Standard kVA Sizes for Three-Phase Medium Voltage Transformers

Electrical engineers constantly deal with various electrical systems and equipment, including medium voltage dry type transformers. These transformers come in a range of standard kilovolt-amp (kVA) sizes to ensure different systems receive efficient and reliable power distribution. By knowing the standard kVA sizes for three-phase medium voltage transformers, you can make informed decisions when specifying, installing or maintaining these critical components.

Whether you work with tertiary educational institutions, medical centers, electrical utilities or manufacturing facilities, selecting the wrong kVA size could lead to inefficient power, safety hazards and increased operational costs. A comprehensive understanding of standard kVA sizes will help you optimize system performance and meet your industry’s electrical needs.

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What Is a Three-Phase Transformer?

A three-phase transformer operates with six windings — three primary and three secondary — to transfer electrical power. They are often constructed by assembling a transformer consisting of three pairs of windings into one laminated core. Three-phase transformers stand out because they can handle three phases of AC power. Each set of windings connects to a different phase of the system, allowing for more efficient power distribution in industrial and commercial settings. With three sets of windings, the magnetic fluxes in the core differ in time-phase by 120 degrees.

In addition, three-phase transformers provide these benefits:

Higher voltage: Three-phase transformers can carry higher voltages than their counterparts.
No power failure: The power supply travels through three conductors and a complicated network. If one conductor experiences a power failure, the others can continue providing power.
Reduced vibrations: Since power distributes evenly throughout the cycle, vibrations in three-phase transformers are significantly lower.
Two types of loads: A three-phase transformer can supply more than three-phase type loads.

Three-phase transformers are ideal for applications requiring higher power loads, such as:

Industrial machinery
Large motors
Commercial buildings
Power transmission systems

While the initial cost of a three-phase transformer is relatively higher than for other types of transformers, their powerful performance, speed and easy parallel operation make them more economical over the long term.

Standard kVA Sizes for Three-Phase Transformers

Calculating the kVA for three-phase transformers is slightly different from other transformers. However, the standard kVA size for a three-phase transformer also depends on the electrical load and supply voltage, which should be available on equipment nameplates or instruction manuals.

Since three-phase transformers consist of three equally sized windings, each winding must have enough capacity to supply its connected load. That means the size of the phase with the largest load will determine the size of the entire three-phase transformer. For a delta-connected transformer, the kVA size is the largest phase power multiplied by three.

The standard kVA sizes for three-phase medium voltage transformers are:

30
45
75
112.5
150
225
300
500
750
1,000
1,500
2,000
2,500

Why Choosing the Right kVA Size Is Important

Dry type transformers generally have lower fire risks. They are environmentally friendly, easy to install and suitable for a variety of environments. It’s important to select a three-phase transformer with a standard kVA capacity equal to or greater than what you need to operate the load.

The kVA size of any transformer determines the amount of current it can carry without overheating or sustaining damage. If the kVA size is too small, the transformer may overheat, which can cause malfunctions or lower efficiency. It could even damage the transformer, leading to costly downtime. In comparison, a too-large kVA size increases no-load loss. Unless you’re considering load growth and future expansions, selecting an oversized transformer will add unnecessary purchasing costs.

Find the Right Size Medium Voltage Transformer From ELSCO Transformers

Choosing the right size transformer is an investment in long-lasting system performance. Whether you require a standard or custom-built kVA size, the experts at ELSCO Transformers will help you determine what you need. We are the leading full-service company for medium voltage transformers for multiple industries, including hospitals, universities and electrical supply houses.

For more information on how our transformers align with your specific industry requirements, get in touch with us at 800-232-9002 or request a quote today.