In the technical data sheets of thermostats or other automatic switches, manufacturers indicate the maximum current value applicable to contacts with resistive load expressed in Amperes and, in brackets, the inductive load. For UL certified products, the manufacturers indicate only the value for resistive load, while they specify the inductive loads through the maximum applicable power expressed in horsepower (hp).
What is the inductive load?
The energy that passes through a system of circuits is defined as “load” and classified according to the transformation it undergoes. Loads that produce work in the form of heat (incandescent lamps, electric heaters) and inductive loads that develop electromagnetic fields (motors, transformers, relay coils or contactors) are classified as resistive. Then there are capacitive loads (capacitor banks or three-phase motor starting) used for accessory functions, which we will discuss shortly.
Thermostats or other automatic switches are devices called to activate or deactivate the power supply of electrical loads and their sizing requires attention to the plate data of the connected devices to avoid malfunctions and deterioration of the contacts over time.
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