3 Phase Pad Mounted Transformer-Daelim Belefic


Pad mounted transformer is a type of distribution transformer, which is widely used in North and South American markets. The large and small green boxes in streets, parks, hotels, countryside, residential or commercial areas are pad mounted transformers. They are 3 phase pad mounted transformers or single phase pad mounted transformers.

Dalim is a professional pad mount transformer manufacturer and supplier with UL/cUL certification. Daelim’s pad mounted transformer is widely used in North American and South American markets. And cooperate with Eaton, Sunbelt Solomon, and Amazon. There are also well-known local transformer distributors and utilities in North America who have become Daelim's partners.

This post will describe the definition of pad mounted transformer, the types of pad mounted transformer, how to test pad mounted transformer, how to install them, how to buy them, etc.

Table of Contents

1. What is a pad mounted transformer?
2. What types of pad mounted transformers are there?
3. Pad Mounted Transformer Manufacturer

4. What is the difference between the IEEE Standard 3 phase pad mounted transformer and CSA Standard?
5. What types of 3 phase pad mounted transformers are there?
6. Dry Type Pad Mounted Transformer
7. Pad mounted residential transformer
8. Pad Mounted Transformer Sizes
9. 3 Phase pad mounted transformer sizes
10. Single phase pad mounted transformer sizes
11. Daelim Custom Pad Mounted Transformer Sizes
12. 3 Phase Pad Mounted Transformer Price List
13. 3 Phase pad mounted transformer connections
14. Three phase pad mount transformer grounding
15. How long does a 3 phase pad mounted transformer last?
16. How to install a three-phase pad mount transformer?
17. How do Bitcoin Projects Choose Transformers?
18. Custom pad mounted transformer 
19. Pad mounted transformer color
20. Pad mount transformers nameplate
21. 3 Phase Pad Mounted Transformer package 
22. Daelim Padmounted transformers transportation
23. Daelim Three Phase Pad Mounted Transformer Application Case
24. What is on a 3-phase pad-mounted transformer nameplate? 
25. What are the electrical properties of the 3 phase pad mounted transformer?
26. What are the mechanical properties of the three phase pad mounted transformer?
27. How to test a 3 phase pad mounted transformer?
28. Three phase pad mounted transformer parts
29. 3 Phase pad-mounted vs substation transformer
30. Customized 3 phase pad-mounted transformer
31. Custom Substation transformer
32. Daelim Transformer Download

What is a pad mounted transformer?

Pad mounted transformer is a transformer mounted on a pad mount. It has an anti-theft and anti-tampering design, and the high and low-voltage cable entry lines are all at the bottom of the front cabin, which is often used in power distribution lines.

What types of pad mounted transformers are there?

There have two types pad mounted transformer: 3 phase pad mounted transformer and single phase pad mounted transformer.

Learn more: How to choose pad mounted transformer for your project?

Pad Mounted Transformer Manufacturer

pad mounted transformerDaelim is a professional pad mounted transformer manufacturer with ANSI, IEEE, DOE, CSA, and NEMA standards. Has been cooperating with many popular brands such as AMAZON, EATON, SOLOMON brands in the US.


Daelim Pad Mounted Transformer has top quality. Design and production standards meet or exceed ANSI, IEEE, CSA, DOE, and NEMA standards. In addition, there is a complete UL, and CUL listing and the voltage level can reach 44kV. All accessories are strictly tested and meet or exceed the UL standard.

The pad-mounted transformer can be installed indoors or outdoors. Pad mounted transformer has a variety of configurations, and a large number of accessories can be paired to meet more requirements and specifications. 


Daelim pad-mounted transformer is a compact power center. It has 3 phase pad mounted transformer and single pad mounted transformer. Design can be well adapted to a variety of types of environments, and is widely used in utilities, commerce, residential, industrial, wind energy, solar energy, crypto mining, and energy storage.


UL certificate

UL is the abbreviation of Underwriter Laboratories Inc. The UL Security Test is authoritative in the United States and is also a larger institution in the world engaged in security tests and appraisal. The UL certification of the transformer, is usually compulsory certification in the United States, mainly for the testing and certification of transformer security performance.


The key components of the Daelim pad-mounted transformer are completely in line with UL certification, such as the bay-o-net fuse, current limited fuse, coil, sealing parts, etc. Daelim Transformer Factory passed the inspectors' various UL rules inspection, obtained the transformer UL certification, and obtained the authorized UL tag.

cUL certificate

The CUL logo is the UL logo for circulating products in the Canadian market. The transformer with such signs has passed the security standards that meet Canada, which are basically the same as the standards of UL references in the United States.


Daelim's 3 phase pad mounted transformer also applied for cUL certification while obtaining UL certification. This shows that the pad-mounted transformer provided by Daelim fully meets the requirements of all provinces in Canada.

CSA certificate

CSA Marking is one of the most well-known product security recognition signs in the world, which is an important basis for the Canadian market for product security.


The CSA institution conducted a strict review and inspection of the production environment of the Daelim Transformer Factory, all electrical components of the transformer, etc. The pad-mounted transformer test results fully complied with the CSA standards to obtain the CSA certification certificate.


In the past five years, In North America, Daelim 3 phase pad mounted transformers are largely used in utility, photovoltaic power generation systems, wind power stations, battery energy storage systems, power distribution systems, etc.


Learn more: Three Phase Pad Mounted Transformer

Local service

Daelim has local transformer service installation and after-sales service teams in North and South American regions such as the United States, Canada, Chile, Ecuador, etc. DAELIM provides 24 hours of pre-sales and after-sales service. For any technical problems, you can contact service@daelim-electric.com and the DAELIM engineer team will solve the customer's problems as soon as possible.

For more detailed service content, please click to check.

 3 phase pad mounted transformer specifications

Pad-mounted Transformer Standard Primary
Voltage Ratings Minimum BIL(kV)
Delta or Wye
2.4kV 45
4.16kV 60
4.8kV 60
7.2kV 75
7.62kV 95
12kV 95
12.47kV 95
13.2kV 95
13.8kV 95
16.34kV 95
Ground Wye Minimum BIL(kV)
4160GrdY/2400 65
12470GrdY/7200 95
13200GrdY/7620 95
13800GrdY/7970 95
22860GrdY/13200 125
23900GrdY/13800 125
24940GrdY/14400 125
34500GrdY/19920 150

Keep on reading: What are the types of prefabricated substations?

 3 Phase Pad Mounted Transformer Built Standards

CSA C227.4

CSA C227.4 is promulgated by the Canadian Standards Association, Canada's safety standard for pad mounted distribution transformer. It means that pad mounted distribution transformer must meet or exceed the CSA C227.4 standard in the Canadian market.

This Standard specifies the requirements for three phase pad mounted distribution transformers, consisting of a transformer and a cable entrance compartment with provision for separable insulated high-voltage connectors


CSA C227.4 applies to three phase 60 Hz pad-mounted liquid-filled distribution transformer, rated at 3000 kVA or below, up to 34.5 kV system nominal voltage, and with separable insulated high-voltage connectors. The transformers are suitable for mounting outdoors on pads without additional protective enclosures.

3750 kva pad mounted transformer

This standard allows for the interchangeability of a dead front pad-mounted unit by another of the same basic physical size from a different manufacturer for transformers rated 125 kV BIL and below, without modifications to cables or pads. This standard covers terminal arrangements for both radial and loop feed systems.


Three Phase Pad mounted Transformer Energy Efficiency

Pad mounted electrical transformer shall meet the energy efficiency requirements of CAN/CSA-C802.1.


Low- and high-voltage electrical characteristics of transformers and assembled terminals

High voltage

Low voltage

Assembled HV terminals, 200 A

Rated voltage (V)

BIL (kV)

Rated voltage(V)

BIL (kV)

Voltage class (kV)

BIL (kV)



























































The capacity of 3 phase pad mounted transformer involved in this standard is 75 kVA, 150 kVA, 225 kVA, 300 kVA, 500 kVA, 750 kVA, 1000 kVA, 1500 kVA, 2000 kVA, 2500 kVA, 3000 kVA.

Learn More: 2500 kVA Pad Mounted Transformer

CSA C227.4: 21 Standard transformer Dimensions are as follows

Rated kVA capacity

Type of feed

Transformer maximum BIL, kV

Width, mm

75, 150




75, 150, 225, 300




75, 150, 225, 300, 500




75, 150, 225, 300, 500




750, 1000, 1500, 2000, 2500,





750, 1000, 1500, 2000, 2500,





Learn more about CSA C227.4 standard

C227.5-082550 kva pad mounted transformer

This Standard specifies requirements for the three-phase live-front pad-mounted distribution transformer

(1) consist of a transformer and a separable or integral cable entrance compartment;

(2) are rated 75 to 3000 kVA and intended for operation on three-phase underground distribution

Systems. With the preferred high voltage in the table below ;

Preferred High Voltage


2 400


4 160 GrdY/2 400


4 160


4 800


7 200


8 320 GrdY/4 800


8 320


12 470 GrdY/7 200


12 470


13 860 GrdY/8 000


13 860


24 940 GrdY/14 400


27 600 GrdY/15 935


24 940


(3)The rated capacity of the rated voltage should be 75 kVA, 150 kVA, 225 kVA, 300 kVA, 500 kVA, 750 kVA, 1000 kVA, 1500 kVA, 2000 kVA, 2500 kVA and 3000 kVA.


(4) are intended for mounting outdoors on pads without additional protective enclosures.


Pay attention: This Standard allows for the replacement of a live-front pad-mounted unit by another unit of the same basic physical size from a different manufacturer without modification to cables or pad.


Transformers shall meet the energy efficiency requirements of CAN/CSA-C802.1.


Daelim's engineers strictly designed three-phase live-front pad-mounted transformers in strict accordance with the C227.5-08 standards, including Electrical Characteristics, Mechanical Features, Bushings, Terminals, Grounding, etc.


Three-phase live-front pad-mounted transformers shall be tested in accordance with CAN/CSA-C2.1.


Dimension of live front pad-mounted transformers

Rated kV•A capacity

 Type of feed

Transformer maximum BIL, kV

 Width, mm Figure

75, 150




75, 150, 225, 300




75, 150, 225, 300, 500




75, 150, 225, 300, 500




750, 1000, 1500, 2000,2500, 3000




750, 1000, 1500, 2000,2500, 3000



1730, 1830

Learn more about live front pad mounted transformer.


In the three-phase pad-mounted transformer exported to the United States, the input voltage does not exceed 34.5 kV; the output voltage does not exceed 600 volts; the rated frequency is 60 Hz; DAELIM complies with the efficiency standard of the US Department of Energy (DOE).


The efficiency of the liquid-filled pad mounted transformer of Daelim shall be no less than that required for the kVA rating in the table below.

750kva pad mounted transformer500kva pad mounted transformer

























Try for free: Cryptocurrency mining power transformer solution

Single Phase Pad Mounted Transformer Built Standardssingle phase pad mounted transformer

Daelim single phase pad mounted transformer meets the IEC60076 ANSI/IEEE C57.12.20, C57.12.38, C57.12.29, CSA C227.3, and DOE 2016.

The high voltage is up to 34.5 kV and the power rating is up to 250 kVA.

The following picture is the single phase pad mounted transformer specification.

single phase pad mounted transformer specification
Pad Mounted Transformer Delivery Time

The delivery time of the DAELIM pad mounted transformer is about 6-10 weeks and specifically depends on the technical requirements and operating environment of the transformer.

DAELIM will do its best to design the drawings according to the plan confirmed by the order, complete the production in time, ensure that the technical requirements are met, arrange the transportation reasonably, and deliver it to the site for normal use. All the production pictures and time schedules will show in our online order tracking system, customer can check it anytime.

Pad Mounted Transformer Free Warranty Period

All the transformers of DAELIM are in strict accordance with the international standard production and related industry standard. The warranty on our transformer is two years. Sold products of DAELIM without the human factors leading to the transformer performance and technical problems, we will the unconditional replacement and bear the corresponding economic losses and damages. For the problems caused by other reasons, our company will actively assist solve the difficulties of the customers in order to ensure the product is put into operation in time and reduce losses to a minimum.

Pad Mounted Transformer Core features

  • Offer two structural designs: live front or dead front2600 kva pad mounted transformer
  • Compact structure, tampered with tampering, easy to maintain
  • You can enter a high-voltage and low-voltage connection and protection device with a front cabin-type partition with a door lock door
  • Pay special attention to the design of the wave protection, so as to avoid damage to other equipment in the circuit
  • Designed for the application of solar photovoltaic generators, it can connect various types of inverter equipment
  • Installed indoors or outdoors, which is convenient and flexible and saves the installation and occupation space
  • Reliable, safe, and environmentally friendly. The use of FR3 liquid filling transformers improves the fire safety level.


Daelim provides a variety of accessories and configuration options to meet wider application needs. There are some power ratings of 3 phase pad mounted transformers in stock to meet your fast delivery time, such as 1500 kVA and 2550 kVA.

Check more three-phase pad-mounted transformers models in stock.

Hot -selling 3 phase pad mounted transformerpad mounted transformer

150 kVA 3 Phase Pad Mounted Transformer

225 kVA 3 Phase Pad Mounted Transformer

300 kVA 3 Phase Pad Mounted Transformer

500 kVA 3 Phase Pad Mounted Transformer

625 kVA 3 Phase Pad Mounted Transformer

750 kVA 3 Phase Pad Mounted Transformer

1000 kVA 3 Phase Pad Mounted Transformer

1250 kVA 3 Phase Pad Mounted Transformer

1500 kVA 3 Phase Pad Mounted Transformer

2000 kVA 3 Phase Pad Mounted Transformer

2500 kVA 3 Phase Pad Mounted Transformer

3000 kVA 3 Phase Pad Mounted Transformer

4 MVA 3 Phase Pad Mounted Transformer

5 MVA3 Phase  Pad Mounted Transformer

7 MVA 3 Phase Pad Mounted Transformer

8 MVA Phase Pad Mounted Transformer

10 MVA Phase Pad Mounted Transformer

If the above capacities cannot meet your needs, please send your specific requirements to service@daelim-electric.com or pingruidan@daelim-electric.com.

What is the difference between the IEEE Standard 3 phase pad mounted transformer and CSA Standard?

The biggest difference between them lies in the technical requirements and the structure of the front cabin.

Technical requirements

Most of the technical requirements of the IEEE standard and the CSA standard are similar, but the energy efficiency value required by the American standard will be higher. Then, the overall capability level of the pad-mounted transformer supplier is required to be higher.

Front cabin structure

csa ieee standard pad mounted transformer
As shown in the figure above: The front compartment of the IEEE standard pad mounted transformer uses a partition to separate the high and low voltage. A ground pad is set in the middle of the low pressure in the front cabin for grounding. There is no compartment for high and low voltage in the front compartment of the CSA standard pad mounted transformer, and a ground bus and ground strip are installed at the bottom of the front compartment for grounding.

What types of 3 phase pad mounted transformers are there?

There are two types of 3 phase pad-mounted transformers, one is Dead front pad mounted transformer and the other is Live front

What is a live front pad mounted transformer?

live-front-transformerThe live front pad mounted transformer is known as "live" because the high-voltage perforated terminals of the transformer are exposed. The high voltage bushing of the Live front transformer is not fully insulated. When the transformer is working, open the high-voltage chamber of the front compartment, you may get an electric shock when touching the bushing.

The high-voltage bushing of the live front pad mounted transformer is a high-voltage bolt-on structure. It is terminated using either a mechanical lug or a crimp plug that's bolted to the terminal, then stick the cable up and tighten that little hex nut that's live.

You may enjoy: How Much You Know For The Different Types Of Transformers?

Dead front pad  mounted transformer  

The high-voltage bushing of the dead front pad mounted transformer is a plug-in structure and is fully insulated. The high-voltage end is connected to the cable with an insulating elbow. Therefore, the dead front transformer is safer than the Live front transformer.


The high voltage bushing of the dead front pad mounted transformer has two amperage ratings, one is 200amp and the other is 600amp.

200amp high voltage bushing has three voltage levels, 15kv, 25kv, and 35kv.
15kv color-coded is red, 25kv color-coded is blue.15kv and 25kv is load break type, it has two-piece assemble.35kv dead front bushing becomes a one-piece assembly, color-coded is purple, design is called the copper purple cuff bushing. This one is less common.

Learn more: The Ultimate Guide to Dead Front Transformers

600amp dead front bushing has only two classes: 15kv and 25kv, the difference with 200amp is that bushing becomes dead break, this structure is all one-piece structure.


Here's a reminder: sometimes you'll use a 200amp casing instead of a 600amp casing. We know that generally, one transformer 60amp is enough. If you have four transformers connected together, then the first transformer needs to bear the amp of all the transformers. Therefore, the amp of the first transformer is 240amp. At this time, you should choose 600amp high voltage bushing.


Therefore, the biggest difference between the live front pad mount transformer and the dead front pad mount transformer is the high-voltage bushings.

We will judge whether it is a dead front pad mounted transformer or a live front transformer according to the high-voltage bushing requirements sent by customers. Most of the customers we meet use dead front pad mounted transformer.

Try for free: The Ultimate Guide To 2500kVA Transformer

Radial feed Transformer and Loop feed Transformer

Both the dead front transformer and live front pad mount transformer have two configurations: Radial feed and Loop feed. The one that can identify the Radial feed or loop feed with the eyes is to look directly at the high-voltage bushing, the radial feed with 3 high-voltage bushings, and the loop feed with 6 high-voltage bushings. It is differentiated according to different power supply lines. The loop feed pad mount transformers are dual power supply, and the radial feed is a single power supply.

What is the difference between the live front and the dead front?

The biggest difference between them is the high bushings. Live Front Transformer's high bushing is porcelain type with metal terminals with holes for high-voltage connection. Dead front bushing is with a bushing well that connects to the cable with an elbow connector to insert it.  Its security is better. Because the front bushing is exposed the safety is not high. Staff needs to be vigilant and prevent electric shock when repairing the transformer.

How do I know whether to choose radial fee or loop feed transformer?


As we mentioned above, the loof feed transformer is a two-way power supply. The loof feed transformer has six high-voltage bushings which are marked H1A, H2A, H3A, H1B, H2B, and H3B, and these can be used to loop off to the next transformer. This type of transformer can be used with multiple transformers in series, when there is one transformer that fails, other transformers can take over the work and supply power normally without affecting the terminal power consumption. So, this type pad mounted transformers have more advantages.


The radial feed transformer is a single-circuit power supply. It has only three high-voltage bushings and is directly connected to the terminal for the power supply. Once a fault occurs, it will affect the power consumption of all terminals and must be repaired by a power outage.


So, you choose loop feed and radial feed pad mount transformers according to your actual needs

Read more: The Ultimate Guide to 1500kVA Transformer

Dry Type Pad Mounted Transformer

dry type pad mounted transformer
The dry type pad mounted transformer has the same high and low pressure zones as the oil filled pad mounted transformer. The difference in structure is that its iron core winding is placed in the high and low pressure cabin area, and there is no oil. Compared with the oil filled pad mounted transformer, because there is no oil inside, it is safer, more environmentally friendly (non-toxic and non-polluting), requires less maintenance, and has higher overall economic benefits. These dry type pad mounted transformers can be safely placed in schools, shopping malls, residential areas, and industrial areas. It is a good substitute for oil-filled pad mounted transformers.


Dry type pad mounted transformer is mainly used in underground power distribution system. Its enclosure is NEMA 3R compliant, which means it can be used indoors or installed outdoors.


Pad mounted residential transformer

pad mounted residential transformer
Pad mounted residential transformer has a beautiful appearance and can blend with the surrounding environment. It is a distribution transformer that can be installed on the ground. All energized lines are in a closed transformer casing, and it is a tamper-proof design structure. It does not require fences and protective measures during installation, and is usually used in construction areas, residential areas, and commercial areas.


single phase pad mounted transformerThe winding material of the pad mounted residential transformer can be copper or aluminum, different usage environments have different technical requirements for the transformer, and the price will also vary. The cost of pad mounted residential transformer depends on the following factors:

1. Voltage and capacity: the greater the voltage, the greater the capacity, and the higher the cost of the transformer;

2. Winding material: Copper winding transformers are more expensive than aluminum windings;

3. Brand and quantity of accessories: ABB, Qualitrol, Eaton, HJ, and other well-known brands will have higher prices;

4. Energy efficiency value: the higher the energy efficiency value, the higher the price;

5. Design standard: The price of design and production requirements for different standards will be different; the price of transformers that meet the US DOE efficiency value standard will be higher;

6. Cooling method

LNAN - immersed in flame-retardant liquid, natural cooling!

ONAN - immersed in oil, natural cooling

The LNAN cooling method will be more expensive than ONAN, because the flame-retardant liquid used in LNAN is vegetable oil, and the price is much higher than the mineral oil used in ONAN.


Pad Mounted Transformer Sizes

Pad mounted transformers come in many different sizes.
pad mounted transformer sizes

3 Phase pad mounted transformer sizes

CSA Standard Size

IEEE Standard Size

75 kVA

45kVA, 75kVA , 112.5kVA ,150 kVA

150 Kva

225 kVA,300kVA,500kVA

225 kVA

750 kVA

300 kVA

1000 kVA

500 kVA

1500 kVA

750 kVA

2000 kVA

1000 kVA

2500 kVA

1500 kVA

3750 kVA

2000 kVA

5000 kVA

2500 kVA

7500 kVA

3000 kVA

10000 kVA

Single phase pad mounted transformer sizes

CSA Standard Size

IEEE Standard Size

25 kVA

15kVA ,25 kVA

50 Kva


75 kVA

100 kVA

100 kVA

167 kVA

167 kVA

250 kVA

Learn more:Ultimate Guide To Transformer Sizes and Ratings

Daelim Custom Pad Mounted Transformer Sizes

Daelim is the world's top professional supplier of pad mounted transformers. We can not only provide pad mounted transformers of the above standard sizes, but also design various sizes according to your requirements.


For example, we have customized for customers in North America and South America: 1600kva, 1700kva, 1800kva, 2550kva, 2800kva, 4000kva, 7000kva, and other sizes, and the maximum can reach 10000kva.


If the above cannot meet your requirements, please send your requirements to 86-13051965423 or pinruidan@daelim-electric.com.

3 Phase Pad Mounted Transformer Price List

pad mounted transformer price list

Pad mounted transformer prices vary widely depending on capacity and voltage. The following table lists prices for standard capacities:

Standard Rating




750 kVA


1500 kVA


2000 kVA


2550 kVA


3000 kVA


3750 kVA


4000 kVA


5000 kVA


The above is a price range, and the accurate pad mount transformer price requires detailed parameters such as specific capacity, voltage, energy efficiency value, and standards. If the above price cannot meet your needs, please send your transformer technical requirements to pingruidan@daelim-electric.com to get an accurate price.


3 Phase pad mounted transformer connections

There are two ways to connect the 3-phase pad-mounted transformer, one is Dyn1, and the other is YNyn0.

Dyn1 transformer

The pad-mounted transformer of Dyn1 connection mode is also called the Delta transformer. A Delta transformer is usually a three-phase three-column pad transformer.


Meaning of Dyn1:

D: Refers to the high-voltage side delta connection;

y: Low-voltage side star connection;

n: Low-voltage side neutral point leads to the ground;

1:Means the angular displacement of transformers shall be 30°

The wiring method is shown in the figure below


The advantages of the Dyn1 connection method:
1) The most economical low-voltage winding of transformers with low voltage and high current
2) It is beneficial to suppress high-order harmonic current;
3) It is beneficial to remove the single-phase grounding short-circuit fault
4) High voltage output quality, lightning protection, stable neutral point
5) The loss is low during no-load operation, which saves electricity.

The disadvantage of the Dyn1 connection method is that when the fuse is overloaded and short-circuit protected, and the fuse of one phase is blown, the voltage value of the two phases on the low-voltage side is half of the rated voltage, and the load device at this time will not be able to start. , a reliable protection device must be installed on the low-voltage side of the transformer;

Keep on reading: Electrical Transformer Protection Knowledge Guide


YNyn0 transformer

The three-phase pad transformer of the YNyn0 connection method is called the Wye transformer, also known as the YNyn0 transformer. Wye transformer is usually a three-phase five-column pad transformer.

Meaning of YNyn0

Y: High voltage side star connection

N: High voltage side neutral point leads to ground

y: Low-voltage side star connection; n low-voltage side neutral point leads to ground

0:Means the angular displacement of transformers shall be 0°.

Get it now: How to purchase a 2 MVA power transformer?

Advantages of the YNyn0 connection method
1) The high-voltage winding adopts graded insulation to reduce costs. The neutral point can be directly grounded to prevent overvoltage and overcurrent operation.
2) When one phase of the high-voltage fuse is blown, the voltage of one phase is zero, and the voltage of the other two phases does not change, which can reduce the power outage range by one-third. The lighting load on the low-voltage side will not be affected;
3) If the low-voltage side is a power load with three phase power supply, it will be equipped with phase loss protection, and it will not be burned due to lack of phase.

The disadvantage of the Dyn1 connection method is that there is no circulation loop for the third harmonic current.


Three-phase pad mount transformer grounding

The three-phase pad mount transformer must be grounded, and it is grounded at one point, that is, the transformer core is grounded at one point. Because the pad transformer is in operation, a large magnetic field will be generated near the windings, and each component in the fuel tank will be in an uneven magnetic field, which will generate electrodynamic differences and cause continuous discharge.


Then why is the pad mount transformer not allowed to ground at multiple points? But just a little ground

Because the transformer has more than two grounding points, a loop will be formed between the grounding points, and a circulating current will be generated inside the transformer, resulting in internal overheating, short-circuit faults, and large iron loss.

Read more: What are the types of prefabricated substations?


How long does a 3 phase pad mounted transformer last?

500kva pad mounted transformerThe long-term normal operation time of the 3 phase pad-mounted transformer under the rated voltage and rated load is called the life of the transformer. Generally, the pad-mounted transformer is designed according to the life of 20 years, and the life of the pad mount transformer is determined by the life of the insulating material in a certain sense.


Under the action of an electric field and high temperature for a long time, insulating materials gradually lose their original mechanical properties and insulating properties. Therefore, the winding temperature is a key factor in the service life of the transformer.


According to the actual winding temperature during the operation of the transformer, the transformer can be used for 30-50 years. Practical studies have shown that the service life of the transformer is shortened by half for every 8 degrees increase in winding temperature.


How to install a three-phase pad mount transformer?

Before installing the pad mount transformer, there has much preparation work that needs to be done.

1. Equipment testing and experiment;

2. Civil construction;

3. Security measures;

4. Cable and transformer connection (including high and low voltage wiring, grounding, etc.);

5. Acceptance summary

Reading on: Step-by-Step Guideline On Installing A Transformer


How do Bitcoin Projects Choose Transformers?

how do bitcoin projects choose transformers
Daelim often encounters cryptocurrency customers who need to provide transformer solutions for themselves or their customers. At this point, how should we make solutions for cryptocurrency projects?

First of all, we need to understand the size of the cryptocurrency project, how many mining machines there are, what the rated power of the mining machines, and calculate how much rated capacity the entire mining farm needs.


Then according to the rated capacity of the entire mine, we can help customers with the optimal solution. For example, Delim has a Canadian customer who has a 100MW cryptocurrency mining farm. The solution for the customer is 52 sets of 2500kva three-phase pad-mounted transformers. With its professional technology and experience, it helps customers save a lot of time and cost. , the customer finally chose to give the order to Daelim.

Learn more: The Ultimate Guide to 2500kVA Transformer


If you have a 20MW crypto mining farm, how do you calculate how much transformer capacity you need?

The formula is as follows: 20MW/power factor (0.8) = transformer capacity (25MVA), that is to say, this mine needs a transformer with a capacity of 25MVA, and usually, the best solution is 10 three phase pad mounted distribution transformers of 2500 kVA.

2500kVA3000kVA/3750kVA are the most specifications pad-mounted transformers used in crypto mining.

Learn more about Crypto Ming: How to Choose Pad-Mounted Transformer for Crypto Mining?


Custom pad mounted transformer 

Pad mounted transformer manufacturer
Daelim is a professional manufacturer of pad mounted transformers. It can comply with international standards such as IEC/ANSI/IEEE/CSA/DOE/AS. Daelim transformer has a CSA test certificate, and Ul certificate, and CSA and UL labeling can be carried out according to your requirements. The 3-phase pad-mounted transformer produced by Daelim is rated from 50kva to 5000kva, and the primary voltages of 4160, 12470, 13200, 13800, 22860, 23900, 24940, and 34500V. Our pad mount transformers can be switched to Live Front or Dead Front primary connections as required. 
Daelim can be customized according to your needs, for example: we have customized the design of the cable inlet above the front cabin, the design of the high and low voltage side-mount, etc. for customers.


Daelim's pad-mounted transformers are exported to North and South America in large quantities and have a rich overseas market and technical experience. You can also choose between Radial-feed or Loop-feed types. The design of 3 phase pad-mounted transformer can be a three or five-legged core construction. The iron core adopts the step seam process or the coiled iron core process, which has the characteristics of low noise, low loss, strong resistance to short circuits, and overload. Whether in North or South America, Daelim has a transformer after-sales service installation team. You can buy Daelim transformers with confidence.

Daelim's three Phase Pad Mounted Transformer Project Cases


Pad mounted transformer color

Generally, the color of the pad-mounted transformer is green and gray. Canadian standard requirements are Munsell 4.82 G 4.07/3.35. You also can choose according to your requirements.

The color of the transformer is into three: Standard color, selection color, and designated color.

Standard color:

1)DAELIM B color: Suitable for medium and low voltage power transmission and transformation

equipment product parts, and indoor environment products.

2)DAELIM C color: Suitable for high-voltage power transmission and transformation equipment

product parts, outdoor use environment products.

Select Color: DAELIM A color.

Specified color: Other colors than the above three colors.

a)When selecting a specific color, you need to provide samples or standard swatches

b)GSB 05-1426-2001Standard color code of paint film color card.

c)RAL(IEC)Color code of Raul powder coating color standard card.

d)Munsell Munsell Color Atlas Color Code


Daelim pad mount transformer nameplate

The Daelim Pad Mount Transformers nameplate is marked with basic technical data, design and manufacturing standards, weight, and other key information. Because Daelim has Ul Listed and CSA, there will be a sign of UL and CSA standards on the transformer nameplate.

transformer nameplate

3 Phase Pad Mounted Transformer package 

Daelim pad-mounted transformer will be shipped on pallets. Fasten the transformer to the tray with straps. And there is a forklift direction sign on the package box, which is convenient for you to load and unload during transportation. There are usually two packaging methods for pad mount transformer packages.

Wooden box packaging

transformers package
When Pad Mount Transformer is packaged in a wooden box, first of all, you need to use a sufficiently firm tray to withstand the weight of the transformer;

Second, fix the transformer to the tray, and the surroundings and top cover are encapsulated with strong logs or plywood. It is important to note that if the logs are used for packaging, you must use fumigable logs, and with a fumigation seal;

Third, the packed wooden box's four corners need to be fixed with corner steel to prevent Padmountod Transformers bump into the transportation process and play a protective role;

Fourth, the packaged wooden boxes need to be clearly marked with the position of the forklift and prohibited forklift position; because the front cabin of the Pad Mount Transformers is relatively light and the mailbox is heavier. If the fork car is wrong when unloading, the transformer will fall to the ground and severely damage the Padmount Transformer.


You may enjoy for: Single Phase Pad Mounted Transformer

Wooden pallet packaging

pad transformer package

When Pad Mount Transformer is packaged in a wooden box, it is also sufficient to withstand the weight of the transformer with a strong enough logic tray. After Pad Mount Transformer is fixed to the tray, you need to wrap it with a plastic film to wrap it on the exposed transformer. It plays the role of protecting the transformer, anyway, bumpy friction during transportation.

Daelim Padmounted transformers transportation

There are two main ways to transport the transportation of Daelim Pad Mount Transformer
Sea transportation

Sea transportation is the most common and most common way for pad mount transformers to transport. Because the overall weight of the transformer is relatively heavy, from several hundred kg to tens of tons.

If pad mount transformers are transported by the entire container, it is usually packed in a wooden pallet, because this is more saved with costs and can be packed and transported. A 40-foot cabinet container can usually accommodate 4 set 2500kva pad-mounted transformers.

If Pad Mount Transformers are transported, Daelim usually uses stronger wooden box packaging to ensure that the transformer can reach the destination safely.

Air transportation

Padmount Transformer is not very common, because we all know that the weight of the transformer is really heavy, and the cost of air transportation is very expensive. However, some customers of Daelim need and quickly use these Pad Mountain Transformers to adopt expensive air transportation.

Daelim has experience with air transport transformers. Although it is much more complicated than sea transport, Daelim can be solved.

Daelim Three Pase Pad Mounted Transformer Application Case

Daelim has helped many customers in the North American market to get projects: for example, 120 sets of 3750KVA pad-mounted transformers for bitcoin projects in the United States; 90 sets of 2500KVA pad mount transformers for bitcoin projects of Canadian customers, and Canadian electricity bidding projects, etc.


Daelim has been manufacturing and delivering power transformers to customers in North and South American markets since 2010. If you need transformers to meet your commercial or industrial needs, Daelim can help you. Our professional technical team and professional marketing team will be able to provide cost-effective solutions for your needs.

Used For Bitcoin Mine

The figure below is 50 sets of 2550kVA pad mount transformers for a relatively large bitcoin mining area in Texas. These Pad Mount Transformers are currently operating safely and efficiently. When Daelim made a solution for Bitcoin customers, he helped customers avoid the requirements of DOE efficiency and saved customers a lot of costs.

pad mout transformers

Used For Solar Photovoltaic Power Generation

The figure below shows a photovoltaic power generation project of 2500kva Pad Mound Mound Mound Mound TranSFormer. It can be seen from the picture that the design of the low-voltage sleeve is a side outlet, order to connect the control cabinet. Pad mounted transformer, which is used in solar projects, requires unique designs because there is a DC harmonic wave. It needs to prevent the shielding layer between high and low pressure and prevent the sense of interoperability between high and low pressure. Transformer oil requires environmental fire prevention.

Read more: Solar Transformer - Your ultimate guide

Daelim can design oil filled pad mounted transformers to match all inverter specifications in solar systems. And there are many project applications in the United States, Canada and other markets. Welcome to contact Daelim for relevant project cases.

Check more Daelim solar photovoltaic solutions

solar transformer

Used For Battery Energy Storage System

The figure below shows 25 3000kva Pad Mounted Transformers for battery storage system projects in Florida, USA.

Pad Mount Transformers are widely used, especially in the current field of renewable energy, which has absolute advantages. If you have related needs or questions, please contact the DAELIM team to give the most suitable transformer solution.

pad mount transformers for bess
What is on a 3-phase pad-mounted transformer nameplate? 

1.3 phase pad-mounted transformer type;pad-mounted-transformer-nameplate

2. Pad mounted transformer Cooling System;

3. Pad mounted transformer Rated Frequency

4. Pad mounted transformer Rated Power

5. High Voltage

6. Low Voltage

7. BIL

8. The temperature rises Winding

9. Oil Weight

10. Total Weight

11. Serial number of BAYONET fuse

12. Load break switch voltage and current

13. Insulation class of Load break switch

14. Transformer Efficiency Value

15. Serial number of Current Limiting Fuse

16. The position of the tap changer

17. Electrical Connection Diagram

18. Transformer Designed Standard

Read more about transformer nameplates: How To Read A Transformer Nameplate

What are the electrical properties of the 3 phase pad mounted transformer?

1. Thre kVA ratings: 75kva, 150kva, 225kva, 300kva, 500kva, 625kva, 750kva, 1000kva, 1500kva, 1700kva, 2000kva, 2500kva, 2600kva, 2750kva, 3000kva, 3750kva, 4000kva, 5000kva;

2. The primary voltages: 4160GRDY / 2400V, 4160V, 8320GRDY / 4800V, 8320V, 12470GRDY / 7200V, 13860GRDY / 8000V, 13860V, 24600GrDY / 15935V, 34500GrDY / 19.92V, 34500Vpadmounted-transformer-delta-wye

3. There are two connection methods for the three-phase pad-mounted transformers: Dyn1&YNyn0, as shown in the following figure
4. The iron core leg of the 3 phase padmount transformer designed by Daelim can be three-legs or five-legs, depending on your padmounted transformer parameter table;

5. The high voltage off-circuit tap of pad mounted transformer generally has five positions, and the voltage regulation range of each position is ±2.5%. If you need a three or seven-position tap changer, Daelim can also meet the design and production;

6. The BIL value of Daelim's 3 phase pad mount transformer is 30-125; the BIL value of the switch is generally 90-130;

7. The radio interference value of the three-phase pad-mounted transformer designed by Daelim is 34-100;

8. The Audibel sound levels of the three-phase pad-mounted transformer designed by Daelim will vary from 51-63 decibels according to the capacity of your transformer

9. The short-circuit capacity of the three-phase pad-mounted transformer designed by Daelim will vary from 25-40 according to the capacity of your transformer.

10. The impedance value of the three-phase pad-mounted transformer designed by Daelim is usually not more than 5%

11. The energy efficiency value of the three-phase pad-mounted transformer designed by Daelim is the value specified in the standards you require, such as CAN/CSA/ANSI and other standards

Try for free: What is a Live Front 25kV Pad Mounted and Substation Transformer Specification?

What are the mechanical properties of the three phase pad mounted transformer?

1. The dimensions of the three-phase pad mounted-transformer produced by Daelim are as follows:

2. The fuel tank of the three-phase pad mounted transformer adopts an anti-corrosion design and special paint treatment. It has undergone strict leakage and deformation testing experiments. It has good sealing performance, strong toughness, and strong corrosion resistance, and can be used in various harsh environments, such as many Stormy and highly polluted areas.

3. The working temperature of the 3 phase pad-mounted transformer designed by Daelim is -40℃ to 60℃;

4. The liquid insulation performance of 3-phase ground-mounted transformer: Daelim generally uses mineral oil as the insulating oil of the transformer, which is divided into mineral oil No. 25 (Class B, Type Ι), mineral oil No. 45 (Class A, Type II); if you need vegetable oil, Daelim can also provide FR³oil;

Learn more: What is the difference between mineral oil and vegetable oil?

How to test a 3 phase pad mounted transformer?

1. Routine test of three-phase pad-mounted transformer750kva pad mounted transformer

(1) The ratio of each connection;

(2) Angular displacement;

(3)No-load loss;

(4)Excitation current

(5)Load losses and impedance;

(6)Applied voltage

(7)Inductive voltage

(8) Transformer tank leak detection test

Daelim can not only do the regular test of the transformer, but also the Type Test if you need it,

2. Type Tests Of Three Phase Pad-Mounted Transformer


b.Temperature rise;

c.Impulse strength;

d.Radio influence voltage;

e.Short circuit;

f.Transformer integrity

g.Audible sound

Daelim's transformers will have strict experiments before leaving the factory to ensure that they fully meet the various international standards and high-quality transformers required by customers. Daelim's transformers are guaranteed for two years, and Daelim will be responsible for helping customers solve any quality problems during the warranty period.

Read more about transformer test: How to test a power transformer?

Three phase pad mounted transformer parts

Daelim's 3 phase pad mounted transformer has the following parts for you to choose from:

1)High voltage bushings(Radial feed transformer 3 HV bushings), Loop feed transformer 6 HV bushings); The high-voltage bushing is used to connect the elbow-type cable plug and the elbow-type fully insulated arrester

2)low voltage terminals


Bay-O-Net-Fuse: is an overload protection device, mainly responsible for small-scale fault current breaking (including short-circuit fault on the low-voltage side). Usually, there are three fuses on a pad-mounted transformer

4)Elsp: Mainly responsible for a wide range of fault current breaking, and short-circuit faults on the high-voltage side inside the transformer, used to quickly cut off the faulty transformer and protect the high-voltage line.

5)Pressure relief device: Daelim's 3 phase pad-mounted transformer variable pressure uses a disc-type relief device, as shown in the following figure:

3-phase-padmounted-transformer-Pressure-relief-device6) Off-circuit tap changer

7)Dual voltage switch;

The dual voltage switch allows the transformer to supply two voltages, which can be switched within the transformer as needed.

8)Load break switch:

Daelim has two kinds of load break switches for you to choose from:

Two-position switch(38 kV/28 kV,300 AMP), Four-position switch(38 kV,200 AMP)

6)Padlocking load break switches;

7) Load break inserts complete with dust cap;

8) Under oil surge arresters;

9)Thermometer of the maximum indicating type;

10) Oil level indicator;

11)Pressure relief valve;

12)Pressure indicator;

13) Parking stand

3 Phase Pad-mounted Transformer divided into the high-voltage compartment and low-voltage compartment. The high-voltage compartment generally has accessories such as HV bushings, Bay O Net fuses, Load break switch, Parking Stand, etc. The low-voltage compartment generally has accessories such as Low voltage terminals, Pressure Relief valves, Pressure Indicators, Tap Changers, Oil Level indicators, Grounding ground copper bar, etc.

Get it free: High Voltage Transforrmer Guide In 2022 

3 Phase pad mounted vs substation transformer
pad mounted VS substation transformer
The same between 3 phase pad-mounted and substation transformer

1. The working principle is the same, using the principle of electromagnetic induction;
2. Both are liquid filled distribution transformers, insulating oil as a cooling medium. The insulating oil can be mineral oil, vegetable oil RAPO, or FR³ oil with fire protection certification.
3. Can be used in Bitcoin mining farms;
4. Can be designed to IEEE/IEC/CSA standards
5. High voltages up to 34.5kV.
6. The cooling method can be ONAN or ONAF, forced air cooling can have up to two stages, one set of fans is turned on for one stage; all fans are turned on for two stages.
7. K factor
The K coefficient range of box transformers and Substation transformers: is K1-k20, but usually the k coefficient is K4 and below; some special projects will have higher requirements on the K coefficient, such as the box transformer in solar projects. The K coefficient is above 13.

Learn more: How much do you know about oil-immersed distribution transformers?

Differences between 3 phase pad-mounted and substation transformers:

1. Different structure

5mva substation transformer
The pad-mounted transformer is a tamper-proof design and is divided into two parts: the front and the back are the high and low voltage operation panels;

The structure of the Substation transformer is relatively flexible, and the radiators and terminal boxes on both sides of the fuel tank are detachable. The high and low-pressure bushings can be designed to be side-out or top-out. Easier to pack and transport.


The pad mounted transformer can be designed as a three-phase three-legged core structure or a three-phase five-legged core structure. The design of the Grdy-Grdy-connected units shall incorporate a five-legged core construction.


Substation transformers are all three-phase three-legged core structures.


2. kVA Rating is different

Pad mount transformer ratings up to 5000kVA(ONAN);

Substation transformer ratings up to 15MVA(ONAN);


3. The weight of the transformer is different

The pad-mounted transformer of the same capacity is about 14% heavier than the substation transformer. Among them, the transformer oil capacity in the pad transformer is about 24% more than that of the substation transformer. Take the 3000kVA capacity as an example: the weight of the pad mount transformer is about 7600kg, of which the oil capacity is 2220L; the weight of the 3000kva substation transformer is about 6500kg, of which the oil capacity is 1675L

Read my article on Skid mount transformer solution with3 phase pad mounted transformer inside


4. Accessories and requirements are different

Some accessories on the pad transformer are unique, that is to say, the pad transformer is dedicated; such as ELSP Fuse, Bay-O-Net-Fuse, Bay-O-Net-Fuse Assemble; Bushing Well; Load Break Bushing Insert, Deadbreak Elbow Connector and Dual-Voltage Switch.


Substation transformers require contacts for many accessories, which are used for alarms, trips, and remote control when the transformer fails.


The temperature equipment of the Substation transformer winding generally has four contacts, the fan stopped, fan start, alarm, and trip; the oil thermometer generally has three contacts: fan stop, fan start, and alarm.


5. Different grounding methods

Different grounding methods

There is a grounded copper terminal board in the front compartment for the grounding of the pad mount transformer, and a grounding copper strip is used to connect X0 of the low voltage terminal.


For the grounding of Substation transformers, some of the low-voltage terminal grounding copper bars are directly grounded; some are grounded copper bars that need to be connected to the low-voltage cabinet for grounding; some are connected to the local grounding wire for grounding.

Customized 3-phase pad-mounted transformer

DAELIM's professional transformer technical team can not only design IEEE, IEC, CSA, ANSI, DOE, AS, and other standard pad transformers, but also can make special customized designs according to your needs and technical requirements. DAELIM's technical team has had thousands of box transformer design experiences, whether you need a single power supply or dual power supply, Dead front or Live front, Loop feed or Radial feed, dimensions, efficiency value, and other special requirements and configurations, can help you customize.


Try for free: The Ultimate Guide to 5mva Transformers

Custom Substation transformer

3000kva substation transformerAccording to ANSITM and IEEETM standards, the normal maximum voltage of Substation transformer can reach 34.5kV, and the maximum voltage of DAELIM's Substation transformer can reach 44kV. For some special requirements such as:

Low losses

DAELIM can achieve lower losses than the standard, and if it is below 1500kva, it can do the efficiency value of DOE.

Special environment

In particularly cold, windy, or corrosive environments, DAELIM can improve the IP protection level of the control cabinet (NEMA3R, NEMA4, NEMA4X) through special designs such as thickened paint, stainless steel fuel tank;

Special/low sound level

DAELIM can design transformers with lower noise levels than standard;

Retrofit to special dimensions: The transformer size can be customized according to the customer's place of use.

Try for free: 5+FAQ About 15kV Transformer

Specified K-factor

DAELIM customers make special designs for transformer K-factor according to project requirements.

Special colors

The normal ANSI standard is gray, DAELIM can make green, yellow, and other colors according to your requirements;

Special standards: In addition to ANSI, and IEEE standards, DAELIM can also make CSA, DOE, AS, and other standards;

Other special features upon request.

Whether it is DAELIM's three-phase Pad-mounted transformer or Substation transformer, it has a UL list, cUL list, and FM approved. DAELIM's professional technical team and years of experience in international transformer project design can make you feel at ease buying DAELIM's transformers.

Daelim Transformer Download

Three-phase pad-mounted transformer catalog

Three-phase pad-mounted transformer manual

Substation  transformer catalog

Substation  transformer manual

Daelim also produces single-phase pad mounted transformers, sing phase transformer,  dry type transformer, and High voltage transformer. If you have any need please contact Daelim Team.

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