Braking Resistor Temperature Control via Electrical Parameter Modeling
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Solution Overview
Problem
Conventional converter systems lack effective safety measures for monitoring and controlling the temperature of braking resistors, which can lead to overheating and potential damage, especially in AC/DC converter systems where direct temperature measurement is complex and unreliable.
Innovation Solution
A converter system with a controllable switch and braking resistor, where the DC voltage-side terminal is connected in parallel to a DC/AC converter, using a parameterizable filter and linear controller to model the temperature characteristic, allowing for indirect monitoring and control of the braking resistor's temperature without direct measurement, and incorporating a galvanically decoupled current-acquisition device for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct temperature measurement is implemented at the braking resistor, then temperature monitoring precision is improved, but device complexity and reliability are worsened due to additional measurement components and potential measurement failures
Solution Approach 1:
The patent introduces an intermediary approach by using electrical parameters (voltage and current) as mediators to indirectly determine temperature. Instead of directly measuring temperature with sensors, the system measures voltage across the braking resistor and current through it, then calculates temperature based on the relationship between electrical power dissipation and temperature rise. This intermediary method avoids the complexity and reliability issues of direct temperature measurement while maintaining sufficient monitoring precision.
Solution Approach 2:
The patent replaces the mechanical/physical temperature measurement system (temperature sensors, thermocouples) with an electrical measurement and calculation system. By substituting direct thermal measurement with electrical parameter measurement and mathematical modeling, the system achieves temperature monitoring without the complexity of direct temperature sensing components.
2Measurement precision
If direct temperature measurement is implemented at the braking resistor, then temperature monitoring precision is improved, but system reliability is worsened due to potential measurement failures and additional failure points
Solution Approach 1:
The patent uses electrical parameters as intermediaries to indirectly assess temperature, thereby improving reliability. By measuring voltage and current (which are already present in the system for power control) and using them to calculate temperature through established physical relationships, the system eliminates the need for separate temperature measurement components that could fail. This approach leverages existing reliable measurements to derive temperature information.
Solution Approach 2:
The system uses its own existing electrical measurements (voltage and current for power control) to serve the additional function of temperature monitoring. The same voltage and current sensors used for controlling the braking resistor's power dissipation also provide the data needed for temperature determination, eliminating the need for separate measurement systems and their associated failure points.
3Device complexity
If a simple temperature modeling approach is used without direct measurement, then device complexity is reduced, but temperature monitoring precision may be worsened
Solution Approach 1:
The patent implements a feedback mechanism where the determined temperature (based on electrical parameters) is continuously fed back to the control system. This feedback allows the controller to adjust the braking resistor's power dissipation in real-time, ensuring that the temperature remains within safe operating limits. The continuous feedback loop compensates for any simplifications in the temperature modeling approach by dynamically adjusting control parameters based on the calculated temperature trend.
Solution Approach 2:
The patent changes the parameters used for temperature assessment from direct physical temperature measurement to electrical parameters (voltage, current, and their derived power). By transforming the measurement domain from thermal to electrical parameters, the system achieves simpler implementation while maintaining sufficient precision through the well-established relationship between electrical power dissipation and temperature rise in resistive elements.
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 solution enhances safety by allowing for precise monitoring and control of the braking resistor's temperature, preventing overheating and enabling detection of internal or external resistors, thus ensuring reliable operation and preventing damage.
Implementation Method 1
a series circuit which has a braking resistor and a controllable switch, the DC voltage-side terminal of a DC/AC converter
Implementation Method 2
the temperature characteristic at the braking resistor is modeled with the aid of the controller including a downstream parameterizable filter
Data Source
AI summary
A system includes a braking resistor and a controllable switch connected in series, the controllable switch adapted to connect to a terminal on a direct-voltage side of an AC/DC converter; an evaluation unit adapted to generate a control signal to control the controllable switch and including a determination device adapted to determine electric power supplied to the braking resistor; a voltage-acquisition device adapted to supply an output signal to the evaluation unit; and a controller adapted to regulate a set value toward an output signal of the determination device, the controller adapted to supply, directly and/or via a limiter, to a parameterizable filter adapted to convey an output signal to a switching element, the switching element adapted to generate an output signal to open and/or close the controllable switch as a function of exceeding and/or undershooting of a threshold value.