Recent advances in the design of large magnetic frequency changers

The design of the magnetic frequency changer, or multiductor, has advanced to the extent that units having a rating of 6.6 MW have recently been designed and built. This paper treats several of the problems and consequent solutions encountered in the design of these large units. Specifically, problems associated with the effective utilization of available conductor in a sheet wound coil are discussed, and methods of reducing the losses to acceptable levels are described. It is shown that excessive losses can occur when the winding geometry is improperly chosen. Secondly, methods of estimating the core losses at the high and distorted flux densities encountered in the frequency changer are described. The load dependent core losses are required when determining the efficiency of the device as well as in assessing the overall system stability. Finally, an efficient method of simulating the behaviour of the multiductor on load is outlined. The simulation includes the input filter network, line characteristics, losses, etc. It is such that sets of design curves or alternatively, specific design configurations, can each be treated with ease and economy.