Elevator Drive Inverter Braking for Machine Brake Failure
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Solution Overview
Problem
Existing elevator systems lack effective alternative or additional braking mechanisms to comply with elevator codes, especially when the machine brake is malfunctioning or insufficient to stop the elevator car.
Innovation Solution
An elevator drive system with dual sets of inverter switches and signal buffers that allow selective control of motor braking, bypassing conventional braking mechanisms to provide supplemental braking through short-circuiting motor phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a machine brake is used to stop the elevator car, then the braking function is provided, but the system lacks alternative or additional braking mechanisms to comply with elevator codes when the machine brake is malfunctioning or insufficient
Solution Approach 1:
The inverter circuit is segmented into two independent sets of switches: a first set (upper switches) for normal motor control and a second set (lower switches) for motor braking. This segmentation allows the braking function to be independently controlled and activated only when needed, providing an alternative braking mechanism that complements the machine brake without interfering with normal operation.
Solution Approach 2:
The inverter switches serve multiple functions: the first set of switches handles normal motor control during elevation movement, while the second set of switches provides motor braking when activated. This multi-functionality allows a single inverter circuit to perform both propulsion and braking, eliminating the need for separate braking hardware and providing code-compliant alternative braking capability.
2Reliability
If dual sets of inverter switches and signal buffers are added to provide alternative braking, then braking versatility and reliability are improved, but the device complexity increases
Solution Approach 1:
The braking function is merged into the existing inverter circuit by adding a second set of switches that share the same circuit topology and control infrastructure. The signal buffers for both switch sets are integrated into the same control system, allowing coordinated operation. This merging approach provides alternative braking capability while utilizing existing circuit elements rather than adding completely separate braking hardware.
Solution Approach 2:
The motor itself provides the braking force through electromagnetic induction when the second set of switches is activated, eliminating the need for external braking mechanisms. The motor's kinetic energy is converted to electrical energy and dissipated through the circuit resistance, providing self-contained braking functionality that reduces overall system complexity.
3Speed
If the second signal buffer bypasses the first signal buffer to activate motor braking, then rapid braking response is achieved, but the control signal routing complexity increases
Solution Approach 1:
The second signal buffer is pre-configured with a bypass path that can immediately activate the lower switches when a braking command is received. The buffer logic is designed in advance to recognize braking conditions and automatically route signals through the bypass path, eliminating the need for complex real-time signal routing decisions and ensuring rapid braking response.
Solution Approach 2:
The signal buffer routing is made dynamic through the use of logic modules that can switch between normal operation mode and braking mode. The bypass path is dynamically activated only when braking is required, allowing the control system to adapt its signal routing configuration based on operational conditions while maintaining simplicity during normal operation.
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
Provides economical and reliable motor braking to control elevator car movement, ensuring compliance with elevator codes and maintaining low-speed movement even when conventional brakes fail.
Implementation Method 1
allowing a control signal from the processor to turn on the second inverter switches to provide motor braking
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An elevator drive configured to control power to an elevator motor includes a plurality of first (upper) inverter switches and a plurality of second (lower) inverter switches. A processor is configured to provide control signals to control operation of the inverter switches. A first signal buffer between the processor and the inverter switches is configured to selectively prevent any control signals from turning on any of the inverter switches when the motor should not receive power. A second signal buffer between the processor and the inverter switches is configured to selectively bypass the first signal buffer, prevent any control signals from turning on the first inverter switches, and allow a control signal from the processor to turn on the second inverter switches to provide motor braking.