2dix-The Student Choice
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To measure the power in 3-φ load by (i) two wattmeter method at different value of load (ii) One watt meter method.

OBJECT: To measure the power in 3-φ load by (i) two wattmeter method at different value of load (ii) One watt meter method.

 

APPARATUS REQUIRED:

Wattmeter, ammeter, connecting loads, 3- φ star connection load, voltmeter.

 

THEORY:

 Two wattmeter method is the most commonly used method for measurement of power as this can be used for balanced & unbalanced of the used is balanced.

                                The reading of W1 wattmeter is given by is a balanced

                                                                W1 = E12 i1 cos (30+ φ)

                    While reading of W2 wattmeter is given by

                                                                W2 = E32 i3 cos (30- φ)

 

Since if it is a balanced circuit

                                                |E12 | = |E32| = √3 |EPN|

                                                |i1 | = |i3| = |i| (say)

 

Therefore   W = W1 + W2

                             W = √3 EPH i cos (30+ φ) + √3 EPH i cos (30- φ)

                                    = 2 √3 EPH i cos 30 cos φ

                                    = 3 EPH i cos φ

                             W = √3 EL i cos φ

 

This is nothing but the 3- φ power in the balanced load.

 

 

 

 

 

CIRCUIT DIAGRAM:

 

Fig. 3.1 Circuit Diagram Of Power factor Meter Using watt meter

CALCULATION:                                 

                             Power Factor = cos φ

                                                φ = tan-1 [√3 (W1-W2) / (W1+W2)]

                                                φ = tan-1 [√3(-160 / 400)]

                                                φ = tan-1 [-√3 × 0.4]

                                                φ = -34.71

                                                P.F. = cos φ = 0.82

 

OBSERVATION TABLE:

 

S.NO.

       E

      I

     W1

      W2

W1 + W2

W1 – W2

    % ERROR

(VOLTS)

(AMP)

(WATT)

(WATT)

(WATT)

(WATT)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Calculation of power factor:

Φ = tan-1 [√3 (W1 – W2) / (W1 + W2)]

P.F. = cos Φ

 

 

RESULT:                                                                                                                     

We have performed the experiment of power factor measurement by 2- Wattmeter method. And the results are……………….

Power (active) = W1 + W2 

Power factor = ……………

 

 

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