What Are Transformer Copper Losses and Iron Losses

Among the losses of the transformer, there are mainly two parts: iron loss and copper loss. So, what is the difference between the iron loss and copper loss of the transformer?

The iron loss of the transformer is the loss caused by the iron core in the transformer, and the copper loss of the transformer is a load loss.

1. Iron loss of transformer

Iron loss, also called no-load loss, is a fixed loss of the transformer. It is the loss caused by the iron core in the transformer, so it is also called core loss.

Iron loss refers to the power consumed in the iron core of the transformer at rated voltage (secondary open circuit), including hysteresis loss and eddy current loss.

Transformer iron losses include:

1) Hysteresis loss

When alternating current passes through the transformer, the direction and size of the magnetic lines passing through the silicon steel sheets of the transformer change accordingly, causing the molecules inside the silicon steel sheets to rub against each other and release heat energy, thereby losing part of the electrical energy. This is hysteresis loss.

2) Eddy current loss

When the transformer is working, magnetic lines of force pass through the iron core, and an induced current is generated on a plane perpendicular to the magnetic lines of force. Since this current forms a closed loop to form a circulating current and becomes a vortex, it is called eddy current.

The existence of eddy current causes the iron core to heat up and consume energy. This loss is called eddy current loss.

2. Copper loss of transformer

The copper loss of the transformer is also called the load loss.

Copper loss (short circuit loss) refers to the sum of energy lost by the primary and secondary currents of the transformer flowing through the coil resistance. Since coils are mostly made of copper wires, they are called copper losses.

The copper loss of the transformer is proportional to the square of the current. The kilowatt number marked on the nameplate refers to the copper loss when the coil passes the rated current at 75°C.

DAC-IR-2C Direct Reading Iron Loss Tester