How do dielectric strength and dielectric loss affect the use of plastics in electrical equipment?

In electrical applications, plastics are primarily valued as electrical insulators. Their utility in this capacity is governed by two critical electrical properties:

Dielectric Strength

Dielectric strength represents a plastic's resistance to electrical breakdown when subjected to high voltages. A high dielectric strength is essential for materials used in insulation, as it ensures the plastic can withstand strong electric fields without failing or allowing an unintended current to pass through.1

Dielectric Loss

Dielectric loss is a measure of the energy dissipated as heat when a material is placed in an alternating-current field. As the polarity of the field alternates, the material's internal charges must displace, overcoming internal opposition that generates heat.21

In electrical equipment, high dielectric loss is generally undesirable because it leads to energy waste and potential overheating of components. However, this same phenomenon is harnessed industrially for specific applications, such as preheating plastics before molding. When selecting plastics for electrical circuits, engineers must consider these properties to ensure the material can manage the thermal and electrical stresses of the specific operating environment.21