UCFTransformer Voltage Regulation (1)

Ideal:

Non-ideal:S

P

NNn

nVV

S

P

UCFTransformer Voltage Regulation (2)

No load (open circuit):

nP

SnlVV

Full load : SeqsSeqsSfl

P jXRn

IIVV

%100/

%100

Sfl

SflP

Sfl

SflSnl

VVnV

VVV

VRVoltage regulation:

UCFTransformer Voltage Regulation (3)

Discussions:

(1) Load is lagging (inductive)

%100/

Sfl

SflP

VVnV

VR

0/ VRVnV SflP

SeqsSeqsSflP jXR

nIIVV

UCF

(2) Load is resistive (unit power factor)

0/ VRVnV SflP

(3) Load is leading (capacitive)

0 bemay bemay / VRVnV SflP

Transformer Voltage Regulation (4)

SeqsSeqsSflP jXR

nIIVV

UCF

Given: (1) VS (fixed)(2) rated apparent power (VA) of the load(3) power factor of the load

Find: IS and thenVP

Transformer VR Calculation (1)

ratedSS SIV loadIV SS

%100/

S

SP

VVnVVR

IS :

SeqsSeqsSflP jXR

nIIVV

UCF

further approximate calculation

Transformer VR Calculation (2)

%100/

S

SP

VVnVVR

cos sinPS eqs S eqs S

V V R I X In

SeqsSeqsSflP jXR

nIIVV

UCFExample 3

For a 15 kVA, 2300/230 V, 60 Hz transformer, the equivalent circuit parameters are:

Find voltage regulation at full load when(1) load is 0.8 pf lagging;(2) load is 1.0 pf;(3) load is 0.8 pf leading.

k 10 ,k 100 ,6 ,5 MCeqeq XRXR

Process is in trans3.m.

UCF Per Unit System (1)

Define Base Values Normalization:

quantity of valueBasequantity Actual unit per in Quantity

UCF Per Unit System (2) Analysis Procedure:

unit per in quantity solved valuebase results of valuesactual (6)

unitper in quantities all with analysiscircuit standard a perform (5)

unit)per quantitiesget :(or quantities theall normalize )4(basecurrent

base voltage base resistance )3(

base voltagebaseVA basecurrent (2)

base voltageand baseVA select (1)

UCF Example 4 (1)

UCF Example 4 (2)

Process is in trans4.m.

UCFNon-ideal Transformer in Per Unit System

Or

UCFVoltage Regulation in Per Unit System

%100/

%100

Sfl

SflP

Sfl

SflSnl

VVnV

VVV

VRVoltage regulation:

Voltage regulation in per unit:%100

,

,,

puS

puSpuP

VVV

VR

puSpueqpuSpuP Z __,, IVV