Inductor, Choke Coil & Transformer Circuit Symbols

In electrical engineering, circuit symbols help make communication clear and simple by providing an easy way to represent different parts of an electrical system. Inductors and transformers are important because they control and change electrical energy. Symbols for inductors and transformers are more than just visual aids, they are used for the design, analysis, and troubleshooting of electrical circuits. These standardized symbols allow engineers to quickly grasp the functional elements of a circuit, facilitating both clear communication and efficient problem-solving.

This article focuses on the symbols used for inductors and transformers, includes diagrams and explains the functions and different types of these components. It looks at various kinds of inductors, like simple air-core and more complex saturable core ones, as well as different transformer designs, such as iron-core and ferrite-core types.

Catalog

Figure 1: Circuit Symbols Examples

Meaning of the Inductor's Symbol

Inductors are shown with curved or zigzag lines, represent a coiled wire. When electricity flows through the coil, it creates a magnetic field. This simple symbol lets engineers quickly spot parts of a circuit that store energy in a magnetic field or help filter signals. The straightforward design makes it easier to understand and work with circuits involving energy storage or current control.

Meaning of the Transformer's Symbol

Transformers are drawn using two inductor symbols next to each other, often with parallel lines between them to represent the core around which the coils are wound. This symbol shows the transformer’s main job: changing voltage levels using electromagnetic induction. The core is made from a magnetic material like iron, helps strengthen the magnetic link between the coils. The transformer symbol ma kes it clear that the device is used to adjust voltage or keep different parts of the circuit separate, which is important in power systems.

Inductor Schematic Symbols

Circuit Symbol	Symbol Identification	Description of Symbol
	Generic Fixed Inductor	This symbol stands for a basic fixed inductor, also called a coil or choke. It has a set inductance value and works by storing energy in a magnetic field. Fixed inductors help control the flow of current, filter signals, and reduce noise by using the energy stored in their magnetic field.
	Variable Inductor	A variable inductor is a device that can change its inductance to suit different circuit needs. It's mainly used in radio frequency circuits to adjust the resonance frequency for better signal quality. Changing the inductance often involves moving a core inside the coil that alters the magnetic field.
	Inductor with Polarity	Some inductors have a dot on one terminal to show the preferred direction for current flow. This marking is important when using two inductors together to ensure proper magnetic coupling. If the dots are aligned, the inductors work together more effectively.
	Iron Core Inductor	An iron core inductor has a core made of iron, a material that can easily carry magnetic energy. This makes the inductor better at storing magnetic energy and increases its inductance.
	Ferrite Core Inductor	A ferrite core inductor has a core made of ferrite because it has useful qualities. Ferrite can hold more magnetic energy due to its high magnetic permeability, and its low electrical conductivity helps cut down energy losses from eddy currents.
	Variable Ferrite Core Inductor	A variable ferrite core inductor lets you adjust its inductance by moving the ferrite core in or out of the coil. Turning the core in increases the inductance, while pulling it out decreases it. This happens because the ferrite material affects the magnetic field inside the coil: more core inside means stronger inductance, and less core means weaker inductance.
	Preset Ferrite Core Inductor	A preset ferrite core inductor is a component with its inductance adjusted once, either during manufacturing or when first setting up the circuit. After this adjustment, the inductance remains fixed, ensuring stable and reliable performance during regular use.
	Shielded Inductor	A shielded inductor has a core that traps its magnetic field inside, preventing it from leaking out and affecting nearby parts. The shield also blocks outside electromagnetic noise, helping the inductor perform better in complex electronic systems.
	Electromagnet Solenoid	A solenoid is a tube-shaped coil of wire that produces a magnetic field when electricity flows through it. The strength of this field depends on how many times the wire is wrapped, the electric current, and the material inside the coil.
	Electromagnetic Deflection Coil	A deflection coil is important for how cathode ray tubes (CRTs) work. It makes a magnetic field that moves the electron beam.
	Bifilar Inductor	A bifilar inductor is made by winding two wires side by side, with each loop of one wire matching the other. If the wires are wound in opposite directions, their currents flow in reverse, cancelling out their magnetic fields and reducing the inductance.
	Variometer	A variometer is a device that adjusts inductance by moving two connected coils. These coils are arranged in a series and can be rotated or slid relative to each other. The inductance is highest when both coils face the same way and lowest when they face opposite directions.
	Saturable Core Inductor	A saturable core inductor is made to fill its core with magnetism. When this happens, it becomes less effective at blocking AC current, allowing more current to flow through.
	Electric Motor Inductor	An electric motor's inductor, turns electrical energy into mechanical power through electromagnetic induction. The coil's design and materials impact the motor's efficiency. The coil generates a magnetic field that interacts with the rotor to make the motor run.
	Analog Delay Line	An analog delay line slows down an analog signal to change its timing. It works by making the signal travel more slowly through materials like coiled wires, similar to how a digital buffer delays signals.
	Tapped Inductor	A tapped inductor is a coil with connection points, called taps, along the wire. These taps allow you to adjust its electrical properties, like impedance, without changing the design.

Transformer Schematic Symbols

Circuit Symbol	Symbol Identification	Description of Symbol
	Air-core Transformer	An air-core voltage transformer for radio frequencies (RF) has two coils linked by magnetism. These coils are wrapped around a non-magnetic core. Since it doesn't use a magnetic core, the transformer avoids problems like energy loss and saturation that occur at high frequencies.
	Iron-core Transformer	An iron-core transformer is a type of single-phase voltage transformer that uses a core made of thin layers of iron to work better. It has two coils of wire, called windings, that are wrapped around the core. The iron core helps direct the magnetic field created by the windings, making sure electrical energy moves efficiently from one winding to the other.
	Power Transformer	A single-phase power transformer, often shown as two linked circles in diagrams. Its main function is to increase or decrease voltage, based on the needs of the power grid.
	Ferrite-core Transformer	A ferrite-core transformer is a type of transformer with two coils wrapped around a core made of ferrite, a compressed material. The core’s special design reduces energy loss and noise, like the humming sound transformers often make.
	Step-down Transformer	A single-phase step-down isolation transformer lowers the voltage from the primary winding to the secondary winding. This happens because the primary winding has more wire turns than the secondary winding. The voltage drop depends on the ratio of wire turns.
	Step-up Transformer	A single-phase step-up isolation transformer increases voltage from the primary side to a higher level on the secondary side. The voltage change depends on the "turn ratio," or how these two sets of windings are connected.

Conclusion

This article gives a clear explanation of how the symbols for inductors and transformers are connected to how they work in real circuits. By explaining the different kinds of inductors and transformers, it helps readers better understand diagrams and the basics of how electromagnetic systems work in electronics. This knowledge is important for improving how devices perform and for solving problems in real-life situations.

Frequently Asked Questions [FAQ]

1. What is an inductor used for?

An inductor can store energy in a magnetic field when electricity passes through it. This feature makes inductors useful for things like filtering signals, controlling voltage, and tuning circuits. For example, in power supplies, inductors help even out changes in current and keep the voltage steady. In radio circuits, they are used to pick certain frequencies, helps in tuning to different stations.

2. What is the basic unit of inductor?

The basic unit of measurement for an inductor is the henry (H). An inductor has one henry when a current change of one ampere per second induces a voltage of one volt across the inductor.

3. How is inductor represented?

An inductor is represented by a series of curved lines or loops, symbolizing the coil of wire that constitutes the inductor. This symbolic representation helps in identifying the component in circuit diagrams and distinguishing it from other elements like resistors or capacitors.

4. What are the 3 types of transformers?

Transformers can be classified into three main types based on their purpose and construction:

Step-up Transformer: Increases voltage from primary to secondary coil, useful in applications where a higher voltage output is needed from a lower voltage input.

Step-down Transformer: Decreases voltage from primary to secondary coil, used in household appliances to convert high mains voltage to lower, safer levels.

Isolation Transformer: Provides electrical isolation between the primary and secondary coils without changing the voltage level, enhancing safety in sensitive electronics.

5. What are the uses of transformers?

Transformers are used in electrical systems due to their ability to change voltage levels, making them suitable for a variety of purposes. Their main functions include voltage control, helps maintain steady voltage in power systems to prevent damage to electrical devices. They adjust impedance, balancing it between circuits to ensure efficient power transfer. Lastly, transformers provide isolation by keeping circuits separate, reduces interference and enhances safety.

6. What is the basic principle of transformer?

The basic principle of a transformer is electromagnetic induction. In simple terms, a transformer works by using two coils of wire (primary and secondary coils) wound around a common core. When an alternating current flows through the primary coil, it creates a varying magnetic field. This magnetic field induces a voltage in the secondary coil. The ratio of the voltages in the primary and secondary coils is directly proportional to the ratio of the number of turns of wire in the respective coils, allowing the transformer to increase or decrease voltage as needed.