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33262737 > EE Mid > Flashcards

EE Mid Flashcards

1
Q

The zero sequence component of the unbalanced 3-phase system of vectors VA, VB, and VC is ______ of their vector sum.

A

one third

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2
Q

In most generators, the output voltage is induced by?

A

relative motion between the field and the armature coils

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3
Q

Wave winding is employed in a dc machine of?

A

low current and high voltage rating

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4
Q

The function of an equalizer ring is? (2)

A
  1. To avoid unequal distribution of current at brushes.
  2. To help get sparkless commutations
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5
Q

The teeth in the armature of a DC machine are sometimes skewed. This is done to reduce?

A

Vibrations

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6
Q

A quantity that contains all the power information in a given load is the?

A

Complex Power

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7
Q

Transient disturbance is produced in a circuit whenever… (3)

A
  1. It is suddenly connected or disconnected from the supply.
  2. It is shorted.
  3. Its applied voltage is changed suddenly.
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8
Q

There are no transients in pure resistive circuit because they…

A

have no stored energy

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9
Q

Transient currents in electrical circuit are associated with… (2)

A
  1. inductors
  2. capacitors
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10
Q

It is the name given to that property of a material which opposes the creation of magnetic flux in it. It, in fact, measures the opposition offered to the passage if magnetic flux through a material.

A

Reluctance

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11
Q

It is a property that implies the case or readiness with which magnetic flux is developed.

A

Permeance

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12
Q

Kirchhoff’s current law is applicable to only…

A

junctions in a network

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13
Q

Maxwell’s loop current method of solving electrical networks…

A

utilizes kirchhoff’s voltage law

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14
Q

One kWh of electric energy equals?

A

860 kcal

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15
Q

The unit of absolute permittivity of a medium is?

A

farad/meter

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16
Q

In parallel resonance, what will happen to the current?

A

Minimum

17
Q

Between no-load and full-load, ________ motor develops the least torque.

A

series

18
Q

The shaft torque of a DC motor is less than its armature torque because of ___________ losses.

A

rotational

19
Q

What DC motor would be suitable for drives requiring high starting torques but inly fairly constant speed such as crushers?

A

compound

20
Q

A 200V, 10A motor could be rewound for 100V, 20A by using _____ as many turns per coil of wire, having _____ the cross-sectional area.

A

half, twice

21
Q

Unlike a shunt motor, it is difficult for a series motor to stall under heavy loading because? (2)

A
  • it develops high overload torque
  • it slows down considerably
22
Q

The quantity which maintains the same direction whether a DC machine runs as a generator or as a motor.

A

Field Current

23
Q

In a DC motor, the mechanical output power actually comes from?

A

electrical input power

24
Q

These are produced when the energized circuit is rapidly de-energized and reaches an eventual steady-state of zero current or voltage, as in this case of short-circuiting an RL or RC circuit suddenly.

A

Subsidence Transients

25
Q

In these transients, the transition occurs cyclically towards states, which when reached, become unstable themselves.

A

Relaxation Transients

26
Q

A smooth output from a generator is obtained by?

A

design of the armature winding

27
Q

In a DC machine, stray loss is the sum of?

A

Iron loss and Mechanical loss

28
Q

A DC generator works on the principle of?

A

Faraday’s Law of Electromagnetic Inductuon

29
Q

These are produced in a circuit, which is originally dead, is energized.

A

Initiation Transients

30
Q

These are produced in a circuit which is simultaneously subjected to two transients due to two independent disturbance or when the disturbing force producing the transients is itself variable.

A

Complex Transients

31
Q

Transient current in an RLC circuit is oscillatory when

A

R<2sqrt(L/C)

32
Q

The transient current in a loss-free LC circuit when excited from an AC source is a/an _______ sine wave.

A

undamped

33
Q

Double energy transients are produced in circuits consisting of… (3)

A
  1. resistance
  2. inductance
  3. capacitance

33262737 (12 decks)

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