Elevator Control Device Inrush Current Suppression
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Solution Overview
Problem
During a power failure in an elevator control device, the switching means are difficult to reopen due to high inrush currents caused by voltage instability between the DC bus lines and the electric power storage means, especially when the device is in a charging mode and cannot supply power.
Innovation Solution
The elevator control device includes a converter, an inverter, an electric power storage means with input voltage adjustment, and a rechargeable battery connected through switching means. Upon power failure detection, the control means opens the first and second switching means, connects the rechargeable battery to the converter, and sets the electric power storage means' input voltage to a constant voltage matching the rechargeable battery's terminal voltage, allowing the second switching means to be closed again while minimizing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second switching means is closed again after opening during a power failure in charging mode, then the elevator can operate using stored electric power, but a large inrush current occurs due to voltage instability between the DC bus lines and the electric power storage means
Solution Approach 1:
The control means performs preliminary voltage adjustment of the electric power storage means to match the DC bus line voltage before closing the second switching means. This preliminary action prevents the inrush current that would otherwise occur when connecting components with voltage differences, thereby enabling reliable elevator operation without harmful current spikes.
Solution Approach 2:
The control means changes the voltage parameter of the electric power storage means to match the DC bus line voltage before closing the second switching means. By adjusting the voltage parameter in advance, the system eliminates the voltage difference that causes inrush current, allowing safe connection and continuous elevator operation during power failures.
2Use of energy by moving object
If the electric power storage means is used to supply power during a power failure, then energy-saving effect is achieved, but the switching means cannot be reopened due to unstable voltage conditions
Solution Approach 1:
Before closing the second switching means to enable power supply from the electric power storage means, the control means performs preliminary voltage adjustment to ensure voltage stability. This preliminary action makes the switching operation feasible while maintaining energy-saving benefits during power failures.
Solution Approach 2:
The control means acts as an intermediary that mediates between the electric power storage means and the DC bus lines by adjusting voltages before connection. This intermediary action ensures voltage compatibility, enabling the switching means to operate reliably while maintaining energy-saving operation during power failures.
3Reliability
If the charging mode is maintained continuously to keep the electric power storage means charged, then the battery is ready for power failures, but the system cannot respond to urgent stop requirements during abnormal situations
Solution Approach 1:
The system dynamically switches between charging mode and power supply mode based on operational needs. The control means can transition the electric power storage means from charging to discharging state, enabling both continuous readiness for power failures and responsive action during emergency situations requiring urgent stops.
Solution Approach 2:
The control means changes the operational parameter of the electric power storage means between charging and discharging states. This parameter change enables the system to maintain power storage readiness while also responding adaptively to emergency situations, resolving the contradiction between continuous charging and emergency response capability.
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 configuration enables the elevator to operate using stored electric power while suppressing inrush currents, ensuring stable voltage and efficient power utilization during power failures.
Implementation Method 1
a converter which converts AC power from an AC power supply connected through a first switching means capable of opening and closing to DC power
Implementation Method 2
an inverter which converts the DC power to AC power to drive an electric motor which moves an elevator car up and down
Data Source
Figure 1
Figure 2
AI summary
An elevator control device includes: a converter (7) which converts an AC power supply (1) to DC power through a first switch (13); an inverter (8) which converts the DC power to AC power to drive an electric motor (2) which moves an elevator car (5) up and down; an electric power storage device (10), having an input voltage adjustment capability, being connected to the output of the converter (7) through a second switch (19), and storing electric power; a rechargeable battery (11) connected to the output of the converter (7) through a third switch (20); and an operation control unit (12) turns off the first switch (13) and the second switch (19) based on a power failure detection signal of the AC power supply (1), turns on the third switch (20) for the connection of the rechargeable battery (11), and then turns on the second switch (19) after setting the input voltage of the electric power storage apparatus (10) to a constant voltage of being an assumed terminal voltage of the rechargeable battery (11).