Reduction of Ripple Current Loss by Electromagnetic Coupling of Air-Core Reactors

摘要

To reduce the loss due to ripple current in a multiphase current-reversible chopper, we investigated electromagnetic coupling of an air-core reactor. We derived the relationship between the amplitude of the ripple current, the duty factor, and the electromagnetic coupling coefficient, and used the results to estimate the effects of electromagnetic coupling in the design of a train energy storage system. We built reactors with electromagnetic coupling coefficients of 0.93 and 0.60. These reactors employed a new winding structure that provides an optimal electromagnetic coupling coefficient. The mass of the former type of reactor was increased by 4.4% over the conventional design, and that of the latter type of reactor was decreased by 17%. Finally, we tested the new reactors. When the chopper employs the former type of reactor and operates with equal-phase switching and cumulative coupling, the loss due to ripple current is decreased by 11%. When the chopper employs the latter type of reactor and operates with shift-phase switching and differential coupling, the loss is decreased to 31%. The test showed that the calculated relationships agreed with the measured values.