The fundamental method of motor protector selection
At present, there is no unified standard for motor protectors on the market, and almost every manufacturer has its own type standard. In order to meet the needs of different customers, manufacturers derive a lot of products with different uses, a wide variety of products that bring a lot of inconvenience to the majority of users, users should fully consider the practical needs of motor protection when selecting models, and reasonably select protection functions and protection methods, so as to achieve outstanding protection effect, improve the reliability of equipment operation, reduce unplanned shutdown, and reduce the purpose of incident losses.
Criteria related to selection:
The selection of motor protection exists in the relationship between the motor and the protector how to reasonably match, the following provides several conditions and elements related to protection, for the user to provide reference when selecting.
1. Motor: the type standard, motor function characteristics, protection type, additional voltage, additional current, additional power, power supply frequency, insulation level, etc. These contents can provide a reference for users on how to correctly select and use motor protectors.
2. Environmental conditions: mainly refer to room temperature, high temperature, high cold, corrosion, sensation, sandstorm, altitude, electromagnetic pollution, etc.
3. The use of the motor: such as fans, pumps, air compressors, lathes, oilfield pumping units and other mechanical characteristics of different loads, such as the pump motor protector, it should have the function of underload, when the pump pumps the water out, the protector needs to give protection instructions.
4. Control system: the control mode includes manual, active, local control, long-distance control, independent operation of a single machine, centralized control of the production line, etc. There are direct, step-down, star-delta, frequency-sensitive rheostat, inverter, soft start and other start-up methods.
5. Other aspects: whether the user is more casual or cautious about the on-site production monitoring, and the severity of the impact of abnormal shutdown on production.
There are many elements related to the selection of motor protectors, such as device orientation, power supply status, and cooperation with the power distribution system; It is also necessary to consider the newly purchased motor protector, the promotion of motor protection, and the improvement of motor protection at the end of the incident; It is also necessary to consider the difficulty of changing the motor protection method and the degree of impact on production; It is necessary to comprehensively consider the selection and adjustment of the motor protector according to the on-site practical operating conditions.
Selection of motor protector type under motor operating conditions
1. The requirements for operating conditions are not high, the operation and control are simple, the monitoring and handling are more arbitrary, and the stand-alone independent operation motor with little impact on the production of shutdown can choose the ordinary protector, because the structure of the ordinary protector is simple, the wiring, replacement, operation of the device in the field is simple and convenient, and it has the characteristics of cost-effective and advanced.
2. The requirements for operating conditions are very high, safety and continuity are very critical, and the degree of automation is high, and the MCC system that requires special personnel to control, monitor and handle, and needs to be networked and monitored, should choose a high-end motor protector with more complete functions.
3. Regarding the explosion-proof motor, because the bearing wear forms eccentricity, it may lead to high temperature of friction at the explosion-proof void, resulting in the risk of explosion, and the wear monitoring function should be selected. For large-capacity high-pressure submersible pumps, because it is difficult to inspect and protect, the wear condition monitoring function should also be selected to prevent serious economic losses caused by sweeping incidents.
4. The motor protector used in the place with explosion-proof requirements should be selected according to the specific requirements of the use site to prevent safety incidents.
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