Reduction in Ripple Current and Self-Inductance by Using Electromagnetic Coupling of Reactor

To produce DC current by using a multiphase reversible chopper, smoothing reactors are needed. When smoothing reactors are employed, the chopper device becomes large and heavy, especially if electromagnetic interference is avoided. The reduction in the ripple current by electromagnetic coupling contributes to making the chopper device smaller and lighter. We deduced the relationships among the ripple current amplitude, duty factor, and electromagnetic coupling coefficient. To determine the loss and gain, we introduced the ratio of the amplitude of the ripple current in each phase and in the total combined current of the multiphase chopper system to that of the ripple current in a one-phase chopper, A(ph),A(sum), respectively. This value indicates the reduction not only in the ripple current amplitude but also in the self-inductance. The minimum value of the above-mentioned ratio obtained analytically is accurately determined. We derived the minimum values and obtained the range within which reduction of the ripple current amplitude for both each phase and total combined is achieved. Finally, we applied an optimal electromagnetic coupling coefficient to the design of on-board reactors of electric railway vehicles. (c) 2013 Wiley Periodicals, Inc.