Question
Download Solution PDFWhich condition is created by two wattmeters W1 and W2 for power factor is zero?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFMeasurement of power
According to Blondel's Theorem, for the measurement of power in n-phase, n-wire without neutral, (n - 1) wattmeters are required.
For measurement of power in 3-phase, (3 - 1 = 2) wattmeters are required.
The readings of both the wattmeters are given by:
\(W_1=V_LI_Lcos(30+ϕ)\)
\(W_2=V_LI_Lcos(30-ϕ)\)
The power factor is given by:
Power factor = cosϕ
At zero power, cosϕ = 0
At, ϕ = 90°, the readings of both the wattmeters are:
\(W_1=V_LI_Lcos(30+90)={-0.5V_LI_L}\)
\(W_2=V_LI_Lcos(30-90)={+0.5V_LI_L}\)
Thus, W1 = -ve, W2 = +Ve
Thus at zero power factor, the reading of both wattmeters are equal and opposite.
Last updated on May 9, 2025
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