What is a 50 kva Distribution Transformer?

DAELIM 50 kva transformer

33kv distribution transformer is the well used power transformer in the electric transmission.

Daelim provide 33KV mini substation transformer, three phase pad mount transformer, dry type transformer and also single phase pad mount transformer comply with USA IEEE standards, Canada CSA standards, Australia AS standards. 

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

Oil immersed transformer

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

Click below for quick review of 3 phase transformer

What is a 50 kva transformer?

Based on the capacity of 50kva, it is a distribution transformer, its cooling type is ONAN, which is use the oil as its insulation, so it is also a oil immersed transformer.
The oil it used can be the mineral oil, or the vegetable oil, if use the mineral oil, the 50 kva transformer should be ONAN type. For the vegetable oil, like FR3 oil, It is an environmentally friendly oil, which does not cause much pollution to the environment, and is also a biodegradable oil.  So the 50 kva transformer can be KNAN, if use vegetable oil, the cooling type should be KNAN.  
If the insulation is not oil, it can be a 50 kva dry type transformer. Epoxy resin as insulating medium, It can be used indoors, in high-rise buildings, docks, etc. The characteristics and advantages of dry type transformers are small size, small environmental pollution, strong reliability, good stability…
Based on the phase: 50 kva transformer can be a three phase transformer, three phase pad mounted transformer or three phase oil immersed distribution transformer. 50 kva transformer also can be a single phase transformer.
The single phase transformer also have different types.

If it is a cylindrical transformer, it named single phase pole mounted transformer.

If is a pad mount ttansformer, it can be a 50 kva single phase pad mounted transformer.

Let’s know learn more about the 500kVA transformer

Features of the 50 kva dry type transformers

Compared with oil-immersed distribution transformers, dry-type transformers have good fire resistance and are safer than oil-immersed transformers, so dry-type transformers can be used in hospitals, airports and other places, which are more reliable and stable.
The use, application and production of dry-type transformers in my country are widely used because of their environmental protection advantages, low noise, reliable quality, etc.
Due to the advantages of dry-type transformers, he is also developing in many aspects, expanding the use of places, and continuously expanding the capacity.

Advantages and Features of Vegetable Oils

Vegetable oil is extracted from different plants, using a special process, because the added ingredients can make vegetable oil stable and reliable.


Each transformer will undergo commercial testing according to the latest revision of ANSI C57.12.90 and the results will be available on request.

Testing must be performed for a CSA certified body. The following tests must be carried out:

. 1 Transformation ratio (ANSI C57.12.90).

. 2 Polarity and angular displacement (ANSI C57.12.90).

. 3 Winding resistance measurement (ANSI C57.12.90).

. 4 Core insulation (ANSI C57.12.90).

. 5 Winding insulation (ANSI C57.12.90).

. 6 Impedance and load losses (at nominal voltage for 35%, 50% and 100% of the
load) (ANSI C57.12.90).

Excitation current and iron losses at 100% V (ANSI C57.12.90).

Induced voltage (ANSI C57.12.90 

Polarity: additive.

Coupling: Dy11.

Impedance: 6% typical.

Complete copper winding, including all conductor bars.

Stainless steel exterior hardware (bolts). Construction :

. 1 Built to CSA C227.4-06 requirements in accordance with CSA C88-16.

Built in a CSA certified factory.

Minimum MOH type core steel. Copper winding.

The cable connection cabinet will be removable and must be fitted with a partition separating the HV and LV sections.

The size of the tank and the radiators will be planned taking into account the cooling via the fans.

CSAW47.1-03 certified welds and factory approved by CWB (Companies for Fusion Welding).

As far as possible, the radiators are fixed to the tank and cannot be dismantled. If the radiators are removable, provide purges and valves to facilitate transport and connection to the site.

Features of the 50 kva oil type transformers

The core shall be of high-grade, non-aging electrical silicon steel of low hysteresis loss and high permeability.

The core laminations shall be free of all burrs and sharp projections.

The core shall be of circular configuration and shall be tightly clamped, the coils shall be securely fixed to the core, and the core and coils shall be rigidly fixed in the tank to prevent movement under short circuit stresses and during handling in shipment.

The core ground of the main transformer core shall be brought out through the sidewall of the tank via a low voltage bushing. A separate core ground for the OLTC associated transformer(s) (if required) shall be brought out via a second low voltage bushing located in the vicinity of the main core ground bushing. A ground pad and a grounding cable for each core ground, and nameplates.

stating “Transformer Core Ground” and “OLTC series transformer core grounds” shall be provided. The nameplates shall be mounted adjacent to the core ground bushings. The core ground bushings and ground pads shall be mounted near the top of the sidewall. The bushings shall be protected against damage due to inadvertent contact or falling objects by a suitable encasement or structure.

Use of on-load power transformer

In substations with large voltage change with load, on-load regulating power transformer should be adopted to ensure stable voltage output.

For terminal substations transformer with large voltage fluctuation, in order to improve the terminal voltage quality, a power capacitor can be installed at the incoming end line of the substation for reactive power compensation to reduce voltage loss and reduce voltage fluctuation.


Three high voltage bushings on three phase transformers.

All porcelain used in bushings shall be wet-process, homogeneous, nonporous, and free from cavities or flaws. The glazing shall be uniform in color and free from blisters, burns, and other defects. Porcelain to be ANSI-70 Sky Gray in color.

All terminal bushings for use at 69kV or above shall conform to the requirements for the most recent version of IEEE standard apparatus bushings.

The bushings shall use porcelain and oil impregnated paper, and shall be of the condenser, oil filled, standard interchangeable type, using a draw lead connection. The draw lead conductor shall be sized such that the ampacity of the high voltage winding is in no way limited by the draw lead conductor.

.5 The low voltage terminal bushings (25kV class) shall be oil-filled and shall use porcelain and oil-impregnated or resin-impregnated paper and shall conform to the most recent version of IEEE Standard requirements. Bushings shall be condenser type. Low voltage terminal bushings will be installed before shipping.

.6 Where possible, all oil-filled and all condenser type bushings shall be provided with liquid level indicators and power factor test taps.


Windings shall be circular wound using a disc or helical wound winding design.
.5 Insulating materials, varnishes, and compounds in contact with oil shall not affect the oil nor be affected by it.

Try for free 1500 kva Pad Mounted Transformer  DAELIM BELEFIC

50 kva single phase transformer

For the single phase transformer, they have standard capacity, 5 kva, 10 kva, 15 kva, 25 kva, 37.5 kva, 50 kva, 75 kva, 100 kva, 167 kva.
About 50 kva single phase pole mounted transformer, it has different type,

One is conventional type, the other is CSP type. The same is , they have bushings, (HV bushing, LV bushings) Lifting lugs, Core, Coil, Tank, There are some difference. CSP type has surge arrester, secondary circuit breaker, fuses.
There have type based on the quantity of the bushings, according to different requirement, they have one High voltage bushing and two High voltage bushings.

About the test of the 50 kva single phase pole mounted transformer


All standard factory testing are to be witnessed by the Technical Service

Start-Up Services

Contractor, the Owner and the Engineer’s Representative. In addition, perform

all other tests

identified in this section and in Section 26 08 01.00 –


STARTUP SERVICE that are not included in the standard testing procedure.

The transformer shall be tested in accordance with the provisions of ANSI C57.12.90. All the tests listed herein are to be done in the order that they are listed. All tests are to be completed on all transformers.

The routine tests are as follow:

1. Polarity and phase  

2. leak test  

3. No load losses and excitation current  

4. Load losses and impedance  

5. Resistance  

6. Applied voltage  

7. Induced voltage  

8. Ratio test  

9. Full wave impulse

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Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.