ABOUT TIANYI

1 Rated capacity Se: refers to the capacity that the transformer can deliver under the rated voltage and rated current specified on the nameplate when it leaves the factory, in kVA. The calculation formula is: Three-phase transformer Se=1.732UeIe Single-phase transformer Se=UeIe

2, rated voltage Ue" refers to the working voltage that the transformer can withstand during long-term operation (the Ue value on the nameplate refers to the rated voltage when the tap changer is in the middle branch); the unit is kV.

3. Rated current Ie: The operating current allowed to pass for a long time under the conditions of rated capacity Se and allowable temperature rise, in A.

4. Short-circuit voltage Ud%: also known as impedance voltage (UK%), short-circuit the secondary winding of the transformer, apply voltage on the primary side, and reach the rated current value, the percentage of the ratio of the voltage on the primary side to the rated voltage Ue. That is: Ud%=Ud/Ue;100%

The parallel operation of the transformer requires the same Ud% value. When the secondary side of the transformer is short, the Ud% value will determine the short-circuit current, so it is an important basis for considering the thermal and dynamic stability of the short-circuit current and the setting of relay protection.

5. No-load current I. ; When the transformer is at the rated voltage of the primary side and the secondary winding is no-load, the current passing through the primary winding is called the no-load current. It plays the role of exciting the transformer, so it is also called the exciting current; it is generally expressed as a percentage of the rated current. The size of the no-load current depends on the capacity of the transformer, the structure of the magnetic circuit and the quality of the silicon steel sheet.

6. No-load loss (iron loss) ΔP0: refers to the loss of the transformer when the secondary side of the transformer is open and the rated voltage is applied to the primary side. It is equal to the eddy current loss and excitation loss of the transformer core, and is an important performance index of the transformer.

7. Short-circuit loss (copper loss) ΔPd: The iron loss of a transformer includes two aspects. The first is the hysteresis loss. When the alternating current passes through the transformer, the direction and size of the magnetic field lines passing through the silicon steel sheet of the transformer change accordingly, causing the internal molecules of the silicon steel sheet to rub against each other and release heat energy, thus losing a part of the electric energy. This is the hysteresis loss. . The other is eddy current loss, when the transformer is working. If there are magnetic lines of force passing through the iron core, an induced current will be generated on the plane perpendicular to the magnetic lines of force. Since this current forms a closed loop and forms a vortex, it is called an eddy current. The existence of eddy current makes the iron core heat up and consumes energy. This loss is called eddy current loss.

8. Copper loss refers to the loss caused by the resistance of the transformer coil. When the current flows through the coil resistance to generate heat, part of the electrical energy is converted into heat and is lost. Since the coil is generally wound by insulated copper wire, it is called copper loss.

9. Voltage ratio: The number of turns of the two sets of transformer coils are N1 and N2 respectively. N1 is the primary and N2 is the secondary. When an AC voltage is applied to the primary coil, an induced electromotive force will be generated at both ends of the secondary coil. When N2>N1, the induced electromotive force is higher than the voltage applied by the primary, this kind of transformer is called a step-up transformer.