Transformer rating

Transformer rating or capacity depend on the  limited of insulation temperature can stand for maximum load.The ratings can be up or down when we reducing a  core and copper losses.

To reduce core and cooper losses,we can improved the rate of heat exchange with proper cooling system or by improving quality transformer insulation that can stand for high temperature.

For larger transformer types,we can remove more heat with increased area for efficient cooling and increased volume of oil to absorb more heat to reduce the temperature.

What is transformer rating?

Transformer must running in their temperature specification for efficient and long lasting for service life.Periodical maintenance and daily checking is very important to ensure the transformer running in good condition.

We must checked the critical parameter such as oil level,cooling fan condition,ambient temperature,working load ampere,transformer temperature.

Also we must perform periodical maintenance such as insulation tester,load tester,major cleaning from dust and tightening the bolt and nut for terminal.

Why maintenance for transformer is so important?

We imagine if one unit transformer fails, that mean whole plant or factory could be shorted for power supply.No production cannot be running.

It very critical because the costing for transformer is very high and can reach until multiple millions of dollars with addition cost to the replacement of  transformer.

Normally we can known the ratings of transformers by simply multiplying the current (ampere ) times the voltage (volt ).For Small transformers are rated in “VA,” or volts amperes.The size are increases such as 1 kilo volt ampere (kVA) until 1 mega volt ampere (MVA).

We can decide the transformer capacity when we have a full load ampere that we need tom operated our plant or factory.We used the transformer rating information when dealing with supplier to purchase the transformer.


  1. haitham hashim says

    Very useful information and valuable Thank you

  2. Rating of a transformer could be increased by fixing cooling fans. For example 34.5/4.16kV transformer rating was increased fro 6 to 9 MVA

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