Different motor overload protector types and working conditions
2, electronic type: The three-phase current value is detected, and the potentiometer or the code switch is used for setting the current value. The circuit is generally analog, and adopts an inverse time limit or a time limit operation characteristic. The protection functions include overload, phase loss, stall, etc. The fault type is displayed by an indicator light, and the running power is displayed by a digital tube.
3. Intelligent type: The three-phase current value is detected, and the protector uses a single-chip microcomputer to realize intelligent comprehensive protection of the motor, integrating protection, measurement, communication, and display. The setting current is digitally set and operated by the operation panel button. The user can modify various parameters on the spot according to the specific conditions of the motor; The use of digital tube as a display window, or the use of large-screen liquid crystal display, can support a variety of communication protocols, such as ModBUS, ProfiBUS, etc., the price is relatively high, for more important occasions; High-voltage motor protection uses intelligent protection devices.
4, thermal protection type: The thermal element is embedded in the motor and protected according to the temperature of the motor winding, and the protection effect is good; However, when the motor capacity is large, it should be used in conjunction with the current monitoring type to avoid the damage of the motor winding due to the hysteresis of the temperature measuring elements when the temperature rises sharply when the motor is blocked.
5, magnetic field temperature detection type:
The magnetic field detecting coil and the temperature measuring element are embedded in the motor, and are protected according to changes in the internal rotating magnetic field of the motor and changes in temperature. The main functions include overload, stall, phase loss, overheat protection and wear monitoring. The protection function is perfect. The disadvantage is that the magnetic field detection coil and temperature sensor need to be installed inside the motor.
(3) Selection of protector type under motor operating conditions
1. For the single-machine independent operation motor with low requirements on working conditions, simple operation control, and no impact on production, normal type protector can be used. Because the common type protector has a simple structure, it is convenient to install and install wiring, replace it, and has simple operation and high cost performance.
2, for the harsh working conditions, high reliability requirements, especially for motors involving automated production lines, should use high-end, full-featured intelligent protectors.
3. For explosion-proof motors, eccentricity due to bearing wear may cause high temperature friction at the explosion-proof gap, which may cause explosion hazard. The wear condition monitoring function should be selected. For special equipment such as large-capacity high-pressure submersible pumps, the wear condition monitoring function should also be selected due to the difficulty in inspection and maintenance. At the same time, the temperature of the bearing is monitored to avoid the Chamber sweeping accidentidental accident causing significant economic losses.
4. Applicable to protectors with explosion-proof requirements, according to the specific requirements of the application site, select the corresponding explosion-proof protector to avoid safety accidents.