Induction motor common failure analysis

Induction motors are widely used in industrial production and daily life. Their operation status has a great impact on industrial production. Once a fault occurs, it may lead to economic losses. Therefore, it is very important to detect the early operation status of induction motors, timely identify abnormalities, and troubleshoot faults.

Components of an induction motor

The main structure of an induction motor consists of stator, rotor, and motor bearings.

• Stator: The stator of an induction motor is made up of thin steel sheets stacked together, with stator windings wound on top. For some small motors, these thin sheets are cut from single thin steel sheets; for high-power motors, these laminations are usually thicker and block-shaped. Each steel sheet is coated with an insulation layer, and they are stacked together by riveting or welding to form the stator magnetic circuit. The stator windings are installed in pre-designed slots, divided into distributed windings and concentric windings. When the mechanical structure of the winding of the induction motor is made by mechanical processing, concentric windings are usually used. The electrical windings and stator core are insulated with insulation materials, and different insulation materials are used for different motor applications.
• Rotor: The rotor magnetic circuit is also made up of thin steel sheets, the same as those used to manufacture the stator. The rotor of an induction motor is divided into two types: wound rotor and squirrel-cage rotor. For squirrel-cage rotors, high-power motors usually use copper bars, while low-power motors use aluminum bars.
• Bearing: Motor bearing is a special type of bearing used specifically for motors. This bearing is a component that supports the shaft, guiding its rotation and also bearing the parts that rotate on the shaft. There are four main types of bearings commonly used in motors, namely rolling bearings, sliding bearings, spherical bearings, and oil-lubricated bearings. The most common type of motor bearing is rolling bearing, which has rolling elements. Most of Lunyee's motors use ball bearings.

Analysis of Motor Failure Causes

There are multiple components inside the induction motor, and there are various faults in its drive system. According to the causes of the faults, they can be divided into two categories: faults caused by internal reasons and faults caused by external reasons. External reason faults are often caused by power supply voltage, mechanical load, and operating environment; internal reason faults are often caused by internal components of the motor, such as magnetic flux, stator/rotor windings, mechanical air gaps, and squirrel cage, etc. Depending on the type of fault, the main faults are mechanical faults, electrical faults, and faults caused by the environment. Any fault will cause distortion of the motor air gap rotating magnetic field. Therefore, harmonics will be included in the measurement signal. By measuring these signals, the motor operating status can be monitored externally. These signals can be electrical signals or mechanical signals, such as current, voltage, magnetic flux, torque, and speed, etc. By detecting changes in these information, the operating status of the motor can be understood in a timely manner, preventive measures can be taken in advance, unnecessary problems can be identified and avoided to prevent losses.