soal soal

1.      The single phase bridge rectifier required to supply an average voltage of Vdc = 400V

to resitive pf R = 20 Ohm, determine the voltage and current rating of diode and transformator !

2.      A three phase bridge rectifier is required to supply voltage of Vdc = 750 V at a ripple current of 9000 A, the primary and secondary of transformer are connected in Wye. Determine the voltage  and current rating of diode and transformer !

ANSWER

1.       Vdc=400V, R=20 ohm

Vdc=0.6366Vm

400=0.6366Vm

Vm=628.34V

ThermsphasevoltageisVrms=Vm/√2=628.34/√2=444.3V

Idc=Vdc/R=400/20=20A

Diodes:

Peakcurrent,I_P = 628.34/20 = 31,417 A

Average current, I_D = I_DC = 20/2 = 10A

RMS current,I_R =31,417/2 = 15,7085 A

Transformer:

RMSvoltage,V_rms= V_M/√2=444.3V

RMScurrent,I_rms= I_M/√2= 22,215 A

Volt-amp,VI=444.3x 22,215=9,87 kVA

P_DC = (0.6366Vm)²/RandP_AC =V_rmsI_rms =V_M²/2R

TUF = P_DC/P_AC =0.63662x2=0.8105

andthede-ratingfactorofthe

Transformeris1/TUF=1.2338.

2.       V_DC=750V,Idc=9000A

V_DC= 1,6542V_m

750 = 1,6542V_m

V_m = 453,39V

The rms phasevoltageis

V_rms=V_m/√2 =453,39/√2 = 320,59V