Electric Heater Ramp-Up Control Under Current Limits
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Solution Overview
Problem
Existing thermal systems with resistive heating elements face inefficiencies in reaching temperature setpoints due to standard ramp rates, leading to non-productive manufacturing time and potential overheating or underheating issues.
Innovation Solution
A method and control system that apply power to resistive heating elements at a variable ramp rate, monitoring electric current and adjusting the ramp rate based on current limits to prevent overheating, while also managing temperature differences across multiple zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a standard ramp rate is used to increase temperature to the setpoint, then the temperature control is simple, but the manufacturing time is lost and productivity decreases
Solution Approach 1:
The patent implements a dynamic ramp rate that adjusts based on real-time current measurements. The system transitions from a fixed standard ramp rate to a variable ramp rate that adapts to changing thermal conditions, allowing faster heating when safe and slower heating when approaching current limits, thereby reducing total heating time while maintaining safety
Solution Approach 2:
The system changes the ramp rate parameter dynamically during the heating process. By monitoring electric current and adjusting the ramp rate accordingly (increasing or decreasing based on current relative to maximum limits), the system optimizes heating speed while preventing overheating, thus improving productivity without sacrificing safety
2Productivity
If a higher ramp rate is used to reduce heating time, then productivity improves, but the risk of overheating and thermal stress increases
Solution Approach 1:
The system continuously monitors electric current flowing through the heating element and uses this feedback to adjust the ramp rate in real-time. When current approaches the maximum limit, the ramp rate is reduced to prevent overheating; when current is well below the limit, the ramp rate can be increased to improve productivity. This closed-loop feedback mechanism resolves the contradiction between speed and safety
Solution Approach 2:
The system establishes a current limit band (e.g., 80-100% of maximum current) before reaching the absolute maximum, allowing proactive adjustment of the ramp rate. By cushioning against the maximum current limit in advance rather than reacting after being exceeded, the system prevents thermal stress and overheating while maintaining optimal heating speed
3Loss of time
If the ramp rate is increased to reach setpoint faster, then non-productive time is reduced, but current limits may be exceeded causing safety issues
Solution Approach 1:
The system dynamically adjusts the ramp rate based on real-time current conditions rather than using a fixed rate. This allows the system to safely maximize heating speed by increasing ramp rate when current is low and reducing it when current approaches limits, thereby minimizing heating time while maintaining system reliability and safety
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 allows for more precise and efficient temperature control, reducing non-productive time and preventing thermal stress across heating zones, thereby enhancing manufacturing productivity and equipment longevity.
Implementation Method 1
A thermal system generally includes a heater having resistive heating elements
Data Source
AI summary
In one form, the present disclosure is directed toward a method for controlling temperature of a heater including a resistive heating element. The method includes applying power to the resistive heating element of the heater at a variable ramp rate to increase temperature of the heater to a desired temperature setpoint. The variable ramp rate is set to a desired ramp rate. The method further includes monitoring an electric current flowing through the resistive heating element of the heater, and reducing the variable ramp rate from the desired ramp rate to a permitted ramp rate in response to the electric current being greater than a lower limit of an electric current limit band. An upper limit of the electric current limit band is provided as a system current limit.