Transformer Load Loss

Transformer Load Loss: An Introduction from a Transformer Selection Perspective

Transformer load loss is a crucial parameter among transformer parameters. To help users better understand this parameter, we will introduce it today, covering its meaning and characteristics, along with some simple examples. For further clarification, please contact us online.

1. Definition of Transformer Load Loss: Transformer load loss should actually be called short-circuit load loss. This terminology relates to the actual method of measuring transformer losses. When measuring the load loss of a pair of windings, one winding is short-circuited (or open-circuited if other windings are present), and the other winding is subjected to a voltage of rated frequency and approximately sinusoidal wave, allowing both windings to pass rated current (or tap current). The power absorbed at a reference temperature is then measured. Because the loss is measured using a short-circuit method, it is also called short-circuit load loss, corresponding to the load current. For a two-winding transformer, there is only one pair of windings, corresponding to a specific load current and a load loss value.

Example: The short-circuit loss at rated current can be called the transformer’s rated load loss. For multi-winding transformers, there are multiple load loss values ​​corresponding to the multiple winding combinations.

2. Next, we will introduce the characteristics of transformer losses.

Load losses include two parts: DC resistance loss (PR) of the windings and stray losses. Stray losses include eddy current losses in the conductors, circulating current losses between parallel conductors, and eddy current and circulating current losses in structural components (such as core clamps and tie plates, winding clamps and steel pressure plates, tank top cover, tank walls and bottom, etc.). Therefore, load losses are related to the following factors:

(1) Conductor material: divided into aluminum conductors, soft copper conductors, semi-hard copper conductors, etc.

(2) Conductor shape: divided into round wires, flat wires, combined conductors and transposed conductors, etc.

The selected current density depends on the transposition method and the type of winding and the material of its components, including circulating steel and low-permeability steel.

(3) Shielding method: divided into magnetic shielding and electromagnetic shielding. The total loss of a transformer is the sum of no-load loss and load loss. If there are auxiliary machines such as submersible pumps or fans, auxiliary machine losses are also included. At rated load, load loss accounts for about 80% of the total loss and plays a decisive role in the transformer’s efficiency.