# Department of Electrical and Computer Engineering EE18B.

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Department of Electrical and Computer Engineering EE18B

Principle of Operation Alternating Voltage level conversion Ferromagnetic, laminated core Primary and Secondary Windings

Principle of Operation Alternating Voltage sets up varying flux in core Varying flux links with windings on secondary side Flux linkage results in voltage source

Non-Ideal Transformer Hysteresis & Eddy Current Losses in Transformer Core Resistive Losses in primary and secondary windings Leakage losses in windings

Equivalent Circuit

Points to Remember when going to the HV side, impedances go up when going to the LV side impedances go down any side can be treated as the primary, all the must be done is that the turns ratio should be adjusted to suit

Open Circuit Test Measure V oc, I oc and P oc Calculate Z oc and  oc I o = I oc cos  oc I m = I oc sin  oc R o = V oc / I o X m = V oc / I m P oc = V oc x I oc x cos  oc

Open Circuit Test

Short Circuit Test Measure V sc, I sc and P sc Calculate Z sc and  sc R s = Z sc cos  sc X s = Z sc sin  sc P sc = V sc x I sc x cos  sc

Short Circuit Test

Summary p.f @  L

a = ( N1 / N2 ) ‘ Coil Turns Ratio’ E1 = N1 ‘ Voltage Turn Ratio ‘ E2 N2 I1 = N2 ‘ Ampere Turn Ratio’ I2 N1 Turns Ratio

1.Power out = V 2 I 2 cos  L 2.I IN = I NL + I 1 3.I NL = I O – jI m { PHASE DIFFERENCE 90 DEG } { -j = Lagging p.f. } 4. N 1 I 1 - N 2 I 2 = 0 Summary

6. ‘Equivalent Losses’ ‘Stored Energy’ 7. V 2 = E 2 8. E 2 = E 1 [ N2 ] [ N1 ]

Summary 9. E 1 = V 1 – I 1 { R S + jX S } 10.  = Output Power x 100 Input Power = Input Power – losses x 100 Input Power = Output Power x 100 Output Power + Losses

Summary 11.  = V 2 I 2 cos  L x 100 V 2 I 2 cos  L + [I O ] 2 R O + [I 1 ] 2 R S = Efficiency (%) 12. Regulation (%) = (V NL2 – V FL2 ) X 100 V FL2