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5. Calculate Transformer Regulation & Losses (As per Transformer Name Plate)

CALCULATE TRANSFORMER REGULATION & LOSSES (AS PER TRANSFORMER NAME PLATE)

Calculate Transformer Regulation and Losses for following Transformer Name Plate Details

  • KVA rating of Transformer(P)=16000VA * Primary voltage(Vp)=11000V * Secondary voltage(Vs)=433V * No load losses(W0)=72Watt * No load current(I0)=0.59Amp * Full load losses(W)=394Watt * Impedance voltage(Vi)=480Volt * LV resistance(Rs) =219.16 miliΩ * HV resistance(Rp) =215.33 Ω * Amb temperature(c)=30 Deg C * Total Connected Load on Transformer(Pl)=10000VA

Calculation:

  • % Loading of Transformer=Pl/P * % Loading of Transformer=10000/16000 = 63%

I2R Calculation:

  • HV Full load current (Ip) =P/Vpx1.732 * HV Full load current (Ip) =16000/11000×1.732=0.84 Amp * LV Full load current (Is)=P/Vsx1.732 * LV Full load current (Is)==16000/433×1.732=21.33 Amp * HV Side I2R losses= IpxIpxRp * HV Side I2R losses= 0.84×0.84×215.33=227.8 Watt—–(A) * LV Side I2R losses= IsxIsxRs * LV Side I2R losses==21.33×21.33×219.16=149.63 Watt—(B) * Total I² R losses @ Amb temp(Ir)=A+B * Total I² R losses @ Amb temp(Ir)=227.8+149.63=377.43 Watt * Total Stray losses @ Amb temp (Ws) =Full Load Losses-I2R Losses * Total Stray losses @ Amb temp (Ws) =394-377.43=16.57 Watt * I² R losses @75° c temp =Irx310/235xc =149.63×310/235×30 =441.52Watt * Stray loses @ 75° c temp =(Wsx(235+c))/310 * Stray loses @ 75° c temp =(16.57x(235+30))/310=14.16 Watt * Total Full load losses at @75° c=441.52+14.16=455.69 Watt * Total Impedance at ambient temp (Ax)=Vix1.732/Ip * Total Impedance at ambient temp(Ax)=480×1.732/0.84=989.94Ω * Total Resistance at amb temp (Ar)=Ir/IpxIp * Total Resistance at amb temp (Ar)=377.43/0.84×0.84=535.15Ω * Total Reactance (X)=√AxxAx+ArxAr * Total Reactance (X)=√989.98×989.94+535.15×535.15=832.82Ω * Resistance at@ 75° c (R)= (310xAr)/(235+c)=310×535.15/235+30 = 626.03Ω * Impedance at 75° c (X1)=√2X+2R=√2×626.03+2×832.82 = 1041.88Ω * Percentage Impedance = (X1x0.5774xIpx100)/Vp * Percentage Impedance = (1041.88×0.5774×0.84×100)/11000=4.59% * Percentage Resistance (R%) =(Rx0.5774xIpx100)/Vp * Percentage Resistance(R%) =(626.03×0.5774×0.84×100)/11000=2.76% * Percentage Reactance(X%) = (Xx0.5774xIpx100)/Vp * Percentage Reactance(X%) = (832.82 x0.5774×0.84×100)/11000=3.67%

Regulation

  • Regulation at Unity P.F =2.76 * Regulation at Unity at 0.8 P.F =((R% x cosØ)+(X% x SinØ))+(0.005x((R% x SinØ)+(X% x CosØ))) * Regulation at Unity at 0.8 P.F =((2.76 x 0.8)+(3.67 x 0.6))+(0.005x((2.76 x0.6)+(3.67 x 0.8)))=4.43

Results

  • Total I² R losses @ Amb. temp(Ir)= 377.43Watt * Total Stray losses @ Amb. temp (Ws) =16.57 Watt * Regulation at Unity P.F =2.76 * Regulation at Unity at 0.8 P.F =4.43