Microprocessor Elevator Backup Power Control
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Solution Overview
Problem
Traction elevator systems require an efficient emergency back-up power system capable of handling high power loads and sequencing with normal power sources to prevent simultaneous operation, especially with the transition to Variable Voltage/Variable Frequency Drive (VVVFD) technology, which demands precise control to manage power imbalances and capacitive issues.
Innovation Solution
A microprocessor-based control arrangement with pulse-width modulator technology that senses power loss or irregularities, disconnects the main power source, initiates back-up power, and ensures a pure three-phase sine wave output, using an inverter timing system and back-up power generation to maintain elevator operation during emergencies, while preventing simultaneous operation with normal power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a back-up power system is designed to provide full power to the traction motor (>20 hp load), then the back-up power capability is sufficient for traction elevator operation, but the system complexity increases due to high power switching requirements and parallel power feed configuration
Solution Approach 1:
A transfer switch is introduced as an intermediary device between the normal power source and the back-up power source. This transfer switch automatically switches the traction motor load between normal power and back-up power, eliminating the need for complex parallel power feed configuration while maintaining full power capability (>20 hp) for traction motor operation.
2Power
If the back-up power system is fed in parallel to the normal control power system, then full power capability is achieved, but the risk of simultaneous operation of both power sources increases
Solution Approach 1:
The transfer switch acts as a mediator that prevents simultaneous operation of normal and back-up power sources by providing exclusive connection to one source at a time. The transfer switch control logic monitors both power sources and automatically connects the load to the available power source, eliminating the risk of parallel operation and associated safety hazards.
Solution Approach 2:
The transfer switch system incorporates feedback mechanisms that continuously monitor the status of both normal and back-up power sources. When a power failure is detected, the system receives feedback signals and automatically switches to the back-up power source. When normal power is restored, the system detects this through feedback and switches back, ensuring reliable sequencing without simultaneous operation.
3Use of energy by moving object
If VVVFD technology is used with capacitive input filtering, then power factor improvement is achieved, but the reactance compensation requires additional inductor system components
Solution Approach 1:
The inductor system for reactance compensation is merged with the existing VVVFD input filtering configuration. The inductors are integrated into the power input circuitry of the VVVFD drive, combining the reactance compensation function with the input filtering function, thereby reducing overall system complexity while maintaining power factor improvement benefits.
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
The solution provides a reliable, efficient, and cost-effective emergency power system for traction elevators, ensuring continuous operation during power outages by managing high power loads and sequencing, allowing for safe transportation of passengers and optimizing battery life through controlled discharge cycles.
Implementation Method 1
microprocessor-based control arrangement with pulse-width modulator technology
Data Source
AI summary
An emergency power supply for a traction elevator system utilizes a microprocessor-based control arrangement with pulse-width modulator technology to create an efficient, cost-effective back-up power system for a traction elevator. The microprocessor-based control arrangement is used to sense a phase irregularity in the power supply. Upon sensing the phase irregularity, the microprocessor-based control arrangement disconnects the elevator system from the main power source and then generates a control signal to initiate the supply of back-up power. Once the elevator electrical system has been stabilized, the elevator control system will sense that recovery has occurred and will then provide an appropriate speed and direction command to the traction motor drive system.