The power of an n-phase circuit can be measured by using a minimum of...
If the load is unbalanced,single-phase than "n wattmeter" If the load is balanced, than "n-l" wattmeter
Blondel's theorem, named after its discoverer, French electrical engineer André Blondel, is the An electrical energy meter is a watt-meter whose measurements are integrated over time; thus, the Electric energy meters that meet the requirement of N-1 elements for an N wire service are often said to be Blondel Compliant.
Hence, the correct option is (A)
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The power of an n-phase circuit can be measured by using a minimum of...
Measure of Power in n-phase circuit
Measurement of power in an n-phase circuit can be done using wattmeter elements. The number of wattmeter elements required for measuring power depends on the number of phases in the circuit. The correct option for the minimum number of wattmeter elements required is option 'A', which is (n-1) wattmeter elements.
Explanation
- Wattmeter: A wattmeter is an instrument that measures the power of an electrical circuit in watts. It consists of two coils, one of which is connected in series with the circuit, and the other is connected in parallel. The wattmeter measures the product of the current and voltage in the circuit, which gives the power consumed.
- n-phase circuit: An n-phase circuit is a circuit that has n phases. A phase is a part of the circuit that carries a sinusoidal voltage or current. For example, a 3-phase circuit has three phases, each carrying a sinusoidal voltage or current that is 120 degrees out of phase with the other two.
- Power measurement in n-phase circuit: In an n-phase circuit, the power can be measured by using wattmeter elements. The number of wattmeter elements required for measuring power depends on the number of phases in the circuit. The minimum number of wattmeter elements required is (n-1).
- Derivation: The power in an n-phase circuit can be expressed as:
P = ∑(3VLILcosθ)
where P is the total power, VL is the line voltage, IL is the line current, and θ is the phase angle between the voltage and current.
For a 3-phase circuit, the power can be expressed as:
P = √3VLILcosθ
This equation shows that the power in a 3-phase circuit can be measured using only one wattmeter element. However, for an n-phase circuit, the power cannot be measured using only one wattmeter element. The minimum number of wattmeter elements required is (n-1).
For example, in a 4-phase circuit, the power can be measured using three wattmeter elements. In a 5-phase circuit, the power can be measured using four wattmeter elements.
Conclusion
The power in an n-phase circuit can be measured using wattmeter elements. The minimum number of wattmeter elements required for measuring power in an n-phase circuit is (n-1). This is because each wattmeter element can measure the power in one phase, and there are n phases in an n-phase circuit.