The Basics of Transformers

NCERT Reference: Chapter 13, Electromagnetism, Class 12 NCERT Physics textbook.

Notes:

• A transformer is an electrical device that transfers electrical energy from one circuit to another through electromagnetic induction.
• It consists of two or more coils of wire wound around a laminated iron core.
• The primary coil is connected to the AC power source, and the secondary coil is connected to the load.
• When an alternating current flows through the primary coil, it creates a changing magnetic field in the core.
• This changing magnetic field induces an alternating current in the secondary coil, which is proportional to the number of turns in each coil.
• Transformers can be used to step up or step down voltage, isolate circuits, and provide impedance matching.

Transformer Theory

NCERT Reference: Chapter 13, Electromagnetism, Class 12 NCERT Physics textbook.

Notes:

• The EMF equation of a transformer is given by: $$E_s = \frac{N_s}{N_p}E_p$$ where $$E_s$$ is the secondary voltage, $$E_p $$is the primary voltage, $$N_s$$ is the number of turns in the secondary coil, and $$N_p$$ is the number of turns in the primary coil.
• The turns ratio of a transformer is the ratio of the number of turns in the secondary coil to the number of turns in the primary coil.
• The current transformation ratio of a transformer is the inverse of the turns ratio.
• The power transfer ratio of a transformer is equal to the product of the turns ratio and the current transformation ratio.
• The losses in a transformer include copper loss, iron loss, hysteresis loss, and eddy current loss.
• The efficiency of a transformer is defined as the ratio of the output power to the input power.
• The regulation of a transformer is defined as the change in the secondary voltage when the load current changes from no load to full load.

Transformer Design

NCERT Reference: Chapter 13, Electromagnetism, Class 12 NCERT Physics textbook.

Notes:

• The design considerations for a transformer include the materials used, the core design, and the winding design.
• The core of a transformer is made of laminated iron to reduce eddy current losses.
• The windings are made of copper wire, and the number of turns in each coil is determined by the desired voltage transformation ratio.
• The thermal design of a transformer is important to ensure that the transformer does not overheat.
• Cooling methods for transformers include oil-filled and dry-type.

Transformer Testing

NCERT Reference: Chapter 13, Electromagnetism, Class 12 NCERT Physics textbook.

Notes:

• Transformer testing is performed to ensure that the transformer meets the desired specifications.
• The no-load test is performed to measure the open-circuit voltage and the exciting current.
• The short-circuit test is performed to measure the short-circuit current and the impedance of the transformer.
• The open-circuit test is performed to measure the core loss.
• The efficiency and regulation of a transformer are determined by performing a series of tests.

Applications of Transformers

NCERT Reference: Chapter 13, Electromagnetism, Class 12 NCERT Physics textbook.

Notes:

• Transformers are used in a wide variety of applications, including power distribution and transmission, isolation of circuits, voltage regulation, impedance matching, and autotransformers.
• Instrument transformers, such as current transformers and potential transformers, are used to measure current and voltage in electrical circuits.