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

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.

Please download and refer to the attached document for more information.

相关产品和解决方案

PZ4000功率分析仪

PZ4000设计用于高频功率测量以及瞬时功率测量。此仪器的实时采集系统可执行按周期的功率测量。一到四个输入单元提供0.2%的基本精度,具备2MHz的带宽和5MS/秒的数字化速率。

功率分析仪 WT500

中等量程的WT500小巧且便于使用。使用其彩色TFT显示器可以观测数值和波形测量。提供1到3个输入单元,基本功率精度为0.1%,带宽为100kHz。

高性能功率分析仪 WT1800系列

高端WT1800是WT1600的升级产品,可应用于从节能到高负载应用在内的各种应用领域。WT1800拥有6单元输入能力,可提供最大的灵活性和5MHz带宽下0.1%的基本功率精度。

高精度功率分析仪 WT3000

WT3000高精度功率分析仪提供最高精度的测量。此产品已成为行业标准,用于变频器、电机驱动器、照明系统和电子镇流器、UPS系统、飞机电力系统、变压器测试和其它电力转换设备的研发。WT3000的基本功率精度达0.02%,带宽为1MHz。

数字功率分析仪

功率计或称瓦特计,可以测量产生、转换或消耗电能的设备各项特征,包括设备的各项参数,如:功率(瓦特)、功率因数、谐波和效率等等。

YOKOGAWA数字功率分析仪,性能优越、测量可靠,支持各种应用,非常值得拥有。尤其是YOKOGAWA WT300E功率计,已经在全球功率计市场份额上遥遥领先。

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