What Is A Pad-mounted Transformer?

A Single Phase pad-mounted transformer is a special type of transformer that you can use in a variety of applications. It has two AC coils, each wrapped around a separate iron core. This type of transformer is compact and easy to install. It can be easily relocated as needed because it doesn’t use an oil reservoir to maintain magnetic flux.

These transformers are not protected in the way overhead lines and substations are. Pad-mounted transformers are visually noticeable, so they serve as a marker for your home’s electrical wiring. And because they can be located anywhere on the property, there is always the potential of environmental risks like faulty wiring or power surges.


Single Phase Pad-Mounted transformer
Single Phase Pad-Mounted transformer

Pad-mounted Transformer

We can provide you single phase and three phase pad mounted transformer

Dry-type Transformer

Type:Cast resin; Rated Capacity: Up to 25MVA; Rated Voltage: Up to 36KV;

Pole Transformer

TypeCSP type Frequency: 50/60Hz; Rated Power: 5~167kva

Dry-type Transformer

Frequency: 50/60Hz Rated voltage:10kv, 20kv,30kv Rated Power: 400~2500kva

These transformers are so powerful that even the slightest spark will blow up the fuse. A high-voltage transformer is a complex arrangement of delicate parts. It can be damaged easily by any number of factors, including poor design or transport damage. 

It is why each transformer must be triple-checked for safety before they’re shipped out to ensure complete protection.

Daelim has been supplying the power tools and industrial market for many years, and they have a lot to offer. Daelim transformers are high-performance, high-efficiency, and safe. Daelim also meets ANSI, IEEE, CSA, and IEC standardization requirements. If you’re looking for a high-performance, high-efficiency, and safe Pad-mounted transformer, you can place your trust in Daelim.


Single Phase Pad-mounted Transformer: The Ultimate FAQ Guide

Single Phase vs. Three-Phase Pad-Mounted Transformer

A pad-mounted transformer main system configuration is commonly used in electronics. It is a type of transformational power distribution system, which is an electrical distribution system that allows multiple transformers to distribute power to all connected loads.

And the use of single-phase pads instead of wire leads to less voltage drop and lower heat generation over other types of transformers.

More importantly, this transformer is good for basic household needs like lighting, heating, and air conditioning. A three-phase transformer is better for commercial use like hydroelectricity, but it’s bulky and expensive. The main difference between the two is that single-phase transformers don’t have a neutral wire.

The configuration of a pad-mounted transformer is either a single-phase or three phases. The single-phase configuration has only one winding, whereas the three-phase structure has three windings.

For many years, pad-mounted transformers were used to convert 230V AC to 24V DC, but they have been replaced by switching power supplies.

Single Phase Pad-mounted Transformer Designs

Essentially, a transformer is a device that will allow a voltage to be raised in one direction and lowered in another, so this device needs to have a “primary” and “secondary” winding. The primary winding is connected to the voltage source, while the secondary is connected to the load.

The Single Phase Pad-Mounted Transformer was used in the United States from the late 1800s to the early 1900s. It was designed by Dr. George Westinghouse, one of the founders of General Electric. The single-phase transformer uses just one winding for all 3 phases, which helps reduce size and weight while also reducing cost.

Additionally, the Single Phase Pad-Mounted Transformers are used for electrical power distribution. They allow a single motor to use a large amount of power up to a certain limit. 

The Single Phase Pad-Mounted Transformers is the most common type of transformer used in North America and Europe. Still, you can also find it in systems that include three-phase transformers.

Lastly, the Single Phase Pad-Mounted Transformers is designed with a circuit breaker and a high voltage winding. They typically contain more than one magnetic field inside them, along with brown and blue iron cores, which help to distribute the magnetic fields evenly.

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Advantages of a Single-Phase System

Transformer manufacturers have been aware of the advantages of a single-phase system for a long time. They have designed transformers with this in mind.

The advantages of single-phase systems include reduction in maintenance costs, possible savings in construction costs, and increased availability of power from renewable sources.

And the advantages of a single-phase system transformer are significant. Single-phase transformers are less expensive than three-phase transformers, so they’re more likely to be used in home and commercial applications.

Lastly, they also offer low voltage protection required by legislative codes, making them ideal for many system designs. Additionally, the single phase’s simplicity means that it is easily accessible and easy to navigate.

Seven Technical parameters of Pad-mounted Transformers

Disadvantages of a Single-Phase System

A single-phase transformer is the most common type of transformer. This type is used in a wide variety of applications, but it does have some disadvantages. The unit has only one winding that must be energized at all times, which means that you can’t use it with an inverter.

A single-phase transformer is an alternating-current (AC) power transformer that changes the current-voltage to match the electrical system’s voltage. The more usual type of power transformer is a three-phase system transformer, which steps up or steps down alternating current to deliver greater or lesser output voltages.

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Three-Phase Transformer Designs

Three-Phase Transformer Designs are used in manufacturing facilities to design rotating electrical devices. Such designs typically use three-phase series-connected three-wire windings, with a separate winding for each phase.

Furthermore, this allows the device to be switched from either AC or DC to the desired voltage. They are also used in power plants and water processing plants to provide a stable source of power.

And they are available in sizes ranging from 10 kilovolts to 5500 kilovolts. They can safely handle high voltages with no risk of explosion. Three-phase transformers come in various designs, but all have three coils wound on laminated paper or aluminum sheets.

​​Additionally, three-Phase Transformer design is a process in which transformers are designed and built to suit the needs of the project at hand. They are typically produced using CAD software that allows for easy visualization and design of components and transformers.

This process uses standard software tools integrated with other engineering disciplines such as structural, electrical, and mechanical engineering.

Advantages of a Three-Phase System

A three-phase system transformer can help reduce the voltage stress on a system by up to 50% over a double-phase system, which may increase the transformer’s life.

As well as reducing operating costs, this type of transformer also offers greater security against start-up failures by automatically shutting down during overload periods.

A three-phase system transformer is the most efficient transformer available. It also provides double the voltage of a standard system transformer, which translates into less energy consumed for each unit of electricity produced.

With a three-phase system, you will never have to worry about anyone else’s power going out again. Unlike the traditional two-phase system, three-phase systems use different phases.

Three phases can also be used as backup power for larger loads like hospitals and large buildings.

Disadvantages of a Three-Phase System

The disadvantages of a Three-Phase System transformer are that it uses three separate transformers, which take up more space and increase the project’s cost. Customers may also find it difficult to locate the switches, which can confuse them. Finally, there is an increased risk of tripping current during installation.

Additionally, the three-phase system uses three separate circuits to connect the primary source of electrical power to your home. It is more expensive than a single-phase system.

The transformer box, housed in the wall, must be powered by electricity from the primary power source or stop functioning.

Lastly, a Three-Phase System transformer is a device that converts the three-phase alternating current of high voltage to direct current. However, these transformers operate at a relatively low voltage. You cannot use them with commercial power systems or industrial loads.

Transformer three-phase dual power supply automatic switching

Defining Single Phase Pad-Mounted Transformers

The use of Single Phase Pad-Mounted Transformers is very common in various industries, from manufacturing to process automation.

This technology is used to transfer electrical power from the primary source to a secondary load. The current transformer design provides an efficient and cost-effective solution for many applications.

A single phase pad-mounted transformer is designed to be mounted to a pad and be connected to either a bus or feeder. The power rating of such transformers ranges from 3KVA up to 220 KVA. The input power must be at least 35 volts, and the output voltage must exceed 208 volts.

A single-phase pad-mounted transformer is a two- or three-way electrical transformer with one winding or plate connected to one phase of the electrical power supply.

This transformer’s other winding, or plate, is connected to the neutral (or common) wire and the center tap for one phase of the power supply.

Furthermore, a pad-mounted transformer is a step-up transformer that places the primary winding on the outside of the transformer body, usually mounted on an insulating base. It’s used to connect one phase of an AC power supply to another degree or with a single-phase load.

Transformer Manufacturers In Canada (Toronto and Mississauga)
Install Pad-mounted Transformer
Install Pad-mounted Transformer

When To Use A Single phase Pad-mounted Transformer?

A single phase pad-mounted transformer is typically installed for permanent power distribution to the load. It is used in fixed installations, such as lighting fixtures, electric motors, and elevator equipment.

You can also use a Single Phase Pad-Mounted Transformer to provide temporary power to a device or group of machines for various purposes.

The Single Phase Pad-Mounted Transformer is an AC/DC power converter that changes the input to the output voltage. It can continuously vary the input voltage in response to input current or input voltage, utilizing a transformer with one primary coil and two secondary coils (direct current) or using a transformer with two primary coils (primary current).

Single Phase Pad Mounted Distribution Transformer (7)
The Complete Guide to a Three-phase Combined Power Transformer

Aside from these, the single phase pad-mounted transformer is typically used in the power distribution circuit of a single-phase supply. This type of transformer is generally mounted on an insulated metal base and connected to the earth potential.

The single phase pad-mounted transformer has a core with a winding capacity of up to 5000VA. You can configure it for upwards of 4000 VAC (60Hz).

Additionally, using this transformer is that this type of transformer fits into small spaces and can be mounted on most surfaces. It makes them suitable for most applications. Other than the cramped locations, they do not require any interruption in service with their low self-noise levels.

Lastly, the Single Phase Pad-Mounted Transformer is perfect for the location with limited space. You can install it in tight places that are hard to reach with traditional transformers. A pad-mount transformer allows for a more robust power distribution system in an emergency, where there might be no other way to power emergency lighting.

Distribution Transformer Selection of An Office Building

Single Phase and Three Phase Pad-mounted Transformer From Daelim
Single Phase and Three Phase Pad-mounted Transformer From Daelim


Transformer manufacturers have been using single phase pad-mounted designs for decades. Today, such transformers are used mostly in the lighting industry and automotive applications. 

And by eliminating the need for housing, these single-phase pads span the transformer’s core for efficient heat dissipation and minimize transformer size and cost.

It is important to note that a single phase pad-mounted transformer is the perfect solution for any size of electrical installation. You can appreciate many benefits, including a low profile design, low cost, reliability, and efficiency. 

And with the right transformer, your application will be safe and efficient.

The Complete Guide to Medium Voltage Transformers


As a transformer pad-mounted unit, the Transformer is heavy and bulky, making it a challenge to install in a small area. The low voltage can damage or shock any person touching the transformer.

There are also safety risks associated with the transformer’s electrical current, as one must be careful not to touch any part of the unit while it is powered up. Another disadvantage is that when troubleshooting a system, the transformer may only operate at certain operating points.

Identically, using a single-phase pad-mounted transformer may impose the lack of electrical isolation. Isolation allows power to flow through one side of the transformer without flowing through the other.

And this creates an isolated magnetizing side that you can use for any application, such as a capacitor or relay coil.

The Complete Guide to Telephone Pole Transformer

Health Safety Checks For Residential Pad-Mounted Transformer

When a residential transformer is not properly mounted, it can have a variety of health risks. Improper mounting can cause an electrical short circuit that may result in fire or other serious damage. In addition, improper mounting can lead to reduced efficiency and reliability for your home’s electric system.

Residential pad-mounted transformer health risks may include, in some cases, residential power transformers can become a fire hazard when they produce excessive heat. In other cases, the transformer can release a chemical or metal vapor that could be hazardous to nearby residents.

How to ground the pad-mounted substation

Single Phase Pad-Mounted Distribution Transformer near house
Single Phase Pad-Mounted Distribution Transformer near house

Generally speaking, residential generators are an excellent way of staying safe from natural disasters and outages while still having power during a blackout.

Identically, managing risks associated with pad-mounted transformers is important to prevent fire, explosions, or other damage. Several remedies can be applied to reduce the risk of these dangers.

One common practice is using a pad-mounted transformer with an isolated transformer at the primary side, which protects the customer from any possible errors induced by the power supply.

The Complete Guide to Industrial Transformer Manufacturers

How Long Does A Pad-Mounted Transformer Last?

The lifespan of a pad-mounted transformer can vary depending on the type you buy. A typical pad-mounted transformer usually lasts anywhere from six to twelve years.

Also, the average lifespan of a transformer without mounting ears is two to three years. Still, this number may be much higher depending on the quality.

Lastly, transformers typically last for thousands of hours and can even last up to 10,000 hours. It is because they constantly recharge their batteries by using the power from the mains electricity.

As long as you don’t turn off your power supply, these transformers will work for a very long time.

The Ultimate Guide To Utility Transformers and Its Benefits

What Is The Difference Between A Pole Transformer And A Pad-Mounted Transformer?

The terms are often used interchangeably, but there are some major differences. The main difference is that a pad-mounted transformer is mounted to the floor. In contrast, a pole-mounted transformer is mounted on an overhead beam.

It has implications for how you can use these transformers in your facility.

Additionally, a pad-mounted transformer is typically smaller, so it can be mounted on the wall. They are also more affordable than a pole-mounted transformer.

And the biggest difference is that the power source is built into the unit, making them easier to maintain.

Single Phase Pad Mounted Distribution Transformer (2)

Does Every House Have A Transformer?

Every house doesn’t have a transformer because it’s on the density of the location. For example, more people stay close together in an urban setting, and you get more pollution. 

And you also get less sunlight than in the countryside where houses are farther apart. These factors all contribute to poor insulation, which requires transformers to power more homes.

The Complete Guide to Power Transformer Failure:Reasons and Methods

What Is A Safe Distance From A Transformer?

Usually, a safe distance from a transformer is 10 feet, allowing room for people and animals. As a general rule, the safe distance from a transformer is to be under the following guidelines: 

  • If you are standing on the ground when working near a transformer, never stand higher than three times the height of the base.
  • The OSHA Standards state that installing transformers away from people exposed to electrical hazards is necessary.
The Complete Guide to Power Transformer Diagram
Residential Three-Phase Pad-mounted Transformers

When you are near an electric transformer, it is important to keep a safe distance, so you don’t get shocked. If the transformer’s insulation gets damaged, it can release high-voltage power that will travel through metal objects like cars and water pipes.

Lastly, the safe distance from an electric transformer depends on the type of transformer. The smaller transformers are about 40 feet in diameter, while the larger transformers are over 300 feet. If you are only working with a small transformer, you can safely stand 10 to 15 feet away from it.

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How Do You Know If A Transformer Blew Up?

There are several signs that a transformer has blown. Suppose your transformer is suddenly noisier than usual. In that case, this could be a sign that your voltage is too high or a shortage in the power system.

Additionally, the most common signs of a transformer explosion are the smell of burning insulation or plastic, smoke coming from the transformer, or if you notice that it’s no longer in the same position as when you were last there.

Where Are Transformers Found At Home?

Transformers are generally found in the basement, but they may be in a utility room or garage in some cases. They can also be built into the walls and ceilings and, in some cases, even outdoors.

What is a single-phase pad-mounted transformer?

The single-phase power system sends the high-voltage power supply directly to the residential load center through the 10kv cable and then delivers it to the residents’ homes through the single-phase pad-mounted. Due to the shortest low-voltage lines, energy consumption is significantly reduced. The full name of a single-phase pad-mounted transformer is the high voltage/low voltage single phase oil immersed pad-mounted transformer.

The single-phase pad-mounted transformer comprises a single-phase transformer, a high-voltage chamber, and a low-voltage chamber, with a compact structure. The transformer core is purchased with an R-type winding structure with low energy consumption and noise. The high and ground voltage windings are wound on a particular core winding machine with high concentricity. The high-voltage room is equipped with a sleeve from Cooper Company of the United States, which is used to connect the elbow-type cable plug with load-breaking capacity.

The elbow-shaped cable plug can be plugged and unplugged when the transformer is fully loaded. The sleeve is connected to the elbow-shaped cable plug, and the live part is sealed in the insulator to form a fully insulated structure. The surface of the high-voltage end is not charged, which can reliably ensure personal safety. The low-voltage room can be equipped with control switches and measuring equipment.

There are two ways to supply power in a single-phase power distribution system: a single-phase two-wire system and a single-phase three-wire system. The single-phase two-wire system means that the high and low voltage sides of the transformer each have a coil, the voltage ratio is 10:0:22, and the low voltage side X is directly grounded through the tank grounding point. The single-phase three-wire system means that the high-voltage side of the transformer has one coil and the low-voltage side has two rings, and the voltage ratio is 10:0:44 (0.22).

The voltage between A and X is 10kv, and the voltage can be preset by ±5% through the non-excitation tap-changer. For the single-phase three-wire system, the low voltage adopts the split operation connection method; that is, the two sets of coils a1, x; a2, x are separately drawn to connect to the load, and X is directly grounded through the fuel tank location, the output of the two low-voltage coils is 220v, and the capacity is the rated capacity. 50%, forming a1, a2, x single-phase three-wire system.

For the single-phase two-wire system, the parallel connection method is adopted; that is, a1 and a2 are connected as a, x through the fuel tank grounding point to be directly grounded, the voltage between a and x is 220v, and the capacity is 100%, forming a, x single-phase two-wire system. ; If the low voltage needs to output 440v, use the series connection method, x is not grounded, the voltage between a1 and a2 is 440v, and the capacity is 100%.

Main features of single-phase pad-mounted transformer

(1) The line loss is significantly reduced. The 10 kV high-voltage network has replaced the original low-voltage backbone network. The power supply mode adopts 10 kV to the household, and the power distribution assumes “small capacity and dense distribution points,” which reduces the line loss on the low-voltage line.

(2) The voltage quality is guaranteed. Since the 10 kV, high voltage is directly connected to the user, and the low-voltage line is short, only the part of the connection line, the actual voltage of the user is close to the rated value and is stable, and the voltage quality is high.

(3) Greatly improve the reliability of power supply. Adopting “small capacity and densely distributed points,” the first floor of the city is changed, or the first floor is changeable, and in the countryside, it is used for several households. At the same time, the single-phase pad-mounted transformer is easy to install, which shortens the time for accident handling and improves the reliability of the power supply.

(4) Beautify the living environment. The single-phase transformer used in the single-phase pad-mounted transformer adopts the international advanced R-type wound core technology, and the noise is very low even if it is fully loaded. The single-phase pad-mounted transformer is placed in the green belt to realize the “rodless” modern residential area.

(5) When the single-phase pad-mounted transformer is used for operation, when the load is unbalanced, a negative sequence current will be generated on the 10 kV distribution network, causing the three-phase unbalance of the distribution voltage, but the impact is negligible. Negative sequence current in regular operation will not affect other current protections. Since the unbalanced load does not generate a zero-sequence current, it does not affect the zero-sequence protection set in the 10 kV distribution network. Therefore, the use of a single-phase pad-mounted transformer will not cause malfunction of relay protection and will not cause the impact of zero-sequence current on communication [2]0

However, the meter loss is relatively fixed for rural users with relatively small loads, and the low-voltage line loss does not decrease significantly. Using a single-phase pad-mounted transformer with a capacity of 10 kVA and below is recommended. In addition, a single-phase pad-mounted transformer cannot meet the needs of users for three-phase electricity.

Problems that should be paid attention to when using a single-phase pad-mounted transformer

(1) The single-phase pad-mounted transformer is the same as the three-phase box transformer. It is widely used because of its flexible scheme, small footprint and convenient use. In actual use, the single-phase pad-mounted transformer should be combined with the three-phase box transformer, and measures should be taken according to local conditions.

(2) The principle of “small capacity, densely distributed points, short radius, and high load rate” should be followed, and the loss reduction benefits of a single-phase power supply should be fully utilized. For residential areas with a simple single-phase load, a single-phase pad-mounted transformer is used for distributed power supply, which has high voltage quality, slight low-voltage line loss, convenient maintenance for users, and small mutual influence.

(3) In urban residential quarters, villa areas, and other cable-supplied places, using a three-phase box transformer is not appropriate. Still, a single-phase pad-mounted transformer should be used, and the transformer capacity should be reasonably selected according to the size of the load to increase the load rate.

(4) Whether it is a single-phase pad-mounted transformer or a three-phase box transformer, if the three-phase load is unbalanced, it will cause the three-phase current to be unstable, thereby reducing the transmission capacity of the distribution line and expanding the Line loss by 10 kV grid. Therefore, when the single-phase pad-mounted transformer is used for power supply, the single-phase pad-mounted transformer should be connected to the three phases as balanced as possible to maintain the three-phase load balance.

(5) The single-phase power supply mode impacts the use of three-phase electrical appliances in rural areas, such as water pumping, threshing, and infrastructure construction. Due to the small power consumption of rural lines, it is appropriate to configure a 10-30 single-phase pad-mounted transformer in natural villages of relatively concentrated residential areas in areas without three-phase loads. However, with the transformation of rural power grids and the reduction of rural electricity prices, the pastoral electricity load will further increase. Its economic benefits will be improved by reducing line losses. There are many three-phase electrical equipments such as water pumping and threshing in rural areas. According to the actual local conditions, proper planning based on the principle of “small capacity, dense distribution of points, and short radius” should be carried out with the three-phase transformer to play the role of a single-phase pad-mounted transformer or three-phase transformer. Advantages of single-phase transformers[3]0

(6) For users who need three-phase power, three-phase box transformers or three-phase transformers can be used, or two single-phase pad-mounted transformers or single-phase transformers can be connected in a V shape to meet the three-phase load requirements.

Custom Pad Mounted Transformer

When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.

We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.

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