The Three Types of Electrical Loads

1) Resistive Load

2) Inductive Load

3) Capacitive Load

Resistive Load

The resistance in a wire conductor causes friction and reduces the amount of current flow if the voltage remains constant. Byproducts of this electrical friction are heat and light. The units measurement of resistance are referred to as ohms. The units of electrical power associated with resistive load are watts. Light bulbs toasters electric hot water heaters and so on are resistive loads.

     Inductive Load

Inductive loads require a magnetic field to operate. All electrical loads that have a coil of wire to produce the magnetic field are called inductive loads. Examples of inductive loads are hair dryers fans blenders vacuum cleaners and many other motorized devices. In essence all motors are inductive loads. The unique difference between inductive loads and other load types is that the current in an inductive load lags the applied voltage. Inductive loads take time to develop their magnetic field when the voltage is applied so the current is delayed. The units measurement of inductance are called henrys. Regarding electrical motors a load placed on a spinning shaft to perform a work function draws what is referred to as real power watts from the electrical energy source. In addition to real power what is referred to as reactive power is also drawn from the electrical energy source to produce the magnetic fields in the motor. The total power consumed by the motor is therefore the sum of both real and reactive power. The units of electrical power associated with reactive power are called positive VARs. The acronym VAR stands for volts-amps-reactive.

   Capacitive Load

A capacitor is a device made of two metal conductors separated by an insulator called a dielectric air paper glass and other non conductive materials. These dielectric materials become charged when voltage is applied to the attached conductors. Capacitors can remain charged long after the voltage source has been removed. Examples of capacitor loads are TV picture tubes long extension cords and components used in electronic devices. Opposite to inductors the current associated with capacitors leads instead of lags the voltage because of the time it takes for the dielectric material to charge up to full voltage from the charging current. Therefore it is said that the current in a capacitor leads the voltage. The units measurement of capacitance are called farads Similar to inductors the power associated with capacitors is also called reactive power but has the opposite polarity. Thus inductors have positive VARs and capacitors have negative VARs. Note the negative VARs of inductors can be cancelled by the positive VARs of capacitors to leading a net zero reactive power requirements. How capacitors cancel out inductors in electrical circuits and improve system efficiency will be discussed later. As a general rule capacitive loads are not items that people purchase at the store in massive quantities like they do resistive and inductive loads. For that reason power companies must install capacitors on a regular basis to maintain a reactive power balance with the inductive demand.