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1000 Design Electrical Machines
Which of the following circuit is designed to dissipate heat produced in the machine?
a) Electric circuit
b) Magnetic circuit
c) Dielectric circuit
d) Thermal circuit
Which of the following materials is generally used in the design of electromagnetic machines?
a) Paramagnetic materials
b) Diamagnetic materials
c) Ferromagnetic materials
d) Core-magnetic materials
What must be mainly ensured to keep the temperature rise within limits?
a) Good efficiency of the machine
b) Proper cooling and ventilation
c) Proper saturation level
d) Good insulation
Which of the following kind of conductors will require thicker insulation?
a) Large sized conductor
b) Small-sized conductor
c) Conductors with high permeance
d) Conductors with low permeance
Which of the following factor mainly determines the type of insulation for an electrical machine?
a) Maximum allowable flux density
b) Maximum operating temperature
c) Maximum efficiency of the machine
d) Maximum allowable loss in machine
How should be the magnetic and electrical loadings in a highly efficient electric machine?
a) It must be small
b) It must be large
c) It must be equal to the current density
d) It must be equal to the flux density
What kind of emf is produced in an electric machine when the coil is stationary and flux varies with time?
a) Transformer emf
b) Motional emf
c) Interactional emf
d) Induction emf
What kind of materials are used to design electrical heating devices?
a) High Conductivity Materials
b) High Resistivity Materials
c) High Weldability Materials
d) High Solderability Materials
What are the main dimensions of a rotating electric machine?
a) Field diameter and Armature core length
b) Armature diameter and Field core length
c) Armature diameter and Armature core length
d) Field diameter and Field core length
What determines the output of a dc electric machine?
a) Only Total Magnetic loading
b) Only Total Electric loading
c) Total loadings
d) Either Total Magnetic loading or Total Electric loading
How will the size and cost of a rotating electric machine be if it is designed with greater speed?
c) large size and more cost
d) large size and less cost
a) small size and more cost
b) small size and less cost
What is the relation between the output coefficient to the volume of active parts in a rotating electric machine?
a) directly proportional
b) inversely proportional
c) equal to
d) No relation can be established
How should be the output coefficient of a rotating electric machine from an economics point of view?
d) Output coefficient does not affect the economics
How should be the specific loadings to design a machine with reduced dimensions?
a) Increased values of specific loadings
b) Decreased values of specific loadings
c) Zero specific loadings
d) Moderate values of specific loadings
Where does maximum flux density occur in a well-designed electric machine?
a) In the rotor
b) In the air gap
c) In the teeth
d) In the poles
Which of these factors does not determine the specific magnetic loading in rotating machines?
a) Magnetizing current
b) Core loss
c) Maximum flux density in iron parts
d) Number of parallel paths
What is the other name for a short-pitched coil electrical machine?
What kind of layer winding does a closed winding of an electric machine usually have?
a) Single layer
b) Double layer
c) Single layer or Double layer
d) Mixture of single layer and double layer
Why are tapered interpoles used in large DC electric machines?
a) To eliminate saturation at root of pole
b) To obtain higher speeds
c) To obtain maximum torque
d) To eliminate eddy current loss
Which part of an electric machine is designed to give the main magnetic flux?
c) Main poles
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