:Electric motors are more prone to burning out windings than in the past, due to the continuous development of insulation technology.
In motor design, there is a requirement to increase output while reducing size, resulting in smaller thermal capacity and weaker overload capabilities for new types of motors. Additionally, with the increased level of production automation, motors are frequently required to operate in various modes such as frequent starting, braking, forward and reverse rotation, and variable loads, which pose higher demands on motor protection devices. Furthermore, motors are now being used in a wider range of applications, often in extremely harsh environments such as damp, high temperature, dusty, and corrosive conditions. C
ombined with manufacturing irregularities and equipment management oversights, this has led to motors being more prone to damage nowadays, with overload, short circuit, phase loss, and commutation-related faults occurring most frequently.The effectiveness of traditional protection devices is not satisfactory. Traditional motor protection devices mainly consist of fuses and thermal relays.
Fuses are mainly used for short circuit protection, and their current rating selection should consider the motor’s starting current. Therefore, using fuses alone for motor protection is not advisable. Thermal relays are the most widely used motor overload protection devices, but they have low sensitivity, large errors, poor stability, and unreliable protection.
In fact, despite many installations of thermal relays, the occurrence of motor damage affecting normal production is still common. Traditional protection devices have also not been able to achieve mechanical wear monitoring of motors or monitoring of rotor eccentricity.Motor protection devices have now evolved from mechanical to electronic and intelligent types.
They have high sensitivity, reliability, multiple functions, and convenient adjustment. They can directly display parameters such as current, voltage, and temperature of the motor, making it easy to identify the types of faults after protection actions and greatly facilitating fault diagnosis, which is beneficial for on-site fault handling and reducing production restoration time. Additionally, motor eccentricity detection technology based on motor air gap magnetic field makes online monitoring of motor wear status possible. By displaying a curve reflecting the change trend of the motor’s eccentricity value and recording the variation of this value over a two-year period, early detection of bearing faults can be achieved, enabling early detection and treatment to avoid commutation accidents.
The purpose of selecting motor protection devices is to enable motors to fully utilize their overload capabilities, avoid damage, and improve the reliability and continuity of power drive systems. When protection requirements can be met, the simplest protection device should be considered first. Only when the simple protection devices cannot meet the requirements, or higher requirements for protection functionality and characteristics are needed, should more complex protection devices be considered, to achieve a balance between economy and reliability.
The specific selection of functions should be based on comprehensive considerations such as the value of the motor itself, load conditions, environmental conditions, the importance of the motor, and the impact of downtime on the production system, striving for economic rationality.An ideal motor protector is not the one with the most functions or the so-called most advanced, but the one that is most practical. What makes it practical? Practicality should meet the requirements of reliability, economy, and convenience, with a high performance-to-price ratio. What makes it reliable? Reliability should first meet the reliability of functions, for example, overcurrent and phase loss protection functions should reliably operate in various situations, processes, and modes. Secondly, the protector itself should have high reliability as it is meant to protect others, especially having adaptability, stability, and durability in various harsh environments. Economy: Adopt advanced design, reasonable structure, specialized and large-scale production, reduce product costs, and bring high economic benefits to users. Convenience: It must be as simple and convenient as possible in terms of installation, use, adjustment, and wiring.
Post time: Nov-14-2023