Understanding the measurement principle is essential to comprehend why HZ2611 supports both the two watt meter method and the three watt meter method, as well as why temperature calibration is necessary. By explaining the principles clearly, on-site operations are no longer mechanically following the steps, but truly understanding what is being done.

Basic measurement circuit

The wiring method for short-circuit impedance test is as follows: the three-phase terminals on the secondary side of the tested transformer are reliably short circuited with a short circuit (commonly known as "secondary short circuit"), and an adjustable AC voltage is applied from the primary side, gradually increasing from low until the primary side current approaches the rated current. At this point, by recording the voltage U, current I, and power P on the primary side, all impedance parameters can be calculated.

The Significance of Watt Meter Method

The purpose of measuring power is to decompose impedance into active component (resistance R, corresponding to copper consumption) and reactive component (reactance X, corresponding to leakage flux):

Short circuit impedance: Z=U/I

Short circuit resistance: R=P/I ² (active power divided by current square)

Short circuit reactance: X=√ (Z ² - R ²)

Impedance voltage percentage: Uk%=(U/rated voltage) × 100%

Two watt meter method (three-phase three wire) and three watt meter method (three-phase four wire)

There are two classic methods for measuring three-phase power:

Two watt meter method (three-phase three wire connection): Only two power meters are needed to measure the total three-phase power, suitable for delta (Δ) connection or star (Y) connection transformers without neutral wire lead out. HZ2611 has built-in implementation of this method.

Three watt meter method (three-phase four wire connection): Each phase uses a power meter, suitable for transformers with neutral point leads or situations where phase separation measurement is required. The results are more direct and the accuracy is higher. HZ2611 is also supported.

The role of built-in inverter power supply

HZ2611 has a built-in three-phase inverter power supply, which automatically generates three-phase AC output when connected to 220V mains power. The voltage rises smoothly from zero, avoiding the trouble of traditional methods that require three-phase voltage regulators. When using the built-in power supply, the instrument defaults to three-phase four wire (three watt meter method) testing, which is the most comprehensive and accurate testing method.