Frequency Converter Thermal Load Redistribution via Voltage Potential Shift
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Solution Overview
Problem
Existing converter motor systems face inefficiencies due to high thermal loads on semiconductor switches and components, leading to increased power losses and reduced utilization, particularly during low-speed operations or standstill conditions.
Innovation Solution
The method involves dynamically adjusting the voltage potential and duty cycle of semiconductor switches to reduce thermal loads by identifying and mitigating the maximum thermal load on switches and associated components, ensuring that the voltage potential is shifted or the duty cycle is altered to maintain efficient operation without permanent conductive states, thereby reducing power losses and increasing the output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the duty cycle of semiconductor switches is increased to maintain motor current during low-speed operations, then the output performance is improved, but the thermal load on semiconductor switches and components increases excessively
Solution Approach 1:
The patent changes the voltage potential parameter (neutral point potential) to redistribute thermal loads among semiconductor switches and components. By shifting the voltage potential, the patent alters which switches and components bear the thermal load, thereby reducing the maximum thermal load while maintaining the same output current. This is achieved without changing the fundamental PWM operation but by introducing an additional degree of freedom in voltage potential selection.
2Loss of energy
If the voltage potential is shifted to reduce thermal load on semiconductor switches, then power losses are reduced, but the control complexity increases
Solution Approach 1:
The patent employs a self-service mechanism where the control system automatically monitors thermal loads on semiconductor switches and components, identifies the maximum thermal load, and autonomously adjusts the voltage potential to redistribute the thermal load. This self-regulating approach reduces power losses without requiring external intervention or complex manual control, as the system serves itself by detecting and correcting thermal imbalances.
3Temperature
If the duty cycle is reduced to lower thermal load on specific semiconductor components, then the thermal stress is reduced, but the motor current and output performance decrease
Solution Approach 1:
The patent changes the voltage potential parameter to redistribute thermal loads among semiconductor switches and components. By shifting the voltage potential, the patent alters which switches and components bear the thermal load, thereby reducing the maximum thermal load while maintaining the same output current. This is achieved without changing the fundamental PWM operation but by introducing an additional degree of freedom in voltage potential selection.
Data Source
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AI summary
The invention relates to a frequency converter (4) for the semiconductor switches (T1, T2, T3, T4, T5, T6) of which a maximum thermal load is repeatedly determined, a switch-on duration and/or a star point voltage potential being modified, at least for the semiconductor switch (T1, T2, T3, T4, T5, T6) for which the thermal load is at a maximum, in such a way that the thermal load for said semiconductor switch (T1, T2, T3, T4, T5, T6) and/or a semiconductor component (D1, D2, D3, D4, D5, D6) associated therewith is reduced.