What to Know About AC Voltage?

AC voltage is a type of electrical voltage that alternates in direction and magnitude over time. AC voltage was invented in 1893 by Nikola Tesla in the World Columbian Exposition in Chicago. The main properties of AC voltages are amplitude, frequency, phase, RMS value, period, wave shape, and peak-to-peak value. All of these properties can be mathematically proved by the equations. AC voltage is generated mainly from the power generator by a rotating magnet and induces a current in the coil.

The generated voltage is converted into high voltage for transmission. According to the distance and power requirement, voltage potential has increased. The high potential voltages are mainly 3 types such as high voltage, extra high voltage and ultra-high voltage. During the transmission, AC voltage power is lost due to environmental and material effects. But power loss can be minimised using thicker wires, quality materials, high voltage, improving power factor, transmission DC and using smart grid technologies.

High voltage can be converted in low voltage using transformers for domestic usage. In North America, Domestic use AC voltage is 120V at 60Hz, and in Europe, it is 230-240V AC at 50 Hz. Both advantages and disadvantages are in the AC voltage. The advantages of AC voltage are easy transformability, easy generation, higher safety, and high compatibility. Disadvantages of AC voltages are power loss, more complxicuty, high frequency and sensitivity with skin effect.

Due to these disadvantages, AC voltages are not directly used in small electric equipment. Therefore DC voltage is used in small electric equipment by using halfwave rectifiers and full-wave rectifiers. DC voltage is a direct current which is good for small electric equipment. Both AC and DC voltages have pros and cons. Among them, AC is good for using and transforming the voltage.

What is Ac Voltage?

AC voltage is the type of electrical voltage that alternates in direction and magnitude over time. AC voltage has a consistently one-direction flow. AC voltage changes its polarity periodically. This oscillation of voltage is achieved through the use of an alternating current generator.

Great Barrington demonstrated the world’s first full AC power system by using step-up and step-down transformers in 1886, Massachusetts. The AC voltage was invented by Nikola Tesla and was demonstrated in 1893 in the World Columbian Exposition in Chicago. Tesla revolutionized power systems by developing the concept of alternating current, which paved the way for the transmission and distribution of electricity over long distances.

What Are the Properties of Ac Voltage?

AC voltage consist of sinosidual wave. Therefore the properties of AC voltage are based on the behaviour of the sinusoidal wave. Hence main properties of the AC voltage are amplitude, frequency, phase, RMS value, period, wave shape, and peak-to-peak voltage.

Amplitude

The amplitude represents the maximum value of the voltage waveform and is denoted by V_peak. It signifies the peak voltage achieved during each cycle of the alternating current. The amplitude of AC voltage determines the maximum potential difference that can be reached, influencing the power and performance of electrical devices.

 V_(t) = V_peak× sin(ωt + φ) + b

Where;

V_(t) is the instantaneous voltage
V_peak is the peak voltage
ω is the angular frequency
t is the time
b is a constant
φ is the phase

Frequency

The frequency of AC voltage refers to the number of complete cycles or oscillations that occur in one second. It is measured in Hertz (Hz) and denoted by f. The period (T) of the waveform is the time for one complete cycle, and it’s related to frequency (f) through the equation T = 1/f. Conversely, the frequency is the reciprocal of the period,

f = 1/T

The frequency determines the rate at which the voltage alternates its direction and magnitude. In power systems, the standard frequency is often 50 or 60 Hz, depending on the country. It is crucial to match the frequency of the power source with that of the electrical device for optimum performance.

Phase

The phase (φ) represents the offset between multiple waveforms. The angular frequency (ω) is related to the frequency by

ω = 2πf

It represents the position of a particular waveform within the cycle of alternating current. The phase is measured in degrees or radians and helps in understanding the relationship between different voltages in a system. Phase synchronization is vital in power systems to ensure efficient and coordinated operation.

RMS Value

The RMS (Root Mean Square) value of AC voltage is a crucial parameter used for various calculations and comparisons. It represents the equivalent DC voltage that would produce the same power as the AC voltage. The RMS value of AC voltage is denoted by V_rms and is calculated using the formula

V_rms = V_max/√2.

It is essential in determining the effective voltage, current, and power consumption of electrical devices.

Period

The period of AC voltage refers to the time taken to complete one full cycle or oscillation. It is denoted by T and is the inverse of the frequency. The period represents the duration of one complete waveform, including both positive and negative halves.

Understanding the period is vital for analyzing waveforms, calculating time-dependent quantities, and designing electrical circuits.

Waveform Shape

The shape of the AC voltage waveform plays a significant role in determining its characteristics and behaviour. There are various types of waveforms, including sine waves, square waves, triangular waves, and sawtooth waves.

The most common waveform in power systems is the sine wave, which exhibits a smooth and continuous variation of voltage over time. The waveform shape affects the efficiency, harmonics, and overall performance of electrical devices.

Peak-to-peak Voltage

The peak-to-peak voltage of AC voltage is the difference between the maximum positive peak and the maximum negative peak of the waveform.  It can be considered as the maximum amplitude of the waveform. The peak-to-peak voltage (V_pp) is the total swing of the waveform, calculated as

Vpp = 2×V_peak

It represents the total voltage swing experienced within one complete cycle. The peak-to-peak voltage is useful in analyzing the range of voltage variations and determining the voltage tolerance of electrical components.

How is Ac Voltage Generated?

AC voltage is generated in various methods, but the most common method is using a power generator. The generator consists of a rotating magnet within a copper coil. As the magnet rotates, it induces a current in the wire. This results in the generation of alternating current voltage. This generated voltage can be utilized for various applications, such as powering electrical devices and lighting homes and industries.

How is Ac Voltage Distributed From Power Plants to Homes?

Ac voltage can be distributed from power plants to home in the main 7 steps. 

Step 1 – AC voltage generation
The process starts in a power plant, where electricity is generated. This can be a thermal, nuclear, hydroelectric, wind, or solar power plant, among others. The voltage at which the electricity is generated is typically relatively low—on the order of a few tens of kilovolts (kV).

Step 2 – Step-Up Transformer 
The electricity from the power plant is first sent to a step-up transformer located nearby. This transformer increases the voltage to a much higher level for transmission—typically in the range of 155 kV to 765 kV. This is done to reduce the energy lost as heat during transmission, which is proportional to the square of the current.

Step 3 – Transmission 
The high-voltage electricity is then transmitted over long distances via power lines. These lines are the tall, metal towers that you often see running across the countryside. Electricity travels at nearly the speed of light.

Step 4 – Step-Down Transformer 
Once the electricity gets close to the area where it will be used (for example, a town or city), it is sent through a step-down transformer. This transformer lowers the voltage to a safer level (generally below 50 kV) for distribution to individual businesses, houses, and other buildings.

Step 5 – Further Step-Down
The voltage is further reduced at local substations and distribution transformers, often seen on utility poles or in large green boxes at ground level in residential areas. The voltage is stepped down to a safe level for household use, typically 120/240 volts in the United States.

Step 6 – Distribution to Homes
From the distribution transformers, the electricity travels through smaller power lines, eventually reaching individual homes. At home, the electricity passes through a meter that measures the amount of electricity used.

Step 7 – In-Home Distribution 
Inside the home, the electricity is distributed through a circuit breaker panel or fuse box to individual circuits that correspond to different parts of the home, such as specific rooms or individual large appliances.

What Are the 4 Types of Ac Voltage?

AC voltages are mainly 4 different types according to their voltage potential. AC voltage varies wide range of between 110V – 765 kV. The voltage is increased to transfer a small current and higher power under a higher voltage to prevent damage to the transmission lines. Below are the most used 4 types of AC voltages in the world. 

1. Sub-transmission – Between 11,000 to 66,000 volts, used for substations near power generation plants.
2. High voltage – High voltage is considered as 115,000 to 345,000 volts (115kV – 345kV) for efficient long-distance transmission up to about 700 kilometres (435 miles) km. It should be above at least 10 feet from the ground.
3. Extra high voltage (EHV) – Extra high voltage is considered as the voltage between 345,000 – 765,000 (345kV-765kV). Extra high voltage can be transferred 2,000 kilometres (1,243 miles). It should be above at least 16 feet from the ground. 
4. Ultra-high voltage (UHV) – Ultra-high voltage is considered as voltage above 765,000V (765kV). The voltage which is essential for extremely long distances transmissions. The ultra-high voltage needs a very high tower clearance of at least 20 feet. It can transfer more than 3,293 kilometres (2,046 miles).

What Causes Power Losses in AC Transmission Lines?

The primary source of power loss in transmission lines is due to resistance and is often referred to as I²R losses or Joule heating. The power wasted can be calculated using the formula:

P_loss = I²R

Where;

P_loss is the power loss,
I is the current flowing through the wire, and
R is the resistance of the wire.

The power loss increases with the square of the current (hence, I²R), and directly with the resistance. That’s why high voltage is used for power transmission, as for a given amount of power (P), using a higher voltage (V) allows for a lower current (I), as

 P = VI. And since power loss is proportional to the square of the current, reducing the current has a significant impact on reducing power loss.

How to Reduce Power Loss in Ac Transmission?

The power loss can be minimized by following the below methods.

Using thicker wires: Thicker wires have less resistance, reducing I²R losses. However, thicker wires are more expensive and heavier, which can be a challenge for long-distance transmission.

Using higher quality materials: The material of the wire also influences its resistance. Copper, for example, has a lower resistance than aluminium but is more expensive.

Using high voltage for transmission: As mentioned above, stepping up the voltage for transmission allows for a reduction in current, significantly reducing power loss.

Improving Power Factor: The power factor is the ratio of real power (used to perform useful work) to apparent power (total power in the system). A lower power factor leads to higher currents for the same amount of work, resulting in higher losses. Power factor can be improved by using power factor correction devices such as capacitors and synchronous condensers.

Using DC Transmission for long distances: DC transmission can be more efficient than AC for very long distances or for undersea cables, as it doesn’t have the reactive power losses that AC systems do.

Investing in Smart Grid technologies: Smart grid technologies, such as advanced metering infrastructure and demand response programs, can help reduce transmission losses by improving the efficiency of the power distribution network and reducing peak demand.

How to Convert High Voltage Into Low Voltage?

In electrical power transmission, a voltage above 1000 volts is typically considered high voltage. High voltage is used in power transmission because it allows for the efficient in long-distance transmission of power. These high voltages are not able to use in domestically. Therefore high voltage should be reduced to 100V – 300V range. In order to convert high voltage to low voltage, “transformers” are used.

Transformers are electrical devices that can change the voltage level of alternating current (AC) power. Transformers are used to do this through the electromagnetic induction process. A transformer consists of two coils of wire (known as the primary and secondary windings) wrapped around a shared magnetic core. The input voltage (in our case, the high voltage) is applied to the primary winding, and the output voltage is taken from the secondary winding.

If the secondary winding has fewer turns of wire than the primary winding, the output voltage will be lower than the input voltage. This is known as a step-down transformer because it steps down the voltage level.

Here’s a simple equation that explains this relationship:

V_p/V_s = N_p/N_s

Where:

V_p is the primary voltage (the input high voltage),
V_s is the secondary voltage (the desired lower output voltage),
N_p is the number of turns in the primary winding, and
N_s is the number of turns in the secondary winding.

What is the Domestic AC Voltage?

The domestic AC voltage and frequency is varied with the regions. The domestic AC voltage is between 100V – 300V, and the frequency is between 60Hz – 50Hz. Below are the main region of the world and related AC voltage and frequencies.

• North America – 120V AC at 60 Hz
• Europe/Asia – 230-240V AC at 50 Hz

Large appliances (stoves, dryers) – 240V AC  

Electric vehicle charging – 240V outlets 

What Are the Advantages and Disadvantages of Ac Voltage?

Advantages of AC Voltage

1. Easy Transformability: Transformability is the most significant advantage of AC voltage. It can be easily stepped up or down using a transformer. Transformability makes it more efficient and economical to transmit over long distances. High voltages can be used for long-distance transmission to minimize power loss, and then the voltage can be stepped down safely for use in homes and businesses.
2. Easy Generation: AC voltage is generated by various types of power stations using, coal, nuclear power, natural gas, hydroelectric, and certain types of renewable energy sources. Therefore, it’s readily available and economical.
3. Higher Safety: AC voltage is considered as safer because it generates less heat for the same amount of power, which reduces the risk of fire. Also, AC current’s zero-crossing points can help minimize the risk of electrical shock.
4. High Compatibility: AC voltage is compatible with various devices and appliances. Most consumer electronics are designed to use 100V – 250V AC voltage.

Disadvantages of AC Voltage

• Power Loss: Even though AC voltage is more efficient for long-distance transmission compared to DC, there are still some power losses due to resistance in the lines, especially over very long distances. These losses are often referred to as I²R losses.
• More Complexity: AC systems can be more complex than DC systems because they require equipment like transformers and circuit breakers that can handle alternating current. Also, the calculations for AC circuits can be more complex due to factors like phase and reactance.
• High-Frequency Sensitivity: Some electronic devices are sensitive to the frequency of the AC power supply. Any deviation from the standard frequency (50 or 60 Hz, depending on the country) can affect their operation.
• Skin Effect: AC current tends to flow near the surface of conductors (known as the “skin effect”), which increases the effective resistance. This can lead to more power loss, particularly at higher frequencies.

How is Ac Voltage Converted to Dc Voltage?

Ac voltage can be converted into DC voltage using halfwave and full wave rectifieres. Ac voltage should be convert into DC voltage because Ac voltage is more complex than DC voltage. Therefore most of consumer products are operated by the DC voltage. Hence AC voltage should be converted to DC voltage in the tools. Therefore AC to DC conversion equipment is included in the related equipment. AC to DC conversion have mainly 2 parts those are half-wave rectifieres and full wave rectifiers.

Half-Wave Rectifiers: A half-wave rectifier uses a single diode to eliminate either the positive or the negative half of the AC waveform. While it’s simple and inexpensive, this type of rectifier isn’t very efficient because it only uses half of the input signal.

Full-Wave Rectifiers: A full-wave rectifier uses multiple diodes in a specific arrangement to flip the negative half of the AC signal and align it with the positive half. This makes it more efficient than a half-wave rectifier because it uses the entire input signal.

What is Dc Voltage, and Where is It Used?

DC voltage, or Direct Current voltage, is a type of electrical power that flows in one constant direction. In a DC circuit, the polarity of voltage doesn’t change over time; the positive and negative terminals remain constant. The magnitude of DC voltage can be constant (like in a battery) or can vary over time, but the direction of flow remains the same.

DC voltage can be used in low-voltage applications and electronics. Here are some areas where it’s used:

• Battery-Operated Devices: Many portable devices, such as smartphones, laptops, flashlights, and electric toothbrushes, operate on DC voltage because they are powered by batteries which produce DC.
• Electronics: Electronic components like transistors and microchips, which form the core of devices like computers, TVs, and audio equipment, all operate on DC. Even when these devices are plugged into an AC outlet, the AC voltage is converted to DC for the internal electronics to use.
• Electric Vehicles: Electric vehicles operate on DC voltage. While the charging stations may use AC voltage, it gets converted to DC to charge the batteries in the vehicle.
• Solar Panels: Solar panels generate DC voltage, which is then often converted to AC for use in the home or to feed into the electrical grid.
• Telecommunications: Telecom networks use DC for various applications due to its reliability and the ability to monitor the flow of electricity.
• High Voltage Direct Current (HVDC) Transmission: While most power transmission is done using AC for very long distances or undersea cables, HVDC is often more efficient and experiences fewer losses.

Comparing Ac and Dc Voltage

AC and DC voltages are different types of voltages. These voltages can be compared by its main properties, such as flow, waveform, transmission, circuits, transformers, motors, electronics and safety. Below is the compared table for AC and DC voltage.