Why brushless dc motor stator winding? What is its purpose?
The stator winding of a brushless motor is usually a three-phase winding of U, V, and W, and its purpose is to generate a magnetic field and drive the BLDC motor to rotate.
What are the bldc motor winding methods?
BLDC motor stator winding usually adopts two types: concentrated winding and distributed winding. Among them, the concentrated winding adopts a delta line connection method, while the distributed winding adopts a star connection method. In addition to the traditional round wire winding, the brushless motor also adopts flat wire winding.
BLDC Stator Concentrated Winding
In a concentrated stator winding, copper wire is wound precisely around a single stator tooth. Alternatively, the completed winding can be pushed onto the stator tooth. The stator tooth design must align with the copper coil design.
Why use concentrated winding?
Advantages Of Concentrated Winding
A key advantage of concentrated winding is the minimized winding heads on the top and bottom of the stator core, which leads to lower ohmic losses at low speeds compared to distributed winding.
Does this mean concentrated winding is more efficient?
Not necessarily. Concentrated winding generates high torque in low-speed ranges, but its efficiency is not high because the winding type introduces harmonics, causing increased losses, especially at high speeds.
Which motors commonly use concentrated windings?
Application Of Concentrated Windings
Concentrated windings are mainly used in short, large-diameter motors, such as hub motors in gearless electric bicycles.
Brushless Motor Stator Distributed Winding
As the name suggests, distributed winding does not wind copper wire on a single stator tooth. Instead, the copper wire winds across at least two stator teeth.
What is the pitch of a distributed winding?
The number of teeth wound in a distributed winding is called the coil pitch or step, which can span 3, 4, 5, or more teeth. The step is not fixed but varies based on the number of slots, typically a multiple of 3.
Advantages Of Distributed Winding
A key advantage of brushless motor distributed winding is its production of a smooth, nearly sinusoidal back EMF, which significantly reduces harmonics and minimizes losses in the stator and winding laminations.
Another advantage is high synchronization, resulting in reduced torque ripple and low motor noise.
Where are distributed winding motors used?
Application Of Distributed Winding
This winding type is used where high efficiency is needed, such as in electric vehicles, industrial water pumps, and fan motors.
Brushless Motor Stator Flat-Wire Winding
BLDC flat-wire stator winding primarily refers to the shape of the copper wire. Traditional copper wire is round, while flat-wire winding uses square-shaped copper wire. Flat-wire winding is classified into hairpin winding, I-Pin winding, S-Pin winding, and X-Pin winding.
Benefits Of Flat Wire Winding
Flat-wire winding in brushless motors offers several advantages:
High slot fill factor, with a pure copper slot fill rate of up to 70%
Efficiency reaching up to 95%
Enhanced heat dissipation capacity
Higher power and torque capabilities
Application Of Flat Wire Winding
Flat-wire motors are widely used in electric vehicle drive motors. For instance, Tesla uses a 10-layer flat-wire winding, while BYD uses a 6-layer flat-wire winding. With market expansion, flat-wire motors will find applications in even more fields.
Brushless Motor Stator Winding Parameters
Copper Wire Diameter
The copper wire diameter usually adopts the international standard AWG wire diameter standard. The larger the AWG value, the smaller the corresponding wire diameter, the smaller the cross-sectional area, and the higher the resistance. For example, AWG14 represents a copper wire diameter of 1.63mm, a cross-sectional area of
Number Of Turns
The number of turns of the coil usually depends on how many copper wires there are in a coil, and how many turns there are. The figure below shows 63 turns, which means there are 63 turns of copper wires.
Winding Coil
The green insulating paper in the middle is a group of coils, some are one strand in a group, some are two strands in a group, and some are even more.
Winding Step Length (Span)
The number of wound teeth is called the coil span or step length. For concentrated windings, the step length is 1. Distributed windings can be wound with 3, 4, 5 or more teeth. The following figure shows a winding with a step length of 6.
Brushless Motor Stator Winding Method
The stator winding technology mainly involves flyer winding, needle winding, and flat wire winding.
How is the flyer winding performed?
Flyer Winding
The flyer winding machines involve a high-speed rotating flyer that drives copper wire around the stator slots. Guide plates assist in directing the wire accurately into the slots, while the winding head moves back and forth, precisely controlled by servo motors. This ensures the wire is laid down in an orderly, layered manner.
What are the characteristics and requirements of flyer winding?
High Speed: Significantly increases production efficiency.
High Precision: Servo motors drive the winding head, ensuring uniform distribution of the wire within the stator slots, enhancing motor performance stability.
Automation: Includes automatic indexing, winding, arranging, slot changing, and wire cutting.
Multi-Station Capability: Available in 2, 4, and 6-station configurations.
Core Specifications: Outer diameter φ10-150mm, thickness 5-150mm, slot count 3-60.
After watching the flying fork winding, are you also curious about the needle winding? Follow my steps and we will continue.
Needle Winding
Brushless motor stator needle winding refers to the process of winding the coils on the stator of a brushless motor using a needle winding technique. After setting the parameters, the tungsten steel wire nozzle moves with the wire, while guide needles move vertically and horizontally to achieve precise winding and wire arrangement.
So what are the characteristics and requirements of needle winding?
High Flexibility and Adaptability: Can handle various stator types and achieve multi-layer and complex winding paths.
Multi-Station Capability: Available in 2, 4, and 6 station configurations.
Automation: Includes automatic winding, precise wire arrangement, slot changing, wire passing, and cutting.
Core Specifications: Outer diameter φ10-150mm, thickness <150mm, slot count 2-36.
Flat-Wire Winding
Flat-wire winding technology for stators includes Hairpin, I-pin, X-pin, and S-winding techniques. Specialized motor software can automatically generate engineering CAD winding diagrams, enabling quick and accurate stator coil winding design for flat-wire motors.
The flat-wire winding process involves several steps: slot paper insertion → hairpin manufacturing → hairpin insertion → end ring forming → end ring welding → impregnation and curing.
Now, do you know how critical the stator winding of a brushless motor is to the motor’s performance? The winding method is more than just “winding a circle”!
Concentrated winding can improve low-speed torque, distributed winding can reduce harmonics and noise, and the emerging flat wire winding can not only increase the slot fill rate, but also enhance heat dissipation and power. It is sought after by major manufacturers such as Tesla and BYD and is widely used in electric vehicles. Do you feel that the “heart” of the motor is also a technical job?
If you need BLDC motor stator lamination stacks or winding services, please contact us.
FAQS
What is a brushless stator?
The stator of a brushless motor is responsible for generating the rotating magnetic field that drives the rotor. It generally consists of a silicon steel sheet, enameled wire, bearings, and a bracket. The rotor, which rotates under the influence of the stator’s magnetic field, is primarily made up of the rotor shaft, magnets, and a bracket. Additionally, the number of pole pairs formed by the stator and rotor affects the motor’s speed and torque.
How do the stator and rotor of a brushless motor affect each other?
The stator of a brushless DC motor is a coil-wound armature and the rotor is a permanent magnet. By detecting the position of the motor rotor in real time and then providing the corresponding current to different phases of the motor according to the rotor position, the stator generates a rotating magnetic field with uniformly changing direction and the motor can rotate with the magnetic field.
