EE MODULE 3

100問 • 1年前

問題一覧

Suppose a voltage surge produce 280 volts at moment, at what percentage to its power output of a 240V, 110 watts increase?

36%

A 600 volts, 30,000 ohms voltmeter is used in making an instrument. The voltmeter when connected across the source it reads 240 volts and when connected in series with the insulation it reads 6 volts Find the insulation resistance.

1.17 mega-ohms

Resistors A B & C are connected in series. Resistor A is 60 ohms, Resistor B takes 40 volts when current is 0.5 ampere. Calculate the value of resistor C when supply voltage is 120 volts.

100 ohms

A 2.4 kW heater is operating 3 hours per night for 30 days The energy cost is P9.0867/kWh Determine the cost of energy used in 30 days.

P654.24

What is the bandwidth of a parallel resonant circuit with 8 ohm resistance, 40mH inductance and 0.25 micro-farad capacitance?

200 rad/sec

What is the Q Factor of a series resonant circuit consisting of 2.4 ohm resistance and 30 micro-farad capacitance. Angular frequency is 1000 rad/sec

13.9

Two impedances Z₁=0.8+j5.6 ohms and Z₂=8-j16 ohms and a single phase motor are connected in parallel across a 200 V rms, 60 Hz supply. The motor draws 5 kVA at 0.8 power factor lagging. A capacitor is connected with the loads, find the kVar to improve the power factor to unity

8 kVar

The force between two equal charges is 500 N when separated by 4mm, Find the number of electrons on the spherical charge.

5.89x10^12

A symmetrical three phase 240 volts supplies a balanced delta connected load of 6-18 ohms per phase. What is the line current?

25+j32 A

The loads consist of a resistance R in parallel with a capacitor of reactance X. The load is fed from a single phase supply through a line of impedance 8.4+j11.2 ohms. The rms voltage at the load terminal is 1200 volts, and the load is taking 30 kVA at 0.8 leading power factor. Find the supply voltage

1.2+j0.35 kV

Given the voltages Van=84.5+j84,5 volts and Vbn=84.5 - i * 84 volts. Find Vab.

0+j169 V

A wye connected load has a per phase impedance of 10+j 1 ohms. It is supplied by a wye connected balance source. The voltage Van 120/0° volts. What is the line A current?

11.88-j1.19 A

In a three phase balanced delta connected load with one line open, line A has 20 A. Assume line A is the reference and the line c is open. What should be the zero sequence of line a current?

An antenna 0.02 sq.m area frequency of 300 MHz at 0.3 mV per km. What is magnetic field intensity H?

0.8 nA/m

A long straight steel metal rod has a radius of 5 cm and a charge per unit length of 30 nCoul/m. Find the electric field 100 cm from axis of rod. The distance measured perpendicular to the axial rod.

540.9 V/m

A coil of inductance 25 H with initial current of 1 ampere is suddenly connected to a source voltage of V=8.9+(3t) volts. What is the current in the inductor after 5sec?

3.329 A

A motor is supplying 70 N-m to a load. If the shaft of the motor rotates at 1500 rpm, determine the power developed of the motor

10,993 W

A 220 volt de shunt motor with armature resistance of 0.6 olim draws armature current of 60 ampere at full load. What is the resistance to be connected in series if the starting armature current is needed to be 150% of full load

1.84

A 4-pole wave-wound armature has 144 slots with two call sides per slot, each coil having two turns. If the flux per pole is 20mWb and the armature rotates at 720rpm. What is the induced voltage?

276.48 V

A 300 HP motor 95% efficient, with 80% power factor. What is the minimum KVA of single phase transformer to be connected open delta?

17/

Taps at the transformer must be done at ______

high voltage

A 15 Hp, 4 pole 60 Hz, wye connected, 208 volts induction motor draw 12 kW from the line have losses as follows: Stator copper loss 900 W, Rotor copper loss 300W, Iron loss 800W and Friction & Windage Loss 100W. Determine the speed of the motor in rpm.

1747

A 3-phase, 60 Hz wye connected round rotor synchronous generator rated 10 kVA, 230 volts has a synchronous reactance of 1.2 ohm per phase and an armature resistance of 0.5 ohm per phase. Calculate the percent regulation at full load with 0.8 lagging power factor.

21.8%

-4.9%

A generator at no-load operates 61 Hz, slope 1MW/Hz. Load 1= 1.0 MW and load 2=0.8MW are connected. Find the frequency before and after adding the load 2

60 Hz & 59.2 Hz

A three phase transmission line with horizontal configuration such that D 12 =D 21 ,=12m. D_{11} = 2D_{74} The diameter of conductor is 3.28 cm. Determine the capacitive reactance if the length is 125 miles

1.619 ohms

The selected bases are the rating of transformer 100MVA, 220/110 kV. What is the base impedance referred to primary?

484 ohms

The positive, negative and zero sequence reactance of a 15 MVA, 11 KV, three phase wye connected generator are 11%, 8% and 3% respectively. The neutral of the generator is solidly grounded and the generator is excited to the rated voltage on open circuit. A line to ground fault occurs on phase a of the generator. Calculate the fault current.

10,736 A

Two bus system has: Z11 = 0.11565 Z12 = Z21 = C 0.04580 and Z22 = -j0.13893 pu, if an impedance Zb =j0 pu is connected between buses 1 and 2. Find the new value of Z22

j0.12352 p.u

A three phase wye-delta connected, 50 MVA, 345/34.5 kV transformer is protected a differential relay Calculate the overline CT ratio on the transformer primary

150:5

What is the standard device number for distance Relay?

A lamp of 80 cd is placed 4cm from an object. If the lamp is to be replaced by a 40 cd, what must be the distance of the object to receive same illumination?

2.83 cm

The power plant have a maximum demand of 100 MW and connected lead of 160MW. Annual Generation of 500 GWH. Calculate the demand factor.

62.5%

A certain amount of fuel can be converted into 3x10 quad's of energy in a power station. If the average load on the station over 24 hour period is 60 MW, determine the number of days the fuel last. Assume 30% overall efficiency of the power station.

183

A 120 volts shunt motor takes armature current of 75 A at full load. Armature resistance is 0.2 ohms and brush contact drop is 2 V. Find the starting resistance to limit the current of 150% of rated load when the counter emf is 25% of the armature voltage Va

0.582 ohms

A balanced delta connected load contains 8+14 2 per phase while a balanced Y-connected load consist of 2-11 2 per phase. Both loads are connected in parallel to three phase three wire system in which 120 volt line voltage at the load. The line extending the loads and the source each have a resistance of 0.2 ohm. Find the power loss in the wires

1.42 kW

A manufacturing plant takes 200 kW at 0.6 power factor, from a 600 volts, 60-cycle 3-phase system. It is desired to raise the power factor of the entire system to 0.9 by means of a synchronous motor, which at the same time to drive a dc generator, requiring that the synchronous motor take 80 kW from the line. What should be the kVA rating of synchronous motor.

154

In the balanced three-phase circuit, Load 1 draws 80 kW and 60 leading kvar, Load 2 draws 120 kW and 160 lagging kvar. The line voltage of the system is 1000 volts. Find the line current at the generator terminals by adding the line currents of the two loads

129 A

A power station supplies 60 kW to a load over 2500 ft of 000, 2-condutor copper feeder the resistance of which is 0.078 ohm per 1000 ft. The busbar voltage is maintained at 600 volts. Determine the current.

107.5 A

A three phase power of 3600 MW is to be transmitted via four identical 60 Hz transmission lines for a distance of 300 km. From a preliminary line design, the phase constant and the surge impedance are given by B=9.46x10^- 4 rad/km and Zc = 343 ohms respectively. Based on practical line loadability criteria, determine the suitable nominal voltage level in kV for each line. Assume Vs=1.0p.u., Vr=0.9 p.u, and power angle delta = 35.87 deg

400

A refrigerator rated 500W has a cooling capacity of 86 kJ/min. What is the Energy Efficiency Ratio (EER)

A battery charger forces 300 coulomb of positive charge across a potential difference of 5 volts. Calculate the potential energy of the battery

1500 joules

The electric field intensity in the space between two charges is 3 kV/m. What is the distance between the charges if the potential difference between them is 500 volts?

16.7 cm

What is the minimum ampacity of conductor to supply a 25 Ampere Electric Heater

31.3 A

A 400m long lossless transmission line of impedance 100 ohms characteristic resistance terminates in a 60 ohm resistance. A 400 volts do source having internal resistance of 300 ohms is connected to the line at t=0. Calculate the sending and regeiving end voltage reflection coefficients of the For Powerline Reviewges Only line

1/2, -1/4

Where multiple rod, pipes or plate electrodes are installed to meet maximum of 25 ohms resistance to ground, they shall not be less than______ mm apart.

1800 mm

Two batteries, 10.5 volts with internal resistance of 1.5 ohm and 9 volts with internal resistance of 1.2 ohms are connected in parallel with load resistance R. What is the value of load resistance if it consume 6 watts?

14.2 ohms

A Industrial plant has a peak load of 80 MW, daily load factor of 90%, daily capacity factor of 75% and plant use factor of 80%. Calculate the daily energy consumption.

1620 MWHR

A three phase transmission line is designed to deliver 190.5 MVA at 220 kV over a distance of 63 km The total transmission line loss is not to exceed 2.5% of the rated line MVA. If the resistivity of the conductor material is 2.84x10 ohm meter, determine the required conductor diameter.

1.89 cm

A transformer has a primary winding of 2000 turns and of 2400 volts. If the secondary winding has 500 turns, what is the value of secondary voltage?

600 volts

It is required to increase the power factor of a 500 kW three phase balance load from 65% lagging to 85%lagging. The line voltage is 2400 volts, 60 Hz. Specify the capacitor required to increase the power factor of this wye connected load in micro-farad per phase

126.5

A generator having a solidly grounded neutral and rated 20 MVA, 13.2 kV has X.= X₂=30% and Xo=15%. Calculate the fault current for a line to line fault?

2525 A

A circuit breaker having a nominal rating of 34.5 kV and a continuous current rating of 1500 amperes has a voltage range factor of 1 75. Rated maximum voltage is 38 kV and the rated short circuit current is 24 kA, Find the rated short circuit current at 34.5 kV

26,000 A

A coil of 500 turns carrying a current of 200 micro- amperes and the axial length of the coil is 3.0 cm. If the torque is 0.5x10 N-m and diameter of the core is 1.0 cm, determine the Flux density in Tesla. Consider the conductor are at right angle to the flux.

1.667 Telsa

Three capacitors are connected in series 6,7 and 18 micro-farad across 100 volts source. Find the voltage across 7 micro-farad capacitor

39 V

A three phase 60 Hz transposed transmission line has a flat horizontal spacing configuration. The line reactance is 0.486 ohm per km. The conductor geometric mean radius is 2.0 cm. Determine the spacing D in meter.

10 m

A factory with 500 kVA load at 0.707 power factor lagging needs 150 kW additional load at 0.8 power factor leading. Find the overall pf and total kVA.

0.9 lagging & 558 kVa

A simple power system consist of Generator of reactance 10.26 p.u., transformer of reactance 10. 16 p.u. and a circuit breaker connected to a system of reactance j0.19 p.u. A three phase fault occurs between transformer and circuit breaker. What is the fault current in per unit?

2.38 p.u

Two port network consist of Z11 = Z22 = j0.16 and Z12 = Z21 = 10.1 ohm. Find Z3 when Zb=0.34 ohm is connected from bus 1 to new .

j0.5

A transformer has induced emf of 220 V at 60 Hz, what is the induced emf when the frequency is 50Hz?

183.3 V

Fuse in motor provides

short circuit protection

In grounding, which is permitted as grounding electrode? I.Building Metal Frame II. Metal Water pipe

both II & I

Which is not a standard branch circuit rating

25 A

A circuit must be protected against

overload, short circuit, earth leakage, voltage spikes

The location of the disconnecting means from the second building I. disconnecting means must be located outside the 2nd building of accessible location II. Disconnecting means must be located inside the entrance of the 2nd building.

both I & II

What is the minimum clearance of service drop above the driveway?

3700 mm

Thermal protection is mainly used as _______ protection?

Overload

What is the modern light sensor used in fax machine

Charged Coupled device

What is/are the fundamental process of resistance welding?

heat and squeeze

In single phase, 3-wire system, the middle conductor must be which of the following

grounded wire

How many three way and four way switches are needed for a lighting system controlled in five different location?

2-3 Way & 3-4 Way

________ is also known as "Cold Standby Reserve

back up reserve

Which of the following is included in the calculation of reliability indices of Distribution Code?

34.5 kV line outages

What is the maximum voltage in dwelling unit?

230 V

What is the minimum diameter of grounding rod?

16 mm

What is the minimum size of underground service lateral conductor?

8.0 sq.mm.copper

Plate electrode shall be installed of not less than _________ mm below the surface of the soil.

750 mm

In the Philippine Electrical code the branch circuit permissible load is _____ %

The main purpose bonding jumper is to connect equipment grounding conductors and _________ to the grounded conductor of the system.

Service disconnect enclosure

In an alternating current circuit, the voltage lags the current. What element should be placed in parallel to the circuit to improve the power factor to unity?

Inductor

Which of the following is not considered exterior wall space in dwelling?

sliding panel

What is the purpose of earthing?

Prevent electric shock

A gas turbine power plant usually suits for

peak load operation

Which of the following plant is expected to have the longer expected life

hydro electric

The purpose of the grid system is to

interconnect the power station

One of the line parameters which is neglected in short transmission line is

capacitance

The economical section of feeder can be obtained by applying

Kelvin's law

Energy radiated continuously in the form of lighting waves is called

luminous flux

The luminous intensity of a lamp is expressed in

candela

The relative permeability of paramagnetic substance is

slighlty greater than one

Which of the following has the highest value of relative permeability

supermalloy

The torque of a synchronous motor when reach its synchronism is called

Pull in torque

Month of March is the fire prevention month, what is the Electrical Safety month?

April

What angle will be the illumination be halved to the object?

Minimum thickness of concrete in a concrete encased electrode is

50mm

The phenomenon of rise in voltage at the receiving end of the open circuited or lightly loaded line is called

Ferranti effect

What is the IEEE standard device number for instantaneous overcurrent relay

Induction motor is running at rated load. What will happen when one winding of a delta connected motor is suddenly cut?

will burn

Energy stored in an inductor is given by

1/2 Li^2 joules

100

Which of the following is a vector quantity?

Magnetic field density

DC CIRCUITS POWERLINE

premopremo remo · 75問 · 2年前

DC CIRCUITS POWERLINE