The wattmeter method is used to measure power in a three-phase load. The wattmeter readings are 200 W and -35 W. Find the respective values of active power and reactive power.

Concept of Three-Phase Power Measurement using Wattmeter Method:

In the two-wattmeter method for measuring power in a three-phase system, the active power (P) and reactive power (Q) are determined using the readings of two wattmeters (W₁ and W₂).

The formulas to calculate active power (P) and reactive power (Q) are:

P = W₁ + W₂

Q = √3 × (W₁ - W₂)

Where,

• W₁ = Reading of the first wattmeter
• W₂ = Reading of the second wattmeter

Given Data:

• W₁ = 200 W
• W₂ = -35 W

Calculation:

Active Power (P):

P = W₁ + W₂

⇒ P = 200 W + (-35 W)

⇒ P = 165 W

Reactive Power (Q):

Q = √3 × (W₁ - W₂)

⇒ Q = √3 × (200 W - (-35 W))

⇒ Q = √3 × (200 W + 35 W)

⇒ Q = √3 × 235 W

Conclusion:

Hence, the respective values of active power and reactive power are 165 W and 235√3 VAR.