How to Disassemble a Small Motor

Author: Ying Qifei
Editor-in-Chief: Gao Ke et al.
Publisher:
Publish Date: 1999-05-01
Features: This book is primarily practical and easy to understand. It starts with an introduction to the basic structure of electric motors and systematically and specifically introduces the disassembly, assembly, fault analysis, inspection, and repair of small three-phase asynchronous motors. It also provides a detailed explanation of the calculation and operational techniques for completely replacing the stator winding of small motors. For clarity and intuitiveness, the book is accompanied by numerous illustrations and essential technical data, enabling readers to perform practical operations by reading the book alone. This book is a highly instructive read and can serve as a self-study and training textbook for electricians. It also holds certain reference value for professional motor repair personnel.
Excerpt: In recent years, the new basic series motors have replaced the JO2 and J2 series. The Y series motors can be further divided into two basic series based on the outer casing protection level: IP44 (enclosed) and IP23 (protected). The Y series IP44 enclosed three-phase asynchronous motors (with frame sizes ranging from 80 to 315) are general-purpose fully enclosed self-cooled squirrel cage three-phase asynchronous motors suitable for driving various machinery and equipment without special performance requirements, such as metal cutting machines, fans, and pumps. Their rated voltage is 380V, rated frequency is 50Hz, and power range is 0.55 to 160kW, divided into 22 power levels. The entire series has 12 frame sizes and 82 specifications. The Y series IP23 three-phase protected squirrel cage asynchronous motors (with frame sizes ranging from 160 to 315) have a protective structure different from the IP44 enclosed type but are superior to drip-proof motors. They can prevent fingers from touching the inner electrified parts or rotating parts of the casing, prevent solid foreign objects larger than 12mm from entering the motor, and prevent the impact of rain at an angle of 60° or less from the vertical line on the motor. Therefore, the outer casing protection level of the Y series (IP23) motors has been significantly improved compared to the J2 series, making motor operation safer and more reliable.
Three-phase asynchronous motors can be roughly divided into two main parts structurally: the stationary part and the rotating part. The stationary part is called the stator, and the rotating part is called the rotor.
Stator Composition
The stator consists of the frame, stator core, and stator winding. The frame serves as the motor's support, primarily used to bear the core and fix the end covers. Frames of small and medium-sized asynchronous motors are generally made of cast iron, while some small motors use aluminum castings. The outer surface of enclosed motor frames has cooling fins, and the sides of protected motor frames are equipped with ventilation holes for better heat dissipation. The inner cavity of the frame is a cylindrical space used to install the stator core, stator winding, and the entire rotor.