Varistors can be used as suppressors to protect devices and circuits from transient abnormal voltages including an ESD (electrostatic discharge) and a lightning surge. For protection from a relatively large surge current (100A to 25kA), leaded disk varistors and SMD disk varistors are suitable. For protection from a larger surge current (approximately 25kA or more), block varistors, and strap varistors are suitable.
This article describes surge protection device applications for LED lighting system, inductive loads such as motors, motor with an electromagnetic brake, SSR (solid-state relay), load dump and field decay, joint boxes and power conditioners of solar power generation systems, important devices using a lightning transformer, and high-energy surge in industrial devices.