Elevator Emergency Drive via Rectifier Voltage Boosting
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Solution Overview
Problem
Elevators lack an effective automatic emergency drive system to safely release trapped passengers in case of power failure, relying on traditional safety relays that are unreliable and costly.
Innovation Solution
An elevator system with a modulated rectifier bridge and DC/DC converter, integrated emergency control, and feedback circuits allows automatic emergency drive by boosting DC voltage and providing AC power for elevator car doors, using a backup power supply to release brakes and open doors, replacing traditional relays with simpler isolation means and improving supervision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional safety relays are used for emergency drive control, then the system has simple hardware structure, but the reliability is low and cost is high
Solution Approach 1:
The patent replaces traditional mechanical safety relays with an electronic control system. The emergency control unit (34) integrated in the controller uses electronic circuits and software logic to supervise and control emergency drive operations, eliminating the need for complex mechanical relay systems while improving reliability through electronic supervision and feedback mechanisms.
Solution Approach 2:
The emergency control unit utilizes the existing controller resources and integrated circuits to perform emergency drive functions. By using the controller's own processing power and integrated emergency control unit, the system serves itself without requiring separate dedicated hardware components, thereby reducing overall system complexity while maintaining high reliability.
2Power
If backup power supply is connected to DC link during emergency drive, then the elevator motor can be driven, but the voltage level must be increased from backup supply to DC link level
Solution Approach 1:
The rectifier bridge (16) is designed to perform multiple functions: normal rectification during regular operation and voltage boosting during emergency drive. By using the same rectifier bridge for both standard rectification and emergency voltage conversion, the patent eliminates the need for separate voltage conversion hardware, reducing device complexity while providing the necessary power conversion capability.
Solution Approach 2:
The patent changes the operating parameters of the rectifier bridge by controlling the firing angle of its semiconductor switches. By adjusting the firing angle, the rectifier bridge can operate in different modes including voltage boosting mode during emergency drive, converting the lower voltage from the backup power supply to the higher DC link voltage level without requiring additional conversion equipment.
3Power
If semiconductor switches in rectifier bridge are controlled for voltage boosting, then the DC link voltage can be increased, but the switching frequency and control precision must be high
Solution Approach 1:
The patent implements feedback control through the emergency control unit (34) that continuously monitors the DC link voltage and adjusts the firing angle of the rectifier bridge semiconductor switches accordingly. This closed-loop feedback mechanism ensures precise voltage control during emergency drive, automatically adjusting the switching parameters to maintain the required DC link voltage level without manual intervention or complex pre-programming.
4Ease of manufacture
If isolation relay is replaced with normal isolation means, then the hardware cost is reduced, but the reliability of isolation is lower
Solution Approach 1:
The patent replaces mechanical isolation relays with electronic isolation control. The emergency control unit (34) uses electronic switching and supervision to control the isolation relay, providing enhanced reliability through electronic monitoring and control logic while maintaining the physical isolation function. This substitution leverages the controller's electronic capabilities to improve upon traditional mechanical isolation systems.
Solution Approach 2:
The isolation relay system is integrated into the controller's self-supervision mechanism. The controller automatically monitors the isolation relay status and the emergency drive conditions, and can autonomously control the isolation relay operation without external intervention. This self-service approach ensures that the simpler isolation means operates reliably within the supervised control system.
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
Enables automatic and economical emergency drive operations, ensuring passenger safety by integrating emergency control with the elevator controller, reducing hardware components, and ensuring reliable power supply during mains failure.
Implementation Method 1
the necessary DC link voltage is provided via a boost activity of at least one of the semiconductor switches of the rectifier bridge connected with the first feed line and the at least one choke provided in the first feed line
Data Source
AI summary
An elevator includes an elevator motor, a motor drive for the elevator motor having a frequency converter including a rectifier bridge, an inverter bridge and a DC link in between, which frequency converter is controlled via a controller, the rectifier bridge being connected to AC mains via three feed lines including chokes, and the rectifier bridge being realised via controllable semiconductor switches, an isolation relay being located between the feed lines and AC mains, a backup power supply at least for emergency drive operation, an emergency control for performing an automatic emergency drive, the backup power supply is via a first switch connectable with only a first of the feed lines. A second and/or third of the feed lines is via a second switch connectable as power supply to a car door arrangement, the first switch as well as the second switch are controlled by the emergency control, and the emergency control is connected to a manual drive circuit having a manual drive switch for a manual rescue drive. The elevator includes a first feedback circuit configured to provide to the emergency control first information indicating the switching state of the isolation relay, a second feedback circuit which is configured to provide to the emergency control second information indicating switching state of the first switch. The emergency control is configured to selectively allow or prevent the emergency drive operation on the basis of the first information and the second information.