Practice Tricky Design Electrical Machines Multiple Choice Questions with Answers Quiz-1

Q.1.

What is the formula for the winding height in the design of the field windings?

a) winding height = height of the pole – height of shoe + space taken by the spool, flanges, etc
b) winding height = height of the pole + height of shoe + space taken by the spool, flanges, etc
c) winding height = height of the pole + height of shoe – space taken by the spool, flanges, etc
d) winding height = height of the pole – height of shoe – space taken by the spool, flanges, etc

Explanation

Q.2.

What is the approximate value of the space taken by spools, flanges, etc?

a) 15 mm
b) 10 mm
c) 12 mm
d) 20 mm

Explanation

Q.3.

What is the winding depth for the pole pitch of 0.1 mm?

a) 25 mm
b) 35 mm
c) 45 mm
d) 50 mm

Explanation

Q.4.

What is the formula for the voltage across each field coil?

a) voltage across each field coil = field current * resistance of each field at 75°C
b) voltage across each field coil = field current / resistance of each field at 75°C
c) voltage across each field coil = field current + resistance of each field at 75°C
d) voltage across each field coil = field current – resistance of each field at 75°C

Explanation

Q.5.

What is the range of the current density in the field conductors?

a) 3 to 5 A per mm2
b) 3 to 4 A per mm2
c) 4 to 5 A per mm2
d) 3 to 6 A per mm2

Explanation

Q.6.

What is the formula for the field current of the synchronous machines?

a) field current = current density * area of conductors
b) field current = current density / area of conductors
c) field current = current density – area of conductors
d) field current = current density + area of conductors

Explanation

Q.7.

What is the formula for the number of field turns of the field windings?

a) number of field turns = field mmf per pole at full load * field current
b) number of field turns = field mmf per pole at full load / field current
c) number of field turns = field mmf per pole at full load + field current
d) number of field turns = field mmf per pole at full load – field current

Explanation

Q.8.

What is the relation between winding space and the depth?

a) winding space is directly proportional to the depth
b) winding space is indirectly proportional to the depth
c) winding space is directly proportional to the square of the depth
d) winding space is indirectly proportional to the square of the depth

Explanation

Q.9.

What is the formula of the resistance of the winding is calculated at 75°C?

a) resistance of the winding = (Number of field turns * pole proportion * length of mean turns of the coil) / area of the field conductors
b) resistance of the winding = (Number of field turns * pole proportion * length of mean turns of the coil) * area of the field conductors
c) resistance of the winding = (Number of field turns / pole proportion * length of mean turns of the coil) / area of the field conductors
d) resistance of the winding = (Number of field turns * pole proportion / length of mean turns of the coil) / area of the field conductors

Explanation

Q.10.

What is the formula of the dissipating surface of the coil?

a) dissipating surface of the coil = 2*length of mean turns of the coil*(winding height * diameter of winding)
b) dissipating surface of the coil = 2*length of mean turns of the coil*(winding height / diameter of winding)
c) dissipating surface of the coil = 2*length of mean turns of the coil*(winding height + diameter of winding)
d) dissipating surface of the coil = 2*length of mean turns of the coil/(winding height * diameter of winding)

Explanation

Q.11.

What is the formula for the cooling co-efficient to the rotating field coils?

a) cooling coefficient of rotating field coils = 0.05 to 0.08 / 1 + armature voltage
b) cooling coefficient of rotating field coils = 0.05 to 0.08 / 1 – armature voltage
c) cooling coefficient of rotating field coils = 0.08 to 0.12 / 1 + armature voltage
d) cooling coefficient of rotating field coils = 0.08 to 0.12 / 1 – armature voltage

Explanation

Q.12.

What is the formula for the temperature rise in the design of field windings?

a) temperature rise = 1 / copper loss in each field coil at 75°C * cooling coefficient of rotating field coils * dissipating surface of the coil
b) temperature rise = copper loss in each field coil at 75°C * cooling coefficient of rotating field coils * dissipating surface of the coil
c) temperature rise = copper loss in each field coil at 75°C / cooling coefficient of rotating field coils * dissipating surface of the coil
d) temperature rise = copper loss in each field coil at 75°C * cooling coefficient of rotating field coils / dissipating surface of the coil

Explanation

Q.13.

If the temperature increases beyond the acceptable limits the depth of the winding should be decreased.

a) true
b) false

Explanation

Q.14.

The increase in the depth of the winding increases the heat dissipating surface.

a) true
b) false

Explanation

Q.15.

What is the minimum clearance between adjacent field coils and pole drawing?

a) 14 mm
b) 15 mm
c) 13 mm
d) 12 mm

Explanation

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