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High current intelligent composite motor overload protector

Article Source:Thermal protectorAuthor:YaxunPopularity:Published time:2019-10-23 11:18

Compound motor overload protector
 
The working current of a large compressor is very large, and the arcing of the overload protector causes arcing and cannot be used. The commonly used protection method is the protection method of the thermistor + electronic module. Several thermistors are arranged in the three-phase winding, and the thermistors are connected in series (also in parallel) and connected to the corresponding terminals of the electronic module (such as S1, S2). When the thermistor temperature reaches a certain critical temperature, its resistance will increase dramatically from a few hundred ohms at normal temperature to several thousand ohms or even tens of thousands of ohms. The control loop (such as M1, M2) in the trigger electronic module is disconnected, and the compressor is stopped; When the temperature drops to the set value, the control loop inside the module will automatically close and the motor will resume operation.

The thermistor is small in size and can be placed in the winding for fast thermal response. In addition, the thermistor is inexpensive, so it can be arranged a few more, greatly increasing the monitoring range. In addition to monitoring the resistance of the thermistor, the electronic module also has functions such as determining the phase loss of the main circuit and phase sequence error. For scroll compressors, screw compressors and centrifugal compressors, phase sequence errors are a big mistake and the module is automatically locked.

Large-scale scroll compressors, multi-cylinder piston compressors, screw compressors, etc. generally use thermistor + electronic module as a thermal protection method.

Intelligent motor overload protector
 
The motor intelligent protector is designed for the protection, measurement and control of 380/660V low-voltage distribution network motors for industrial and mining enterprises. It has real-time measurement, protection, monitoring, display, communication and other functions.

The protector gives cash to the integrated circuit and microcomputer technology, using the micro-processing chip as the core computing unit, and the operation speed is fast. High reliability, complete communication function and analog transmission output capability. It provides comprehensive and comprehensive protection for the motor, reliable performance, convenient operation, but easy to install and maintain. The protection range and sensitivity are higher than the thermal relay, which can effectively avoid the situation that the motor is often burnt out and the thermal relay does not work. It is an ideal upgrade product for the thermal relay.
Ambient temperature: -20°~55°C, relative humidity: “90%, no corrosive gas, no severe vibration, impact.

Intelligent motor protectors are divided into conventional and pure protection. The relay of the conventional relay device K1 is a normally closed point, and the protection action is opened. The node can be manually reset automatically and can be automatically reset to directly replace the thermal relay. The purely protected K1 outlet is a normally open point.

contradiction:
1. Use the normally open contact of the relay to implement the protection scheme. The characteristic is that the contact is normally open when the main circuit is not working, so the contact must be connected in series with the self-protection circuit of the contactor. Thus, even if the user feels inconvenient to install, it cannot be used for the circuit of automatic control;
2. Implement the protection scheme with the normally closed contact action of the relay. Although its control contacts can be directly connected to the control loop like a thermal relay, they are also not suitable for automatic control systems due to their automatic reset. This greatly limits the range of use of electronic motor protectors. On the one hand, it is necessary to change the control circuit when replacing the thermal relay, and on the other hand, it cannot be used for equipment that needs to be automatically controlled due to unattended, long-term work, and relatively high failure rate, such as pumps and compressors.

 
Compound motor overload protector