AC Winding Design: Concentrated and Distributed Winding

AC Winding Design

• Concentrated and Distributed Winding:
  • Concentrated winding: all turns of a coil are wound in the same location or coil span.
  • Distributed winding: turns of a coil are spread out over a significant portion of the core.
  • Characteristics: simplicity, current carrying capacity, electromagnetic stress, and applications.

Concentrated Winding

• Definition: entire winding is concentrated in a specific region of the core.
• Characteristics:
  • Simple construction
  • Suitable for low to moderate current applications
  • Higher electromagnetic stress, leading to higher losses and reduced efficiency
• Applications: small motors, transformers, and other low-power devices

Distributed Winding

• Definition: turns of a coil are spread out over a significant portion of the core.
• Characteristics:
  • Complex construction
  • Higher current carrying capacity
  • Reduced electromagnetic stress, leading to lower losses and improved efficiency
• Applications: high-power machines such as large motors, generators, and power transformers

Integral Slot and Fractional Slot Winding

• Integral Slot Winding:
  • Number of coils per pole per phase is an integer (whole number).
  • Each coil is placed in a single slot, and the number of slots is a multiple of the number of poles.
  • Characteristics: simplicity in manufacturing, robust, and suitable for machines with a small number of poles.
  • Disadvantages: may exhibit higher cogging torque, limited ability to optimize performance characteristics.
• Fractional Slot Winding:
  • Number of coils per pole per phase is a fraction.
  • Typically, there are more coils per pole per phase than the number of poles.
  • Characteristics: improved performance characteristics, higher efficiency, and better utilization of the machine.
  • Disadvantages: more complex manufacturing, increased chances of manufacturing errors.

Full Pitch and Short Pitch Windings

• Full Pitch Windings:
  • Distance between the centers of two consecutive turns is equal to the length of one complete turn.
  • Characteristics: improved voltage regulation, efficiency, and better utilization of the winding area.
  • Disadvantages: may lead to higher leakage reactance.
• Short Pitch Windings:
  • Distance between the centers of two consecutive turns is less than the length of one complete turn.
  • Characteristics: reduced leakage reactance, suitable for applications where a lower reactance is desired.
  • Disadvantages: slightly increased losses.

Single Layer and Double Layer Winding

• Single Layer Winding:
  • Each turn of the coil is wound side by side, without any turns being placed on top of each other.
  • Characteristics: simplicity, better cooling, and limited space utilization.
  • Applications: small transformers and certain electric motor designs.
• Double Layer Winding:
  • Each coil turn consists of two layers: one on top of the other.
  • Characteristics: efficient use of space, lower resistance, and better performance.
  • Disadvantages: complex manufacturing, reduced cooling.

Distribution Factor

• Distribution Factor (Kd):
  • Accounts for the distribution of the coil turns along the winding.
  • Formula: Kd = (sin(m.β)/2)/(m.sin(β/2))
  • Ranges from 0 to 1, indicating the level of distribution or concentration of the winding.

Coil Pitch Factor and Winding Factor

• Coil Pitch Factor (Kp):
  • Accounts for the distribution of coil turns along the core of a machine.
  • Formula: Kp = sin(mβ/2)/(m sin(β/2))
• Winding Factor (Kw):
  • Accounts for the spatial distribution of coil turns within a winding.
  • Formula: Kw = Kp * Kd (for single-layer winding)
  • Formula: Kw = Kp * Kd * Ks (for concentric multilayer winding)

Development of Winding Diagrams

• Importance of Drawings:
  • Drawings are essential for communication between designers and manufacturers.
  • They help in planning processing, machining, material requirements, and cost estimation.
• Software for Designing Electrical Equipment:
  • Finite element methods (FEM) are used to solve magnetic field problems.
  • However, FEMs have limitations, such as requiring exact geometrical data and being time-consuming.
• MATLAB Programs:
  • Implemented to solve various AC windings in electrical engineering.
  • Can reduce the burden and save time for designers.
  • Can be used for verification of solutions obtained theoretically.

Types of AC Windings

• Armature Winding:
  • Mainly of two types: Lap winding and Wave winding.
  • Can be designed as single layer or double layer winding.
  • Single layer winding can be classified as Un-bifurcated and Bifurcated winding.
  • Most synchronous machines and induction machines have double layer winding in the armature.