Three 10 ohm resistances are connected delta on a balanced three phase source. If the equation of the phase voltage is \(V_{an} = 120 \sin \omega t\), what is the equation of the phase a line current?
A\(36 \sin \omega t\)
B\(13.15 \sin(\omega t - 30^\circ)\)
C\(11.22 \sin(\omega t + 30^\circ)\)
D\(11.88 \sin(\omega t - 56.6^\circ)\)
#2📜 EE Pre-Board August 2012📘 PowerhouseMedium
A 220 V, 3 phase, 4 wire abc system supplies unbalanced wye connected resistances of \(R_a\) = 10 ohms, \(R_b\) = 15 ohms, and \(R_c\) = 20 ohms. Determine the total power of the system.
A3,495 W
B3,385 W
C3,560 W
D3,895 W
#3📜 EE Pre-Board August 2012📘 PowerhouseMedium
Power in a balanced 3 phase system is measured by two wattmeter method and it is found that the ratio of the two wattmeter readings is 2 is to 1. What is the power factor of the system?
A0.9
B0.82
C0.866
D0.707
#4📜 EE Pre-Board March 2013📘 PowerhouseMedium
An unbalanced wye-connected load connected to a 3-phase, 4-wire abc system consists of \(Z_a = 10 + j5\ \Omega\), \(Z_b = 8 + j4\ \Omega\) and \(Z_c = 20 + j0\ \Omega\). If the line to neutral voltage is 120 V, find the total power in watts.
A4,125
B3,312
C5,520
D2,843
#5📜 EE Pre-Board March 2013📘 PowerhouseMedium
In a 230 V, 3-phase, 3-wire system, two wattmeters are connected to measure the power. The ratio of the readings of the wattmeters is 2.5 is to 1. What is the power factor of the system?
A80.3%
B76.6%
C83.1%
D86.6%
#6📜 EE Pre-Board August 2013📘 PowerhouseMedium
A 220 V, 3-phase, 4-wire abc system supplies unbalanced wye-connected resistances of \(R_a\) = 10 Ω, \(R_b\) = 15 Ω and \(R_c\) = 20 Ω. Determine the total power of the system in watts.
A3,495
B3,560
C3,385
D3,895
#7📜 EE Pre-Board March 2014📘 PowerhouseMedium
Power in a balanced 3-phase system is measured by the two-wattmeter method and it is found that the ratio of the two wattmeter readings is 2 is to 1. What is the power factor of the system?
A0.9
B0.866
C0.82
D0.707
#8📜 EE Pre-Board March 2014📘 PowerhouseMedium
Two parallel connected loads A and B are supplied by a 440 v, 3 – phase, 60 Hz generator. Load A draws and apparent power of 100 kVA at 0.80 power factor lagging and load B draws an apparent power of 70 kVA at unity power factor. Determine the feeder current.
A202 A
B214 A
C212 A
D208 A
#9📜 EE Pre-Board August 2014📘 PowerhouseMedium
A 200 V, three-phase source is connected to two equal impedances of 7.07 + j7.07 ohms in parallel, with both connected in wye. What is the current per phase of the combination?
A−16.26 − j16.26 A
B16.26 + j16.26 A
C16.26 − j16.26 A
D−16.26 + j16.26 A
#10📜 EE Pre-Board August 2014📘 PowerhouseMedium
Three 40 Ω non-inductive resistances are connected in delta across 200 V, 3-phase lines. Calculate the power taken from the mains if one of the three resistors is disconnected.
A500 W
B1,000 W
C1,500 W
D2,000 W
#11📜 EE Pre-Board August 2014📘 PowerhouseMedium
Power in a balanced three-phase system is measured by the two wattmeter method and it is found that the ratio of the two readings is 2:1. What is the power factor of the system?
A0.5
B0.8
C0.866
D1
#12📜 EE Pre-Board March 2015📘 PowerhouseMedium
The phase b line voltage and the phase a line current of a balanced three phase system are \(v = 220\sin(\omega t + 210^\circ)\) and \(i = 10\sin(\omega t - 30^\circ)\), respectively. What is the power of the system?
A1,905 W
B5,716 W
C3,300 W
D3,810 W
#13📜 EE Pre-Board August 2015📘 PowerhouseMedium
A delta connected load of 9 + j12 Ω/phase is supplied by a 230 V, 3-phase source through a line with an impedance of 0.06 + j0.12 Ω/conductor. Find the load voltage in volts.
A220
B222
C224
D226
#14📜 EE Pre-Board March 2016📘 PowerhouseMedium
Three identical resistors are connected in wye across 220 v, 3-phase lines. The line current is12.7 A. To what value in volts should the line voltage be changed the same line current with the resistors connected in delta?
A98.6
B132.8
C120
D73.3
#15📜 EE Pre-Board March 2017📘 PowerhouseMedium
A 220 V, 3-phase, 4-wire abc system supplies unbalanced wye-connected resistances of 10 Ω, 15 Ω, and 20 Ω. Determine the total power of the system in watts.
A3,895
B3,560
C3,385
D3,495
#16📜 EE Pre-Board March 2018📘 PowerhouseMedium
A 480-V rms line feeds two balanced three-phase loads. If the two loads are rated as follows, Load 1: 5 kVA at 0.8 p.f. lagging Load 2: 10 kVA at 0.9 p.f. lagging Determine the magnitude of the line current from the 480-V rms source.
A17.97 A
B14.94 A
C13 A
D7.36 A
#17📜 EE Pre-Board August 2018📘 PowerhouseMedium
Three impedances \(Z_{ab} = 4 - j3\) Ω, \(Z_{bc} = 3 + j4\) Ω and \(Z_{ca} = 10 + j0\) Ω are connected in delta across a 220 V, three phase balanced source. What is the total power of the circuit?
