The Design And Implementation Of Fake Load Cabinet For Airfield Lighting Constant Current Regulator

The constant current regulator is the core control equipment to ensure the normal operation of the airfield lighting system.Aging test and functional test must be carried out in the factory and maintenance of the constant current regulator.Aiming at the method of short circuit test and the loading lamp test,if the protective function of the constant current regulator is not perfect,it is easy to cause the problem that extensive lamps may burn out.Most of the existing fake load cabinets are designed for generators or voltage serial products,and can not be directly applied to the current source of the regulator.This fake load cabinet for airfield lighting constant current regulator can replace halogen lamps and can meet the needs of regulator such as the load current performance test,the maximum load capacity test,open circuit test,over current impact test,dynamic constant current test and etc.According to the technical requirements of airfield lighting system of the airport,a kind of fake load cabinet is designed in this paper.The minimum step size of fake load cabinet is 25 W and its power is continuous and adjustable from 0 to 30KW.The controlling of 12 relays in any combination is realized through local and remote ways,in which the cascaded structure of high voltage resistors is used.Each resistor parallel with the normal open contact of the vacuum relay.The local control is realized by the manual switch or the singlechip key while the remote control is realized by the touch screen.In this way,the function of the automatic switching of loading and the adjustment of the voltage and power are accomplished and the requirements of different kinds of light regulator can be met.In this paper,the selection of the resistor,relay,switch power,touch screen,singlechip and the cooling way of the load cabinet is introduced.On the hardware,the ATmega168 microprocessor is used as the main control chip,and the I/O expansion and the other circuit are used as the auxiliary unit so that the liquid crystal display(LCD),temperature detection,voltage and current detection and communication interface are accomplished.On the software,the operation process of the main program and subprogram including the initialization,liquid crystal display,MODBUS communication,keyboard processing,controlling functions,relay output,indicating lamps processing and the voltage,current and temperature detection are introduced.The software flow chart is shown.In the design of human-computer interaction interface,simulation interface and testing interface are accomplished.According to the requirements of the engineering,the set of loading is realized through the input of resistor,voltage or power value on simulation interface while the controlling of a single relay coil is fulfilled on the testing interface.The test of the hardware circuit of load cabinet and the function of local and remote controlling are following after the design of hardware and software.From the result of loading experiment finished by connecting the load cabinet with a dimming device,the functional requirements are met.