A transformer is a device used to convert AC voltage, current, and impedance. It operates based on the principle of electromagnetic induction and is a static electrical apparatus. Transformers come in many types, including pulse transformers, intermediate-frequency transformers, trigger transformers, shielding transformers, and more.
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Definition of a Transformer
A transformer transfers electrical energy or signals from one circuit to another using the principle of electromagnetic induction. It is an essential component for electrical power conversion or signal transmission.
A transformer consists of:
- Core (iron or magnetic core)
- Windings (two or more)
The winding connected to the power supply is the primary winding, and the others are secondary windings.
Working Principle of a Transformer
A simple single-phase transformer consists of two conductive windings. When alternating current or pulsed DC flows through one winding, it generates a varying magnetic field, which induces a voltage in the second winding according to the principle of mutual induction.
The voltage ratio between primary and secondary windings is proportional to their turns ratio:
VsVp=NsNp\frac{V_s}{V_p} = \frac{N_s}{N_p}Vp Vs =Np Ns Similarly, the current ratio is inversely proportional to the turns ratio.
While transformers can step up or step down voltage, they do not amplify power. Excluding losses, the power on both sides is approximately equal:
VpIp≈VsIsV_p I_p \approx V_s I_sVp Ip ≈Vs Is
Functions of a Transformer
Transformers play a critical role in power transmission:
- For long-distance transmission, higher voltages reduce current and drastically lower conductor size and line cost.
- Step-up transformers raise the voltage for transmission.
- Step-down transformers reduce voltage for industrial, commercial, and household use.
Transformers are therefore essential components in any electrical power system.
Transformer Model Explanation
Transformer models vary widely. Different types have different naming rules. Below are typical examples:
Dry-Type Transformer Example
SCB10-1000kVA / 10kV / 0.4kV
Meaning:
- S – Three-phase
- C – Cast resin dry type
- B – Foil winding
- R = wire-wound winding
- L = aluminum winding
- Z = on-load tap changer (copper is default)
- 10 – Design sequence number
- 1000 kVA – Rated capacity
- 10 kV – Primary voltage
- 4 kV – Secondary voltage
Power Transformer Example
SFSZ9-31500/110
Meaning:
- S – Three-phase
- F – Forced-air cooling
- S – Three-winding
- Z – On-load tap changer
- 9 – Design sequence
- 31500 – Rated capacity (kVA)
- 110 – Primary rated voltage (kV)