Most electrical components are tested using high voltage testers. This is the basic capacity test for any electrical component. It is used instead of testing AC components with DC, which was found to wear out the component. A high voltage, very low frequency test is used instead which tests to a high capacity but with a low current and frequency that doesn't wear out the components. Brands such as High Voltage, Megger, Metrohm, Neumann Elektrotechnik and T&R Test Equipment offer this type of product.