Peak Transformer

a transformer with a ferromagnetic core, used to convert electric current or voltage pulses. Peak transformers are used to match pulse source and load, to change pulse polarity, to separate DC and AC circuits, to add signals, and to fire flash lamps in radar, pulse radio communication, automation, and computer technology.

Distortion-free transmission of pulse shape is the primary requirement for a peak transformer. The operation of a peak transformer during the formation of the pulse front differs substantially from its operation during the formation of the pulse top. To improve the reproduction of the pulse front and drop-off, the turn-to-turn capacitances of windings, stray capacitances of wiring, and leakage inductance must be minimized. A decrease in turn-to-turn capacitance can be achieved by the use of small cores and the proper winding and relative location of coils, as well as by reduction of the number of turns (thereby reducing the turn ratio). Cores for peak transformers are made of Permalloy, transformer silicon steel, ferrites, and other materials having a high magnetic permeability. To reduce eddy-current losses peak transformer cores are wound using ferromagnetic ribbons up to 10 microns thick; the surface of the ribbon is covered with an insulating layer. Ferrite cores with low eddy-current losses are manufactured by methods of powder metallurgy. The primary winding of a peak transformer usually contains 50–200 turns, and a turn ratio of 0.25 to 5 is usually chosen, but in some cases it may be as high as 100 or higher. Peak transformers are manufactured to deliver pulse powers from a few milliwatts to several megawatts. Peak transformers make possible the transmission without substantial distortion of pulses with a duration of 1.1–0.3 microsec.