Motor protector performance knowledge
The function of the motor protector is to provide comprehensive protection control for the motor. Overcurrent, undercurrent, phase failure, stall, short circuit, over voltage, under voltage, leakage, three-phase unbalance, overheating, grounding, bearing wear, When the rotor is eccentric, the winding is aged to give an alarm or protection control.
Motor protection daily knowledge
1. Why is the current motor easier to burn the windings than in the past?
Due to the continuous development of insulation technology, in the design of the motor, it is required to increase the output and reduce the volume, so that the heat capacity of the new motor is getting smaller and smaller, the overload capacity is getting weaker and weaker; The electric motor often runs in various ways such as frequent starting, braking, forward and reverse rotation, and variable load, which puts higher requirements on the motor protection device. In addition, the application of the motor is more widely used in environments where the environment is extremely harsh, such as humidity, high temperature, dust, corrosion and the like. In addition, the irregularity of the motor repair, the omission of equipment management. All of this has caused the current motor to be more susceptible to damage than in the past, especially for faults such as overload, short circuit, phase loss, and broom.
2. Why is the protection of traditional protection devices not satisfactory?
The traditional motor protection device is mainly composed of a fuse and a thermal relay. The fuse is mainly used for short-circuit protection. The selection of the fuse current needs to consider the starting current of the motor. Therefore, it is not advisable to use a fuse alone to protect the motor. The thermal relay is the most widely used motor overload protection device, but the thermal relay has low sensitivity, large error, poor stability and unreliable protection. This is also the case. Although many devices have thermal relays installed, the phenomenon that the motor is damaged and affects normal production is still widespread. Traditional protection devices have not yet been able to achieve mechanical wear monitoring of the motor and eccentricity monitoring of the stator and rotor.
4. What is the current status of motor protectors?
At present, the motor protector has evolved from the past mechanical type to electronic and intelligent type, with high sensitivity, high reliability, many functions and convenient debugging. The current, voltage, temperature and other parameters of the motor can be directly displayed, and the types of faults after the protection action are clear at a glance, which greatly facilitates the judgment of the fault, and is beneficial to the fault handling at the production site and shortening the recovery production time. In addition, according to the motor air gap magnetic field, the motor eccentricity detection technology makes it possible to monitor the wear state of the motor online. The curve shows the change trend of the value reflecting the eccentricity of the motor, and records the change of the value in two years, so that the bearing fault can be found early. Do early detection, early treatment, and avoid broom accidents.
5. The principle of protector selection?
The purpose of the motor protection device is to enable the motor to fully exert the overload capability and avoid damage, and to improve the reliability and continuity of the electric drive system. When the protection requirements are met, the simplest protection device is first considered. When a simple protection device fails to meet the requirements, or when higher requirements are imposed on the protection function and characteristics, it is considered to apply complicated protection devices to achieve economical efficiency. Unification of reliability. The specific function selection should be based on comprehensive consideration of the value of the motor itself, the load situation, the quality of the environment, the importance of the motor, whether the exit operation has serious impact on the production system, etc., and strive to be economic and reasonable.
6, the ideal motor protector?
The ideal motor protector is not the most functional, nor the most advanced, but should be the most practical. So what is practical? Practical should meet the requirements of reliability, economy, convenience, etc., with a high performance-price ratio. So what is reliable? Reliable first of all should meet the reliability of the function, such as over current, phase failure function must be able to operate in various occasions, various processes, various ways of overcurrent, phase failure can be reliable. Secondly, its own reliability (since the protector is to protect others, especially high reliability) must have adaptability and durability to various harsh environments. Economical: Adopt advanced design, reasonable structure, professional and large-scale production, reduce product cost, and bring high economic benefits to users. Convenience: It must be as simple and convenient as possible in terms of installation, use, adjustment, wiring, etc.
