ALstmct--The North East Line (NEL) traction system is operating at 1500V DC obtained from a 22kV distribution network supplying 16 stations, a depot and a route length of 20km. There are two power intake points from the PowerGrid, one at the Sengkang Depot (66kV) and the other at the Stamford Intake (22kV). Inverters are installed in some traction subsfations to convert excess DC power generated from trains' regenerative braking to the 22kV AC network and improve the tine recepff vity.The power supply for a transit system is different from that supply to the nomral electcic network for other purposes. DC traction systems bave elements of equipment, design or operational philosophy which are considered special, NEL is no exception and is unique by itself. Moreover, it is the first MRT tine in Singapore using a 1500V DC overhead catenary system instead of the 750V DC third-rail collection system in the existing lines. This paper describes the NEL traction system from conceptualization to completion and the design considerations in terms of enf$neering, operational and maintenance requirements. The di"lties encountered d d n g construction, testing and commissioning phi=, and finally, experience gained in operation so far are also presimted.
The digitally dimming control method is suitable for lighting application in buildings, offices, conference rooms and classrooms, and it features remote control capability. The conventional RS-232-based digitally dimmable lighting system for two-area fluorescent lamps consists of two power factor correctors and two half-bridge resonant inverters as the main circuit, and a microcontroller-based driver and two drivers/dimmers for two inverters. The drawbacks of the conventional lighting system are limited transmission length and transmission speed, and each lighting area needs its own driver and dimmer, which results in a large number of circuit components and low cost-effectiveness for application of multi-area lighting control for fluorescent lamps. Therefore, this paper presents a digitally wireless dimmable lighting system for fluorescent lamps. The main purpose of this paper is to utilize USB-based protocol instead of the RS-232-based one and increase dimming controlled nodes (devices) with the use of ZigBee transmission interface, which is a new wireless communication technology. In addition, a micro-controller is adopted to fulfill remote wireless dimming controlled electronic lighting system for two area fluorescent lamps. A prototypical electronic lighting system has been developed to drive a 32W-rated (T8-type) fluorescent lamp for each area with the use of a LabVIEW man-machine interface software to carry out the remote dimming control. The experimental results demonstrate the functionality of the presented electronic lighting system.
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