3. Methodology

Start

Emperical review

Design the program"Projecting DC bias current "

Testing the program

"Generate midpoint locus"

Error occur Troubleshoot

Data analysis

Design the experiment circuit

End

No

Testing the circuit

Error occur

Data analysisCompare between simulation

and experiment results

Reporting the result

No

Yes

Yes

Troubleshoot

Figure 1. Project flowchart

In the simulation phase, the student will calculate the average flux in the core by assuming

terminal voltage equal to induce voltage in which the maximum flux can be obtain when sinω t =

1 where, ω = 2πf . After this, the student will consider placing dc flux in the core known as

unipolar flux that flow in one direction only with zero frequency. Then, the dc and AC flux in the

core will be induced with the net flux in the core as follow:

1. φnet=φdc + φac

2. φnet=φdc + φmaxSinωt

In addition, the student will consider the existing current and flux of a power transformer iron

core by considering M as the knee peak and Is along with saturation current and flux. This study

will consider both aspects of k1 and k2 as the gradients of the piecewise magnetizing settings. As

the transformers are set to the knee point at rated conditions, transformers will be apt to saturate

at a smaller direct current as shown in Figure 2.

Figure 2. Excitation current and flux of power transformer with dc and without dc bias

3.1Experimental phase

The student need to analyzes and compare the effect of different direction of DC

bias to B-H curve, flux density and magnetizing current from simulation and

experimentation. An experiment conduct to investigate the effect of DC bias on real

power transformers. The experiment used single phase power transformer prototype. The

experiment is set up with two difference connection to represented different direction of

DC bias. An AC input voltage to primary winding is connected to AC power supply with

voltage variable to achieved the certain magnetize flux densities (Tesla). The equipment

and apparatus used in the experiment are AC power supply, single phase power

transformer, variable resistor, switching diode, AC power analyzer, and the variable DC

bias current be found by variable resistance adjusted. Figure 3.3 shown the experiment

set up for difference direction DC bias of power transformer.

Figure 3.3: Experiment set up for positive direction of DC bias

on power transformer