The reasons of producing electric particle of gas and the condition of air flowing in large current enclosed busbar with forced air cooling are analysed. The finite element method is used to calculate the electric-field distribution on the port of the planar and cylidrical deionization device. The movements of electric particle in airflow by the action of electric field are analysed. By the test measurement of deionization device on the model
the scheme of the deionization device is identified.