# Trigonometry on a transformer

1. Apr 22, 2014

### johann1301

On a trafo i just bought, it says COS Ø = 0,99. What does this mean?
Is there some angle involved in changing the voltage?

2. Apr 22, 2014

### PhysicoRaj

That is the 'Power factor'. To be simple, the ratio of actual power consumed to the product of voltage and current through the trafo is 0.99, it means.
See this:
http://en.wikipedia.org/wiki/Power_factor

Last edited: Apr 22, 2014
3. Apr 22, 2014

### PhysicoRaj

Here's a simpler version:http://www.tvss.net/pq/pf.htm

4. Apr 22, 2014

### jim hardy

trafo ?

http://www.trafo.co.in/

To your trig question:

cos-1(0.99) = 8.1 degrees
and that's the angle between primary side volts and amps at rated resistive load.

draw a right triangle with a hypotenuse of 1, base of 0.99 and an opposite side of 0.1424
this represents primary current at rated conditions with resistive load
small angle is 8.1 degrees
base is 0.99 units and is load current corrected for turns ratio
opposite side is 0.1424 units and is magnetizing current
hypotenuse is total current flowing into primary

so this transformer draws 14.24% magnetizing current.

Last edited: Apr 22, 2014