What is Electrical Load? Definition, Types, Calculations and Examples

What is Electrical Load? Definition, Types, Calculations and Examples
What is electrical load

The main components of the electrical circuit include power source, conducting material like conducting wires, and electrical loads. This forms a complete circuit. In this article I will discuss electrical load types and examples.

Electrical Load Definition

“Electrical load” refers to the electrical circuit that converts current into something practical—for instance, a lightbulb, a resistor, and a motor. A load transforms electricity into heat, light or motion. In other words, the component of a circuit that connects to a clearly defined output terminal is regarded as an electric load. The electrical load can be resistive, inductive or capacitive, or a combination of these.

What are electrical load types?

Three fundamental loads are present within circuits:

  1. capacitive
  2.  inductive
  3. resistive loads

They differ in how they use power in an alternating-current (AC) configuration.

Resistive Loads:

The loads that contain any heating element are categorized as resistive loads. A device that draws power in a sinusoidal waning and waxing pattern in sync with a sinusoidal fluctuation of voltage – the highest, lowest and zero points of the current and voltage values in time and is solely resistive. In resistive loads, the voltage and current remain in phase. Therefore, the power factor, in this case, is unity. Talking about the units, the resistive load is measured in Ohms, while power is measured in watts.

Inductive Loads:

All devices and equipment with coils are inductive in nature. Contrary to a resistive load, in an inductive load, the current follows the sinusoidal pattern and peaks immediately after voltage sine wave’s peaks, which means that the maximum, minimum and zero points aren’t in the phase. We measure inductive load in Henry and power in VAR. While the power is the sum of Reactive and real power.

Capacitive Load:

In the field of engineering, capacitive loads are not able to exist as a separate form. There are no devices classified as capacitive in the same way light bulbs are classified as resistive, while air conditioners are categorised as inductive. Capacitance is measured in Farads while power in VAR. The value of VAR in capacitive load is negative because the polarity of reactive power is negative.

Electrical Load Examples

As we discussed before, we have three types of electrical load examples of each type of load is mentioned below: 

Resistive Loads Examples:

  • incandescent lighting
  • Toasters
  • Ovens
  • Heaters
  • Coffee Makers

Inductive Load Examples:

  • Motors
  • Solenoids
  • contactor coils
  • compressors
  • speakers
  • relays
  • transformers
  •  inductors

Capacitive Load Examples:

Capacitors used in large circuits help regulate power usage. They are typically used in electrical substations to increase the system’s overall “power factor“.

 What are the examples of three phase load except motors?

Three phase induction motors are the majority loads but not the only loads in the power system, Three phase heaters are an example of three phase loads except motors, they are widely used in electric furnaces. These furnaces are common loads in iron and steel factories.

Hereunder some examples of three phase loads except motors:

  • Three-phase rectifiers
  • Three phase heaters.
  • Three phase rectifiers circuits.
  • Three phase capacitor banks.

Now let’s go in some details. The three-phase loads come in two kinds: mechanical loads connected directly to three-phase Induction Motors. The other one is electrical three-phase loads that are directly connected to their output connections of generators like the alternator, IG.

There are two types of electrical three-phase loads except motors:

  1. Leading load.
  2. Lagging load.

A three-phase leading load uses active power; however, its deliver reactive power back into the system. This creates an over-excited system.

Three-phase lagged load consumes both reactive and active power simultaneously and makes the system overexcited.

Three-phase rectifiers can be used as load because they convert the AC power of an alternator to higher-voltage DC. These days, HVDC lines are the most cost-effective way to transfer power than HVAC lines since HVDC lines are only composed of resistors, which means that line losses are minimal and the voltage drop in the HVDC line is significantly lower than those in the HVAC line.

There are some examples of lagging loads such as arc furnaces and three-phase transformers which directly connected with the alternator’s output.

Leading loads are utilized exclusively to correct the power factor of the alternators, such as capacitor banks, series compensators or a series combination of capacitors and resistors. The TCR (thyristor-controlled reactors) are utilized to increase the efficiency of power systems.

A stand-alone IG requires the use of a capacitor bank to ensure enough reactive VAR that is an energized load that is three phases …

Is battery an electrical load?

Batteries are not electrical load; they are primarily used to generate Direct Current. They are source. However, they have an internal resistance because of the non-conductive nature of electrolytes and plates compared to the material used in the conductor. A conventional battery does not have inductive or capacitive elements.

The plates that are positive and negative could be separated, as in a capacitor; however, the electrolyte that lies between them isn’t dielectric and allows electrons to move freely to allow charge and a different potential to be created between the two plates as well as the cathodes and anodes attached to the plates.

What is electrical load list?

The Electrical Load List is an estimated list of electric power consumption which is sub-summarised using an entire circuit, a sub-facility (sub-station), as well as the whole facility (main-substation). This is also called load Schedule.

This Electrical Load list is an approximate listing of electrical power consumption, which is summarized using an entire circuit, sub-facility, and the complete infrastructure.

A load schedule can help find out the power needed for the installation. The information can then use data to correctly determine the proper size of conduits and conductors and the proper overload protection and other control systems.

The schedule of loads is the summaries of data needed to make it easy to identify and assist with the required quantities and equipment ratings that must be utilized to power any installation.

Load scheduling is one type of load management that helps companies save energy by reducing their demands. To have an effective load schedule, the energy manager or company should perform the power logging process and keep track of every session to assess the amount of energy used during a certain period. This helps the customer find large loads that might be running simultaneously.

The preparation of an electric load plan simplifies the process of creating the system according to equipment size and power system research. This process requires a thorough understanding of the installation, all the equipment to be put in place, the frequency of operation, and the importance or significance of each.

A load plan should be established as early as possible during the design phase. It is essential to know the main voltage levels needed in the construction and all the other aspects of the purpose of the building or facility, and the nature of non-process and process loads.  

The benefits of a load schedule:

  • Provides an accurate estimation of the electrical load in the normal and peak load.
  • The design allows for an additional load capacity or handling any extra load or expansion.
  • When you understand the load and the times when peak consumption is probable to happen, it’s possible to design a power management system that will ensure that the load stays in line all the time and avoid instances of switching between very low and intense peak consumption periods.
  • When properly managed, it lowers the cost of electricity during peak times; however, it also helps the power company, which will use less energy.
  • The design can accommodate future demands.
  • The estimation assists in determining the size of conduits, conductors, the control and protection equipment.

How to calculate electrical load schedule for a house?

Here’s a method used to calculate the load Schedule for a house:

  1. Take the total wattage capacity of all branches of lighting circuits.
  2. Include the wattage rating of each outlet plug-in circuit.
  3. Incorporate the wattage ratings of every permanent appliance (ranges dryers, stoves, water heaters, etc.)
  4. Subtract 10,000.
  5. Then multiply this answer by 40% (0.4).
  6. Then Add 10,000.
  7. Check the full wattage rating for permanent air conditioners and the wattage rating of heating appliances and then add either Larger Value from both of these. Because (You can’t cool and heat simultaneously; therefore, you don’t have to include each number.)
  8. Divide the sum by the totall voltage if your electricity connection is three-phase then value will be different for each phase also need to calculate the load separately for three phase appliances’ in-case of three phase you have to divide the sum of total by phase-to-phase voltage not with single phase voltage.

This formula gives the recommended amperage required to supply the home with enough power. It is easy to evaluate the current electricity service applying this formula.

Some recommended simpler guidelines:

  1. 100-amp service is typically enough to supply a small-medium-sized or larger home’s main branch circuits as well as one or two electrical appliances like a cooking range or water heater, or clothes dryer. If the heating appliances use gas, the service could be adequate for homes with less than 2500 square feet.
  2. 200-amp service can take on the same amount of load as 100-amp service. It also includes electric appliances and electric heating and cooling equipment for homes that are up to 3,000 square feet.
  3. 300or 400-amp services are recommended to big homes (more than 3500 square feet) with all-electric appliances and electric heating and cooling equipment. This service size is suggested for homes where the anticipated electric heat load exceeds the 20,000-watt mark. 300- or 400-amp service is typically offered by installing two panels, one offering 200 amps and the second one that provides 100 amps or 200 amps.

Electrical load calculations, formula and examples

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Single-Phase Formula and example:

Single Phase Load = I = P(Watt) ÷ V× P.F

Let’s Take the values of P (Watt) and Voltage

P= 800W

V= 230V

(power factor) P. F= 0.9

Now put these values into the formula

I = 800 / 230× 0.9

Single Phase Load = I = 3 Ampere

Three-Phase Formula and example:

Three Phase Load = I = P(Watt)÷ 1.73 × VL-L × P.F

Let’s Take the values of P (Watt) and Voltage

P=1000 W

VL-L= 440 V

P.F = 0.9

Where 1.73 is the value of √3  and VL-L represents the Line-to-Line Voltages.

Now put these values into the formula

I=1000 ÷ 1.73 × 400 × 0.9

Three Phase Load =I = 1.60 Ampere

KW and KVA calculations formula

KW (Kilowatts) Load Calculation formula:

The unit used to estimate the real power is KW.

For Single-Phase

KW= (V × I × PF) ÷ 1000

Example:

Let’s assume the values of current and volts

V (Voltage)=220 Volts

I (Current)=5 Amp

Power factor = 0.9

Put the values in formula

KW= (220 x 5 x 0.9) ÷ 1000

Total Load= 0.99KW

Three Phase

KW= (V × I × PF × 1.732) ÷ 1000

Formula:Load=KW= (√3 x V x I x P.F) ÷ 1000

Example:

Where V=Average Voltage= (V1 + V2 + V3) ÷3

I = Average Current = (I1 + I2 + I3) ÷3

Let’s assume the values of current and volts

V= (440+430+435) ÷3

V= 435 Volts

I = (22+28+25) ÷3

I=25 Amp

Now put all values in Formula

Load=KW= (1.732 x 435 x 25 x0.9) ÷1000

Load=KW=16.95 KW

Where V is volts, A is total amp load, PF is power factor and 1.732 is the value of √3.

 KVA (Kilovolts Ampere) load calculation formula:

The unit that calculates apparent power is KVA.

Single-Phase

KVA= (V × I) ÷ 1000

Example:

V (Voltage)=220 Volts

I (Current)=5 Amp

Put the values in formula

KVA= (220 x 5)÷ 1000

Total Load = 1.1KVA

Three-Phase

KVA= (V × I× 1.732) ÷ 1000

Where V=Average Voltage= (V1 + V2 + V3) ÷3

 I =Average Current = (I1 + I2 + I3) ÷3

Let’s assume the values of current and volts

V= (440+430+435) ÷3

V= 435 Volts

I = (22+28+25) ÷3

I=25 Amp

Now put all values in Formula

Load=KVA= (435 x 25× 1.732)÷1000

Load=KW=18.835 KVA

Where V is volts, A is total amp load, and 1.732 is the value of √3.

Difference Between kW load and kVA load

The primary difference between kW (kilowatt) and the kVA (kilovolt-ampere) is their power factors. kW is the term used to describe the real power unit, and kVA is the apparent power unit. Although as well-known, the power ratio is consequently an approximate figure (typically 0.8). When comparing kW to kVA calculations, the value of kVA will always be greater than the kW value.

For industrial and commercial generators, the kW number is the most frequently used in US generators. Most of the rest of the world utilizes kVA as the main generator set.

What is the measuring Unit of Electrical Load?

The measuring Unit of the Electric Load is Watt and Kilowatt.

Electrical power is expressed in power units known as Watts, named in honor of James Watt, the inventor of the steam engine. 

One Watt is just a small quantity of energy. Some devices need only some Watts to function, whereas others require more. Power consumption for smaller devices is typically measured in Watts. In contrast, bigger devices are measured using Kilowatts (kW), equivalent to 1,000 Watts.

Electricity generation capacity is typically expressed in multiples of Kilowatts in megawatts (MW) and gigawatts (GW). One megawatt is 1000 thousand kW (or one million Watts), while one gigawatt is 1000 milliwatts (or 1,000,000 Watts).

What type of load is motor?

Electrical motors, single or three phase, are inductive loads. They are the most common inductive load in the power system. Ans are used in a wide range of household devices and household items that use moving parts, like vacuum cleaners, fans, dishwashers, washing machines, and compressors found in refrigerators and air conditioners.

Is a transformer an inductive or capacitive load?

The transformer draws an inductive current to perform its operation. The magnetizing current required for setting the flux needed within the central core of the transformer is inductive. This secondary current reflects the primary portion of the transformer. It is the sum of the no-load current and the secondary current referred to by the primary. The primary current is influenced by secondary current.

 The secondary current could be either inductive, resistive, or capacitive, based on the kind of load being connected to those secondary connections of the transformer. If the primary transformer connects to a capacitive load, the primary current will be capacitive. The primary current is inductive if the secondary is connected to an inductive load.

It’s all depends on the type of load connected by the secondary side of the transformer.

  • If the secondary is an open circuit, the primary acts as a high inductance coil.
  • However, when you short the secondary, the primary behaves like an actual coil with less inductance. Only the leakage inductance remains “visible”; the rest is removed.
  • If the secondary is connected with a resistor, it acts in sequence with the leakage inductance. Practically, if the leakage inductance is negligible, the transformer will appear like a pure resistor. The resistance is changed up or down depending on the ratio of turn.
  • The same as capacitors on the secondary; however, the capacitance will be changed in inverse proportion to the turn ratio. The main will remain the capacitor with a low inductance when in series.

What is critical load in power system?

Critical loads are those loads where the power supply needs to be maintained in any conditions. The power supply to these loads shouldn’t ever be cut off.

These types of loads are classified as Critical loads, those loads that directly affect the capability for an organization to run; special measures are implemented to ensure a continuous supply of power to these loads, even if the power supply to the industry fails because these loads need to be maintained running (without interruption in power) when the mains power source is shut down in a timely way to avoid computer crashes or data corruption, as well as life-shortening hardware damages. 

This is why uninterruptible power supply and other standby power solutions like generators play a crucial function in ensuring continuity of business by providing immediate backup to the essential electronic devices, systems, and equipment in the event of a significant power outage.

Critical loads are often found in processing plants where processes cannot be stopped.

Factors To Classifying Loads as Critical or Non-Critical:

load is classified as critical or non-critical is based on the importance it has to the company in relation to:

  • Health care centers and hospitals.
  • Financial penalties, loss of business, and impacts on customer service
  • Service delivery
  • Productivity and production lost
  • Quality, safety, and health as well as environmental protection systems
  • Security breaches and the loss of control
  • Stakeholder trust and reputation of the company

After critical loads have been discovered, they need to be prioritized according to their importance and the length of time they will need to remain in operation during a primary outage.

For specific critical loads, such as local file servers, the server may need to be protected from shutting down a secure system. Like the medical systems for life or telecom networks, others might require maintaining the longest time it is feasible.

What is the function of an electrical load in circuit?

The circuit’s load is the actual device that performing the necessary task like a clothing Dryer or washer: the dishwasher, television, and toaster or oven. A circuit could be nothing without an associated load. The load takes the required current to enable the device to function.

The load is formed of the power required for its work, dependent on the current and voltage. The method by which load draws the current is by conducting the current through the device by load resistance; the less resistance, the easier it is to draw the current from the device. The conductor material must be an electrically conducting material.

Using Ohms and Watts law, we can observe what the power source draws from the current pushed by the voltage from the resistance.

Another term used to describe load in the electric circuit is impedance. Impedance can be in three forms: capacitance, resistance, and inductance.

A load can be composed of any of the three types of impedance or, more often, the combination of all three or two to create the load within the circuit. As an explanation, take an electric induction motor.

The majority of its circuit impedance comprises conductors that are winding around the stator that are affected by the movement of magnetic fields around the rotor. This creates an induced back-emf within the windings. This is the reason for the inductance-related impedance.

Most of the impedance is due to the conductors’ resistance in the windings (a tiny percentage that contributes to heating the stator and leads to the requirement to cool down the motor by a massive air volume).

Another smaller percentage that is a part of impedance comes from the capacitance that results from the relatively substantial conductor surfaces packed together in the windings.

They are separated by thin layers of insulation made from varnish. In the end, the total load or impedance of a motor itself is the one that combines all the three impedance components.

To calculate the entire burden of the motor circuit includes the impedances of these feeder wires and motor starter, the isolator switch, and any capacitances for power factor correction within the motor circuit

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