Elevator Drive Safety Circuit Without Main Contactors
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Solution Overview
Problem
Existing elevator drive systems rely on main contactors, which are expensive and increase the complexity of the drive, while also posing safety concerns.
Innovation Solution
The implementation of a drive device with two separate safety input circuits that can interrupt the connection between the control circuit and the motor bridge, providing redundant safety signaling and input circuits to ensure safe operation even in case of breakdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If main contactors are used in the elevator drive system, then the safety level is improved, but the device complexity and cost increase
Solution Approach 1:
The patent removes main contactors from the elevator drive system entirely. Instead of using mechanical main contactors for safety functions, the invention implements safety functionality through semiconductor switches and control circuits that can interrupt power to the motor bridge, thereby eliminating the need for separate main contactor components while maintaining safety requirements.
Solution Approach 2:
The patent replaces mechanical main contactors with an electronic control system consisting of semiconductor switches (IGBTs), control circuits, and safety input circuits. This substitution allows safety functions to be achieved through electronic interruption of control signals rather than mechanical contactor operation, reducing complexity while maintaining or improving safety performance.
2Reliability
If main contactors are used in the elevator drive system, then the safety level is improved, but the cost increases
Solution Approach 1:
By removing main contactors from the system, the patent eliminates the need to manufacture, source, and maintain expensive mechanical contactor components. The safety functionality is integrated into the existing semiconductor switch structure, reducing overall system cost while maintaining safety integrity level 3.
Solution Approach 2:
The semiconductor switches and control circuits in the patent serve multiple functions: they control motor operation during normal operation and simultaneously provide safety shutdown functionality. This multi-functionality eliminates the need for separate dedicated safety contactors, reducing component count and cost while maintaining safety requirements.
3Reliability
If redundant safety input circuits are implemented, then the safety level is improved, but the device complexity increases
Solution Approach 1:
The patent divides the safety input function into two separate safety input circuits that independently monitor safety conditions. Each circuit can independently interrupt the control signal to the motor bridge. This segmentation provides redundancy and fault tolerance while using simple, discrete circuit implementations that minimize overall complexity.
Solution Approach 2:
The patent implements safety functionality at the local level within the control circuitry adjacent to the semiconductor switches. The safety input circuits are integrated directly into the control path, allowing localized interruption of control signals without requiring complex system-wide safety mechanisms. This local implementation reduces overall system complexity while ensuring safety.
Data Source
Figure 1
AI summary
The invention refers to a drive device of an elevator (10), comprising a frequency converter (12) to be connected to a public AC supply network (15) and an elevator motor (22), the frequency converter (12) comprising a network rectifier (14) configured to be connected to the AC supply network (15), a motor bridge (16) to be connected to the elevator motor (22) and a DC intermediate circuit (18) located between the network rectifier (14) and the motor bridge (16), the motor bridge being controlled by a control circuit (20) which feeds the motor bridge (16) with control pulses to regulate the motor speed, the drive device further comprises at least one drive prevention circuit (23) connected between the control circuit (20) and the motor bridge (16), which drive prevention circuit is configured to obtain a safety signal from an elevator safety circuit (30), characterized in that the drive prevention circuit (23) comprises two separate safety input circuits (24a, 24b) each configured to be connected to the elevator safety circuit (30) to receive a safety signal, and that each of the safety input circuits (24a, 24b) is configured to interrupt the connection between the control circuit (20) and the motor bridge (16) in response to the safety signal status.