When electricity passes through a circuit, there is a point in the circuit, called a load, where the energy is consumed. An electrical load, of course, is something that uses electricity, like an induction motor. There are different classification systems, but one way to divide loads is into resistive, capacitive, inductive, or a combination of these types. In this article, I will try to clear about the concept of electrical load.
What Is Electrical Load?
An electrical load is simply a component in a circuit that consumes electrical power or energy. In our home, obvious examples of electrical loads include light bulbs, fans and other household appliances which are connected to the electricity. In a broad sense, any resistor or electric motor in a circuit that converts electrical energy into useful light, heat, or motion is a load in the circuit.
A load on a circuit is inversely proportional to the current because a larger load reduces the current and a smaller load increases the current in the circuit. However, if there is no appreciable load in the closed circuit, it can cause a short circuit and potentially major damage.
Classifications of Electrical Load
An electrical load can be classified in different ways. However, in this article, I will focus on two different sectors that are very crucial for classifying the load.
(a) Nature of Load
The nature of the load depends on the power factor, the demand factor, the load factor, and the diversity factor of the system. The different types of loads are explained in detail below.
(i) Resistive Load
Resistive loads obstruct the electrical flow in the circuit and convert it into heat, causing an energy drop in the circuit. Lamps and heaters are examples of resistive loads. Resistive loads consume electrical power in such a way that the current and voltage waveforms remain in phase. Therefore, the power factor of the resistive load remains unity.
Some major properties of a resistive load are:
- Resistive load always consumes active power.
- It does not make any phase difference between voltage and current.
- A resistive load can’t store electrical energy, in fact, it dissipates electrical energy in the form of heat.
- Resistive load always has the same characteristics for AC and DC power.
- Resistive load always causes unity power factor.
- The resistive load cannot produce reverse power to the circuit.
(ii) Inductive load
Inductive load uses magnetic fields to operate. Examples of inductive loads are motors, generators and transformers. An inductive load consists of a coil that stores magnetic energy when current flows through it. The current wave of the inductive load is behind the voltage wave, and the power factor of the inductive load is also lagging.
Inductive loads are not constant in nature. Their characteristics vary with the type of power source. In fact, they can change the characteristics of supply power. Inductive loads are the more power-consuming or heavy loads among others because they can also drive mechanical loads. Unlike a resistive load, it can draw any amount of current depending on the application.
Some major properties of an Inductive Load are:
- Inductive load consumes both real and reactive power.
- The inductive load makes a phase difference between voltage and current.
- A pure inductive load causes the power factor “zero lagging” but as there is no pure inductive load so an inductive load causes the power factor “lagging”.
- A pure inductive load has zero resistance although this is impossible because every inductive load has some internal resistance.
- Inductive load has different characteristics for AC and DC power. In fact, its properties also depend on the system frequency.
- The inductive load can store electrical energy in magnetic form for a short period of time.
- The inductive load can consume heavy energy compared to resistive and capacitive loads.
- The inductive load can produce reverse power to the circuit.
- A pure inductive load does not waste electrical energy like a resistive load.
(iii) Capacitive load
Electrical loads that are capacitive in nature and cause their current consumption to lead the voltage are called capacitive loads. Like inductive loads, capacitive loads consume both active and reactive power. A purely capacitive load draws a current and voltage that is 90 degrees ahead of phase. In practice, purely capacitive loads are not available. All capacitive loads have capacitive and resistive characteristics.
Some major properties of a Capacitive Load are:
- Capacitive load consumes both active and reactive power.
- The current consumed by a capacitive load always leads behind the voltage applied across the load.
- A pure capacitive load causes the power factor zero leading but as there is no pure capacitive load so a capacitive load causes the power factor leading.
- A pure capacitive load has zero resistance although this is impossible because every capacitive load has some internal resistance.
- Capacitive load does not show the same effect for AC and DC, it gives high reactance in DC and low reactance in AC.
- A capacitive load can store electrical energy in form of electric charge and can return it to the circuit or source.
- Capacitive load consumes less energy compared to resistive and inductive loads.
- The capacitive load can produce reverse power to the circuit.
- A pure capacitive load does not waste electrical energy like a resistive load.
(b) Power System Load
The total loads of an area depend on the population and living standard of the residents. The different types of loads in electrical systems are given below.
(i) Domestic Load/Residential Load
Domestic load refers to the total energy consumed by appliances in household work. It depends on living standards, weather and housing type. Household loads mainly include lights, fans, refrigerators, air conditioners, mixers, heaters, ovens, small pumps, motors, etc. Household loads consume very little power and are independent of frequency. This load mainly consists of lighting, cooling or heating.
(ii) Commercial Load
The commercial load consists of electrical load intended for commercial use, such as in restaurants, shops, supermarkets, etc. This type of load takes place for more hours a day compared to a home domestic load.
(iii) Industrial Load
Industrial loads consist of load demands from different industries. It includes all electrical appliances used in industry as well as machines used. Industrial loads can be connected throughout the day.
(iv) Municipal Load
Loads of this type include street lighting, water supply and drainage systems, and more. Street lighting is almost constant at night. Water can be pumped to an overhead storage tank during off-peak hours to increase the load factor of the system.
(v) Irrigation Load
Motors and pumps are used in irrigation systems to provide water for agriculture systems in this category. Typically, irrigation loads are provided at off-peak times or at night.
(vi) Traction Load
Electric trains, trams, etc. are subject to traction load. This type of load peaks in the morning and evening.
Is Battery Considered an Electrical Load?
Batteries are primarily used to store DC power and then supply power to DC loads. In most cases, they are the source. However, they have internal resistance, due to the non-conductive nature of the electrolytes in the plates compared to the materials used.
If you charge the battery, it consumes energy. In this condition, it is considered a load for the charger.
After that, the battery supplies your phone with DC power, it works as a DC power source in this case.
Measuring Unit of Electrical Load
The Measuring Unit of the Electric Load in terms of power is Watt.
Electrical power is expressed in units of power called watts, named in honour of James Watt, the inventor of the steam engine. One watt is just a small amount of power. Some devices require only a few watts to operate, while others require more. The power consumption of small devices is usually measured in watts. By comparison, larger devices or combinations of more than one load are measured in kilowatts (kW), or megawatts (MW).
What Is Critical Load In Power System?
The critical load is the load on which the electricity must be kept on under any conditions. Power to these loads should never be interrupted.
Often, there are critical loads in processing plants that cannot stop certain processes. Special measures have been taken to ensure that these loads are powered even if the industry power is interrupted.