Electrical Transformer Selection: Key Factors.
- Grupo Edmar
- Sep 8
- 4 min read
September 08, 2025 - Electrical Transformer Selection
Electrical Transformer Selection: Key Factors.
Selecting an electrical transformer is not something to be taken lightly. This equipment directly impacts the safety , energy efficiency , and operational continuity of a facility. A mistake in its selection can translate into financial losses, technical failures, and higher maintenance costs. Below, we analyze the key factors you should consider when choosing the right transformer for your project.
Actual capacity and future projection
The first step is to calculate the electrical load that needs to be supplied. This is measured in kVA (kilovolt-amperes) . To determine this:
The demand of all the equipment that will be connected must be added together.
Consider peak starting of engines or heavy machinery.
Project the growth of the plant or building in the medium term.
A common mistake is to scale only for current needs. However, if more capacity is required in two or three years, another transformer will need to be purchased, which means a higher expense.
Real-life example: A textile production plant that currently requires 900 kVA but plans to expand its capacity by 30% in three years should opt for a 1.2 MVA transformer instead of a 1 MVA one.
Types of windings and cabinet.
The windings are the heart of the transformer. They can be manufactured in:
Copper: more efficient, with better conductivity and greater durability. Often used in highly demanding industrial projects.
Aluminum: cheaper and lighter, recommended for installations where initial cost is a decisive factor.
Regarding the cabinets:
Carbon steel: suitable for interiors and areas with controlled conditions.
Stainless or galvanized steel: ideal for corrosive environments, coastal areas, or outdoors where there is high humidity.
This factor not only influences the durability but also the safety of the installation.
Cooling system.
Heat is one of the main enemies of a transformer. There are two main types of cooling:
Dry type (encapsulated resin):
Safer indoors because they don't use flammable oils.
They require less maintenance.
Ideal for hospitals, buildings, shopping centers, or areas with high density of people.
Oil type (mineral or vegetable):
They offer greater heat dissipation capacity.
They are most common in substations, industries and large electrical networks.
Vegetable oil (natural ester) is considered a more environmentally friendly option with better fire performance.
The choice depends on both the installation environment and the budget and capacity required.
Energy efficiency level.
Not all transformers convert energy equally. Energy losses in the cores and windings generate heat, which translates into lost money.
Investing in a high-efficiency transformer can mean:
Up to 10% less electrical losses.
Reduction in operating costs throughout the useful life.
Lower environmental impact due to energy savings.
In some countries, transformers are already required to meet minimum efficiency levels according to international standards (such as DOE in the US or NOM in Mexico).
Quality, support and delivery times.
The choice of supplier is just as important as the choice of transformer. Factors to consider:
Extended warranty: ensures support against any premature failure.
Technical support: Get advice before, during, and after installation.
Stock availability or short delivery times: Urgent projects can't wait months for equipment.
At Grupo Edmar , for example, we offer transformers with fast delivery, a solid warranty, and personalized support , making us strategic partners for companies seeking operational continuity without delays.
Total cost of ownership.
The initial purchase price does not reflect the actual cost of a transformer. Considerations such as:
Energy consumption throughout its useful life.
Preventive and corrective maintenance costs.
Durability of the equipment according to the quality of materials.
Possible costs for operational downtime if it fails.
Example: A cheap transformer may seem like a good option, but if it loses more energy as heat, the cumulative expense over 10 years will far exceed the cost of an efficient transformer.
Reliability and Lifespan of the Transformer.
When choosing an electrical transformer, it's not enough to focus solely on capacity or initial cost; it's also essential to consider its lifespan and the level of reliability it can offer your facility. A reliable transformer not only reduces the risk of unexpected failures but also prevents financial losses due to unscheduled shutdowns, damage to the power grid, or even accidents.
The lifespan of a transformer is directly related to factors such as:
The quality of the materials : copper coils instead of aluminum, silicon steel cores and adequate insulation can make all the difference.
Manufacturing design : Equipment manufactured under international standards (such as the NOM or IEC standard) guarantees greater durability.
The operating environment : Transformers installed in humid or dusty climates require special specifications to maintain their performance.
Good preventive maintenance : Although we at Grupo Edmar do not offer maintenance, we always recommend our clients have a plan that extends the life of their equipment.
Investing in a new, high-quality transformer may represent a larger initial outlay, but it ensures stable and reliable performance in the long run. At Grupo Edmar, we always strive to provide our customers with equipment that not only meets their immediate needs but is also a secure investment that will last for years.
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