What is Tap Changing Transformer & It's Working Principle?

 Taps changing into Transformers

It is a common occurrence that an increase in load will lead to a decrease in voltage that is supplied to the load. This is why the voltage delivered through the power transformer needs to be kept within the specified limits. This can be achieved by adjusting the transformer's turn ratio.

The taps are the leads or connections that are provided at different points along the winding. The ratio of turns varies between taps and consequently different voltages could be obtained from every tap.

The need for a system to control the voltage

Control of voltage is vital to:

1. Adjusting the voltage at the terminal that is supplied to the customer within limits of the manufacturer's specifications.

2. Variable voltage adjustment dependent on changes in load.

3. To control the actual and reactive power.

4. Variable secondary voltage in accordance with the need.

Taps with different types

Taps can be primary, positive, or negative. Principal taps are those where secondary voltage is rated and can be achieved in addition to the primary voltage that is rated. The name implies that positive taps and negative taps are those in which the secondary voltage is greater than or less than the primary tap.

Taps are installed in the HV windings on the transformer for these reasons.

Taps are available on the HV windings of the transformer due to one of the reasons listed below.

1. There are many turns involved in the high voltage winning is huge, and therefore the possibility of a precise voltage variation be observed.

2. The currents on the low voltage windings of large transformers are excessive. So, stopping high currents is a challenging job.

3. LV winding is situated closer to the core while HV winding is situated in the outer. Thus, obtaining taps for this winding will be simpler than the winding of the LV.

Location of Taps

The taps may be located at the ends of the phase or at the point of neutralization or at the center of the winding. The number of bushing insulations is reduced by putting taps at the ends of the phase. If the taps are installed at the neutral points, the insulation between the various components will be decreased. This arrangement is cost-effective, particularly crucial for large transformers.

Tap changing methods

The change in taps causes an increase in the leakage reaction loss to the core copper loss, as well as possibly some issues with running parallel in transformers that are not similar. There are two ways of changing the tap.

1. Off load tap change

2. The load tap changes

1. Offload (No load or circuit off) tap switching

The name suggests the method of tapping changes are made by disconnecting the transformer's load. Off-load tap changing is usually available in low-power transformers, which are low voltage. It is the least expensive method of changing the tap. The change of taps is made by hand using the handwheel that is included within the cover. In certain transformers, configurations to alter taps by using the mechanical switches are also offered.

1. Offload Tap Changer Principle

The winding is connected at different locations. Since taps are installed at different points of the winding, only one tap has to be connected at the same moment or else it could cause short circuits. Therefore, the switch for selecting is activated when the load is disconnected. To stop the unauthorized operation of an off-load tapping changer, the lock is mechanical. To avoid accidental operation electromechanical latching devices are installed to activate the circuit breakers and shut off the transformer when the handle of the tap changer is moved.

2. When the load tap is changed

On-load tap changers allow you to adjust the turn ratio while not disconnecting the load from the transformer. It is possible to change the tap regardless of whether the transformer is providing the load. On-load tap changers greatly improve the effectiveness that the transformer can provide. At present, almost all large power transformers come with On-load Tap changers. The reasons for having a load tap changer on power transformers is 1. When operating on-load tap changers the main circuit stays unaffected.2. The risk of sparking is reduced. The windings' taps are redirected to a separate compartment that is filled with oil in which the switch that controls on-load load is located. Tap changers are an example of a mechanical selector switch that operates with a motor via remote or local control.

A handle that is designed for manual operation in the event of an emergency. Selector switches are a type of make-before-break switch. It is in the process of switching tap changers between taps the connection for the momentary must be made between adjacent taps. This causes an interruption in the circuit between adjacent taps. The short circuit current has to be limited using an inductor or reactor. So, every type of on-load tap changer has an impedance in order to limit the short circuit current when switching. The impedance could be an impedance or a center-tapped reaction. In modern design, it is performed by a pair of resistors.

Procedure

Think about high-speed resistor on-load tap changers that are located at the neutral end of each phase as illustrated. The load now comes through tap 1. Selector switches 1 and 2 have been placed connected to taps 1 and 2. In order to switch to tap 2 the selector switch must follow the steps below:

Switch to change the tap

Switch that changes the direction of the tap

1. Contacts A and B are closed. The current flowing through the load is from tap 1 to contact B.

2. The external mechanism is able to move this diverter switch away from B to b. Now loads are supplied by the resistor R1 through a contact.

3. If the diverter switch moves further, it closes the contact d, and both R1 and 2 are connected to taps 1 and 2, and the current of the load is able to flow through these resistances until its midpoint.

4. If S3 shifts farther to left the contact is opened and load current flows through tap 2 and resistor R2 as well as d.

5. When the contact is reached, it reaches C, and resistor R2 becomes short-circuited. The current flowing through the load goes from tap 2 to contact C.

In order to switch between taps 2 and 3, switch S1 first moves to tap 3 before the previous steps are reversed. To limit the loss of power it is essential that transformers remain inside the circuit for the short a time as is feasible.

Tap changers that are smaller and have excellent reliability and performance are made using vacuum switches within the diverter switches.

Know about the importance of transformers and their uses in different sectors?

 Industrial units require transformers since they typically work with electric supply lines and electrical power sources. Transformers aid in regulating the voltage and make it easier to work the use of low voltage devices. However, their applications in the industry vary because the voltage fluctuates significantly. There are special industrial transformers that are put in place to control devices of various sizes and shapes. They're used to create electricity that is transported across large distances.

What type of transformers is best to use in industrial applications? There are a variety of transformers that industrial companies can utilize for a variety of applications. Some are specially designed to meet the demanding demand for current of different equipment. Customized transformers are capable of enduring the most extreme voltage conditions. So an electrician distribution transformer manufacturer can ensure that every industry will have the correct one for their specific needs.

In this article, we'll concentrate on the various transformer types that are used for industrial use. We will examine the factors that make these transformers distinct. The goal is to show how these transformers will save money and energy, while also meeting the demands of industrial energy. Let's examine the various varieties of transformers and their characteristics

Types of transformers employed in industrial applications

We will go over the various types of transformers that are used in the business. Transformers are specifically designed for processes and projects, too. We will focus on the most common transformers that are used by industries to regulate the flow of current

Rectifier transformers

In conjunction with a diode or thyristor rectifier, they are suitable for various industrial applications ranging from large aluminium electrolysis to a variety of medium-sized operations. They require an electrical voltage that does not have a change in the tap of the loading. In reality, these kinds of transformers come with a built-in or independent voltage regulator.

The same tank as the transformer could be used to create an automatic-connected controlling transformer. It allows for a variety of variations of shifts as well as vector groupings. They are either water- or air-cooled transformers that don't overheat due to regular use.

Rectifiers are dependable transformers for industrial use since they trigger a chemical reaction in their DC energy supply. There are a variety of data on specifications to help users make the best choice when selecting the correct transformer.

Converter transformers

Converter transformers work well for all industrial applications, such as rolling stock, pumping stations blast furnaces, rolling stock and much more. These particular industrial transformers come with two secondary windings. This allows rectifier operations with 12 pulses. Additionally, there is a winding to block the harmonics. There is a chance of using different phases and vector groups.

There are big drives multi-pulse, variable and large electric speed drives that operate via the transformer. They can be used with a variety of voltages and are used mostly for static voltage compensation as well as static frequency changes.

The converter transformers are custom-designed by an electric distribution transformer producer to function flawlessly in extreme conditions. They place a lot of emphasis on temperature, cooling, and cooling mediums in the specifications.

Furnace transformers

The electric furnace transformer is available as well as DC electric transformers for arc furnaces. They are energy-efficient and perform flawlessly in all types of weather conditions. They are mostly made of ferroalloy or steel furnaces. Electric Arc furnace transformers are comparable to submerged furnace transformers. They can handle the frequent overcurrents and overvoltages generated through short circuits inside the furnace.

Furnace transformers are made to withstand extreme thermal stress. DC electric furnace transformers are designed to work with steel furnaces equipped with a rectifier thyristor. They are cyclically loaded and rectifier transformers to support furnace operation.

Transformers in Three Phase

The three-phase transformer's core contains 3 sets of wires. Three-phase transformers are composed of three separate sets secondary and primary windings. Each set is wrapped around the iron core. In essence, it appears like three single-phase transformers that share the same core.

Three-phase, also known as 3ph or 3-phase transformers are utilized for power generation transmission, distribution, and commercial, as well as for industrial use in all aspects. Three-phase transformers possess a number of advantages over single-phase models in regards to performance and efficiency.

Because they can be used with both AC or DC furnaces. These transformers can provide large currents up to 200kA. They come with secondary bushing configurations and designs. They are available as water or air-cooled, which allows for the control of heating while in operation.

In addition, is a line feeder transformer. It aids in making that connection between the power grid and the power source for the train. They must be extremely reliable to make sure that the train can run in a safe manner on tracks. These are used exclusively on railway lines, and they have no capability in other industrial zones.

Everything You Should Know About The Three Phase Transformer Connections

 Three-phase transformer connections In a three-phase system, the three phases are often connected in either star or delta configuration. just just in case you are not familiar with those configurations, study the next image which explains star and delta configuration. In any of those configurations, there'll be a phase difference of 120° between any two phases.

Star delta configuration three phase

Three Phase Transformer Connections

Windings of a 3 phase transformer are often connected in various configurations as (i) star-star, (ii) delta-delta, (iii) star-delta, (iv) delta-star, (v) open delta and (vi) Scott connection. These configurations are explained below.

Star-Star (Y-Y)

Star-star connection is usually used for little, high-voltage transformers. due to star connection, the number of required turns/phase is reduced (as phase voltage in star connection is 1/√3 times of line voltage only). Thus, the quantity of insulation required is additionally reduced.

The ratio of line voltages on the first side and therefore the secondary side is adequate to the transformation ratio of the transformers.

Line voltages on each side are in phase with one another.

This connection is often used as long as the connected load is balanced.

Delta-Delta (Δ-Δ)

This connection is usually used for giant, low-voltage transformers. The number of required phase/turns is comparatively greater than that for star-star connection.

The ratio of line voltages on the first and therefore the secondary side is adequate to the transformation ratio of the transformers.

This connection is often used even for unbalanced loading.

Another advantage of this sort of connection is that albeit one transformer is disabled, the system can still operate in an open delta connection but with reduced available capacity.

Star-Delta OR Wye-Delta (Y-Δ)

The primary winding is a star (Y) connected with grounded neutral and therefore the secondary coil is delta connected.

This connection is especially utilized in a step-down transformer at the substation end of the cable.

The ratio of secondary to primary line voltage is 1/√3 times the transformation ratio.

There is 30° shift between the first and secondary line voltages.

Delta-Star OR Delta-Wye (Δ-Y)

The primary winding is connected in delta and therefore the secondary coil is connected in star with neutral ground. Thus it is often wont to provide a 3-phase 4-wire service.

This type of connection is especially utilized in the transformer at the start of the cable.

The ratio of secondary to primary line voltage is √3 times the transformation ratio.

There is a 30° shift between the first and secondary line voltages.

Above transformer, connection configurations are shown within the following figure.

transformer connection star-star-delta-delta-star

Open Delta (V-V) Connection

Two transformers are used and first and secondary connections are made as shown within the figure below. Open delta connections are often used when one among the transformers in Δ-Δ bank is disabled and therefore the service is to be continued until the faulty transformer is repaired or replaced. It also can be used for little three-phase loads where installation of a full three transformer banks makes no sense. the entire load-carrying capacity of an open delta connection is 57.7% then that might be for a delta-delta connection.

open delta or V-V connection transformer

Scott (T-T) Connection

Two transformers are utilized in this sort of connection. one among the transformers has centre taps on both primary and secondary windings (which is named as the main transformer). the opposite transformer is named a teaser transformer. Scott connection also can be used for 3 phase to 2 phase conversion.