Three single-phase transformers connected delta-delta fed a three-phase rotary converter at \(2{,}300\) V. This converter supplies power to a DC load that draws \(100\) kW at \(250\) V. If the rotary converter operates at an efficiency of \(95\%\) at unity pf, calculate the current in the secondary windings of the transformer bank.
A397 A
B355 A
C229 A
D240 A
#2📘 1001 RojasHard
An open delta bank is serving a three-phase rotary converter. The converter supplies \(175\) A of current to a \(1.4\) ohm dc resistive load. If the machine draws an AC current of \(100\) A at \(0.8\) pf lagging, determine minimum size of transformer needed.
A15.0 kVA
B24.7 kVA
C25.9 kVA
D19.4 kVA
#3📘 1001 RojasHard
A 4-phase star connected rotary converter operating at \(0.90\) efficiency and \(0.85\) power factor is connected across a \(220\) V, \(60\) Hz mains and draws \(50\) A. Determine the DC load current.
A208.46 A
B220.54 A
C216.37 A
D212.25 A
#4📘 1001 RojasHard
The dc output of a six-phase star-connected converter is \(500\) kW at \(400\) V. If the pf and efficiency of the machine is \(0.866\) and \(0.92\) respectively, determine the ac current drawn from the supply?
A762 A
B740 A
C732 A
D729 A
#5📘 1001 RojasHard
A \(600\) kW, 6-phase, Y-connected, 18-pole, synchronous converter has simplex lap wound armature with \(1000\) conductors. The flux per pole is \(60\) mWb. The machine runs at \(600\) rpm at rated load. Determine the ac current in the slip rings. Assume the operating power factor and efficiency of the machine equal to \(1.0\) and \(0.9\) respectively.
A496.21 A
B488.42 A
C462.25 A
D472.07 A
#6📜 EE Board April 1992📘 1001 RojasHard
A \(500\) kW, \(600\)-V DC, 12-phase synchronous converter operates as a direct converter at a full load efficiency of \(92\%\) and a power factor of \(0.93\). Calculate the AC voltage between slip rings and the AC current drawn from a 12-phase transformer fed supply.
A112 V, 229 A
B112 V, 215 A
C110 V, 229 A
D110 V, 215 A
#7📜 EE Board October 1998📘 1001 RojasHard
The pulley of an old gen-set has a diameter of \(20\) inches. The belt exerts a pull of \(353\) pounds on the pulley. The gen-set runs at \(900\) rpm. What is the approximate kW rating of the gen-set?
A75
B250
C200
D37.5
#8📜 EE Board October 1991📘 1001 RojasHard
A moving coil ammeter, a resistance of \(1500\) ohms and a diode are connected in series across a \(125\) V sinusoidal AC supply. The diode has a linear current / voltage characteristics over the range \(I = 0, E = 0\) V to \(I = 200\) mA, \(E = 200\) V. Calculate the power dissipated in the \(1500\)-ohm resistor.
A0.76 W
B0.83 W
C0.71 W
D0.86 W
#9📜 EE Board October 1987📘 1001 RojasHard
In the electronic laboratory, a diode rectifier tube has a plate resistance of \(600\) ohms (assumed constant) and is connected as a half-wave rectifier to a load resistance of \(1{,}400\) ohms. The energizing supply voltage is \(440\) volts effective, \(60\) Hz alternating current. Find the average load voltage.
A138.5 V
B132.8 V
C133.6 V
D150.2 V
#10📘 1001 RojasHard
Three identical transformers are used to supply power to an iodizing plant requiring \(1000\) A at \(28\) V DC through a 3-phase half wave rectifier. The transformers are connected delta-wye. What are the secondary current and voltage of each transformer?
A1042 A, 28.47 V
B1017 A, 16.44 V
C1042 A, 16.44 V
D1017 A, 28.47 V
#11📜 EE Board October 1987📘 1001 RojasHard
In the electronic laboratory, a diode rectifier tube has a plate resistance of \(600\) ohms (assumed constant) and is connected as a half-wave rectifier to a load resistance of \(1{,}400\) ohms. The energizing supply voltage is \(440\) volts effective, \(60\) Hz alternating current. Find the rms rectified current.
