Transformers operate on the principle of electromagnetic induction, which relies on the changing magnetic field produced by alternating current (AC). This principle doesn’t apply to direct current (DC) because DC does not produce the changing magnetic fields necessary for induction.
In a transformer, an alternating current in the primary winding creates a changing magnetic field around the core. This changing magnetic field induces a voltage in the secondary winding through electromagnetic induction. The relationship between the turns in the primary and secondary windings determines the voltage transformation (step-up or step-down).
However, when you apply a constant DC voltage to the primary winding, the magnetic field remains steady, without the necessary changes required for induction. As a result, there is no induced voltage in the secondary winding, and the transformer doesn’t function as intended.
In contrast, devices called choppers or converters are used for DC voltage conversion. These electronic circuits can step up or step down DC voltages by controlling the switching of semiconductor devices, such as transistors or thyristors. Choppers operate on the principles of pulse width modulation (PWM) to regulate the average voltage delivered to the load.
In summary, transformers are inherently designed for AC voltage transformation based on electromagnetic induction, making them unsuitable for direct application to DC voltage. Specialized electronic circuits like choppers are more appropriate for stepping up or stepping down DC voltages.