What is Phase Shifting Transformer?

Phase Shifting Transformer | Source: Siemens Energy

Phase shifting transformers are used to control the phase angle of an alternating current (AC) voltage. The main purpose of phase shifting transformers is to balance the load on a power transmission system, which helps to improve the system stability and reduce the risk of blackouts. 

This device work by shifting the phase of the voltage waveform, either advancing or delaying it, in order to control the flow of power from one point to another in a power system. This allows electric utilities to optimize the use of their transmission capacity and improve the overall efficiency of the power grid.

Theory of Operation

Phase shifting transformers are electrical devices used to control the phase angle of an alternating current (AC) voltage waveform. They work by shifting the phase of the voltage waveform, either advancing or delaying it, in order to control the flow of power from one point to another in a power system. When an AC voltage is applied to the primary winding of the transformer, it induces a magnetic field in the magnetic core. This magnetic field then induces a voltage in the secondary winding, which is used to control the phase angle of the voltage waveform.

Phase Shifting Illustration | Source: Researchgate

The phase shift can be achieved through the use of a number of different winding configurations and techniques, including the use of multiple winding layers, the introduction of a resonant circuit, or the use of tapped windings. The specific design will depend on the requirements of the application and the desired level of phase shift accuracy.

Related Article: What are the Basic Characteristics of an Ideal Transformer?

In order to control the phase angle, the relationship between the primary and secondary windings is adjusted. By changing the number of turns in the secondary winding, the phase angle of the voltage waveform can be advanced or delayed. This allows for control over the flow of power from one point to another in a power system, which helps to improve the system stability and reduce the risk of blackouts.

Applications of Phase Shifting Transformers

Phase shifting transformers have a number of important applications in the field of electrical power transmission and distribution. Some of the most common applications of phase shifting transformers include:

Power Flow Control

One of the primary applications of phase shifting transformers is power flow control, which involves adjusting the flow of power from one point to another in a power system. This can be done by shifting the phase angle of the voltage waveform, either advancing or delaying it, in order to control the flow of power. By optimizing the use of transmission capacity and improving the overall efficiency of the power grid, phase shifting transformers can help to reduce the risk of blackouts and improve the stability of the power system.

Reactive Power Control

Another important application of phase shifting transformers is reactive power control, which involves adjusting the balance between active and reactive power in an electrical system. Reactive power is the power that is not being used to perform work, and it can cause inefficiencies and losses in the system. By controlling the phase angle of the voltage waveform, phase shifting transformers can be used to adjust the balance of reactive power, which can help to improve the efficiency of the system.

Voltage Regulation

Phase shifting transformers can also be used for voltage regulation, which involves adjusting the voltage level in a power system to ensure that it remains within a specified range. By shifting the phase angle of the voltage waveform, phase shifting transformers can be used to control the voltage level in the system, which can help to improve the stability and reliability of the system.

Interphase Power Flow Control

In addition to controlling the flow of power between different parts of a power system, phase shifting transformers can also be used for interphase power flow control, which involves adjusting the flow of power between different phases within a three-phase system. By shifting the phase angle of the voltage waveform, phase shifting transformers can be used to control the flow of power between phases, which can help to improve the stability and reliability of the system.

Type of Phase Shifting Transformers

Phase shifting transformers are classified into several types based on the manner in which they shift the phase of the voltage waveform. Some of the most common types of phase-shifting transformers include:

• Fixed Phase Shifting Transformers - These are transformers that have a fixed phase shift between the input and output windings. They are used for applications where a constant phase shift is required. 
• Variable Phase Shifting Transformers - These transformers have a variable phase shift between the input and output windings, which can be adjusted as needed. They are used in applications where the phase shift needs to be adjusted based on changing conditions. 
• Off-Load Tap Changer Phase Shifting Transformers- These transformers have a tap changing mechanism that can be adjusted while the transformer is not under load. They are used for applications where the phase shift needs to be adjusted quickly and easily. 
• On-Load Tap Changer Phase Shifting Transformers - These transformers have a tap changing mechanism that can be adjusted while the transformer is under load. They are used for applications where the phase shift needs to be adjusted continuously during operation. 
• Resonant Phase Shifting Transformers - These transformers use a resonant circuit to shift the phase of the voltage waveform. They are used in applications where a high degree of phase shift accuracy is required. 
• Hybrid Phase Shifting Transformers - These transformers use a combination of fixed and variable phase shift elements to provide a flexible and accurate phase shifting solution. They are used in applications where both constant and adjustable phase shift is needed.

Each type of phase shifting transformer has its own advantages and limitations, and the best type to use depends on the specific requirements of the application. While they offer many advantages in terms of improving the stability, efficiency, and reliability of power systems, they also come with some disadvantages, including cost, maintenance requirements, complex design, limited availability, and vulnerability to environmental factors. Additionally, the accuracy of the phase shift can be affected by changes in the load, which can negatively impact the stability of the power system. It is important to consider these factors when evaluating the suitability of phase shifting transformers for a specific application.

The future of phase shifting transformers is likely to be shaped by advancements in materials science and engineering, the increasing use of renewable energy sources, the integration of smart grid technologies, and the continued development of HVDC transmission systems. These developments are expected to result in more efficient, cost-effective, and reliable phase shifting transformers, playing an increasingly important role in managing the flow of power and ensuring the stability and efficiency of power systems. 

With growing concern about the environmental impact of energy generation and consumption, there will likely be an increased emphasis on energy efficiency, and phase shifting transformers will play a critical role in achieving this goal.