Electric Motor Overload Detection via Speed-Adaptive Heat Estimation
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Solution Overview
Problem
Existing electric working machine systems fail to accurately detect overload operations due to reliance on estimated heat generation based on motor current and conduction time, which can lead to unnecessary motor restrictions and impaired performance, especially at high rotation speeds.
Innovation Solution
An electric working machine system comprising a motor, speed setting unit, load detection unit, determination unit, and parameter setting unit, where the determination unit calculates an estimated heat generation value from detected load and sets parameters based on rotation speed to accurately detect overload operations without being affected by speed, including the use of counters for heat generation and dissipation to refine this detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat generation amount is estimated by integrating current magnitude and conduction time, then motor protection can be implemented, but overload detection accuracy deteriorates due to rotation speed variations
Solution Approach 1:
The patent applies dynamics by making the heat generation estimation adaptive to rotation speed. The determination unit dynamically adjusts the heat generation amount calculation based on detected rotation speed, recognizing that heat dissipation capacity varies with speed. This resolves the contradiction by making the protection system reliable across varying speeds while maintaining accurate overload detection through speed-compensated estimation.
Solution Approach 2:
The patent changes the parameter used for heat generation estimation from a fixed current-integration method to a rotation-speed-adjusted method. By modifying the estimation parameter to account for rotation speed's effect on heat dissipation, the system achieves both reliable motor protection and accurate overload detection regardless of operating speed conditions.
2Reliability
If motor driving is restricted based on estimated heat generation, then motor deterioration is prevented, but productivity decreases due to unnecessary restrictions at high rotation speeds
Solution Approach 1:
The system dynamically adjusts driving restrictions based on real-time rotation speed detection. At high rotation speeds where heat dissipation is effective, the determination unit allows more flexible operation while still monitoring for true overload conditions. This resolves the contradiction by maintaining motor protection reliability while avoiding unnecessary productivity loss through speed-aware control decisions.
Solution Approach 2:
The patent changes the control parameter from a static heat generation threshold to a rotation-speed-dependent threshold. This allows the motor protection system to adapt its restrictions based on current operating conditions, preventing deterioration while maintaining productivity by allowing operation at high speeds where heat dissipation naturally occurs.
3Device complexity
If a fixed threshold is used for overload determination, then the system is simple to implement, but detection accuracy varies with rotation speed
Solution Approach 1:
The patent implements a dynamic threshold determination unit that adjusts the overload threshold based on detected rotation speed. While this increases complexity compared to a fixed threshold, it achieves consistent detection accuracy across all rotation speeds by compensating for the speed-dependent heat dissipation characteristics of the motor.
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 approach enhances the accuracy of overload detection, enabling timely protection measures such as motor stoppage or deceleration, thereby preventing damage and ensuring consistent performance across varying rotation speeds.
Implementation Method 1
the motor generates heat in accordance with the magnitude of current flowing at the time of driving the motor and a conduction time to the motor
Implementation Method 2
when the motor rotates at a high speed, the motor tends to dissipate heat more than when the motor rotates at a low speed due to rotation of the motor itself
Data Source
AI summary
An electric working machine according to one aspect of the present disclosure comprises a motor, a speed setting unit, a load detection unit, a determination unit, and a parameter setting unit. The determination unit calculates an estimated value of a heat generation amount of the motor, and determines that the motor is in an overload operation state when the estimated value reaches a predetermined threshold. The parameter setting unit sets a parameter to be used for calculating the estimated value and/or the threshold in accordance with a rotation speed set by the speed setting unit.