Why are asynchronous motor (induction motor) often considered the “workhorse” of the industrial world? As an evergreen player in the industry, they excel in applications such as industrial equipment, blowers, and water pumps.
So, what’s so special about this mysterious motor?
Asynchronous Electric Motor Overview
An asynchronous motor is an AC motor that operates differently from a synchronous motor. Because its rotor speed is different from the speed of the magnetic field generated by the stator current, it is called an asynchronous motor.
Why is it also called an induction motor?
The absence of direct electrical contact between the stator and rotor enables electromagnetic induction to facilitate the conversion of mechanical and electrical energy. Hence, it’s also known as an induction motor.
How are asynchronous motors classified?
Classification of Asynchronous AC Motor
By Phase: Single-phase and three-phase induction motors.
By Rotor Structure Design: Squirrel cage induction motors and wound rotor induction motors.
How are induction motors designed, and how do they convert electrical energy into mechanical energy?
Structure of Asynchronous Motor
The primary components of an asynchronous motor are the stator and rotor, separated by an air gap. Additional components include end covers, bearings, and housing.
Stator
The stator is the stationary part of the motor, comprising the stator lamination core and stator winding.
Stator Core
The stator core forms part of the motor’s magnetic circuit and holds the stator winding.
Induction motor stator is typically constructed from silicon steel sheets, 0.35–0.5 mm thick, with an insulating layer on the surface. These sheets are stamping and lamination stacking.
The inner circle of the motor stator lamination contains evenly distributed slots (ranging from 12 slots to 72 slots) to house the windings.
Slot Types
There are three types of slots in the asynchronous motor stator core: semi-closed slots, semi-open slots and open slots.
Semi-enclosed slots: Found in small motors with round wire windings.
Semi-open slots: Used in low-voltage medium-sized motors with preformed coils.
Open slots: Employed in high-voltage large motors with insulated, varnished coils.
Stator Winding
The stator winding is the circuit part of the motor, inducing electromotive force, passing current, and establishing a rotating magnetic field to achieve electromechanical energy conversion.
The induction motor winding is usually wound with enameled copper wire or aluminum wire. Small asynchronous motors use single-layer stator windings, which are wound with high-strength enameled round copper wire or aluminum wire. Large and medium-sized asynchronous motors use double-layer short-distance, that is, rectangular-section copper or aluminum wires to make coils embedded in the stator slots.
The winding is separated from the stator slot wall by insulating material. Most induction motor stator cores and windings are insulated with insulating paper.
Stator Winding Connection Form
There are two ways to connect the stator winding of an asynchronous motor: star (Y) and triangle (△). The stator winding can only be connected according to the specified method and cannot be changed arbitrarily, otherwise the three-phase motor will be damaged.
Rotor
Asynchronous motor rotor comprises the rotor core, rotor winding, and shaft.
Rotor Core
The rotor core is made of 0.35mm-0.5mm thick silicon steel sheets, which are punched, stacked, and laminated. Scrap silicon steel sheets from stator core production are often used to make rotor cores.
In small motors, the rotor lamination is directly pressed onto the shaft, while in larger motors (with a rotor diameter of 300-400mm or more), it is mounted on the shaft using a rotor frame.
The outer surface of the rotor lamination core features evenly distributed slots, and the choice of slot design depends on the motor’s operational and starting performance requirements.
Rotor Winding
The rotor winding can be classified into squirrel cage windings and wound rotor windings.
Squirrel Cage Rotor Winding
The squirrel cage winding, when the core is removed, resembles a cage.
Slots on the rotor core contain copper or aluminum bars as conductors. Short-circuit rings connect the ends of these bars, forming a closed circuit.
In medium and large induction motors, the bars are made of copper, inserted into the slots, and welded to copper rings at both ends. In small motors, aluminum bars are used and are cast along with the rotor core and internal fan in one mold.
Wound Rotor Winding
The wound rotor winding is similar to the three-phase winding of the stator. These windings are placed in the rotor slots, and the three-phase winding ends are connected in a star configuration. The lead wires extend from the rotor shaft to slip rings, allowing external resistance connections through brushes. This design improves the motor startup and speed regulation capabilities.
Shaft
The shaft, usually made of medium carbon steel, supports the rotor core, secures it, and transfers mechanical power effectively.
Air Gap
The air gap between the stator and rotor is a critical part of the main magnetic circuit. The size of the air gap significantly impacts the performance of an asynchronous motor.
A smaller air gap reduces magnetic resistance, decreases excitation current, and improves the motor’s power factor.The air gap should be as small as possible while avoiding mechanical friction during motor operation. In small and medium-sized motors, the air gap length typically ranges between 0.2mm and 1.5mm.
Asynchronous Motor Working Principle
When symmetrical voltage is applied to the stator winding of a three-phase asynchronous motor, a rotating magnetic field is generated. This field cuts through the rotor conductors, inducing an electromotive force. As the rotor windings are short-circuited, current flows, which interacts with the magnetic field to generate electromagnetic torque, driving the rotor.
Where are the stator and rotor cores of asynchronous motors used?
Applications of Asynchronous Stator and Rotor Cores
Asynchronous motor stator and rotor lamination core are widely used in:
Water Pump motors
Compressor motors
Blower motors
Electric Vehicles
Asynchronous motors are indispensable industrial devices, known for their simple and reliable design. The tight integration of stator and rotor, combined with either squirrel cage or wound structures and optimized air gap design, ensures efficient and stable operation.
Can Lamnow Manufacture Induction Motor Lamination?
Asynchronous Motor Core Lamination: Choose Lamnow
The answer is yes. Lamnow, a Chinese manufacturer of motor cores, produces high-quality asynchronous motor cores. Utilizing high-speed and compound stamping, they manufacture stator and rotor laminations with precision. The interlocking technique used in high-speed stamping is particularly advantageous for mass production. Additionally, Lamnow provides services such as winding stator cores and die-casting rotor cores to meet customer-specific needs.
Standard asynchronous motor cores for water pumps and blowers, such as the 90*47E. Stator customized option include: V slot, welding slot, hole, groove.Rotor customized option include: skew rotor, rotor die-casting ring shape(circle ring, pin, and fan). Our public mold, please refer to the table below for details. If there are products you need, please feel free to contact us.
| 64*38 | 73*38 | 80*45 | 90*47 | 90*48 | 90*50 | 90*52 |
| 110*55 | 110*66 | 120*70 | 125*65 | 125*80 | 135*70 | 135*80 |
| 140*55 | 140*56 | 140*70 | 140*75 | 150*80 | 150*90 | 152*90 |
| 160*80 | 160*88 | 170*90 | 170*103 | 173*90 | 173*103 | 200*100 |
