What are Taps on a Welding Transformer?

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Welding transformers are necessary especially where AC machines are used. They help in alternating the current from the line of power and transform them into a lower voltage. Thus, the welding transformers need some taps to help different functions when the AC machines are used.

This article will help you understand the use of the taps and why they are installed on transformers. The article outlines how the articles are used in welding transformers and what to do if a tap is not well fixed or in case anything happens to the transformer.

So, what are taps on a welding transformer? The primary use of taps in a welding transformer is to regulate voltage and the current. In addition, the taps make it easier for the welder to adjust the voltage to the level needed by the device. These specific taps are usually plugged into the secondary coil but in different configurations.

What are taps on a welding transformer?

It is important to note that transformers are used to regulate voltage by providing a stepped variation on the output which allows them to adjust 0.625%. When we think about tapping transformers during our jobs, it’s crucial to know what they do and how they work on your equipment so you can properly use them without damaging anything.

These control systems are used to regulate voltage by providing a stepped variation of output. They usually have 33 taps, with one in the center tap that is set at rated settings and 16 more for ramping up or down their turn ratio. This allows ±10% variance from nominal transformer rating which gives them the ability to adjust 0.625% per step- an impressive level of precision.

This is why it's so important to understand how taps work before using one because improper use could cause major damage.

If you’re curious about how they work and what they do, keep reading for more information.

The Simple Design Of A Welding Transformer

Operations Of Welding Transformers

This welding transformer is usually just an away-down transformer containing a magnetic core with a thin primary winding. It also includes several turns on one of its arms. It also includes a secondary winding different from the primary winding as the secondary winding contains fewer turns, but on the other arm, it has a large cross-sectional area.

The primary and the secondary welding make it behave as a step-down transformer. Thus, there is less voltage from the secondary winding and a high current from the winding output. Requirements when constructing an AC welding transformer include;

  • An AC supplier
  • The welding transformer
  • A core
  • An electrode
  • The pieces to be wired

The dc welding transformer has no significant difference from the ac welding transformer. The main difference is that the dc transformer has to be connected to a rectifier. A rectifier converts the ac to the dc. An inductor is also needed to construct a dc welding transformer which helps smoothen the current of the dc.

The following items are needed in the construction of a DC welding transformer;

  • A high AC voltage of about 230 volts
  • A functioning switch
  • A bridge rectifier
  • A smoothening capacitor
  • A DC output
  • Step down transformer

Operations Of Welding Transformers (Parallel Processes)

There are times when the need for one current exceeds the other one. There is mostly a need for current exceeding the current obtained from one transformer. In such circumstances, a welding current is obtained from the operation of parallel welding transformers. Precautions should always be observed when dealing with any electrical appliance.

The number one precaution to be followed here is that all the open circuit voltages should be different. None should be similar to the other. This precaution is usually essential in types of transformers where the open circuit and the transformation ratio vary. Such type of a welding transformer is the high reactance type of a welding machine.

If transformers are connected for parallel operations, the primary windings should always be plugged into identical wires of the supply mains. It ensures the coincidence of e.m.f phases. The like terminals of the secondary windings should then be connected in pairs.

How do welding transformers work?

The main working principle of a welding transformer is that the welding transformer can convert AC power into DC power and vice versa.

There are two main parts of a welding transformer, primary coils, and secondary coils. The voltage in an alternating current (AC) circuit is produced by periodically reversing the direction of the flow of electric charges through a conductor--the more often these reversals occur, the higher the frequency or greater number of cycles per second.

The electricity from a wall outlet usually has a 60-hertz frequency, which means it flips back and forth between positive to negative for every cycle at least 60 times each minute. One type of furnace uses 240-volt current instead and requires three wires to transmit this kind of electrical energy: one wire carries live electricity while the other two act as a return.

The transformer steps down the voltage from 240 volts to 120-volt and also carries the current over three wires, one for live electricity that converts AC power into DC power with an AC frequency of 60 hertz or less.

In contrast, the secondary coils transform low-frequency (60 Hz) alternating currents back into high-frequency currents by using an induction process--turning mechanical energy into electrical energy without changing its direction of flow.

A person standing next to a wire carrying an electric charge will feel nothing because electrons strike his body at equal intervals on both sides; however if he stands in such a way so that there is more metal between him and the wire, he will feel a greater sense of electric charge.

The voltage from this transformer is then distributed by wires to the welding rod through the holder.

The holder is used to hold the welding rod in place. It also has a resistor that limits the current of electricity flow from the power supply and prevents it from flowing through your hand if you are holding onto or touching the metal part of the holder with an ungrounded piece of equipment, such as gloves.

Types Of Welding Transformer

There are four known primary welding transformers. The four types are;

01. The External Reactor Welding Transformer

It is usually a negative volt-ampere achieved when the reactor is placed in the welding circuit's secondary. This external reactor comprises a steel core and also a winding wound. It consists of a wire in which it carries current to the highest level allowed.

02. The Integral Reactor Welding Transformer

This type of welding transformer consists of different windings. It has the primary winding, the secondary winding, and the reactor winding. Other than the common main limbs, this type of transformer has another limb that carries the reactor winding.

The current type of welding machine is adjusted by moving the core C, usually between the extra limbs. In summary, the transformer is the part that carries the primary and the secondary winding, while the reactor is the part carrying the reactor.

03. High Reactance Welding Transformer

When this transformer supplies current, some magnetic fluxes are produced around the transformer's windings. The resultant magnetic flux lines and the transverse cut the primary and the secondary windings, which does not apply to all transformers. Both the primary and secondary windings do not cross between as they tend to have their paths in the air.

04. The Saturable Reactor Welding Transformer

Here, a low voltage circuit is established to change the working of the magnetic core and its magnetic characteristics. For one to achieve this, large amounts of AC are used or are controlled. Controlling the large amounts of AC is done by using a small amount of direct current.

When this is done, the production volt-ampere can be regulated from minimum to maximum. When no dc flows in the reactor coil, the reactor has a minimum resistance, and this will cause a high-level output of the welding transformer.

A rheostat in the dc circuit helps increase the magnitude. If this is achieved, it leads to raised magnetic lines of force, thus increasing the impedance of the reactor as the output current of the transformer decreases. It is helpful as it helps remove the movable and flexing parts.

It is usually for gas arc welding.

The Multi-Operator Transformers

This type of welding transformer utilizes high constant voltage power, which provides several welding circuits simultaneously. It is primarily used when there are large concentrations of welding points in a small operating area.

Why would I need to use them?

Welding Transformers are the key to changing high-voltage AC into low voltage, high amperage current that can power an electric machine.

Since heating is a function of welding current and thicknesses being welded together, this parameter gives an indication of how thick your materials must be in order for them to fuse properly - minimizing the risk of overheating or even melting your materials from the electrical current.

A general rule of thumb is that most electric welding requires a transformer with at least 100 amps, but heavier wire - or thicker material to be welded together will require more amperage and therefore a larger welder transformer.

In order for this device to work properly, it needs to complete an AC circuit which means your power source must have electricity in alternating directions (alternating).

Welding transformers are typically heavy-duty devices used on construction sites where high voltage could pose danger if handled improperly.

It's important for anyone who works around these types of machines to follow safety guidelines specifying safe distances when working near live wires as well as what tools should not be touched by bare skin such as gloves or other protective clothing required for the job.

Common mistakes people make when using taps

When you are in the welding process need sound knowledge about using welding transformer tap which is an important component of the transformer? Common mistakes people make when using taps are given below.

 Common mistake no.  One:

People may use the wrong tap size for the specific application, this is known as "tap undersizing." For example, using an M12 x 50 when you need a T15 x 60 tap to weld with a 20 mm diameter rod.

Common mistake no.  Two:

Not following safe operating procedures and good safety practices can lead to accidents and injury such as burns or electric shock if exposed live electrical terminals are touched by bare skin while working on wiring that has 240 volts present at any given time so make sure always wear appropriate personal protective equipment in order to avoid injuries.

Common mistake no. Three:

Failing to properly prepare the worksite before beginning welding which includes removing all debris and clutter, providing good ventilation so fumes can dissipate in the air not to be breathed into the lungs.

Common mistake no. Four:

Using old equipment that is worn out or has corrosion build-up on it which may cause a decrease in the quality of weld bead appearance as well as performance due to higher energy losses during the welding process.

General Highlights on a Welding Transformer

As mentioned above, welding transformers are commonly used when using AC machines since they regulate currents and reduce voltages. Ratings on a welding transformer are usually expressed in Kilovolt amperes (KVA) and only for specified duties. It indicates the energy that the transformer can deliver in a given time.

The given time is usually a minute, and the amount of energy is generally expressed as a percentage and with the required temperature rate. The welding transformer also contains an RMS short circuit used to indicate the highest level of the current that the transformer can produce. Also, it gives the maximum thickness of materials to be used.

What is required of welding transformers?

  • Welding transformers should always have a static volt-ampere characteristic
  • In circumstances where there is a short circuit, always reduce the welding current.
  • The open voltage should never be above 80 volts and should never get to 100 volts
  • There should be a straightforward control way of the output all through to the maximum range
  • The open voltage should be high enough but not extremely high as it can destroy the welding economics.

Effects of tap switch on welding transformers

There are two different ways of wiring taps on a single transformer. First, there is usually a series of parallel transformers. The upper range of the welding transformers should be wired in parallel, while the lower range should be wired in series since it produces the most insufficient power.

Due to the many transformer designs, the first tap should always have the lowest voltage. Therefore, the first tap should always contain the lowest voltage and an available power option since the other taps may be different depending on the model or the design of the welding transformer.

The location of taps in a welding transformer

Taps are mainly located on the secondary coil. They can easily be found at different positions so long as they are on the secondary coil. The primary way of providing the taps is by joining the last layer of the coil, usually located at the far end of the finish line. Depending on the design of the transformer, you may find some breaks between taps. In most transformers, you will find these breaks between tap four and tap five. A jumper is also given for a coil, and it helps select the favorable voltage at the exact nameplate.

In other ways, a tap may be configured to connect the loop of the secondary coil and the taps with no breaks between the taps. The very last tap is usually located just near the finish line. The nameplate determines how this tap will work as the delta connection on the input side is closed at the tap. Configuration of taps is in a more straightforward way known as the line taps.

These tap jumpers always join two coil terminals, whereas the tap jumpers may only connect one terminal to another transformer. Thus, the location of the taps depends on the voltage amount required.

Summary on how the taps help in adjusting the voltage

Taps always provide whether higher or lower secondary voltage levels depending on the line voltage, and hence the transformer's voltage ratios will change once the taps are opened for use. In circumstances where the transformers are large, the taps will help in variations that are offset in the voltages. Invariably, the tap connections should be set as the default of the line voltage.

If the welder needs a change in the voltages, he should change the taps to get the required voltage. Large transformers only allow for fewer turns when compared to small transformers. Hence, when using large transformers, taps should not be placed at exact voltages.

Steps on testing the welding transformer

  • Always conduct a visual inspection of your welding transformer. You can do this by referring to your manual document, and it will help you get to know the location of all parts in your transformer.
  • Ensure you know how the wiring pattern has been brought together. Get to know where the primary, secondary windings and taps are located.
  • Get yourself a multimeter that will help you measure the AC and DC voltages, resistance, diode, and continuity.
  • Disconnect all the power sources to bleed out the capacitors meaning you should allow power to drain off.
  • Recheck to ensure the transformer has no power and all the energy has drained off. Refer to the owner's manual where you are unsure of what to do.
  • In your transformer, check the input voltage to help you know where to reduce or increase the voltage.
  • Check your output voltage from your welding transformer. If you cannot tell which wiring holds the output voltage, refer to the manual's guide.
  • Carry out a test on continuity in the primary windings
  • Once you are done, proceed to carry out the continuity test in the secondary windings.
  • Finally, you need to have known the issues on your transformer and troubleshoot them.


You may need to differentiate between an inverter and a transformer or not sure what you have precisely. The main difference between transformers and inverters is that transformers regulate the alternating currents by increasing or decreasing from a single voltage to the other. Inverters only take the direct current electricity, act as input, and then produce the AC electricity.

The maximum number of taps a transformer can have is seven. Always follow the precautions given to avoid significant occurrences like electrocutions. In case you are unable to understand the guidelines on the manual's owner, do not attempt to connect or do the wiring. It is always advisable to contact a professional where the need is and observe utmost care when handling these appliances.

Last Updated on July 10, 2021 by weldinghubs

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