CFE AC/DC Machines

What is the work of the frame of dc machines?

• to reduce the voltage

• to reduce the flux

• to carry the flux

• to carry the current

Why is the length of the yoke made larger?

• to protect the armature windings

• to cover the armature windings

• to cover the field windings

• to cover and protect the field windings

What is the formula for the depth of the yoke?

• depth of yoke = thickness/2

• depth of yoke = thickness

• depth of yoke = 2*thickness

• depth of yoke = 3*thickness

In large machines, the thickness is relatively larger to the diameter.

• true

• false

What is the formula in order to check the rigidity?

• moment of inertia ≥ (weight of magnetic frame * radius2 * 10-6) / 225

• moment of inertia ≤ (weight of magnetic frame * radius2 * 10-6) / 225

• moment of inertia = (weight of magnetic frame * radius2 * 10-6) / 225

• moment of inertia < (weight of magnetic frame * radius2 * 10-6) / 225

What is the formula for the thickness of the ac machines?

• thickness = 40 * inner diameter of frame/12

• thickness = 40 + inner diameter of frame/12

• thickness = 40 - inner diameter of frame/12

• thickness = 40 * inner diameter of frame*12

What is the formula for the breadth of the ac machine?

• breadth = 6 + 0.01 * inner diameter of frame

• breadth = 6 - 0.01 * inner diameter of frame

• breadth = 6 * 0.01 * inner diameter of frame

• breadth = 6 / 0.01 * inner diameter of frame

What is the formula for the checking of rigidity of induction machines?

• moment of inertia ≥ radius / length of stator core * 90

• moment of inertia ≥ radius * length of stator core * 90

• moment of inertia ≥ radius * length of stator core / 90

• moment of inertia ≤ radius / length of stator core * 90

What is the formula for the radius at the centre of gravity?

• radius at the centre of gravity = inner diameter1.5/6.3

• radius at the centre of gravity = inner diameter2/6.3

• radius at the centre of gravity = outer diameter1.5/6.3

• radius at the centre of gravity = outer diameter2/6.3

What is the formula of the centrifugal force?

• centrifugal force = weight of revolving body * 39.43 * speed2 * radius of circular path

• centrifugal force = weight of revolving body / 39.43 * speed2 * radius of circular path

• centrifugal force = weight of revolving body * 39.43 / speed2 * radius of circular path

• centrifugal force = weight of revolving body * 39.43 * speed2 / radius of circular path