Why do transformers only work on alternating current?
Time：2024-12-12 Auther：ZTelec-www.ztelectransformer.com
Transformer is a crucial equipment in power system. Its core function is to transform AC voltage, current and impedance to achieve the transmission and distribution of electric energy. However, the working principle of the transformer determines that it can only work under alternating current and can not play a role in the direct current environment.
The working principle of the transformer
A transformer is a power transmission and conversion device. It uses the principle of electromagnetic induction to change the ratio of voltage and current between the input and output terminals. The transformer is mainly composed of an iron core and coils. When AC voltage is applied to the input, eddy currents will be generated in the core, thus making the core ferromagnetic. The magnetic flux in the core changes with the input voltage, which will cause the output voltage and current to change.
Why can transformers only be used in alternating current?
The working principle of transformers is based on the law of electromagnetic induction. When alternating current passes through the primary coil of the transformer, an alternating magnetic field is generated. If another coil is placed in this magnetic field, a voltage is also generated in this coil, which transfers electrical energy to the other circuit. By changing the winding proportion of the coil, the voltage can be changed. However, the direction of direct current is unchanged and the alternating magnetic field cannot be generated. So the principle of electromagnetic induction cannot be used for electric energy transmission.
Transformer uses mutual inductance phenomenon of alternating current to change the voltage. Mutual inductance phenomenon exists only in AC circuit and DC has no mutual inductance phenomenon . When the alternating current passes through the primary winding of the transformer, the alternating magnetic field will be generated in the core. And the voltage will be induced at both ends of the secondary winding through the change and coupling of the magnetic field in the core. Direct current cannot produce this alternating magnetic field, so no induced voltage is generated at both ends of the secondary winding.
Characteristics of alternating current and direct current
1. Features of alternating current
Alternating current (AC) refers to the current whose direction and magnitude change periodically from time to time. In alternating current, the size and direction of the current constantly change, which causes the magnetic field to change with it. This changing magnetic field is the key to the transformer’s ability to work. When alternating current passes through the primary coil of the transformer, it creates an alternating magnetic field in the iron core. This magnetic field passes through the secondary coil and induces an electromotive force in the secondary coil. Due to the periodic change of alternating current, the magnetic field will also change. Therefore the electromotive force in the secondary coil will also change, so as to achieve the transformation of voltage.
2. Characteristics of direct current
Direct current (DC) refers to the current direction is always the same. In direct current, the magnitude of the current may change over time, but its direction always remains the same. This means that in direct current, a changing magnetic field cannot be generated. If you try to pass direct current into the primary coil of the transformer, it will only produce a constant magnetic field. This constant magnetic field cannot induce electromotive force in the secondary coil, so the transformer cannot work.
