DC Bus Power Supply for Rack and Pinion Lifts
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Solution Overview
Problem
Rack and pinion lifts face challenges with high energy demands due to the lack of counterweights, leading to oversized and costly power supply systems, particularly in high-rise buildings, where the weight and stiffness of electrical power lines become significant issues, and the power supply system must handle peak demands during acceleration and braking efficiently.
Innovation Solution
Implementing a DC bus power supply system that allows for energy storage during regenerative braking, enabling the reuse of energy during acceleration phases, thereby reducing the overall energy consumption and system size, and facilitating the use of alternative power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional AC power lines are used to supply power to the lift car, then the power supply system can deliver sufficient current to the motors, but the weight and stiffness of the power lines become excessive for high-rise buildings
Solution Approach 1:
The patent changes the electrical parameters from AC to DC and implements a dual-voltage system (650V/480V). By converting to DC power transmission and using voltage switching, the system reduces power line current requirements, which directly reduces power line weight while maintaining adequate power delivery capability to the motors.
Solution Approach 2:
The patent introduces a dynamic voltage switching system that alternates between 650V and 480V based on operational conditions. This dynamic adaptation allows the system to optimize power delivery efficiency at different voltage levels, reducing the overall current demand and enabling the use of lighter power lines compared to traditional fixed-voltage AC systems.
2Power
If the power supply system is designed to handle peak power demands during acceleration, then sufficient power is available for motor operation, but the system size and installation cost increase
Solution Approach 1:
The patent implements periodic action through regenerative braking, where energy during downward motion or braking is captured and stored in the DC link capacitor. This stored energy is then available to assist during acceleration phases, reducing the peak power demand on the mains supply and allowing for a smaller, less complex power supply system.
Solution Approach 2:
The patent converts the normally wasted energy during regenerative braking into a useful resource. By capturing and storing this energy in the DC link capacitor, the system transforms what would be a loss into a beneficial energy source that reduces peak power requirements and enables smaller system components.
3Length of stationary object
If the electrical power line is extended to accommodate high lift heights, then power can be supplied to upper floors, but the cable length, stiffness and deadweight create control and handling difficulties
Solution Approach 1:
The patent changes from AC to DC power transmission and implements a dual-voltage system, which reduces the current required for power delivery. This parameter change allows for the use of lighter, more flexible power lines that are easier to handle and control, even at extended lengths required for high-rise buildings.
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 approach reduces the weight and dimensions of the power cable, optimizes energy usage by recycling energy during braking, and allows for more efficient power distribution, minimizing the peak power requirements during acceleration, thus lowering installation costs and improving operational efficiency.
Implementation Method 1
energy storage during regenerative braking, enabling the reuse of energy during acceleration phases
Data Source
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AI summary
The invention concerns a power supply system for a lift of the type in which drive machinery is supported by a load carrier (1, 2) and drives by means of a cogged wheel and cogged rod the load carrier along a track on a mast (5) and in which the drive machinery of the load carrier is supplied with power from a unit at ground level. In order to achieve a more efficient system, the invention is characterised in that: a) an electrically operated electric motor (3, 4) that is a component of the drive machinery arranged to drive the load carrier (1, 2) in first and second directions along the mast (5) and to generate electrical energy during the driving of the load carrier in a second, opposing, direction through regenerative operation of the electric motor, b) an energy storage system (10) that is a component of the unit at ground level that includes an energy store (11) for the storage of energy, c) a principal power network (12) arranged at ground level, from which electrical energy can be withdrawn, d) a power transfer bus (13, 13') with which it is possible to transfer electrical energy between the drive machinery of the load carrier (1, 2), the energy storage system (10) and the principal power network (12) that produces power, e) a control and monitoring system (17) for the monitoring and control of the flows of electrical energy between the electric motor (3, 4) of the load carrier, the energy store (11) at ground level and the principal power network (12).