Exam Details
| Subject | electrical | |
| Paper | paper 2 | |
| Exam / Course | ||
| Department | ||
| Organization | Reserve Bank of India Services Board | |
| Position | technical manager | |
| Exam Date | 2014 | |
| City, State | central government, |
Question Paper
............... (..... .....) P.Y.- 2014
R.B.I.S.B. (MANAGER ELECTRICAL) P.Y. 2014
Instructions
Answer any five questions. All questions carry equal marks.
Answers must be written either in English or in Hindi. However, all the questions should be answered in one language only. Answer-books written partly in English and partly in Hindi will not be evaluated.
Each question should be answered on new page and the question number must be written on the top in left margin.
The answers of parts of the same question, if any, should be written together. In other words, the answer of another questions should not be written in-between the Parts of a question.
The Name, Roll No. and other entries should be written in the answer-scripts at the specified places only and these should not be written anywhere else in the answer script and supplements.
Candidate should use only Blue or Black ink pen to write the answers.
Answers will be evaluated on the basis of logic, brevity and clarity in exposition.
Marks will be deducted for illegible hand-writing.
Use of non-programmable electronic calculator/log table is permitted.
PAPER II (DESCRIPTIVE TYPE)
Q.1a Define the various torque associated with synchronous motor?
b Consider the circuit composed of a series R-L Branch in parallel with capacitance with R 0.5ohm X1 0.8ohm and Bc 0.6 Siemens, across voltage 200 at an angle of 0 degree, 50Hz supply. Calculate 1. Total current 2. Active Power 3. Reactive power 4. Apparent Power. Also draw Power triangle.
Q.2a.The four arms of a Wheatstone bridge have the following resistance AB 115ohm, BC 15ohm, CD 10ohm and DA 53ohm, A galvanometer of 20ohm resistance is connected across BD. Use Thevenin's theorem to compute the current through the galvanometer when a potential difference of 15 volt is maintained across AC.
2b.The hydroelectric generating station is supplied from a reservoir of capacity 6million m3 at head of 180m. What is the available energy in kWh if the hydraulic sufficiency be 0.8 and the electrical efficiency 0.9? Find the fall in reservoir level after a load of 12000 kW, has been supplied for 3 hours the area of the reservoir is 2.5 km2.
Q.3a.State various types of electrical breaking and give the advantage of electrical breaking over mechanical breaking?
b.A steel ring of 25cm mean diameter and of circular section 3cm in diameter has an air-gap of 1.5mm. It is wound uniform with 700 turns of wire carrying a current of 2A. Calculate Magneto motive force ii) Flux density iii) magnetic flux, iv) Relative permeability. Neglect the leakage and assume that iron path takes 35% of total MMF.
Q.4a.The arm of a dc shunt motor starter is held in the ON position by an electromagnet having a pole face area of 4cm2 and air-gap of 0.6mm. The torque exerted by the spring is 12 N-m and effective radius at which the force is exerted is 15cm. What is the minimum number of AT required to keep the arm in the ON position
b.A 75 kW 3 phase Y connected, 50Hz 440V Cylindrical rotor synchronous motor operates at rated condition with 0.8pf. leading. The motor efficiency excluding filed and stator losses is 95% and Xs =2.5ohm Calculate i. Mechanical power developed ii. Armature current iii. Back emf iv. Power angle v. Maximum or pull out torque of the motor
Q.5a.An overhead transmission n line at a river crossing is supported from two towers at height of 40m and 90m above water level,the horizontal distance between the towers being 400m. If the maximum allowable tension is 2000 kg, find the clearance between the conductor and water at mid way between the towers. Assume weight of the conductor is 1 kg/m.
b.A generating station has three section bus-bar connected with the tie-bar through reactors rated at 5000 kVA. Each generator is of 5000 kVA with 12% reactance and is connected to one section of bus-bars. Find the total input to a dead short circuit between the lines on one end of the section of bus-bar with reactors and ii) without rectors
Q.6a.Three impedances of 5-j10, and 3+j15 ohms are connected in star to red yellow and blue lines of 3300V 3 phase 3 wire supply. The phase sequence is RYB. Calculate the line current in red line.
b.A single phase AC system supplies a load of 200kW and if this system is converted to 3 phase 3 wire AC. system by running a third wire similar conductor material and cross-section area. Calculate the three phase load that can now be supplied if the voltage between the conductors is the same. Assume the power factor and transmission efficiency to be the same in the two cases
Q.7a.Derive the inductance and capacitance values for three phase three wire symmetrical transmission line?
b.An Aluminium wire 7.5m long is connected in parallel with a copper wire 6m long. When a current of 5A is passed through the parallel combination, it is found that the current in the aluminium wire is 3A. The diameter of the aluminium wire is 1 mm. Determine the diameter of the copper wire. Resistivity of copper is 0.017µ ohm-m; and that of the aluminium is 0.028µ ohm-m.
Q.8a.Draw the phasor diagram for synchronous motor running at following conditions i. At unity power factor
ii. At leading power factor
iii. At lagging power factor
b.A generating station has the maximum demand of 75MW and a yearly load factor of 40%. Generating cost inclusive of station capital cost are Rs60 per annum per kW demand plus 4 paisa per kWh transmitted. The annual capital charges for transmission system are Rs2000000 and for distribution Rs.1500000, the respective diversity factor being 1.2 and1.25. The efficiency of transmission system is 90% and that of the distribution system inclusive of substation losses is 85%. Find the yearly cost per kW demand and cost per kWh supplied i. At substation ii)at consumer premises
R.B.I.S.B. (MANAGER ELECTRICAL) P.Y. 2014
Instructions
Answer any five questions. All questions carry equal marks.
Answers must be written either in English or in Hindi. However, all the questions should be answered in one language only. Answer-books written partly in English and partly in Hindi will not be evaluated.
Each question should be answered on new page and the question number must be written on the top in left margin.
The answers of parts of the same question, if any, should be written together. In other words, the answer of another questions should not be written in-between the Parts of a question.
The Name, Roll No. and other entries should be written in the answer-scripts at the specified places only and these should not be written anywhere else in the answer script and supplements.
Candidate should use only Blue or Black ink pen to write the answers.
Answers will be evaluated on the basis of logic, brevity and clarity in exposition.
Marks will be deducted for illegible hand-writing.
Use of non-programmable electronic calculator/log table is permitted.
PAPER II (DESCRIPTIVE TYPE)
Q.1a Define the various torque associated with synchronous motor?
b Consider the circuit composed of a series R-L Branch in parallel with capacitance with R 0.5ohm X1 0.8ohm and Bc 0.6 Siemens, across voltage 200 at an angle of 0 degree, 50Hz supply. Calculate 1. Total current 2. Active Power 3. Reactive power 4. Apparent Power. Also draw Power triangle.
Q.2a.The four arms of a Wheatstone bridge have the following resistance AB 115ohm, BC 15ohm, CD 10ohm and DA 53ohm, A galvanometer of 20ohm resistance is connected across BD. Use Thevenin's theorem to compute the current through the galvanometer when a potential difference of 15 volt is maintained across AC.
2b.The hydroelectric generating station is supplied from a reservoir of capacity 6million m3 at head of 180m. What is the available energy in kWh if the hydraulic sufficiency be 0.8 and the electrical efficiency 0.9? Find the fall in reservoir level after a load of 12000 kW, has been supplied for 3 hours the area of the reservoir is 2.5 km2.
Q.3a.State various types of electrical breaking and give the advantage of electrical breaking over mechanical breaking?
b.A steel ring of 25cm mean diameter and of circular section 3cm in diameter has an air-gap of 1.5mm. It is wound uniform with 700 turns of wire carrying a current of 2A. Calculate Magneto motive force ii) Flux density iii) magnetic flux, iv) Relative permeability. Neglect the leakage and assume that iron path takes 35% of total MMF.
Q.4a.The arm of a dc shunt motor starter is held in the ON position by an electromagnet having a pole face area of 4cm2 and air-gap of 0.6mm. The torque exerted by the spring is 12 N-m and effective radius at which the force is exerted is 15cm. What is the minimum number of AT required to keep the arm in the ON position
b.A 75 kW 3 phase Y connected, 50Hz 440V Cylindrical rotor synchronous motor operates at rated condition with 0.8pf. leading. The motor efficiency excluding filed and stator losses is 95% and Xs =2.5ohm Calculate i. Mechanical power developed ii. Armature current iii. Back emf iv. Power angle v. Maximum or pull out torque of the motor
Q.5a.An overhead transmission n line at a river crossing is supported from two towers at height of 40m and 90m above water level,the horizontal distance between the towers being 400m. If the maximum allowable tension is 2000 kg, find the clearance between the conductor and water at mid way between the towers. Assume weight of the conductor is 1 kg/m.
b.A generating station has three section bus-bar connected with the tie-bar through reactors rated at 5000 kVA. Each generator is of 5000 kVA with 12% reactance and is connected to one section of bus-bars. Find the total input to a dead short circuit between the lines on one end of the section of bus-bar with reactors and ii) without rectors
Q.6a.Three impedances of 5-j10, and 3+j15 ohms are connected in star to red yellow and blue lines of 3300V 3 phase 3 wire supply. The phase sequence is RYB. Calculate the line current in red line.
b.A single phase AC system supplies a load of 200kW and if this system is converted to 3 phase 3 wire AC. system by running a third wire similar conductor material and cross-section area. Calculate the three phase load that can now be supplied if the voltage between the conductors is the same. Assume the power factor and transmission efficiency to be the same in the two cases
Q.7a.Derive the inductance and capacitance values for three phase three wire symmetrical transmission line?
b.An Aluminium wire 7.5m long is connected in parallel with a copper wire 6m long. When a current of 5A is passed through the parallel combination, it is found that the current in the aluminium wire is 3A. The diameter of the aluminium wire is 1 mm. Determine the diameter of the copper wire. Resistivity of copper is 0.017µ ohm-m; and that of the aluminium is 0.028µ ohm-m.
Q.8a.Draw the phasor diagram for synchronous motor running at following conditions i. At unity power factor
ii. At leading power factor
iii. At lagging power factor
b.A generating station has the maximum demand of 75MW and a yearly load factor of 40%. Generating cost inclusive of station capital cost are Rs60 per annum per kW demand plus 4 paisa per kWh transmitted. The annual capital charges for transmission system are Rs2000000 and for distribution Rs.1500000, the respective diversity factor being 1.2 and1.25. The efficiency of transmission system is 90% and that of the distribution system inclusive of substation losses is 85%. Find the yearly cost per kW demand and cost per kWh supplied i. At substation ii)at consumer premises