Induction Motor Overheat Monitoring via Phase Angle
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Solution Overview
Problem
Existing induction motor overheat monitoring systems require multiple sensors, increasing costs and installation challenges, particularly in restricted spaces or harsh environments, and reducing sensor numbers complicates reliability and accuracy.
Innovation Solution
An induction motor overheat monitoring method that estimates motor temperature using current sensor data, calculating resistance and temperature based on phase angle differences during startup, eliminating the need for speed and temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors (speed sensor, temperature sensor) are added to achieve accurate overheat monitoring, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the temperature measurement function from dedicated temperature sensors and implements it through software calculation based on current sensor data. The equivalent resistance is calculated from current phase angle differences, and temperature is derived from this resistance, thereby extracting the temperature monitoring capability from hardware sensors to computational methods.
Solution Approach 2:
The current sensor serves multiple functions: it provides current magnitude information for motor control and simultaneously provides phase angle information for temperature estimation. By utilizing the phase angle difference information that would otherwise be unused, the system achieves temperature monitoring without adding dedicated temperature sensors, making the current sensor multi-functional.
2Measurement precision
If multiple sensors are installed to improve monitoring accuracy, then measurement precision is improved, but ease of operation deteriorates due to installation difficulties in restricted spaces
Solution Approach 1:
The patent removes the requirement for physical temperature sensors and speed sensors by extracting temperature information from electrical signal characteristics. This eliminates the need for mechanical installation of additional sensors in difficult-to-reach motor locations, significantly improving ease of operation.
3Ease of operation
If the number of sensors is reduced to simplify installation, then ease of operation is improved, but reliability deteriorates due to fewer redundant measurement channels
Solution Approach 1:
The system continuously monitors current phase angles and calculates equivalent resistance in real-time, providing continuous feedback on motor temperature. This continuous electrical measurement feedback compensates for the reduction in physical sensor redundancy, maintaining reliability through persistent electrical domain monitoring.
Solution Approach 2:
The patent replaces mechanical/physical sensor-based temperature measurement with an electrical signal-based measurement system. By substituting physical temperature sensors with electrical calculation methods, the system achieves similar or better reliability since electrical measurements are less susceptible to environmental degradation and mechanical failure.
4Measurement precision
If additional sensors are added to achieve accurate monitoring, then measurement precision is improved, but manufacturing precision requirements worsen due to stricter sensor placement tolerances
Solution Approach 1:
The patent eliminates the need for precise physical placement of temperature sensors by extracting temperature information from electrical signals that are already present in the motor control system. This removes the manufacturing precision requirements associated with sensor mounting positions, cable routing, and electrical connections.
5Measurement precision
If multiple sensors are used to improve monitoring accuracy, then measurement precision is improved, but loss of time increases due to more maintenance work required
Solution Approach 1:
The patent removes the maintenance burden of temperature sensors and speed sensors by extracting temperature monitoring capability from current sensor data. This eliminates the need for calibration, replacement, and troubleshooting of multiple sensor types, significantly reducing maintenance time and effort.
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
Enables reliable overheat monitoring and reduced maintenance costs by using current sensor data to estimate motor temperature and detect overheating states without additional sensors, improving system reliability and reducing wiring complexities.
Implementation Method 1
calculating a resistance of the induction motor by using the feature amount of the motor and the resistance calculation reference data, and then calculating a temperature of the induction motor from the calculated resistance
Data Source
AI summary
An induction motor overheat monitoring method and device detects overheating of an induction motor from a detection value of a current sensor. A resistance calculation relationship data indicating a relationship between a resistance and a feature amount at the time of starting of the induction motor and a determination reference value for determining overheating are stored in advance. At each starting, a current of the induction motor is detected, a signal regarding a phase angle difference is calculated, and a feature amount of the motor is calculated from the signal regarding the phase angle difference. Further, a resistance of the induction motor is calculated by using the feature amount of the motor and the resistance calculation reference data stored in advance. Then, a temperature of the induction motor is calculated from the resistance of the induction motor, and it is determined if the motor is overheated.