The working principle of special transformers is based on electromagnetic induction, similar to that of conventional transformers, but with expanded design, structure, and function due to their special applications. It generates an alternating magnetic field through alternating current in the primary winding, which in turn forms a magnetic flux in the iron core. The secondary winding cuts this magnetic flux, inducing an electromotive force, thereby achieving voltage, current, or phase transformation.
Unlike ordinary power transformers, special transformers not only perform voltage transformation but also undertake specific tasks such as frequency conversion, phase number transformation, power quality regulation, isolation and interference suppression, and precise measurement. For example:
1. Rectifier Transformer: Powers rectifier equipment, capable of withstanding non-sinusoidal currents and high-order harmonics, and works with rectifier circuits to convert AC to DC.
2. Welding Transformer: Features a steep droop characteristic, providing large current during short circuits while limiting overload and ensuring stable welding.
3. Isolation Transformer: With a 1:1 turns ratio, primarily used for electrical isolation between circuits, preventing lightning surges and interference signals from entering sensitive equipment; widely used in medical and precision instruments.
4. Test Transformer: Used to generate high voltage for insulation testing; typically operates in single-phase mode for short periods, with low magnetic flux density to reduce waveform distortion.
5. Electronic Power Special Transformer (e.g., SEPT): Incorporates power electronics technology, achieving flexible voltage regulation through high-frequency AC/AC conversion, and possesses power quality management capabilities, eliminating harmonics and balancing three-phase loads.
