Elevator Brake Controller Semiconductor Switches Wear
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Solution Overview
Problem
Elevator brake safety systems face challenges due to the wear and limitations of electromechanical relays, particularly in high-duty applications, and semiconductor switches lack the necessary safety features like normally closed contacts for fault diagnosis, making them unsuitable for strict elevator safety regulations.
Innovation Solution
A brake controller design using semiconductor safety switches in series and parallel configurations with a voltage and/or current sensor to ensure safe operation, where the second safety switch short-circuits the brake coil to prevent energy flow in case of failures, and a fuse is used to ensure proper cut-off, eliminating the need for mechanical contactors and allowing for diagnostic monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical relays are used in brake control circuits, then the brake can be reliably activated through mechanical contact, but the relay is prone to wear out and has limited operation life
Solution Approach 1:
The patent replaces electromechanical relays with semiconductor switches (IGBT transistors) in the brake control circuit. This substitution eliminates mechanical moving parts and contacts, thereby eliminating wear and extending operational life while maintaining reliable brake activation through electronic switching.
2Ease of operation
If electromechanical relays are used for inductive load switching, then the brake coil can be switched on and off, but the switch off operation is very stressing for the relay due to contact arcing
Solution Approach 1:
The patent replaces mechanical relay contacts with semiconductor switches (IGBT transistors) that are specifically designed for inductive load switching. These semiconductor devices can handle the high di/dt and voltage spikes associated with inductive loads without the contact arcing problems that plague mechanical relays, thereby improving both ease of operation and reliability.
3Reliability
If semiconductor switches are used in brake control circuits, then inductive load switching is improved, but the switches lack normally closed contact for fault diagnosis
Solution Approach 1:
The patent incorporates feedback mechanisms including voltage sensors and current sensors that continuously monitor the state of the semiconductor switches and brake coil. This feedback enables real-time fault detection and diagnosis, compensating for the lack of physically visible contact positions by providing electronic monitoring and diagnostic capabilities.
Solution Approach 2:
The patent introduces diagnostic circuits and monitoring systems as intermediaries between the semiconductor switches and the control system. These intermediaries provide the fault diagnosis functionality that would otherwise be naturally available through mechanical contactor position indication, allowing the system to detect switch failures, short circuits, and other anomalies.
4Duration of action of stationary object
If semiconductor switches are used instead of mechanical contactors, then wear is eliminated, but the level of safety for elevator brake may be compromised
Solution Approach 1:
The patent implements redundant safety mechanisms including backup semiconductor switches, diagnostic monitoring systems, and fail-safe control logic that detect and respond to failures before they compromise brake safety. This beforehand cushioning ensures that even if a semiconductor switch fails, the system can detect the failure and activate alternative safety measures.
Solution Approach 2:
The patent changes the operational parameters and control strategies to accommodate semiconductor switches while maintaining safety. This includes implementing soft switching techniques, controlled turn-off sequences, and monitoring of voltage and current parameters to ensure the semiconductor switches operate within safe limits and maintain brake reliability.
Data Source
AI summary
The invention refers to an elevator brake controller, comprisinga brake supply circuit comprising a rectifier with a mains input side and a DC link output side, whereby in the mains input side and/or in the DC link output side at least one fuse is connected,a brake control circuit with at least one brake coil of an elevator brake, which brake coil is connected in series with a control switch configured to be controlled by an elevator control, which series connection of brake coil and control switch is connected to the DC link,a brake safety circuit which is connected between the brake supply circuit and the brake control circuit, which brake safety circuit comprises a first safety switch being connected in series with the brake coil as well as a second safety switch which is connected in parallel to the brake coil, whereby the first and second safety switches are configured to be controlled by an elevator safety circuit. This brake controller offers an improved cut-off safety in safety relevant situations.