Elevator Power Converter Switching for Balanced Service Life
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Solution Overview
Problem
The control device for an elevator experiences a significant difference in service life between the inverter and the regenerative converter, particularly due to varying stress levels when the elevator car is frequently accelerated or decelerated, which affects the overall device's longevity.
Innovation Solution
The control device incorporates two power converters that can switch between operating as inverters and regenerative converters, with temperature detection and switching mechanisms to balance their operational loads, allowing each to assume different roles based on temperature thresholds and the state of the electric power generator, utilizing wide bandgap semiconductors for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single inverter is used to drive the motor during acceleration and deceleration, then the control structure is simple, but the inverter experiences high stress and reduced service life
Solution Approach 1:
The single inverter function is segmented into two separate power converters: a first power converter and a second power converter. During acceleration, the first power converter operates as the inverter while the second operates as the regenerative converter. During deceleration, their roles are reversed. This segmentation distributes the stress load across two devices, preventing any single inverter from experiencing excessive wear and extending overall system service life.
Solution Approach 2:
The system dynamically switches the operational roles of the two power converters based on whether the elevator is accelerating or decelerating. The switching means changes the circuit configuration to assign inverter function to one converter and regenerative converter function to the other, alternating their roles over time. This dynamic role assignment ensures balanced utilization and prevents any single converter from being continuously overloaded.
2Productivity
If the inverter operates continuously under high stress during frequent acceleration and deceleration, then the elevator responds quickly to operational demands, but the inverter's service life is reduced
Solution Approach 1:
The two power converters operate in periodic alternation, with each converter serving as the inverter during specific operational phases (acceleration or deceleration) and serving as the regenerative converter during other phases. This periodic switching of roles ensures that each converter experiences high stress only intermittently rather than continuously, thereby extending their service lives while maintaining the elevator's ability to respond quickly to acceleration and deceleration demands.
Data Source
AI summary
Provided is a control device for an elevator, including: a first power converter; a second power converter; and switching means. The switching means being configured to selectively achieve: a first circuit configuration that causes the first power converter to operate as the regenerative converter, and also causes the second power converter to operate as the inverter; and a second circuit configuration that causes the second power converter to operate as the regenerative converter, and also causes the first power converter to operate as the inverter.