# To find power factor of the ac circuit given only the source and load voltages

1. Feb 12, 2012

### sathishj

how to find power factor of the load, the three voltmeter readings are V1=220v,V2=122v,V3=136v

#### Attached Files:

• ###### pf.JPG
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2. Feb 13, 2012

### Staff: Mentor

Start with the vector sum of two of these voltages equalling the third, and determine the triangle representing this.

3. Feb 13, 2012

### technician

The load must be a combination of resistance,R, and reactance,X, because 220^2 does not equal 122^2 + 136^2
this means that for the load Vr^2 + Vx^2 = 136^2
this will give 2 equations which can be solved for the Vr in the load and the Vx for the load

4. Feb 13, 2012

### Staff: Mentor

No calculations are needed beyond what I outlined:

5. Feb 13, 2012

### technician

Some calculation is needed to get a value for Cosθ, either from a vector diagram or by algebra.
Does anyone have an answer? I got 0.83. Purely for personal preference I took the reactive part of the load to be inductive but it could have been capacitative.

6. Feb 14, 2012

### Staff: Mentor

I get pf=0.453

7. Feb 15, 2012

### technician

NascentO
Here is what I did, I interpreted the question as asking for the power factor for the load connected to the supply voltage of 220V (this is what is usually meant for power factor).
The question however does say 'the load' and 'the load' is clearly marked onthe diagram.
I would say there are 2 correct answers !!!
Sorry!! attachment not there.... I will do it again

Last edited: Feb 15, 2012
8. Feb 15, 2012

### technician

Attachment for power factor calculation

#### Attached Files:

• ###### power factor.jpg
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9. Feb 15, 2012

### Staff: Mentor

I interpreted it as a lossy transmission line. Otherwise, I agree with your answers.