Design And Implementation Of Temperature Compensating Unit For 4.6GHz/250KW Circulator

The circulator is an important part of the transmission line of the 4.6GHz/6MW LHCD system.When the EAST discharges,the circulator can absorb the high power microwave energy reflected from the tokamak plasma,which protects the klystron from being damaged.In the high-power and long-pulse working conditions,the performance of the circulator will be affected by temperature.The temperature compensating unit is designed to compensate for this effect.This paper elaborated the working principle and the hardware and software design of the temperature compensator,and studied and solved the problem that the performance of the circulator is affected by temperature.In this paper,the EAST LHCD system was briefly introduced.Then the function and working principle of the circulator were described.After that,the effect of the temperature on the performance of the circulator was analyzed in detail.On this basis,it was proposed to use temperature compensating unit to compensate for effect of the temperature.The working principle and the hardware and software design of the temperature compensator are the focus of this paper.The circulator is able to transmit the microwave in a specific direction,which is mainly achieved by the ferrites.However,the properties of the ferrites and the magnets are affected by temperature,resulting in the performance of the circulator being affected.The magnets in the circulator are wound around with coil.The temperature compensating unit compensates for the effect of the temperature by putting a current into the coil.The value of the current is calculated by measuring the inlet water temperature,the outlet temperature and the ambient temperature of the circulator.The hardware design of the temperature compensating unit contains temperature measurement module,signal transmission module,controllable DC current source,main control module and display module.The controllable DC current source and main control module are the main parts of the hardware design,which are designed based on the TMS320F28027 and PIC18F44J11.The software design of the temperature compensating unit contains the research of the temperature compensation algorithm,the software design of the current source and the software design of the master MCU.The temperature compensation algorithm is based on the theoretical model and test data.The controlling method of the current source is digital incremental PI control,and the communication protocol of the current source is the basic master-slave response mode.The software design of the master MCU contains the Modbus communication protocol,LED driver design and LCD driver design.At the the end of this paper,the test of the temperature compensating unit was introduced.The test results show that the temperature compensating unit can lead to the steady-state operation of the circulator.