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WorksheetsEE8002 DESIGN OF ELECTRICAL APPARATUS MCQ TYPE IA 1 /MAR21
Total questions: 45
Worksheet time: 23mins
The major consideration to develop a good design is
A. Durability
B. Cost
C. Compliance with performance criteria as laid down in specifications
D. All of the above
The main areas of Electrical design are
A. Magnetic circuit
B. Electrical circuit
C. Insulation
D. All of the above
The basic needs of a good conducting material used for winding of electrical machines are
A. Highest possible conductivity and least possible temperature Coefficient of resistance
B. High tensile strength and absence of the brittleness
C. Reliability, durability, good weldability and solderability
D. All of the above
Correct order insulating material based on temperature classification
A. A E Y B F H C
B. Y A E B F H C
C. F Y A H C E B
D. H C Y A E B
One slot pitch Ys equal to
A. Ws-Wt
B. Ws+Wt
C. Ws*Wt
D. Ws/Wt
The maximum flux density (wb/m2) used in the electrical machine design is (Beyond which the core goes saturation)
A. 0.9 wb/m2
B. 1.4 wb/m2
C. 1.6 wb/m2
D. 2.4 wb/m2
The dielectric circuit design involves
A. armature core design
B. conductor design
C. Insulating material design
D. Heat dissipation circuit design
The thermal circuit design involves
A. armature core design
B. conductor design
C. Insulating material design
D. Heat dissipation circuit design
Soft magnetic material is a one in which
A. B-H loop is wider
B. B-H loop is narrow
C. made of very soft material
D. made of very hard material
Hard magnetic material is a one in which
A. B-H loop is wider
B. B-H loop is narrow
C. made of very soft material
D. made of very hard material
A Magnetic material permeability cannot be altered by magnetizing Force is known as
A. Diamagnetic materials
B. Ferro magnetic materials
C. Para magnetic materials
D. none of the above
A Magnetic material permeability can be altered by magnetizing force is Known as
A. Diamagnetic materials
B. Ferro magnetic materials
C. Para magnetic materials
D. none of the above
Permeabilty is a sign of magnetic materials
A. ability to conduct current
B. ability to resist current
C. ability to allow flux
D. ability to block flux
Slot in armature design used to
A. Provides a space conductor
B. Provides a space to allow flux
C. Provides a space for insulation
D. Provides a space conductor and insulation
Tooth in armature design used to
A. Provides a space conductor
B. Provides a space to allow flux
C. Provides a space for insulation
D. Provides a space conductor and insulation
The main dimension design in rotating machine is
A. Design Armature core diameter (D)
B. Design Armature core Length (L)
C. Design Armature core diameter (D) & core Length (L)
D. Design Armature core Height (H) & core width (W)
Total magnetic loading defined as
A. N*I
B. P*ϕ
C. Iz *Z
D. ϕ *A
Total Electric loading defined as
A. N*I
B. P*ϕ
C. Iz *Z
D. ϕ *A
The height and width in transformer normally represented as
A. limp only
B. yoke and limp
C. limp and yoke
D. yoke only
In transformer EMF equation ϕm represents
A. maximum flux
B. minimum flux
C. mutual flux
D. average flux
Window space factor (KW) in transformer design defined as
A. conductor area in window / total area in window
B. total area in window /conductor area in window
C. conductor area of core / total area of core
D. total area of core/conductor area of core
The output equation for DC machine (Pa)
A. Q = (Co) D2L*n kVA
B. Pa = (Co) D L*ns kW
C. Q = (Co) D L*n kVA
D. Pa = (Co) D2L*n kW
MMF for teeth is calculated using the following methods
A. Graphical method
B. Simpson Rule
C. Bt 1/3Method
D. All the above
The output equation for single phase core type transformer is
A. Q= 3.33 f Bm Ai KW AW δ 10-3 kVA
B. Q= 2.22 f Bm Ai KW AW δ 10-3 kVA
C. Q= 1.11 f Bm Ai KW AW δ 10-3 kVA
D. Q= 4.44 f Bm Ai KW AW δ 10-3 kVA
Gap contraction factor for slot (Kgs)
A. reduces the flux area in cross section (D)
B. increases flux area in cross section (D)
C. Neither increases nor decreases the flux area in cross section (D)
D. Reduces the flux area in core length section (L)
Gap contraction factor for ducts (Kgd)
A. reduces the flux area in cross section (D)
B. increases flux area in cross section (D)
C. Neither increases nor decreases the flux area in cross section (D)
D. Reduces the flux area in core length section (L)
Gap contraction factor (Kg)
A. Kgs+Kgd
B. Kgs*Kgd
C. Kgs/Kgd
D. Kgs-Kgd
The concept of real flux density (Breal) in tooth area originated because of following
A. assuming no slot flux
B. assuming slot flux with δ value
C. assuming no tooth flux
D. assuming tooth flux alone
Leakage coefficient is defined as
A. total flux / useful flux and its value is >1
B. total flux / useful flux and its value is <1
C. useful flux/ total flux and its value is >1
D. useful flux/ total flux and its value is <1
The concept of real flux density (Breal) in tooth area originated because of following
A. assuming no slot flux
B. assuming slot flux with δ value
C. assuming no tooth flux
D. assuming tooth flux alone
(2M) The copper conductors are preferred in place of aluminium conductors due to the following reason in windings
A. high conductivity & current ratings improved by 22%
B. low conductivity & current ratings improved by 22%
C. high conductivity & current ratings reduced by 22%
D. low conductivity & current ratings reduced by 22%
(2M) Stacking factor (Ki) of core material is equal to and its value is
A. L + Li nd Wd, 0.9
B. L / Li nd Wd, 0.86
C. Li nd Wd – L, 0.95
D. L – Li nd Wd, 0.95
(2M)Specific magnetic loading (Bav) defined as
A. Pϕ/πD
B. Pϕ/πDL
C. Iz Z/ πD
D. Iz Z/ πDL
(2M) Specific electrical loading (ac) defined as
A. Pϕ/πD
B. Pϕ/πDL
C. Iz Z/ πD
D. Iz Z/ πDL
(2M)The real flux density (Breal) in tooth area defined as
A. total flux in the slot pitch / tooth area
B. actual flux in the slot pitch / tooth area
C. actual flux in the slot pitch /slot area
D. total flux in the slot pitch / slot area
(2M) The real flux density (Bapp) in tooth area defined as
A. total flux in the slot pitch / tooth area
B. actual flux in the slot pitch / tooth area
C. actual flux in the slot pitch /slot area
D. total flux in the slot pitch / slot area
(2M) The Lap winding and wave winding are used
A. Increase current ratings and voltage ratings respectively
B. Decrease current ratings and voltage ratings respectively
C. Increase voltage ratings and current ratings respectively
D. Decrease voltage ratings and current ratings respectively
(2M) In transformer design LV windings are placed near the core and HV windings placed after LV winding
A. to reduce insulation thickness and uses LV winding as insulation for HV windings
B. to reduce current and uses HV winding as insulation for LV windings
C. to reduce voltage and uses HV winding as insulation for LV windings
D. to change frequency, power and flux.
Common data questions
The stator of a DC machine has a smooth surface but its rotor has open type of slots with slot width = tooth width=Ws, Wt=12mm and the length of air gap lg=2mm. Assume there is no ventilating radial ducts.
(2M) Carter’s co-efficient for slots is
A. 0.456
B. 0.545
C. 0.546
D. 0.547
(2M)The slot pitch Ys equal to
A. 25 mm
B. 23 mm
C. 21 mm
D. 24 mm
(2M) Gap contraction factor for slots
A. 1.39
B. 1.38
C. 1.40
D. 1.37
(2M) Gap contraction factor for Tooth
A. 1.00
B. 1.50
C. 1.25
D. 0.50
(2M) Total Gap contraction factor is
A. 1.37
B. 1.38
C. 1.39
D. 1.40
(2M) Effective length of air gap is
A. 2.75 m
B. 2.73 mm
C. 2.71 mm
D. 2.74 mm
(2M) Armature core of DC machine has a gross length of 0.33m including 3 ducts each 10mm wide iron space factor is 0.9
Net iron length Li is
A.0.27m
B. 0.28m
C. 0.29m
D. 0.295m
