EE MODULE 1

100問 • 1年前

問題一覧

The power factor of a load on a 120 volt. 60Hz source is raised from 0.707 to 0.866 lagging by connecting a 53 micro-farad capacitor across the load. What is the true power of the load in watts?

682

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 negative sequence of line a?

10+j5.77 A

A capacitor of 2 microfarad is supplied from a source voltage 2 sin 2710 I volts instantaneous value. What is the maximum value of current?

25.13 A

Find live work in kWhr to in ton of a height of 55 ft for 10 gec The motor gear eficiency in 50%

0.091

The resistance 100 ohm, inductance 50 mH and capacitance 50 micro-farad are connected in series and across 240 volts source. What is the resonant frequency?

100 Hz

A circuit has impedance of 3.464+12.0 ohm is supplied from a source voltage of 240 Volts, 60 Hz. What is the current when resistance is reduced by 50%

91 A

An induction motor has 8 poles, 60 Hz, 3% slip. What is the rotor speed in rpm

873

Two transformers each rated 100 kVA, 13200/240 Volts are connected open delta. Determine the maximum kVA of the load.

173.2

The illumination at a certain distance is 800 lux what is the illumination in lux when the distance to the point is doubled?

200

The net energy required of a certain country in year 2000 was approximately 3x10 GWH. What is the equivalent value in quad?

10.24

The complex expression of voltage is 300 cis 90 deg. What is its instantaneous equation?

424.4 sin(wt+90°)

Power system has receiving current of 1.2 p.u. or current at the receiving end. 0.6 p.u voltage at the receiving end and 0.5 p.u. receiving power. When the base current is 160 amp and base voltage is 20 kV what is the power factor at the receiving end?

0.69

A circuit has 125 A base current and 25 ohms base impedance, find the KVA base?

390.625

A current is given by this equation i=2t^2+t2+3 a capacitor has an initial charge of 6.83 Coulomb What should be the charge of the capacitor in Coulomb after 5 sec?

375.8

A single band transmitter has a voltage supply of 230 volts. Voice peak produces a current of 15 ampere. What is the peak envelop power?

345

An 80 cm long conductor carrying a current of 3.6 ampere and seen right angle to the flux density of 0.95 tesla. What is the force in the conductor?

2.736 N

A three phase wye connected balanced load of 10 ohms each resistor connected to a 220 volts source. Determine the power in watts.

4.48

If the certain conductor has an area of 336,400 cmils, what is the radius of this conductor in cm?

0.737

A 110 V dc motor draws current of 30 A and is located 500 ft from the power source. What is the supply voltage if the diameter of the copper wire is 0.25 inch? Resistivity is 10.4 ohm-cmil per ft

115 Volts

A series loop contains the following circuit elements in order a 8-volt source, a 2 ks) resistor a 3 x resistor a\cdot16-v source and a 7 kt) resistor, Voltage sources are additive. What is the power absorbed by the 3 kΩ resistor?

12 mW

A 6 V car radio draws a current of 6 5 A. What resistance in ohms must be connected in series with it to operate it in a car with a 12 V battery?

0.923

Three resistors R1=9kΩ, R2=9 kΩ and R3=9 kΩ are connected in parallel across a 12-V power supply whose internal resistance is 1 kΩ. How much current is drawn from the source?

3 mA

Two batteries are connected in parallel to feed a 12 ohm load Batory and an internal remd of 6.3V atid intermal resistance of 1.5 ohms. Battery B has an open circuit emf of 6 V and an internal resistance of 2 ohms. What is the load current?

0.48 A

The resistance of a length of copper wire is 2.6 ohms at 20°C. The temperature coefficient of resistance at 20°C for copper is 0.0393/°C. What is its resistance at 75°C?

3.162 ohms

A certain copper wire has a resistance of 25 ohms at 10°C. Take the temperature coefficient at 10°C to be 0.00409/°C What must be the maximum operating temperature of the wire if its resistance is to increase by most 20%?

58.89°C

A 120 cm long conductor is carrying a current of 1.2 A and is situated at right angles to a field of flux density of 0.65 Tesla. Calculate the force on the conductor

0.936 N

What is the complex expression for a given alternating current = 250 sin (wt-25 degrees)?

160+j75 Amp

Find the value of impedance which requires -1540 VAR at 230 V rms and 10 A rms.

17.09-j15.39 ohms

For a series RLC circuit with elements R = 50Ω L = 8 mH and C=2.22 uF . What is the equivalent impedance of the circuit if its frequency is 796 Hz?

50-j50 ohns

Two impedances, Z1= 0.8+15 and Z2 = 8-j16 and a single-phase motor a od tincted in paralles across 200 Vrms, 60 Hz motor supply. The motor draws 5 KVA at 80% power factor lagging. Find the complex power of impedance Z₂?

1-j2 kVA

What are the two elements in a series circult connection having a current and voltage of i=13.42 sin (500- 53.4 degrees) A and v = 150 sin (500t+10 degrees) V?

R = 5.0 ohms and L = 20 mH

The impedance Z3 in series to the two impedances Z1=10+j10 ohms and Z2=20-j30 ohms that are connected in parallel. What is the value of the impedance Z3 in ohms that will produce resonant circuit?

-j5.4

A 100 pico-farad capacitor is connected in series with a coil having inductance of 100H and a resistance of 100 ohm. At what frequency will this network have unity pf

1.6 MHz

Find the current through a 0.1 microfarad capacitor at t = 0, if the voltage across it is -2e^-10^71 V

2 A

A balanced three-phase wye-connected load of 150 kW takes a leading current of 100 A, when the line is 2400 V, 60 Hz. What is the capacitance per phase?

205 uF

A balanced delta connected load of 14-B ohms per phase is fed by a 380 V, three-phase system. Find the reactive power.

52 kVARS

The phase currents in a wye-connected unbalanced load are la=44-133, lb=-32-124. and Ic=-40+2i A. What is the positive sequence current for phase A?

40.8 - j8.9 A

A 240 V (line to neutral) three-phase source is connected to three 10 ohm resistance loads with both source and load in the Y-configuration. Determine the current in each phase

24 A

Given the following sets of symmetrical components currents, determine the phase B current Current Magnitude Angle, degrees Ia0 1.0 75 Ia1 1.0 15 Ia2 1.0 -45

0.259+j0.966 amp

A transformer when it is operated as a conventional two winding transformer is rated 10 MVA, 12/1.2 KV, 60 Hz. Under these conditions, its series resistance and reactance are given as 2% and 7% pu respectively. This transformer is to be used as 13.2/12 kV step-down autotransformer in a power distribution systern, What is the autotransformer's new capacity in MVA?

110

A single phase induction motor is rated 240 V, 150 A and 0.707 power factor. What is the size of the capacitor in KVAR which must be place in parallel with the circuit to improve the power factor to 95% lagging?

17.1

A transmission line cable consists of 26 strands of identical copper conductor, each 1.255 mm in diameter. The length of the cable is 10 km but because of the twist of the strands, the actual length of each conductor is increased by 5%. If the resistivity of the copper is 1.72x10^-8 ohm-meter, what is the resistance of the cable in ohms?

5.66

A single-phase transmission line 90 km is made up of hard drawn copper 500 mils in diameter. If the resistivity of the hard drawn copper at 20°C is 1.77 x 10 ohm-meter. Determine the resistance at 20°C

0.1394 ohms

A 69-kV three phase transposed line is composed of one ACSR 336,400 cmil, 36/7 Linnet conductor per phase with a horizontal configuration D12=5ft.D23=5 ft and D13=10 ft. The conductors have a diameter of 0.721 inch, resistance of 0.306 ohm per mile and gmr of 0.0244 ft. What is the reactance for 12 miles line.

8 ohms

A single circuit, transposed overhead transmission line is composed of two-conductors per phase. The diameter of each conductor is 5 cm. The distance between the center of the bundle is 5 m. What is the inductance per km per phase of the line. Use 30 cm spacing between conductors of the bundle

0.8825 mH

A three-phase circuit, 60 Hz, 230 kV transposed transmission line is composed of two 1272 MCM, 54/19 conductors per phase with horizontal configuration. The bundle spacing is 50 cm while phase spacing between the centers of the bundle is 10 m. If the GMR of the ACSR conductors is 0.0466 ft, find the inductive reactance in ohm/km/phase of the transmission line?

0.3775

A 115-kV three-phase transposed transmission line in composed of two ACSR 336,400 cmil, 36/7 Oricle conductors per phase with horizontal configuration D₁₂=7 ft. D=7 ft and D. 14 ft. The line spacing as measured from the center of the bundled conductors is 6 inches. The conductors have a diameter of 0.741 inch a GMR of 0.02265ft. Find the capacitance per phase for 20 km of the line in microfarads

0.2609

A 75 kVA, 13.2 kV/240 V delta-wye distribution transformer has a resistance of 1% pu and reactance of 8% pu. What is the transformer's phase impedance referred to the high voltage side?

69.70 + j557.57 ohms

A generator of 50 MVA, 4 kV, X'd = 25% and a transformer of 50 MVA, 4 kV delta/115 kV wye-grounded operating on a 3.8 kV tap where Xt"=10% to be connected into a single equivalent reactance. What is the single equivalent reactance on a 100 MVA, 110-kV base?

j 0.8241 pu

The effect of the dielectric is to

increase the working voltage

What will happen to an insulating medium if subjected to a voltage more than its basic impulse insulation level? It will

punctured

What type of motor is used for food mixer?

Universal

Receptacle outlet shall be located not more than

500

A Diesel Power plant is best suited as

Standby Plant

What is the minimum distance between receptacle outlets in meters of a show window

In Philippine Distribution Code Purposes. Which of the following is riot belong?

To ensure that distribution system will be operated by only one distribution company.

The resistance of conductor increases

when length of conductor increased

Which type of DC motors is not directly connected to the load?

Shunt

In a dc motor which one is not considered in determining the speed?

Thickness of armature lamination

What is the device used and connected to a generator to prevent motorizing?

Reverse power relay

In dwelling units, at least one receptacle outlet for hallways more than _______ m

A device used for switching, carrying and interrupting a system for both fault and full load condition

Circuit breaker

Factor in determining specific resistance

Nature of material

Appliance receptacle outlet in dwelling , unit for specified appliances shall be installed within __________ mm of the intended location

1,800 mm

What is the minimum ampacity of feeders w/ motor and other load connected.

125% motor FL current plus other current

Insulation of wire is based on

Peak

Outdoor outlets of one-family dwelling shall be installed not more than ______ mm above grade level at the front or back of the family dwelling

2000

What is the best conductor of electricity?

Graphite

In Philippine Grid Code, which notice issued by than the capacity of the largest Generating unit is higher. system operator when the contingency reserve is less or power import from a single interconnection, whichever

Yellow alert

In Philippine Grid Code, which alert issued by system operator when the contingency reserve is zero, a generation deficiency exists, or there is critical loading or imminent overloading of transmission lines and equipment.

Red alert

In Philippine Grid Code, which notice issued by system operator when peace and order problems exists which may affect the grid operations

Security alert

In Philippine Grid Code, which notice issued by system operator a weather disturbance has entered the Philippine Area of Responsibility.

Weather Disturbance alert

Refers to the condition when the loading of transmission lines or substation Equipment is between S0 percent and 100 percent of the continuous rating.

Critical Loading

In Epira law. A voltage level exceeding 1000 volts up to 34,5kV is classified as

Medium Voltage

The grid shall be considered at normal state when the loading levels of the transmission line and substation equipment are below _______ of their continuous rating.

90%

The grid shall be considered at normal state when the frequency is within limits of _______ and _______

59.7Hz & 60.3Hz

The companent of contingency reserve, which is synchronized to the grid and ready to take on load

Spinning Reserve

Spinning reserve is also called

Hot standby Reserve

Refers to a generating unit that has fast start capability and can synchronize with the grid to provide its declared capacity for a minimum period of 8 hours.

Back-up Reserve

Back-up reserve is also called

Cold Standby Reserve

Generating Capacity that is intended to take care of the loss of the largest Synchronized Generating unit or the power import from a single grid interconnection, whichever is larger

Contingency Reserve

If the transmission voltage is increased, the percentage resistance drop will

decrease

The power transmission capacity of the transmission line is

proportional to the square of the voltage

The material used for fuse wire must have

low melting point and high specific resistance

The Buchholz relay is used to protect the

oil immersed transformers against all internal faults

To protect the power transformer (Y-Y woth neutral grounded) against fault, the CT will have

∆ - ∆ connection

The location of the lightning arrester is

near the transformer

Which of the following distribution systems gives the greater reliability

ring system

The power intended to be available even under emergency condition is called

cold reseve

Series capacitor are used to

compensate for line inductive reactance

The short circuit in any windings of the transformer is the result of

impulse voltage

Which of the following relays are used for phase fault on long line?

impedance relays

The protection from negative seqeunce currents is provided for

generators

AC system has the following, disadvantages over DC sytem

charging current exists

The voltage reguationis an imprtant factor for the design of

feeder

Which of the following breaker has high reliability and minimum maintenance?

SF6 circuit breaker

If the capacitance of the transmission line is increased, the transmitted power will

increase

Which of the following method may be used to inject reactive power in the transmission line?

shunt capacitor

The guard wire is firmly connected with

earth wire

100

What is the complex expression for a given alternating current=250 sin (wt-25 degrees)?

160-j75 Amp

DC CIRCUITS POWERLINE

premopremo remo · 75問 · 2年前

DC CIRCUITS POWERLINE