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1st National Certification Exam Energy Managers 2004 Paper 3

7 pages, 70 questions, 2 questions with responses, 2 total responses,

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Paper EM3 Energy Manager Set A NATIONAL CERTIFICATION EXAMINATION 2004 FOR ENERGY MANAGERS PAPER EM3: Energy Efficiency in Electrical Utilities Date: 23.05.2004 Timings: 0930-1230 HRS Duration: 3 HRS Max. Marks: 150 General instructions: o o o o o Please check that this question paper contains 7 printed pages Please check that this question paper contains 65 questions The question paper is divided into three sections All questions in all three sections are compulsory All parts of a question should be answered at one place Section I: OBJECTIVE TYPE (i) (ii) (iii) 1. Answer all 50 questions Each question carries one mark Put a ( ) tick mark in the appropriate box in the answer book In electricity distribution, if the voltage is raised from 11 kV to 33 kV for the same loading conditions, the voltage drop in the distribution system would be lower by a factor of a) 1/4 2. b) 1/2 c) 1/3 b) 1/3 c) 1/6 d) none of the above Select the location of installing capacitor bank, which will reduce the electricity distribution losses to the maximum extent a) main sub-station bus bars c) motor control centre 4. d) none of the above If the voltage level of the distribution system is raised from 11 kV to 33 kV for the same loading conditions, the distribution losses are reduced by a factor of a) 1/9 3. Marks: 50 x 1 = 50 b) motor terminals d) distribution board bus bars The power factor indicated in the monthly electricity bill for industry is a) peak power factor of the day b) peak power factor achieved during the month c) average monthly power factor d) instantaneous power factor taken at the time of meter reading taken by the utility staff 5. The vector sum of active power and reactive power is a) apparent power _______________________ Bureau of Energy Efficiency b) true power c) shaft power d) none of the above 1 Paper EM3 Energy Manager Set A 6. The nearest kVAr compensation required for improving the power factor of a 100 kW load from 0.8 lag to unity power factor is a) 50 kVAr 7. b) 1450 rpm b) ambient temperature d) none of the above b) 3 7 c) 8 - 10 b) decrease b) replacing it with a correctly sized motor d) none of the above For every 4 C reduction in the air inlet temperature of an air compressor, the power consumption will normally decrease by .. percentage points for the same output. b) 1 c) 3 b) 0.5 bar c) 1.0 bar b) centrifugal compressors d) none of the above A 100 cfm compressor has a loading and unloading period of 10 seconds and 20 seconds respectively during a compressed air leakage test. The air leakage in the compressed air system would be a) 10.6 cfm 16. d) 2 bar Dynamic air compressors are mainly of the type a) two stage reciprocating compressors c) two stage screw compressors 15. d) 4 The acceptable pressure drop in mains header at the farthest point of an industrial compressed air network is a) 0.3 bar 14. d) none of the above One low investment measure to improve efficiency of a squirrel cage induction motor, which operates consistently below 40% of its rated capacity, is by a) 2 13. d) 10 and above c) not change a) operating it in star mode c) operating in delta mode 12. d) 1000 rpm With decrease in design speed of induction motors the required capacitive kVAr for reactive power compensation for the same capacity range will a) increase 11. c) 960 rpm The full load efficiency of energy efficient squirrel cage motors (in comparison with standard squirrel cage induction motors) can be generally higher by . percentage points a) 1 10. d) none of the above What determines the thermal loading on the motor? a) duty/load cycle c) age of the motor 9. c) 100 kVAr A four pole induction motor operating at 50 Hz, will have a synchronous speed of a) 1500 rpm 8. b) 75 kVAr b) 20.8 cfm c) 33.3 cfm d) 47.3 cfm Higher chiller COP can be achieved with a) lower evaporator temperature and higher condensing temperature b) higher evaporator temperature and lower condensing temperature c) higher evaporator temperature and higher condensing temperature d) lower evaporator temperature and lower condensing temperature _______________________ Bureau of Energy Efficiency 2 Paper EM3 Energy Manager Set A 17. Vertical type reciprocating compressors are used in the capacity range of a) 50 150 cfm c) 500 - 1000 cfm 18. One ton of refrigeration (TR) is equal to a) 3024 kcal/hr 19. b) 200 500 cfm d) above 1000 cfm b) 3.51 kW b) pure water b) 0.65 0.70 b) cube of flow rate d) none of the above b) tube-axial fan d) forward curved centrifugal fan b) 6 times c) 8 times b) 2 times c) 8 times d) 16 times What is the impact on flow and pressure when the impeller of a pump is trimmed? a) flow decreases and pump head increases b) both flow and pump head increases c) both pressure and flow decreases 28. d) 4 times If the speed of a pump is doubled, the pump head goes up by a) 4 times 27. b) dry bulb temperature d) all of the above If the speed of a pump is doubled, pump shaft power goes up by a) 2 times 26. d) none of the above Name the fan which is more suitable for high pressure application a) propeller type fan c) backward curved centrifugal fan 25. c) 0.75 0.80 System resistance in water pumping system varies with a) square of flow rate c) square root of flow rate 24. d) lithium bromide The essential parameters to estimate cooling load from airside across air handling unit (AHU) or a fan coil unit (FCU) is a) air flow rate c) RH% or wet bulb temperature 23. c) freon Li Br water absorption refrigeration systems have a COP in the range of a) 0.4 0.5 22. b) ambient wet bulb temperature d) none of the above The refrigerant used in vapour absorption systems is a) steam 21. d) all of the above In water cooled refrigeration systems, condenser cooling water temperature should be closest to a) ambient dry bulb temperature c) dew-point temperature 20. c) 12,000 BTU/hr d) none of the above Shaft power of the motor driving a pump is 20 kW. The motor efficiency is 0.9 and pump efficiency is 0.6. The power transmitted to the water is a) 20.0 kW _______________________ Bureau of Energy Efficiency b) 18 kW c) 12 kW d) 10.8 kW 3 Paper EM3 Energy Manager Set A 29. For fans, the relation between flow discharge Q and speed N is 2 Q1 N 1 a) = Q2 N 2 30. b) 32oC c) 29oC d) 3oC Cooling tower effectiveness is a) approach / (range + approach) c) approach / range 32. d) none of the above If inlet and outlet water temperatures of a cooling tower are 40oC and 32oC respectively and atmospheric WBT is 29 oC then the approach of cooling tower is a) 40oC 31. 3 Q1 N 1 c) = Q2 N 2 3 Q1 N 1 b) = Q2 N 2 2 b) range/ (range + approach) d) none of the above The lowest theoretical temperature to which water can be cooled in a cooling tower is a) DBT of the atmospheric air b) WBT of the atmospheric air c) average DBT and WBT of the atmospheric air d) difference between DBT and WBT of the atmospheric air 33. Which of the following ambient conditions will evaporate maximum amount of water in a cooling tower a) 35 oC DBT and 25 oC WBT c) 35 oC DBT and 28 oC WBT 34. b) 40oC DBT and 38oC WBT d) 38 oC DBT and 37 oC WBT The ratio of dissolved solids in circulating water to the dissolved solids in make up water for cooling tower is termed as a) cycles of concentration c) cooling tower effectiveness 35. Normally a manufacturer s guaranteed best approach of a cooling tower is a) 5 oC 36. b) 12 oC b) CFL b) luminaire b) HPMV d) none of the above c) lumens d) none of the above c) HPSV d) LPSV If voltage is reduced from 230 V to 200 V for a fluorescent tube light, it will result in a) reduced power consumption c) increased light levels 40. c) Sodium vapor lamp Luminous efficacy of which of the following is the highest? a) CFL 39. d) 2.8 oC The unit of illuminance is a) lux 38. c) 8 oC An ignitor is a control gear to start a a) FTL 37. b) blow down d) none of the above b) increased power consumption d) no change in power consumption and light levels What is the typical frequency of a high frequency electronic ballast? a) 50 Hz _______________________ Bureau of Energy Efficiency b) 10 kHz c) 30 kHz d) 50 kHz 4 Paper EM3 Energy Manager Set A 41. The compression ratio in diesel engines is in the range of a) 5:1 to 10:1 42. b) 10:1 to 13:1 b) 50% 60% b) 5 c) 10 The operating efficiency of a DG set also depends on b) inlet air temperature d) all of the above The core losses of a transformer are the least if the core is made up of a) silicon alloyed iron (grain oriented) c) amorphous core metallic glass alloy 47. d) none of the above b) 210 to 240 C d) none of the above a) turbo charger performance c) % loading 46. d) above 70% Typical exit flue gas temperature of a 5 MW DG set operating above 80% load is in the range of a) 550 to 560 C c) 340 to 370 C 45. c) 60% 70% The maximum unbalanced load between phases should not exceed % of the capacity of the DG set a) 1 44. d) none of the above The rated efficiency of a diesel generator captive power plant has a range of a) 43% 45% 43. c) 14:1 to 25:1 b) copper d) none of the above The basic functions of an electronic ballast fitted to a fluorescent tube light exclude one of the following a) to ignite the lamp b) to stabilize the gas discharge c) to supply power to the lamp at supply frequency d) to supply power to the lamp at very high frequency 48. Modern electronic soft starters are used for motors to a) achieve variable speed c) improve the loading 49. The approximate kVA rating required for a DG set with 1000 kW connected load, with diversity factor of 1.5 and 84% loading and 0.8 power factor is a) 500 kVA c) 1500 kVA 50. b) provide smooth start and stop d) none of the above b) 1000 kVA d) 2000 kVA Maximum demand controller is used to a) switch off non-essential loads in a logical sequence b) switch off essential loads in a logical sequence c) controls the power factor of the plant d) all the above. . End of Section I . _______________________ Bureau of Energy Efficiency 5 Paper EM3 Energy Manager Set A Section II: SHORT DESCRIPTIVE QUESTIONS (i) (ii) S-1. Marks: 10 x 5 = 50 Answer all Ten questions Each question carries Five marks A maximum demand recorder for a plant will record the following loads over a period of 30 minutes. Compute the MD as the recorder would do - 800 kVA for 5 minutes - 200 kVA for 5 minutes - 400 kVA for 10 minutes - 800 kVA for 8 minutes - 1500 kVA for 2 minutes S-2. How does the power factor of a motor reduce with the reduction in the applied load on the motor? S-3. Briefly explain about the importance of maintaining optimal pressure settings of a compressed air system S-4. Chilled water enters evaporator at 110C and leaves at 80C. The flow rate of chilled water was measured as 350 m3/hr. Calculate the tons of refrigeration capacity. S-5. A fan is delivering 10,000 Nm3/hr of air at static pressure rise of 60 mm WC. If the fan static efficiency is 70%, find out the shaft power of the fan. S-6. What do you mean by the term cavitation and describe its undesirable effects on the pumping system. S-7. How size of cooling tower and wet bulb temperature are related? What Cooling Tower approach value is normally used by Cooling Tower manufacturers. S-8. Highlight advantages of CFL (compact fluorescent lamp) over GLS lamp. S-9. What is the impact of unbalanced loading on DG set? S-10. Briefly describe the principle of variable frequency drives used along with squirrel cage induction motors. . End of Section - II . Section III: LONG DESCRIPTIVE QUESTIONS (i) (ii) L-1. Marks: 5 x 10 = 50 Answer all Five questions Each question carries Ten marks Explain the benefit of reducing maximum demand. Explain step-by-step approach in controlling the maximum demand. _______________________ Bureau of Energy Efficiency 6 Paper EM3 Energy Manager Set A L-2. A 10 HP, 415 V, 4 pole, 50 Hz, 3 Phase squirrel cage induction motor has a full load efficiency of 90% and power factor of 0.88. Find the following if the motor operates at full load rated values. a) current drawn by the motor b) input power in kW c) RPM at a full load slip of 1% L-3. In an engineering industry, a 500 cfm rated capacity reciprocating compressor is operated at 7 kg/cm2g to find out the system leakage loss in the plant during lunch timings when no equipment using compressed air is operated. A free air delivery test was carried out before conducting the leakage test and it was observed that, the compressor was delivering 90% of its rated capacity. The following was observed during the conduct of leakage test: a) compressor on load timing is 10 seconds and unloading pressure is 7 kg/cm2g b) compressor power drawn during on load is 75 kW c) compressor unload timings and loading pressure are 40 seconds and 6.5 kg/cm2 g respectively. Find out the following: (i) % air leakage in the system (ii) leakage quantity in cfm. (iii) power lost due to leakage L-4. A water pump is delivering 300 m3/hr at ambient conditions. The impeller diameter is trimmed by 10% and its speed is reduced by 10%. Find out the water flow at the changed conditions. L-5. (a) What is `lux ? State its units. (b) What are the advantages of high frequency electronic ballasts? . End of Section III . _______________________ Bureau of Energy Efficiency 7

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