Design And Implementation Of Program-Controlled AC Constant Current Source

AC constant current source products are widely used in motor electronics,lowvoltage electrical detection,aerospace and other industries.Compared with similar products abroad,the accuracy of constant current source products in China is lower.Most of the situations that need to use AC constant current source in China are using AC voltage source with a voltage regulator,coupled with the converter method to get an equivalent AC constant current source,which is difficult to apply to the research occasions with high accuracy requirements.High-precision AC constant current source purchased from abroad is expensive.Therefore,the study of a constant current source product with various technical indicators reaching the same level abroad and complete functions can not only meet the needs of many domestic units for constant current source,but also enrich the research content of constant current source technology in China.It has great application value and practical significance for the localization of this kind of products.In this paper,a design method of ac constant current source based on cascade control is proposed by analyzing the research status and related product characteristics of ac constant current source.Based on the theory of cascade control and embedded real-time operating system as the core of software design,this method designs a programmable AC constant-current source system.In the cascade control method,the inner loop adopts analog control circuit to control the stability of current output.The outer loop USES digital control circuit to collect and analyze the output current signal,adjust the output amplitude frequency,and realize the accurate control of the current.In addition,by adding a quick amplitude modulation module,the amplitude and frequency are controlled separately,which speeds up the response speed of the system to a certain extent.In the embedded real-time operating system as the core of software design,the need by the function of the digital circuit implementation,such as the input signal,produce sine signals,fault detection,data sampling analysis and real-time adjustment,etc,is divided into independent tasks,there was a link run in parallel in the system,so as to realize the rapid response of the various functions.When the software and hardware platform is completed,a friendly human-computer interaction interface is designed,which can perform current calibration,parameter setting and other operations remotely through the network,which is very convenient and fast.The test results show that the AC constant current source has an output current range of 0 ~ 30 A,an output current accuracy of 0.1%,a stability of 0.03%,a frequency accuracy of 0.1%,and an output power of 90 w.And the use of full CNC operation,with high output current accuracy,stability,low cost and other characteristics,can meet many applications.