionVSAvoidpower device operation

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent introduces an intermediate protection mechanism that operates between the motor and the power device. This intermediate layer monitors motor current and provides early warning or protective action before the current reaches levels that would trigger the main overcurrent protection circuit, thereby protecting the motor without unnecessarily stopping the power device operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary monitoring and assessment of motor current conditions before the actual damage can occur. By detecting abnormal current trends early in the startup phase or during operation, the system can take preventive measures before the current reaches dangerous levels, avoiding both motor damage and false power device shutdowns

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If the overcurrent protection circuit operates at a very high operating level to avoid false trips, then the power device operation stability is improved, but the motor may be damaged due to high current flowing

Engineering Contradiction:

Improvepower device operation stabilityVSAvoidmotor damage from high current

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The protection system is segmented into multiple monitoring levels: a primary monitoring layer that tracks current trends and motor performance parameters, and a secondary protection layer that activates only when primary monitoring detects abnormal patterns. This segmentation allows the system to maintain high operating levels for stability while providing layered protection against motor damage

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If position estimation is performed in sensorless motors to detect start-up failure, then the start-up detection accuracy is improved, but the system complexity increases

Engineering Contradiction:

Improvestart-up detection accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The motor itself provides the information needed for start-up detection through its own electrical characteristics. By monitoring current consumption, voltage drops, and power factor changes during startup, the system uses the motor's inherent electrical behavior as the detection mechanism, eliminating the need for separate position estimation algorithms or additional sensors

Inventive Principle:

Principle #25Self-service

4Reliability

If current monitoring is continuously performed to detect abnormal start-up, then the motor protection is improved, but the energy consumption and system complexity increase

Engineering Contradiction:

Improvemotor protectionVSAvoidenergy consumption for monitoring

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Instead of continuous monitoring, the system performs current measurements at periodic intervals during critical phases such as startup. The monitoring frequency is adjusted based on the operational phase - higher frequency during startup when damage risk is greatest, and lower frequency during steady-state operation, thereby reducing overall energy consumption while maintaining effective protection

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS7358694B2Apparatus and method for determining normal start up of sensorless motor

Publication Date: 2008.04.15 LG ELECTRONICS INC

AI summary

An apparatus and method determine a start-up of a sensorless motor. The apparatus includes an elapsed time determination unit, a motor velocity determination unit and an abnormal start-up determination unit. The elapsed time determination unit determines whether a predetermined time has elapsed after a start-up of the motor is initiated. The motor velocity determination unit determines whether a velocity of the motor exceeds a predetermined velocity value when the predetermined time has elapsed. The abnormal start-up determination unit determines that the motor was abnormally started up when the velocity of the motor does not exceed the predetermined value, and an amount of current flowing in the motor does not exceed a predetermined current value.