Energy Efficient Electrical Systems For Buildings 1st Edition Moncef Krarti - Solutions

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Using your location, estimate the total electricity generate from a PV system per unit of roof area using a single crystal technology with a rated efficiency of 13.5%. You may use PV Watts or any other analysis tool to estimate the electricity generation for your PV rooftop PV system.
Compare the electricity generated by a rooftop PV system for various tilt angle for your specific house location. You can use PV Watts or a similar tool. Conclude on the optimal tilt angle.
Determine the wire size needed to maintain the voltage drop below 2% for a 48-V PV array located 200 ft away from the electrical panel. The short-circuit current for the array is estimated at 36.5 A.
Design the specifications and the layout for the following standalone PV system made up of six, 12 V, 51 W module. Each module has the following characteristics: ISC = 2.85 A and VOC =18.2 V.• A set of batteries rated at 600 Ah at 12 V• An inverter rated at 400 W with 90% efficiency with a
Design the specifications and the layout for a grid-connected PV system made up of 12, 50 V, 200 W modules. Each module has a short-circuit current of 4.5 A and open circuit voltage of 58 V. The array is configured to have 4 parallel connected panels with three modules each. An inverter rated at
Provide the actual efficiency and the PURPA efficiency for 10 MW cogeneration system with an electrical efficiency of 30% and thermal efficiency of 40%.
A small cogeneration system rated at 100 kW rated at 80% overall efficiency and 30% electrical efficiency. Estimate the potential cost-effectiveness of deploying this system for a building that purchased electricity at $$0.15/kWh$ and generate heat from 85% efficient boiler using natural gas at
Determine the efficiency of 500 kVA, three-phase transformer if the open test indicates a loss of 0.900 kW, and the short-circuit test provides a loss of 2.550 KW.
Determine the percent regulation of a three-phase 480 Y/277-V transformer if the secondary voltage for full-load conditions is measured to be 269 V.
Determine the percent impedance of a 480 Y/277–208 Y/120 V transformer if the short-circuit test provides a primary voltage of 25 V.
Determine the change in the size of the service entrance including the main feeder and panel rating required to electrify an 800-ft2 (74 m2) apartment unit served by 208Y/120-V with the following electrical loads: 8 kVA range (208-V), 3 kVA water heater (208-V), 0.8 kVA dishwasher (120-V), and 0.7
Determine the circuit breaker and the feeder size using THW(Cu) for a 480Y/277 V lighting panelboard serving 100-kW load with a power factor of 0.95 for a commercial building.
Determine the circuit breaker and the feeder size using THW(Cu) for a 208Y/120 V power panelboard serving 100 receptacles in an office building. The power factor for the load associated with the receptacles can be assumed to be 0.90.
Determine the breakeven costs for installing a 1,000-kVA transformer for a new building with an efficiency of 99.28% rather than 98.90%. If the annual load factor is 80%, the average building’s power factor is 0.90, and the electricity cost is $0.12/kWh. Consider two options for the economic
A building has an electrical load of 500 kVA at 0.70 power factor, lagging.Among the load is a 50 HP induction motor with an efficiency of 0.93 and a power factor 0.90 (lagging). It has been decided to replace the induction motor with a synchronous motor of the same size, efficiency, and power
A one-phase motor rated at 5-hp and 240-V with an efficiency of 0.90, and a power factor of 0.85, lagging. Determine the equivalent impedance for the motor.
A three-phase motor rated at 100-hp and 460-V with an efficiency of 0.92, and a power factor of 0.90, lagging. Determine the equivalent impedance for the motor.
A coil of # 12 AWG copper wire wound in a single layer on a cylindrical form so that the mean diameter of each turn is 6.0 in., and it has a resistance of 4.0 Ω. How many turns of wire are there in the coil?
Consider the following circuit setup shown below. Determine the voltage drop across the 7 Ω resistor. 120 V DC 12 www 5 H 402 www 50 70 V
An automobile generator with an internal resistance of 0.5 Ω develops an open-circuit emf of 9.0 V. The storage battery has an internal resistance of 0.03 Ω and open- circuit emf of 7.0 V. Both sources are connected in parallel to 0.8 Ω load.Determine the generator current, battery current, and
A 5 A current flows when a neon lighting fixture is supplied by a 120 V power source. If the current lags the voltage by 75°, determine the power factor and the real power consumed by the fixture.
Determine the rating of a generator in kVA for a home in order to ensure that the following systems and appliances can be operated in case of a long-term power outage:(a) Air conditioner rated at 9.5 A, 120 V, and pf = 0.90 (lagging)(b) Freezer rated at 4.5 A, 120 V, and pf = 0.85 (lagging)(c)
A 240 V, single-phase load has a resistance of 3 Ω and an inductive reactance of 4 Ω. Calculate(a) The impedance of the load(b) The power factor of the load(c) The power consumed by the load
For a single-phase circuit served by an AC power source:(a) Determine the total impedance at 60 Hz of a circuit consisting of a 0.25 H inductor with a 100 Ω resistance and a 50 μF capacitor, all connected in parallel.(b) If the resistance, inductor, and capacitor are connected to 120 V AC source,
A 1 horsepower motor is connected to 120 V, 60 Hz AC source and has a pf = 0.80 (lagging) and an efficiency of 0.90. A capacitor is connected in parallel with the motor in order to correct its pf to 0.95. Determine(a) The current drawn from the source with and without the capacitor.(b) The rating
A motor for a blender can be modeled as a resistance of 10 Ω and an inductance of 25 mH connected in a series and supplied by a 120 V, 60 Hz source. Determine(a) The real power consumed by the motor(b) The power factor of the motor(c) The capacitor needed to be connected in parallel to the motor
A single-phase induction motor draws 250 W at a power factor of pf = 0.80 (lagging) when connected to 120 V, 60 Hz source. Find the capacitance needed to correct the pf of the motor to unity (i.e., pf = 1.0).
Find the real power and the power factor for a load whose impedance is 60 Ω < 60° when connected to an AC source of 120 V and 60 Hz.
Determine the capacitance that can increase the overall power factor to 95% lagging when connected in parallel with a load that draws 1.0 kW at a 70% lagging power factor from a 240 V, 60 Hz source.
Find the capacitance that minimizes the source current when connected in parallel with a single-phase induction motor drawing 10 A at a power factor of pf = 0.80 (lagging) when connected to 120 V, 60 Hz source.
A synchronous motor capable of operating with a leading power factor draws 10 kW from a transformer while driving a fan. The remainder load on the transformer consists of 100 kW with 0.80 lagging power factor. Determine(a) The reactive power needed from the motor for the overall power factor to be
Consider a motor rated 840 W with 70% power factor operating from a 120 V, 60 Hz, one-phase source. Determine(a) The source current if a 308 μF capacitor is added to the motor in series(b) The value of the capacitance that must be placed in parallel with the motor to increase the overall power
A 200 HP induction motor with a power factor of 0.65 and an efficiency of 90% is supplied by a 3-ϕΔ-connected 480 V AC source.(a) Show the power triangle for the motor.(b) Determine the impedance of the motor (assume three equal impedances, one per phase).(c) Calculate the capacitance in kVAR
A manufacturing plant has an electrical load of 5000 kW at 0.80 power factor, lagging. It has been decided to replace a 500 HP induction motor that drives a pump. This motor operates at an efficiency of 96% and a power factor of 0.90, lagging. A synchronous motor is purchased as the replacement and
For one-phase 10 kVA transformer, determine the turns ratio if the primary and secondary voltages are 120 and 240 V, respectively. Estimate the primary and secondary currents.
A one-phase transformer has 220 V in the primary and 110 V and 125 A in the secondary. Assuming it as an ideal transformer (i.e., 100% efficient), determine the rating of the transformer in kVA.
If the secondary phase current of a 480Y/277–208Y/120 V transformer, a three-phase transformer, is 10 A, estimate the primary line current and the total primary power used by the transformer in kW if the load has a power factor of 90%. Assume the efficiency of the transformer to be 99.0 %.
A three-phase transformer 13.6 kV–480Y/277 V serves a building. Determine the primary and secondary line currents if the rating of the transformer is 500 kV. Estimate the turns ratio of the transformer.
A three-phase transformer in a large building steps down the primary voltage of 13.8 kV (line-to-line) to a secondary voltage of 208 V (line-to-line). The transformer rating is 5000 kVA. Specify the line and phase voltages and currents of the transformer’s primary and secondary windings for the
A one-phase 500 kVA 240/120 V transformer is reconnected as an autotransformer:(a) Calculate the currents in each part of the autotransformer and determine its power rating if it is reconnected as a step-down 360/240 V autotransformer. Show the connection details of the autotransformer.(b) Repeat
In a building, it is found that 60 fluorescent luminaires are needed as well as 90 receptacle outlets. Each receptacle has a load of 180 VA and operates at 120 V with a power factor of 0.90 while each fluorescent luminaire has four lamps and is designed to operate at 120 V and requires 2.5 A. Each
Estimate the cost savings for replacing a 750 kVA transformer of an efficiency of 99.2 % by an energy-efficient transformer of 99.6 % if the average power factor of the transformer load is 85% and the cost of electricity is $$0.12/kWh.$ The total annual full load hours for operating the
A 200 HP induction motor with a power factor of 0.65 and an efficiency of 90% is supplied by a three-phase Δ-connected 480 VAC source.(a) Show the power triangle for the motor.(b) Determine the impedance of the motor (assume three equal impedances, one per phase).(c) Calculate the capacitance in
A commercial building has an electrical load of 2000 kW at 0.80 power factor, lagging. It has been decided to replace a 100 HP induction motor that drives a pump. This motor operates at an efficiency of 94% and a power factor of 0.90 , lagging. A synchronous motor is purchased as the replacement
Determine the motor speed in rpm and rad/s for an induction motor with a 2% slip and six pole for two cases of voltage source frequency(a) f = 60 Hz and(b) f = 50 Hz.
A four-pole squirrel-cage motor has the following characteristics:• Power input at a rated load is 4200 W with a power factor of 0.60.• Rated speed is 1150 rpm.• Resistance of each stator windings (there are three) is Rs = 0.16 Ω.The motor is supplied by a three-phase source with
Consider a 50 HP induction motor with a nameplate rated energy efficiency of 92% and a power factor of 0.85.Determine the required size in kVAR of a capacitor to be installed in parallel with the induction motor so that the power factor becomes at least 0.95.
A commercial building is subject to an electricity rate schedule that requires a demand charge of $2.50 per kVA per month. The electrical load of the building consists of (a) a group of ten (10) identical induction motors, (b) a plug load of 200 kW with a power factor of 0.90, and (c) of lighting
The load in a building panel is 120 kW at 480 V and is three-phase with a low power factor of 0.75 lagging. This power factor is to be corrected to 0.95 lagging. A motor rated at 60 Hz, 70 HP, 1200 rpm, and an efficiency of 0.88 is used to correct the system power factor. The panel is operating
A building has a total load of 150 kVA and a power factor of 0.85 (lagging). Among the electrical load, there is a 40 HP, three-phase, 60 Hz, 480 V induction motor with an efficiency of 0.92 and a power factor of 0.80 (lagging). Calculate the following:(a) The line current required by the
For a 20 HP three-phase induction motor with a nameplate rated voltage of 208 V energy efficiency of 90.5 % and a power factor of 0.87. Determine the impact of 5% overvoltage on the energy efficiency, the full-load current, and the power factor of the motor.
A supply fan motor for an air handling unit of a variable air volume system is rated at 20 HP with 88% energy efficiency. The fan is operated during 5500 h/year according to the following load profiles:(a) 100% load, 5% of the time(b) 80% load, 40% of the time(c) 60% load, 50% of the time(d) 40%
A 50 HP motor is to operated 4500 h/year at 80% load. A premium-efficiency motor has an energy efficiency of 93.4 %, compared to 91.2 % for the standard-efficiency motor. Calculate the annual energy use savings in kWh when using the premium efficiency instead of the standard-efficiency motor.
An induction motor is rated 60 HP, three-phase, 60 Hz, 460 V, 1760 rpm, and a power factor of 90%.(a) Estimate the efficiency of each motor if its line current is 70 A.(b) Determine the number of poles, the slip (%), and the torque delivered by the motor.
A motor control center (MCC) has three induction motors each rated at 40 HP and 480 V and four induction motors each rated at 30 HP and 480 V. Each 40 HP motor has an energy efficiency of 0.92 , a rated speed of 1772 rpm, and a power factor of 0.85 . Each 30 HP motor has an energy efficiency of
For a series R–L circuit, it can be shown that the rms (I.E., effective value) of the asymmetrical fault current is given by the following equationwhere θ = f × t is time in cycles X = L/ω = 2π × f × L is the reactance of the inductance Iac is the rms of the ac fault current (also called
A dwelling unit is supplied by a single-phase, 120/240 V service. The electric load of the unit includes.(1) 7000 VA water heater, 240 V; (2) 800 VA vent fan, 120 V;(3) 1200 VA compactor, 120 V; (4) 5000 VA dryer, 240 V; and (5) 6500 VA range.Each appliance is served by one branch protected by a
Determine the size of molded-case circuit breakers and associated number of poles for the following loads in a dwelling served by 120/240 V system: 1.8 kVA dishwasher, 120 V; 1.2 kVA compactor, 120 V; 1.0 kVA disposal, 120 V; 0.5 kVA vent fan, 120 V; 16 kVA range, 240 V; 4.5 kVA dryer, 240 V; 15
Consider a panelboard for a commercial building supplied by a 480Y/277 V, threephase feeder. The panel has the following loads:• A lighting system of a total power 45 kVA with a power factor of 0.93• A 15 kVA resistive water heater with a power factor of 1.0• A motor rated at 10 kVA and a
Consider the distribution system of a commercial building shown in the following diagram. Select the frames and trip ratings for all the power circuit breakers for the various panels and motors as well as the power circuit breaker at the secondary main feeder for the two options:(a) The secondary
Determine the size of the equipment grounding copper conductors for a panel that is served by 2/0 THW (Cu) and 400 A circuit breaker.
Consider a 480Y/277 V panelboard that serves the following loads for an office building:• Lighting: 15.0kVA at pf = 0.95• Resistance Heater: 9.0 kVA at pf =1.00(a) Select the proper circuit breaker for the panelboard.(b) Size the equipment grounding conductor (Cu) for the panelboard.
For an office building, a 208Y/120 V power panel has the following loads:• Receptacles with a total load of 30.00 kVA at PF = 0.90• Heaters with a total load 12.00 kVA at PF = 1.00(a) Determine the proper frame size and trip rating for the power circuit breaker protecting the panel. Assume an
Determine the copper service grounding conductor required for a service entrance with 3 parallel 300 MCM copper feeders.
Determine the potential damages incurred by an electrical distribution system when 2000 A ground-fault current occurs for 10 cycles.
Determine the ampacity rating of each of the 12 #4 THW (Cu) conductors placed in the same conduit.
Determine the ampacity of each of 5 #8 THHN (Cu) conductors installed in an area with a surrounding ambient temperature is 45°C.
Check if a #12 THW (Cu) conductor can supply power to 10 fluorescent lighting fixtures each rated at 1.8 A.
Determine the size of THHN (Cu) conductors needed to supply eight rows of fluorescent lighting fixtures with seven fixtures in each row with each fixture rated at 1.5 A. If only 20 A circuits are used, estimate the number of the circuits needed to serve all the lighting fixtures and the size of the
Determine the symmetrical short-circuit current a #1/0 XHHW (Cu) conductor protected by a circuit breaker rated at 480 V.
Estimate the maximum asymmetrical short-circuit current that #1/0 THW (Cu) conductors can handle if circuit breakers are used as overcurrent protection devices.
Calculate the voltage drop in percent for a feeder that serves a load of 100 kW, 480 V, three-phase, power factor of 85%, and length of 300 ft. The feeder is #1 XHHW copper conductors in an aluminum conduit.
Calculate the percent voltage drop of a 240 V, 1-phase feeder consisting of 150 ft one way of #10 THW copper conductors in steel EMT conduit carrying a load of 20 A, 90% PF.
Calculate the percent voltage drop of a 120 V, 1-phase branch circuit consisting of 25 m one way of 2 #12 THHN copper conductors in EMT conduit carrying a load of 16 A, 85% PF.
Calculate the percent voltage drop of a 240 V, 3-phase feeder consisting of 190 ft one way of 2 #4 THW copper conductors in steel EMT conduit carrying a load of 40 A, 85% PF.
A building is supplied by 750 ft, three-wire, 480 V, three-phase feeder. The total load of the building is 250 kVA with a power factor of 0.8. Determine(a) The size of the feeder and conduit using THW copper conductors(b) The voltage drop in the feeder (assume a steel conduit)(c) The size of the
Three 120/240 V panelboards are supplied with three subfeeders: A, B, and C. A is 50 ft, B is 100 ft, and C is 50 ft in length. The load on A is 15 kVA with a pf of 1.0; load B is 25 kVA with a pf of 0.95; and load C is 35 kVA with pf of 0.9. The three subfeeders are supplied with a 75 ft long main
Select the size of conductors and conduit for a feeder that services a lighting panel with the following features:• Load is 275 kW with a power factor of 90% and is continuous.• More than 50% of the load has high third-harmonic components.• The panel is supplied by 480Y/277 V, three-phase,
A 208Y/120 V panelboard for an office building has the following loads:• Receptacles with a total load of 30.00 kVA at pf = 0.90• Lighting with a total load of 20.00kVA at pf = 0.95• One Motor with a load of 5 kVA at pf = 0.92• Heaters with a total load 12.00 kVA at pf = 1.00 Determine the
A panelboard for a commercial building is supplied by 250 ft, four-wire, 480Y/277 V, three-phase feeder. The panel has the following loads:• A lighting system of a total power 30 kVA with a power factor of 0.93• A 15 kVA resistive heater with a power factor of 1.0• A motor rated at 8 kVA and
Calculate the motor circuit conductors for a 30 HP, 460 V, 3-phase squirrel cage motor; use copper, 75°C THW.
Determine the size of the disconnecting means for a 50 HP, 230 V, 3-phase squirrel cage motor.
Size the branch circuit for an induction motor rated at 50 HP, three-phase, 60 Hz, 460 V, 1175 rpm, a service factor of 1.15, and a power factor of 90%. The motor is protected by time-delay fuses. Assume that the motor is out of sight of both the power supply and the controller (but the controller
Determine the size of THHN copper branch circuit conductors required to supply a 20 kVA, single-phase, 240 V heating unit (continuous duty) with a 10 A blower motor.
Estimate the size of THW copper conductors that are required to supply a group of three-phase, 230 V motors 230 V rated at 7.5, 15, and 25 HP.
An MCC serves 9 identical motors, each motor is rated 50 HP, three-phase, 60 Hz, 460 V, 1175 rpm, a service factor of 1.00, and a power factor of 90%. All the motors are protected by time-delay fuses and have FVNR starter type. Determine the size of the conductor, conduit, time-delay fuse, and
A motor control center has three induction motors each rated at 40 HP and 480 V and four induction motors each rated at 30 HP and 480 V. Each 40 HP motor has an efficiency of 0.92 , 1772 rpm, and a power factor of 0.85. Each 30 HP motor has an efficiency of 0.90, and a power factor of 0.90, a
Determine the size of the service entrance THW (Cu) conductors required for phases A and B and the neutral of a 310 m2 (3200 ft2) dwelling with the following loads: 12.0 kVA range; 6.0kVA dryer; 30.0 kVA heating system; 6.0 kVA water heater; 1.5 kVA dishwasher; 0.9 kVA compactor no. 1; 0.8 kVA
A dwelling unit is supplied by a single-phase, 120/240 V service. The electric load of the unit includes:(1) 7000 VA water heater, 240 V; (2) 500 VA vent fan, 120 V;(3) 1200 VA compactor, 120 V; (4) 7500 VA dryer, 240 V.Each appliance is served by one branch protected by a circuit breaker.(a)
Determine the size of the service entrance THW (Cu) conductors required for phases A and B using the optional method of a 310 m2 (3200 ft2) dwelling with the following loads: 12.0 kVA range; 6.0 kVA dryer; 30.0 kVA heating system; 6.0 kVA water heater; 1.5 kVA dishwasher; 0.9 kVA compactor no.
A 274 m2 (2950 ft2) dwelling is supplied by a single-phase, 120/240 V service and has the following loads: 1.8 kVA dishwasher, 120 V; 1.2 kVA compactor, 120 V; 1.0 kVA disposal, 120 V; 0.5 kVA vent fan, 120 V; 16 kVA range, 240 V; 4.5 kVA dryer, 240 V; 15 kVA heating unit, 240 V; 9 kVA air
Determine the size of the service entrance conductors required for phases A and B and the neutral of a 186 m2 (2000 ft2) residence having the following load: 15 kVA space heating (five electric baseboards separately controlled); 10 kVA range; 4.5 kVA dryer; 1.5 kVA dishwasher; 5 kVA air
A 348 m2 (3750 ft2) house has the following loads: 12 kVA range, 240 V; 15 kVA air conditioning unit, 240 V; and 8 kVA water heater, 240 V.(a) Using the standard method, size the THW service entrance conductors.(b) Determine the minimum number of 15 A circuits for general lighting and
A 316 m2 (3400 ft2) house has the following loads: 1.5 kVA compactor, 120 V; 1.2 kVA ceiling fan, 120 V; 14 kVA range, 240 V; 30 kVA heating unit, 240 V; 40 A air conditioning unit, 240 V; and 10 kVA water heater, 240 V.(a) Using the standard method, size the THW service entrance conductors.(b)
Determine the size of the service entrance conductors required for phases A and B and the neutral for twenty (20) 83.5 m2 (900 ft2) units in a multifamily dwelling. The units have the following loads:• General lighting and receptacle loads.• Two small kitchen appliance loads and one laundry
A 480Y/277 V lighting panelboard has the following loads:• Lighting (4 circuits at 277 V) with a total load of 16.0kVA at PF = 0.95 (continuous load)• Appliances (2 circuits at 277 V) with a total load of 9.0 kVA at PF = 0.90 (noncontinuous load)• A/C system (1 circuit at 480 V) with a total
A 208Y/120 V panelboard for an office building has the following loads:• Receptacles with a total load of 50.00 kVA and a power factor of 0.90• Lighting with a total load of 80.00 kVA and a power factor of 0.95• One 20-HP motor with an efficiency of 0.90 and a power factor of 0.92• Heaters
A panel for a commercial building is supplied by a 500 ft four-wire 208Y/120-V three-phase feeder. The panel serves three major loads:• A lighting system of a total power of 70 kVA with a power factor of 0.8• 500 receptacles connected to loads with an average power factor of 0.90• Heaters
A panel for an office building is supplied by a 200 ft four-wire and a 480Y/277 V feeder. The loads of the panel include• A lighting system of a total power of 10 kVA with a power factor of 0.8• 100 receptacles with an average power factor 0.90• Heaters rated at 7.5 kVA and a power factor of
A 208Y/120 V panelboard for an office building has the following loads:• Receptacles with a total load of 30.00 kVA at PF = 0.90• Lighting with a total load of 20.00 kVA at PF = 0.95• One motor with a load of 5 kVA at PF = 0.92• Heaters with a total load 12.00 kVA at PF = 1.00 Determine the

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Energy Efficient Electrical Systems For Buildings 1st Edition Moncef Krarti - Solutions

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