Three-phase three-wire load star connection circuit

Three-phase three-wire power supply In the three-phase j-wire power supply system, no matter whether the three-phase load is
symmetrical or not, and whether the load is "" connection or "△" connection, the two-wattmeter method can be used
to measure the active power of the three-phase load. The measurement circuit is shown in Figure 613. If the readings of the two power meters are wl and wZ, then the three-phase power P+Wi+
Wz =UJlicos(300-{o)+Uilicos(304十J), where donkey is the load Impedance angle (i.e.
power factor angle), the readings of the two power meters have the following relationship with the school;
    1) When the load is a pure resistance, Wl=W2, that is, the readings of the two power meters are equal;
    2) When the load power The factor co is printed as 0.5. Mine=±60. , there will be a power meter reading
of zero}
    3) When the load power factor cosp<o_5, lAI>60. , then one power meter has
a negative reading, and the power meter pointer will deflect in the opposite direction. At this time, the two terminals of the current coil of the power meter should be exchanged (the voltage coil terminals cannot be exchanged
). The reading should be recorded as a negative value, and a negative reading will appear for a digital meter.