Power loss: Energy losses in magnetic and electrical systems

Power loss describes the energy that is lost in a system as heat or other unwanted forms of energy instead of being converted into usable energy. Power loss plays a decisive role in magnetics and electrical engineering as it influences the efficiency of devices and systems.

Types of power loss

Different types of losses occur in magnetic and electrical systems:

• Eddy current losses: These are caused by induced currents in conductive materials that are permeated by an alternating magnetic field. These losses lead to heating of the material.
• Hysteresis losses: Occur in ferromagnetic materials when the material is repeatedly magnetised and demagnetised. They result from the internal friction of the magnetic domains.
• Conduction losses: Occur due to the electrical resistance of conductors, which converts part of the energy into heat.
• Dielectric losses: Occur in insulating materials when they are in an alternating electric field. These losses are caused by the movement of electric dipoles in the material.

Mathematical description of power loss

Power loss can be described mathematically for various systems. In electrical systems, it is calculated using the formula:

P = I²R

where:

• P: Power dissipation (in watts)
• I: Current (in amperes)
• R: Resistance (in ohms)

For magnetic systems, such as transformers or electric motors, the power loss is often modelled as the sum of hysteresis losses and eddy current losses:

P_loss = P_hysteresis + P_{eddy current}