Armature Winding Fundamentals

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Questions and Answers

What is the defining characteristic of single-phase winding?

The windings are arranged at 90 degrees to each other.

The induced emfs are exactly sinusoidal.

The output emf is obtained from one winding. (correct)

Multiple windings are placed on the armature.

Which type of winding results in a more sinusoidal wave form of induced emf?

Concentrated winding

Distributed winding (correct)

Short pitch winding

Single layer winding

What is a key advantage of using short pitch winding over full pitch winding?

It enhances the sinusoidal nature of the induced emf.

It increases the overall emf induced.

It minimizes the required space for windings.

It decreases the length of end-connections and saves copper. (correct)

How many pole slots are typically used in concentrated windings?

Only one slot per pole Signup and view all the answers

In which configuration are both coil sides placed in one slot?

Double layer winding Signup and view all the answers

What type of armature winding employs more than one winding producing multiple emfs?

Poly-phase winding Signup and view all the answers

What happens to the emf induced in a winding when it is short pitched?

It decreases compared to full pitch winding. Signup and view all the answers

Which of the following best describes full pitch winding?

It achieves the maximum induced emf. Signup and view all the answers

What is the primary advantage of using short pitch winding in generators?

It helps in reducing the slot reactance and improves emf wave shape. Signup and view all the answers

In which type of winding do coil sides overlap each other consecutively?

Lap winding Signup and view all the answers

What is the expected effect of harmonics in the wave form of generated emf?

They distort the wave form and can lead to inefficiencies. Signup and view all the answers

What is pole pitch in relation to armature winding?

The distance between the neutral axes of adjacent poles. Signup and view all the answers

Why is lap winding preferred over wave winding in practical applications?

The connections are simpler than those of wave winding. Signup and view all the answers

Which winding type is best suited for large diameter, low-speed synchronous machines?

Concentric winding Signup and view all the answers

What relationship exists between electrical angle and mechanical angle in armature winding?

Electrical angle equals mechanical angle multiplied by the number of pairs of poles. Signup and view all the answers

What is a potential disadvantage of short pitch winding?

It requires additional turns to achieve the same induced voltage. Signup and view all the answers

What defines a multi-turn coil?

It contains multiple turns connected in series with coils placed in slots. Signup and view all the answers

In a full pitch winding, how is the total induced emf calculated?

Total induced emf is twice the induced emf of one side of the coil. Signup and view all the answers

What determines the coil pitch in a full pitch winding?

It is always equal to 180 electrical degrees. Signup and view all the answers

What is the effect of short pitching a winding?

It reduces the total induced emf due to less angular separation. Signup and view all the answers

What constitutes distributed winding?

Conductors of one phase are distributed across several slots under a single pole. Signup and view all the answers

What is the slot pitch in the winding scheme described?

15 degrees Signup and view all the answers

In a three-phase winding with a 4-pole, 24-slot armature, how many slots are allocated per phase?

6 slots Signup and view all the answers

What is the role of the coil span factor in winding?

To define the relationship between coil span and pole pitch. Signup and view all the answers

Study Notes

Armature Winding Overview

The armature is the stationary part of large synchronous machines, located within the stator core.
It consists of multiple slots, primarily open parallel-sided, where armature windings are placed.

Types of Armature Winding

Single-phase and Poly-phase Windings
- Single-phase: Involves one winding producing one emf.
- Poly-phase: Involves multiple windings that induce different emfs, typically three-phase windings.
Concentrated and Distributed Windings
- Concentrated windings: Utilize one slot per pole and maximize induced emfs but yield non-sinusoidal waveforms.
- Distributed windings: Have multiple slots per pole, producing slightly lower induced emfs but sinusoidal waveforms.
Single Layer and Double Layer Windings
- Single layer: Only one coil side is placed in each slot.
- Double layer: Two coil sides are stacked within one slot.
Full Pitched and Short Pitched Windings
- Full pitch: Coil sides are 180 electrical degrees apart, maximizing induced emf.
- Short pitch: Coil sides are closer than 180 degrees, leading to less induced emf but reduced copper usage and improved waveform.
Concentric (Spiral), Lap, and Wave Windings
- Concentric winding: Coils arranged in a spiral, preferred for low-speed, large diameter synchronous machines.
- Lap winding: Coils overlap, simplifying connections.
- Wave winding: Coils are always forward connected, resulting in a more complex structure compared to lap winding.

Important Terms in Armature Winding

Electrical Angle: Correlates one cycle of emf induced in a conductor to the number of poles, expressed as Electrical angle = Mechanical angle × Pair of poles.
Pole Pitch: Distance between the neutral axes of adjacent poles; can be calculated as Number of slots per pole = Total slots (S) / Number of poles (P).
Coil: A configuration of conductors placed in two slots, either full pitch or short pitch.

Winding Design Example

For a three-phase, 4-pole, 24 slot armature:
- Total slots per phase: 2 (24 slots / 12 slots per phase).

Coil Span Factor

In full pitch windings, coil span equals pole pitch (180 degrees).
Short pitched windings have a coil span less than 180 degrees, reducing total induced emf due to less angular separation.

Distribution Factor

In concentrated windings, all conductors of one phase under a pole reside in a single slot.
In distributed windings, conductors are spread across several slots, creating coils connected in series with similar emf waveforms but phase differences determined by slot pitch.
Slot pitch for a specific system can be calculated using slot pitch = 180° / Number of slots per pole.

Summary

Armature windings play a critical role in the electrical output of synchronous machines, with various types influencing performance, waveform characteristics, and material efficiency.
Understanding winding types, design configurations, and key terms is essential for optimizing machine design and efficiency.

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Description

Explore the essential concepts of armature winding in synchronous machines. This quiz covers various types of windings, including single-phase, poly-phase, concentrated, and distributed windings. Test your understanding of how these winding types affect electromagnetic induction and waveform production.