The motor windings can be divided into concentrated windings and distributed windings. In the case of distributed windings, the windings are always wound on at least two stator teeth. On the other hand, in the case of concentrated windings, only one stator tooth is wound.
Both types of windings have different advantages and disadvantages, and when to use concentrated windings and when to use distributed windings depends on the size of the motor and its application.
The number of slots and the way the motor is manufactured also affects the choice of winding type. Features important to winding design are fractional slot windings and integer slot windings, as well as single-layer windings and double-layer windings.
This article aims to delve into the disparities between concentrated and distributed windings, elucidating their characteristics, applications, and technical variances.
Concentrated Windings
Concentrated windings involve winding the stator around a single tooth, simplifying the manufacturing process significantly. This approach results in minimal winding heads at the motor’s top and bottom, leading to lower ohmic losses, particularly at lower speeds.
Advantages of Concentrated Windings
Simplified manufacturing process due to winding around a single tooth.
Reduced ohmic losses, especially at lower speeds.
Well-suited for short, large-diameter electric motors like hub motors in electric bicycles.
Disadvantages of Concentrated Windings
Concentrated windings are more localized and don’t cover the entire core periphery which can lead to a less uniform magnetic field.
Higher harmonic losses, particularly at higher speeds.
Potential torque ripple issues, which can be addressed through rotor design modifications.
Distributed Windings
On the contrary, with distributed winding, at least two teeth of the stator are always wound, and the number of teeth wound is called the coil pitch or step size, although 3, 4, 5, or more teeth can also be wound. The coil span depends on the number of teeth on the stator and the number of pole pairs on the rotor.
In distributed winding, the windings overlap at the top and bottom of the motor. This area of the motor is also called the winding head. Due to the overlap, the winding heads in distributed windings are larger than those in concentrated windings.
Advantages of Distributed Windings
Smooth sinusoidal back electromotive force (EMF), reducing harmonics and losses.
Higher efficiency, making it suitable for applications such as electric vehicles.
Low torque ripple and noise, ideal for precision applications like machine tool spindles.
Disadvantages of Distributed Windings
Increased winding losses in very short electrical machines due to overlapping windings.
Technical Differences
The primary technical difference between concentrated and distributed windings lies in the nature of the back EMF. Concentrated windings generate a trapezoidal back EMF, resulting in higher torque but increased losses.
Conversely, distributed windings produce a smoother sinusoidal back EMF, leading to higher efficiency, particularly crucial in applications like electric vehicles.
Conclusion
The choice between concentrated and distributed windings depends on various factors, including motor size, application requirements, and efficiency considerations. While concentrated windings offer simplicity in manufacturing and higher torque capabilities, they come with increased losses.
Distribution windings, though more complex to manufacture, provide smoother operation, higher efficiency, and reduced torque ripple, making them indispensable for precision and energy-efficient applications.
