A single-phase rotary converter has an output voltage of \(110\) volts. Determine the line current in the AC side when the machine delivers a DC output of \(50\) A. Assume the machine is operating with a pf of \(0.85\) and efficiency of \(95\%\).
A70.71 A
B90.34 A
C87.57 A
D82.23 A
#2📜 EE Board April 1994
In a three-phase synchronous converter, the ratio of the AC voltage to DC voltage is
A0.612
B1
C0.5
D0.707
#3
A three-phase rotary converter delivers \(150\) A at \(500\) VDC. Determine the current on the AC side if the operating power factor of the machine is \(0.8\) and the efficiency is \(90\%\).
A179 A
B157 A
C189 A
D196 A
#4
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
#5
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
#6
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
#7
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
#8
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
#9📜 EE Board April 1992
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
#10
A 4-pole \(230\)-V, \(60\) Hz, three-phase induction motor directly drives a 6-pole alternator. Determine the output frequency. Assume a slip of \(3\%\) in the motor.
A90.0 Hz
B88.4 Hz
C86.6 Hz
D87.3 Hz
#11
A 4-pole, three-phase synchronous motor connected across a \(60\) Hz supply drives a 6-pole alternator through a belt. If the diameter of the driver and driven pulleys are \(6\) and \(10\) inches respectively, determine the operating frequency of the alternator.
A53 Hz
B54 Hz
C55 Hz
D52 Hz
#12📜 EE Board April 1992
A generator is rated \(600\) kVA, \(240\) V, \(60\) cycles, 3-phase, 6-poles and wye-connected. What will be the speed of the driving pulley if the driven and driving pulleys are \(1\) ft and \(2\) ft in diameter respectively?
A2400 rpm
B1200 rpm
C600 rpm
D900 rpm
#13📜 EE Board October 1998
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
#14
A \(230\)-V, 3-phase motor belt drives a \(50\) kW, \(250\) V DC generator. The motor, belt and generator efficiencies are \(0.91\), \(0.95\) and \(0.86\) respectively. If the motor operates at a pf of \(0.866\) lagging, determine the current drawn.
A189 A
B195 A
C192 A
DNone of these
#15
A single-phase motor is connected across a \(230\)-V, \(60\) Hz supply and draws \(30\) A at \(0.85\) pf lagging. This motor drives a \(120\)-V DC generator through direct coupling. If the motor, coupling and generator efficiencies are \(0.85\), \(0.96\) and \(0.88\) respectively determine the current delivered by the generator using the above condition.
A35 A
B32 A
C38 A
D48 A
#16
A \(230\)-V, \(60\) Hz, 3-phase motor drives a \(25\) kW, \(250\) V DC generator through belt and pulley. The motor and generator efficiencies are \(0.90\) and \(0.88\), respectively. If the motor draws a line current of \(98\) A at \(0.85\) pf lagging, how much is the combined efficiency of the belt and pulley?
A95.12%
B96.04%
C95.33%
D94.81%
#17📜 EE Board October 1991
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
#18
A half-wave rectifier draws power from a power transformer at \(24\) volts and delivers \(200\) mA to a load. Determine power drawn by load.
A0.48 W
B1.25 W
C2.16 W
D2.05 W
#19
An AC ammeter is connected in series across the output of a full wave rectifier. This meter reads \(8\) A. If a moving coil ammeter is replaced instead of the AC ammeter, what will be its expected reading?
A8.0 A
B7.6 A
C7.2 A
D5.6 A
#20📜 EE Board October 1987
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.
