Elevator Drive Inverter Braking Using Lower Switch Short-Circuiting
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Solution Overview
Problem
Existing elevator systems face challenges in providing adequate braking, especially when the machine brake is malfunctioning or insufficient to handle large loads, necessitating additional braking methods to comply with elevator codes.
Innovation Solution
An elevator drive system utilizing a processor-controlled configuration of first and second inverter switches, with signal buffers and logic modules, allows for selective motor braking by bypassing the first signal buffer and activating the second inverter switches to short-circuit the motor phases, providing resistance against traction sheave rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the machine brake is used to stop the elevator car, then the braking function is provided, but the braking may be insufficient when malfunctioning or handling large loads
Solution Approach 1:
The braking function is segmented into two independent parts: the traditional machine brake and the newly added motor braking capability through inverter switches. This segmentation allows each braking mechanism to operate independently, providing redundant braking assurance without requiring complete system redesign.
Solution Approach 2:
The inverter switches, originally designed solely for motor control, are given a dual function by enabling them to also provide braking capability. This multi-functionality eliminates the need for entirely separate braking components, reducing overall system complexity while improving reliability.
2Reliability
If additional braking methods are added to comply with elevator codes, then the braking reliability is improved, but the device complexity increases
Solution Approach 1:
The control system achieves multi-functionality by enabling the inverter switches to perform both motor control and braking functions. This eliminates the need for separate control circuits for braking, maintaining code compliance while avoiding significant complexity increases.
Solution Approach 2:
The motor itself provides the braking force through the inverter switches, eliminating the need for entirely separate braking mechanisms. The system uses its own existing components (motor and inverter switches) to provide the additional braking function required by elevator codes.
3Reliability
If the inverter switches are activated for motor braking, then the supplemental braking is provided, but the control signal management becomes more complex
Solution Approach 1:
Signal buffers are introduced as intermediary components between the processor and inverter switches. These buffers manage and isolate the control signals, ensuring that braking commands are properly transmitted while preventing unintended signal interference, thus simplifying the overall control architecture.
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
This solution effectively provides supplemental braking that is economical and can be easily integrated into existing systems, ensuring controlled movement of the elevator car even when the machine brake is insufficient, maintaining low-speed stability.
Implementation Method 1
allow a control signal from the processor to turn on the second inverter switches to provide motor braking
Data Source
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.