Motor Heat Estimation Control for Load-Time Overtemperature Protection
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Solution Overview
Problem
Existing electric work machines may excessively protect motors from heat due to assumptions about load times and ratios of loaded states, leading to unnecessary protection even when the motor can handle further temperature rise.
Innovation Solution
An electric work machine is designed with a heat estimation circuit that calculates an estimated heat value based on electric current and a parameter adjusted according to load time, allowing for appropriate protection of the motor based on actual load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the increment value of the counter is set to a large value to ensure motor protection during long load periods, then motor protection reliability is improved, but unnecessary protection occurs during short load periods
Solution Approach 1:
The patent applies dynamics by making the counter increment value variable rather than fixed. The control circuit dynamically adjusts the increment value based on the measured load time, using a larger increment value for longer load times and a smaller increment value for shorter load times. This dynamic adjustment resolves the contradiction by ensuring adequate protection during extended load periods while preventing unnecessary shutdowns during brief load periods, thereby maintaining both protection reliability and productivity.
2Reliability
If the counter increment value is set to a large value assuming large load ratio, then motor is protected during extended load, but motor is excessively protected during short load time
Solution Approach 1:
The patent applies parameter changes by modifying the counter increment value parameter based on the load time condition. When the load time exceeds a predetermined threshold, the control circuit sets the increment value to a first (larger) value for enhanced protection. When the load time is within the threshold, it sets the increment value to a second (smaller) value, allowing continuous operation. This parameter adaptation resolves the contradiction between heat protection and operational flexibility.
3Device complexity
If a fixed counter increment value is used, then the protection system is simple, but it cannot adapt to varying load time conditions
Solution Approach 1:
The patent implements dynamics by transitioning from a fixed increment value to a dynamic adjustment mechanism. The control circuit measures the actual load time and automatically adjusts the counter increment value accordingly, enabling the protection system to adapt to varying load conditions. This dynamic approach increases adaptability while maintaining reasonable system complexity through automated control logic.
Solution Approach 2:
The patent applies feedback by using the measured load time information to adjust the counter increment value. The control circuit continuously monitors the load time and feeds this information back to modify the protection parameters in real-time. This feedback mechanism enables the system to adapt to varying load conditions without requiring complex manual configuration, resolving the contradiction between simplicity and adaptability.
Data Source
AI summary
An electric working machine in one aspect of the present disclosure calculates an estimated heat value based on an electric current value and a parameter. The estimated heat value corresponds to an estimated heat generation amount of a motor. The electric current value corresponds to a magnitude of an electric current delivered from a power source to the motor. The electric work machine varies the parameter based on a load time. The load time corresponds to a time period during which a first load is continuously imposed on the motor. The first load has a specified magnitude or more. The electric work machine performs a protective operation for over temperature protection of the motor based on the estimated heat value having reached a heat threshold.