Any kind of electrical equipment will suffer losses during long-term operation, and power transformers are no exception. In the loss of power transformers, it is mainly divided into two parts: copper loss and iron loss.
Copper Loss
copper plays an important role in the transformer, the winding of the transformer usually uses copper wires, and the "copper loss" in the transformer is the loss of copper wires. The "copper loss" of the transformer is also known as the load loss, that is, the variable loss, whch is changing. When the transformer is running under load, the current will have resistance through the wire, resulting in resistance loss. According to Joule's law, the current flowing through this resistor will generate Joule heat, and the greater the current, the greater the power loss. Thus, the resistance loss is proportional to the square of the current and is independent of the voltage. It is precisely because it changes with the size of the current, so the copper loss (load loss) is a variable loss, it is also the main loss in transformer operation.
Influencing Factor
Current size: As mentioned above, copper loss is proportional to the square of the current, so the size of the current is a key factor affecting copper loss.
Winding resistance: The resistance of the winding directly affects the copper loss. The greater the resistance, the higher the copper loss.
The number of coil layers: The more the number of coil layers, the longer the path of current flow in the winding, the resistance will increase correspondingly, resulting in increased copper loss.
Switching frequency: The effect of switching frequency on the copper loss of the transformer is directly related to the distribution parameters of the transformer and the load characteristics. When the load characteristics and distribution parameters are inductive, the copper loss decreases with the increase of switching frequency. The copper loss increases with the increase of switching frequency when they are both capacitive.
Temperature effect: The load loss is also affected by the temperature of the transformer, while the leakage flux caused by the load current will produce eddy current loss in the winding and stray loss in the metal part outside the winding.
Formula Mode
1. copper loss(unit:kW) = I² × Rc × Δt, I is the rated current of the transformer, Rc is the resistance of the copper wire, and Δt is the operation time of the transformer.
2. copper loss = I² × R, I is the rated current of the transformer, R is the total copper resistance of the transformer.
R = (R1 + R2) / 2, R1 is the primary side copper resistance of the transformer, and R2 is the secondary side copper resistance of the transformer.
Methods of reducing copper damage
1. Increase the winding cross-sectional area of the transformer: reduce the conductor resistance, thereby effectively reducing the transformer copper loss.
2. Use high-quality conductor materials such as copper foil or aluminum foil to reduce winding resistance.
3. Reducing the light-load operation time of the transformer: limiting the proportion of the light-load operation time of the transformer is conducive to reducing the copper loss of the transformer.
