PSPCL RECRUITMENT 2021

Punjab State Power Corporation Ltd. (PSPCL), a power generating and distributing company of the Government of Punjab state, has released the notification for recruitment to the post of Clerk, Revenue Accountant, Junior Engineer (Electrical), Assistant Lineman & Assistant Sub Station Attendant Posts .
A total of 75 vacancies have been announced for the recruitment process of JE ELECTRICAL Engineering.

Exam Dates: 10 N0V-21 to 17 Nov-21

PSPCL-JE’21 EE: Daily Quiz

PSPCL-JE’21 EE: Daily Practices Quiz 11-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which motor should not be used for centrifugal pumps?
(a) Series
(b) Shunt
(c) Cumulatively compound
(d) Differentially compound

Q2. DC series motors are very suitable for heavy duty applications such as electric railways, rolling mills because of
(a) Nearly constant speed
(b) Possibility of speed control
(c) High starting torque
(d) Low initial as well as maintenance cost

Q3. Which of the following loss in a transformer is zero at all operating conditions?
(a) Iron loss
(b) Eddy current loss
(c) Hysteresis loss
(d) Friction loss

Q4. A circuit is disconnected by isolators when:
(a) Line is on full load
(b) Line is energized
(c) There is no current in the line
(d) Circuit breaker is not open

Q5. A 3-phase, 6-pole, 50 Hz induction motor has a slip of 1 % at no load and 3 % at full load. The frequency of rotor current at standstill will be:
(a) 50 Hz
(b) 100 Hz
(c) 1.5 Hz
(d) Zero

Q6. Which of the following relation is correct for current carrying capacity of fuse element?
(a) I ∝ d
(b) I² ∝ d²
(c) I² ∝ d³
(d) I² ∝ d
Where d = diameter of fuse element

SOLUTIONS

S1. Ans.(a)
Sol. Series motors is best suited for electric traction work because of its large starting torque characteristics.

S2. Ans.(c)
Sol. Series motors is best suited for electric traction work because of its large starting torque characteristics. It is not suited for centrifugal pumps as in case of centrifugal pumps the starting torque is usually less than the running torque.

S3. Ans.(d)
Sol. Transformer is a static device.
Friction losses are involved with rotating parts of a machine. Since in a transformer all parts are stationary, friction losses will always be equal to zero, irrespective of the loading condition.

S4. Ans.(c)
Sol. Isolators operation occurs, when there is no current in the line.

S5. Ans.(a)
Sol. f_r=sf
At standstill condition: slip(s)=1
So, frequency of rotor current at standstill=supply frequency=50 Hz.

S6. Ans.(c)
Sol. Heat produced per sec = Heat lost per sec (convection, conduction, radiation)
⇒ I²R = K × d × l
⇒ I²(ρl/A) = K × d × l
⇒ (I^2∝d^3 ) also called fuse law.

GATE 2022

GATE 2022 Important Dates: Organizing Institute for GATE 2022 is the Indian Institute of Technology Kharagpur. For GATE 2022 Exam IIT Kharagpur has released the official notification and Important dates regarding the GATE 2022 Exam. Aspirants preparing for GATE 2022 must check the details regarding GATE 2022 Important Dates. Read the complete article below for the information related to GATE 2022 Important dates.

GATE’22 EE: Daily Practices Quiz

GATE’22 EE: Daily Practices Quiz 09-Oct-2021

Each question carries 2 marks
Negative marking: 0.66 mark

Total Questions: 10
Total marks: 20
Time: 20 min.

Q1. A co-axial cable of inner radius a and outer radius b. The space between conductor is filled with dielectric of permittivity ∈ and length of cable 4m. what is the capacitance of the cable?
(a) (2π∈)/ln⁡(b/a)
(b) ln⁡(b/a)/(2π∈)
(c) (π∈)/(2 ln⁡(b/a) )
(d) (8π∈)/ln⁡(b/a)

Q2. In a two-unit insulator string, voltage across the unit near to line conductor is 18.5 kV and string efficiency is 75%. The voltage of line conductor will be:
(a) 37 kV
(b) 48.07 kV
(c) 27.75 kV
(d) 30 kV

Q3. A step-down chopper connected to a d.c. supply, supplies a separately excited d.c. motor at a duty ratio of α. The ripple factor in the terminal voltage of the motor assuming continuous current conduction is-
(a) α/(1-α)
(b) (1-α)/α
(c) √((1-α)/α)
(d) √(α/(1-α))

Q5. In a three-phase induction motor, the ratio power across air gap, rotor copper loss and gross mechanical power output is
(a) PG:sPG:(1-s) PG
(b) PG:sPG:(s-1) PG
(c) PG:(1-s) PG:sPG
(d) PG:sPG:(1+s) PG

Q7. Consider a network function H(s)= (2(s+3))/((s+2)(s+4)). What is the steady state response due to step input?
(a) ½
(b) ¾
(c) 2
(d) 1

Q8. Which of the following is a non-maskable interrupt of 8085 microprocessors?
(a) INTR
(b) TRAP
(c) RST 6.5
(d) RST 7.5

Q9. For a JFET I_DSS = 8 mA and peak voltage V_p = –8V, what will be the drain current for gate to source voltage of –2V?
(a) 4.5 mA
(b) 8 mA
(c) 16 mA
(d) 12 mA

Q10. Determine the deflection factor (in V/m) of a CRO, when the deflection sensitivity of the CRO is 5 m/V.
(a) 0.25
(b) 0.35
(c) 0.20
(d) 0.40

SOLUTIONS

S5. Ans.(a)
Sol. In a three-phase induction motor, the ratio power across air gap, rotor copper loss and gross mechanical power output is-
P_G= Air gap power
sP_G = rotor copper loss
P_G (1-s) = gross mechanical power
So, ratio is-
P_G:sP_G ∶(1-s) P_G

S6. Ans.(c)
Sol. Peak current=I_0+(△i_c)/2=5+1.6/2=5.8 A

S7. Ans.(b)
Sol. steady state response=lim┬(s→0)⁡〖sC(s)=〗 lim┬(s→0)⁡= s×(2(s+3))/((s+2)(s+4))×1/s=3/4

S8. Ans.(b)
Sol. The hardware vectored interrupts are classified in to maskable and non-maskable interrupts.
TRAP is non-maskable interrupt.
RST 7.5, RST 6.5, RST 5.5 and INTR are maskable interrupt.

S9. Ans.(a)
Sol. I_D=I_DSS (1-V_GS/V_P )^2=8×10^(-3) (1-(-2)/(-8))^2=4.5 mA

S10. Ans.(c)
Sol. Deflection factor=1/(deflection sensitivity)=1/5=0.2 V/m.

PSPCL RECRUITMENT 2021

Punjab State Power Corporation Ltd. (PSPCL), a power generating and distributing company of the Government of Punjab state, has released the notification for recruitment to the post of Clerk, Revenue Accountant, Junior Engineer (Electrical), Assistant Lineman & Assistant Sub Station Attendant Posts .
A total of 75 vacancies have been announced for the recruitment process of JE ELECTRICAL Engineering.

Exam Dates: 10 N0V-21 to 17 Nov-21

PSPCL-JE’21 EE: Daily Quiz

PSPCL-JE’21 EE: Daily Practices Quiz 08-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which of the following instruments has the same calibration in AC and DC?
(a) Moving iron type
(b) Moving coil type
(c) Induction type
(d) Electrodynamometer type

Q2. A slip test is conducted on synchronous generator to determine:
(a) Slip
(b) Direct and quadrature axis reactance
(c) Sub-transient reactance
(d) Positive and negative sequence reactance

Q3. Which of the following insulators is selected for HV application?
(a) Suspension type
(b) Strain type
(c) Disc type
(d) Pin type

Q4. In the salient pole of 3-phase synchronous machine the rotor will have
(a) Larger diameter, shorter axial length
(b) Smaller diameter, larger axial length
(c) Larger diameter, larger axial length
(d) Smaller diameter, shorter axial length

Q5. In a two-value capacitor motor, the capacitor used for running purposes is
(a) Air capacitor
(b) Paper spaced oil filled type
(c) Ceramic type
(d) A.c electrolyte type

Q6. A negative sequence relay is commonly used to protect
(a) An alternator
(b) A transformer
(c) A transmission-line
(d) A bus-bar

SOLUTIONS

S1. Ans.(d)
Sol. Electrodynamometer type instruments has the same calibration in AC and DC.
NOTE: A transfer instrument is one that may be calibrated with a d.c. source and then used without modification to measure a.c This requires the transfer type instrument to have the same accuracy for both a.c and d.c., which have electrodynamometer instruments have.

S2. Ans.(b)
Sol. A slip test is conducted on synchronous generator to determine Direct and quadrature axis reactance.
From slip test: X_d=V_max/I_min &X_q=V_min/I_max

S3. Ans.(a)
Sol. In higher voltage, beyond 33KV, it becomes uneconomical to use pin insulator because size, weight of the insulator become more. Handling and replacing bigger size single unit insulator are quite difficult task. For overcoming these difficulties, suspension insulator is used for HV application.

S4. Ans.(a)
Sol. 3-phase synchronous machine rotor construction:
• Salient pole rotor: larger diameter, shorter axial length
• Cylindrical pole rotor: smaller diameter, larger axial length

S5. Ans.(b)
Sol. Two-value capacitor motor also known as capacitor start capacitor run induction motor.
In a two-value capacitor motor:
At the starting, the two capacitors are connected in parallel.
Starting capacitor is short time rated and is almost electrolytic.
The run capacitor is long time rated and is made of oil filled paper.

S6. Ans.(a)
Sol. A negative sequence relay is commonly used to protect an alternator.
A relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay.
The negative sequence relay protects the generator(alternator) and motor from the unbalanced load which mainly occurs because of the phase-to-phase faults.

NHPC JE Recruitment 2021

National Hydroelectric Power Corporation (NHPC) has released the recruitment notification for engagement of the following posts as Senior Medical Officer, Assistant Rajbhasha Officer, Junior Engineer & Sr. Accountant posts. NHPC expects applications from High Performing, Dynamic & Achievement-Oriented Professionals candidates to fill up these 173 vacancies.

NHPC-JE’21 EE: Daily Practices Quiz

NHPC-JE’21 EE: Daily Practices Quiz 08-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which part of DC machines converts the alternating current induced in armature conductors into unidirectional current in the external load circuit?
(a) Pole coils
(b) Commutator
(c) Armature windings
(d) Armature core

Q2. Power transformers are generally designed to have maximum efficiency around
(a) No load
(b) Half load
(c) Near full load
(d) None of the above

Q3. Thin laminations are used in a machine in order to reduce
(a) Eddy current losses
(b) Hysteresis losses
(c) Both a and b
(d) None of the above

Q4. Which of the following theorems can be applied to any network linear or non-linear, active or passive, time-variant or time-invariant?
(a) Norton theorem
(b) Thevenin theorem
(c) Superposition theorem
(d) Tellegen theorem

Q5. The bandwidth of an AC series circuit consisting of R, L & C is
(a) L/RC
(b) RC/L
(c) R/L
(d) L/R

Q6. Which of the following statement is true?
(a) At higher voltage, cost of transmission is reduced
(b) At higher voltage, cost of transmission is increased
(c) Both a and b
(d) None of the above

SOLUTIONS

S1. Ans.(b)
Sol. The commutator will convert AC to DC in DC generators and vice versa in DC motors.
In the generator, the main function of the commutator is to facilitate the collection of current from the armature conductors and to convert the alternating emf induced (AC) in the armature conductors to unidirectional emf (DC) in the external load circuit.
In the motor, the main function of the commutator is to supply current to armature from the external DC circuit and to convert this unidirectional emf (DC) of the external DC circuit to alternating emf in the armature.

S2. Ans.(c)
Sol. Power transformers are generally designed to have maximum efficiency near full load, whereas distribution transformers have maximum efficiency at 50% of full load.

S3. Ans.(a)
Sol. Thin laminations are used in order to reduce the eddy current losses only. Due to laminations the area of the eddy currents loops is minimized and the losses due to eddy current losses are minimized.

S4. Ans.(d)
Sol. Tellegen theorem can be applied to any network linear or non-linear, active or passive, time-variant or time-invariant.

S5. Ans.(c)
Sol. The bandwidth of an AC series circuit consisting of R, L & C: BW=R/L

S6. Ans.(a)
Sol. At higher voltage, the volume of the conductor is reduced. Area of conductor A ∝ 1/Vs² Where Vs = Supply voltage. So that material requirement is reduced and hence cost of the material and transmission is reduced.