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Two wattmeter method is used for measurement of power in a balanced three-phase load supplied from a balanced three-phase system. If one of the wattmeters reads half of the other (both positive), then the power factor of the load is
  • a)
    0.532
  • b)
    0.632
  • c)
     0.707
  • d)
     0.866
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
Two wattmeter method is used for measurement of power in a balanced th...
Explanation:
The two wattmeter method is used for measuring power in a balanced three-phase load supplied from a balanced three-phase system. In this method, two wattmeters are connected in the circuit and the readings of these wattmeters are used to calculate the power consumed by the load.

Working of Two Wattmeter Method:
The two wattmeter method is based on the principle that the sum of the readings of two wattmeters connected in a balanced three-phase circuit is equal to the total power consumed by the load.

Power Factor (PF):
Power factor is a measure of the efficiency of electrical power usage in a circuit. It is the ratio of the real power (W) to the apparent power (VA) in a circuit and is expressed as a decimal or a percentage.

Given:
One of the wattmeters reads half of the other (both positive).

To determine the power factor of the load, we can use the formula:

PF = (W1 - W2) / (W1 + W2)

Where,
W1 = Reading of the first wattmeter
W2 = Reading of the second wattmeter

Since one wattmeter reads half of the other, we can assume that the reading of the first wattmeter is 2x and the reading of the second wattmeter is x.

Substituting the values:
W1 = 2x
W2 = x

PF = (2x - x) / (2x + x)
= x / 3x
= 1 / 3

The power factor of the load is 1/3.

Conversion from Power Factor to Decimal:
To convert the power factor to decimal form, we can divide 1 by the power factor:

PF = 1 / 3
= 0.333

The power factor of the load is 0.333.

Comparing with Given Options:
The correct answer is option 'D' (0.866).

Therefore, the given options do not match the calculated power factor.
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Community Answer
Two wattmeter method is used for measurement of power in a balanced th...
Explanation:

The two-wattmeter method is used to measure the power in a three-phase load supplied from a three-phase system. In this method, two wattmeters are connected to two different phases of the load. The sum of the readings of the two wattmeters gives the total power.

Let's assume that the readings of the two wattmeters are W1 and W2, where W1 is greater than W2.

The power factor (PF) of the load can be calculated using the formula:

PF = (W1 - W2) / (W1 + W2)

Given that one of the wattmeters reads half of the other (W1 = 2W2), we can substitute this value into the formula:

PF = (2W2 - W2) / (2W2 + W2)

Simplifying the equation:

PF = W2 / (3W2)
=> PF = 1 / 3

The power factor (PF) of the load is 1/3, which is equivalent to 0.33. However, none of the given options match this value. Hence, the given answer is incorrect.

Correct Answer:
The correct answer should be "None of the above" as none of the given options match the calculated power factor (PF) of 1/3.

Note: It's important to cross-verify the answer options with the calculated value to ensure accuracy. In this case, none of the options match the calculated value, indicating that the given answer is incorrect.
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Two wattmeter method is used for measurement of power in a balanced three-phase load supplied from a balanced three-phase system. If one of the wattmeters reads half of the other (both positive), then the power factor of the load isa)0.532b)0.632c)0.707d)0.866Correct answer is option 'D'. Can you explain this answer?
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