Transformer for transistor operated inverter - has control windings linked with part of the core by passing through holes in it

摘要

The transformer can be used in transistorised inverters operating at an output frequency of several tens of kHz. Powerful turn on and turn off pulses are applied to the switching transistor. The transistor base current is reinforced by windings which pass through holes in the transformer core. One winding is in series with the load current in the primary coil. The other, linked with it, is in the base-emitter circuit of the switching transistor. The holes are arranged such that the windings do not link with the main flux when the core is unsaturated. The windings thus act in current transformer mode. As the main flux increases the positioning of the holes gives selective core saturation such that the main flux is forced to link the windings. The induced base current thus suddenly collapses and turns the switching transistor off.