Characteristics of a special-isolation transformer capable of protecting from high-voltage surges and its performance

Rapidly expanding computer-control systems and information networks must be protected from high voltage surges and made immune from noise. The usual method employed for this purpose is isolation transformers. Conventional electrostatic-shielded transformers, however, are insufficient for a number of reasons. The first is that many fine and complicated local resonant circuits are created by the inhomogeneously distributed circuit parameters inside the coil. The second is that common-mode surge noises traveling on both the active conductor of the line through some common-mode component, change into normal-mode noise because of the unbalance between their respective impedance values to ground. The third is the problem that component changed into normal mode, propagate due to the electromagnetic inductance from the primary to the secondary coil. In order to remedy this set of problems, one must eliminate the high-frequency magnetic flux linking the primary coil to the secondary coil through the air. In this paper, the authors propose a design for a transformer that does not propagate high-frequency components, even noise in a normal mode. They demonstrate dramatic noise reduction in their experiments with the new design. They thus validate the utility of the coil arrangement for the purpose of noise reduction.