In a generator, electric potential can be induced in the coil, whether the coil is moving through a magnetic field or whether the magnetic field is moving through a fixed coil. In both cases, the value of magnetic flux remains constant, but the amount of magnetic flux intersecting the coil changes, which is the principle of mutual inductance. A transformer is a device that uses electromagnetic mutual inductance to convert voltage, current and impedance.

Transformer capacity tester includes two aspects. One is hysteresis loss. When the ac current passes through the transformer, the direction and size of the magnetic field lines of the silicon steel plate passing through the transformer will change accordingly, so that the molecules inside the silicon steel plate rub against each other, releasing heat energy, and thus losing a part of the electric energy, known as hysteresis loss. The other is the eddy current loss during transformer operation. A magnetic field line runs through the core and an induced current will be generated in a plane perpendicular to the field line.

Because this current forms a circulating loop and an eddy current, it is called an eddy current. The presence of eddy current causes the core to heat up and consume energy. This loss is called eddy current loss. The efficiency of a transformer is closely related to its power level. In general, the higher the power, the smaller the ratio of loss to output power, the higher the efficiency. Conversely, the lower the power.

The instrument displays three-phase voltage, three-phase current, three-phase power, the instrument displays the distortion rate of the applied power waveform, automatically calculates the transformer's no-load current converted to the rated voltage and the no-load loss corrected by waveform distortion, and displays the type of oil-immersed or dry-type distribution transformer core.

Can be used to check transformer single-phase defects or used in the absence of three-phase power on site. The instrument can record three single phase measurement data, and can calculate the transformer no-load current, no-load loss, impedance voltage and load loss according to different transformer connection.

Instrument built-in rechargeable lithium battery, itself can output three-phase sine wave inverter power supply, automatically adjust the output voltage, with soft opening and soft stop function, without any external power supply which can realize the measurement of distribution transformer capacity and judgment of the model, at the same time shows the transformer impedance voltage and temperature conversion), rated power flow load loss.