# Why are the Measured Values Negative When Measuring a Balanced Three-Phase Load?

#### Resources:

In the three-phase three-wire, or 3V3A wiring scheme, the phase angle of voltage and current input to each input differs from that of the actual load because it is the line to line voltage that is measured.

In three-phase signals where the phase angle of voltage and current is 0°, if you wire the WT1600 for 3V3A:

• For input element 1, the phase difference of voltage and current is +30°
• For input element 2, the phase difference of voltage and current is -30°
• For input element 3, the phase difference of voltage and current is +90°(Notated with a + if the current lags the voltage, and a - if the current leads)

In an actual three-phase load, if the phase difference of phase voltage and phase current is α°, the phase difference of each input element of the power meter is:

• For input element 1, the phase difference of voltage and current is α° +30°
• For input element 2, the phase difference of voltage and current is α° -30°
• For input element 3, the phase difference of voltage and current is α° +90°

As for the total value of α (the phase difference of phase voltage and phase current in the acutal load) on a given element, the value α° +30°, or α° -30°, or α° +90° can be larger than 90°

In that case, the measured power value for that input element may be - (negative). However, this is due to the fact that the measureing method is "apparent" or "for purposes of line to line voltage measurement," and does not reflect the true value of the load, which can never by negative.

### Related Products & Solutions

#### Precision Power Analyzer WT3000

With 0.02% accuracy and 1MHz bandwidth, the WT3000 delivers where the highest precision measurements are required. It is the industry standard for R&D work on inverters, motor drives, lighting systems and electronic ballasts, UPS systems, aircraft power, transformer testing, and other power conversion devices.

#### PZ4000 Power Analyzer

The PZ4000 is designed for High Frequency Power Measurements as well as Transient Power Measurements. Its real-time acquisition system can perform cycle-by-cycle power measurements. One to Four input elements offer Basic Power Accuracy of 0.2% with 2 MHz Bandwidth and 5MS/sec digitizing rates.

#### WT1600 Digital Power Meter

The High-end WT1600 is designed for a wide range of applications, from energy-saving to large load applications. The WT1600 has a six element input capability to provide maximum flexibility, and Basic Power Accuracy of 0.1% with 1 MHz Bandwidth.

#### WT1800 High Performance Power Analyzer

The WT1800 Power Analyzer offers maximum flexibility with up to six wattmeter elements, high bandwidths, simultaneous high speed digitizing, and wide voltage and current ranges. Although this model is still available, the newer WT1800E offers higher accuracy.

#### WT2010/WT2030 Digital Power Meters

The WT2000 digital powermeter series has been designed with emphasis on basic performance (bandwidth, accuracy, response speed, and noise immunity) from the viewpoint of measurement of electrical quantities. The broad range of functions of these power analyzers enable them to be used in various fields of applications.

#### WT500 - Mid Range

• Power and Harmonic (THD) Measurements with Independent Range Controls
• Efficiency measurements of AC/DC or DC/AC Inverters & Motors

#### Power Analyzers and Power Meters

Yokogawa, the world's largest manufacturer of energy and power analyzers and meters, provides a broad choice of digital power analyzers to satisfy all requirements.

Top