Harmonics in transformer result in

Increased core losses
Increased I2R losses
Magnetic interference with communication circuits
All of the above

The correct answer is D. All of the above.

Harmonics are unwanted frequencies that are multiples of the fundamental frequency. They can be caused by a variety of factors, including nonlinear loads, such as rectifiers and inverters. Harmonics can have a number of negative effects on transformers, including:

  • Increased core losses: Harmonics cause the core of the transformer to heat up, which can reduce its lifespan.
  • Increased I2R losses: Harmonics cause the current in the transformer to increase, which also increases the transformer’s losses.
  • Magnetic interference with communication circuits: Harmonics can cause interference with communication circuits, such as telephone lines and radio receivers.

To reduce the effects of harmonics, it is important to filter them out at the source. This can be done using a harmonic filter, which is a device that is designed to absorb harmonics.