The significance of overcurrent protection and the factors that affect current protection

When there is a fault or abnormality in the system, the current increases abnormally, and the overcurrent protection acts when the current is greater than the setting value, and automatically cuts off the faulty equipment or detachs the protection equipment from the system. Therefore, the over-current protection can protect the equipment, remove the faulty equipment from the system, and ensure the safety and stability of the system operation.

Overload protection, meaning, is equivalent to a substitute for the dead. Got it? If the circuit is too large, the overload protection trips or fuses, and the entire circuit is protected from damage, or the person is electrocuted will not cause much damage. It's almost like a ghost for the dead, sacrificing the ego to protect the ego

Overcurrent, i.e. overload protection, i.e. thermal protection. Prevent the equipment from running overload for a long time and even burning.

Overcurrent protection means that the current in the line exceeds the rated current, and the protection device (relay, circuit breaker, etc.) trips, so as to cut off the process of line protection electrical appliances is called overcurrent protection.

Overcurrent protection mainly includes two types: short-circuit protection and overload protection. Short-circuit protection is characterized by high setting current and instantaneous operation. Electromagnetic current trippers (or relays) and fuses are often used as short-circuit protection components.

Overload protection is characterized by a small setting current and anti-time operation. Thermal relays and time-delay electromagnetic current relays are often used as overload protection components. In the absence of much inrush current, fuses are also often used as overload protection components.

Summary. To put it simply, there are three reasons for the overcurrent of the compressor: 1. The condensing pressure of the refrigeration system is too high; 2. Too much refrigerant in the refrigeration system; 3. The compressor lacks refrigeration oil.

Factors influencing current protection.

To put it simply, there are three reasons for the overcurrent of the compressor: 1. The condensing pressure of the refrigeration system is too high; 2. Too much refrigerant in the refrigeration system; 3. The compressor lacks refrigeration oil.

1. Poor heat dissipation of the external unit, short circuit of the external unit, exhaust air: If the external unit is installed in a closed balcony, in a narrow aisle, in an unventilated place such as the house, there are obstructions in front of the tuyere. The air volume of the external unit is small, and the heat dissipation speed is slow

If the condenser of the external unit is too dirty or blocked by dust and oil, the fan motor speed is slow, the fan capacitance becomes smaller, and the temperature around the external unit is high. 2. The external power supply voltage factor is low or high, both of which will cause the compressor working current to be high, while the domestic voltage is low and accounts for the vast majority, especially during the peak of electricity consumption. If the power supply voltage (i.e. the voltage before powering on) is too low:

If the voltage is about 190V, you can consider installing a voltage regulator, if it is too low, it will be invalid. Check the voltage drop after starting: under normal circumstances, the voltage drop is only a dozen volts, and if the voltage drop is too large, the power cord should be thickened or rewired, and the fault such as poor line contact should be eliminated.

3. Refrigeration system failure: If there is air in the system, the air is often accumulated in the upper part of the condenser, because it cannot pass through the condenser's liquid accumulator, whether there is air in the system, generally can be determined by the beating of the system pressure, if there is air in the system, it should be re-evacuated and fluoridated. Excessive fluoride:

The compressor is in a state of overload for a long time, which will eventually lead to the overcurrent of the compressor and jumping. In this case, some fluorine should be released to the outside world. 4. The internal temperature of the shell is high, and the compressor is poorly lubricated

The height difference between indoor and outdoor units is greater than 5 meters, and no oil return bend is made, or only an oil return bend is made on one pipe, the system can not return oil smoothly, and the temperature of the compressor slowly rises during operation due to lack of lubrication, and finally leads to overheating and jumping. Too much impurities and moisture in the system: the lubricating oil deteriorates, carbonizes, and cannot play its normal effect, resulting in a sharp rise in compressor temperature and overheating and jumping.

This situation generally occurs on machines that have been repaired or used for a long time, and if the substances in the inspection system are black, then this must be the case, at this time, nitrogen should be used to clean the system, replace the compressor, capillary assembly, and re-evacuate and add fluorine. 5. The cooling effect of the compressor is not good, the system fluorine is too small, and the temperature of the compressor is not when it is working.

5. The cooling effect of the compressor is not good, the system fluorine is too little, the temperature of the compressor is very high when working, the high temperature coil is cooled by the inhaption refrigerant, if the fluorine is too little, the system flow is small, and it can not meet the load of 100% of the evaporator, resulting in the increase of suction superheat, coupled with the small suction flow of the compressor, the cooling efficiency is greatly reduced, so that long-term operation can lead to compressor thermal protection.

1. Causes of overcurrent.

1. Overload current: The electrical circuit is overloaded due to too much connected electrical equipment or overload of the supplied equipment (such as excessive mechanical load of the connected motor).

2. Short-circuit current: When the circuit insulation is damaged due to various reasons (including overload), the conductor with unequal potential is turned on through the fault point with negligible impedance. The path of this short-circuit circuit is all metal paths, so it is classified as metallic short circuits, and its short-circuit current value can reach hundreds to thousands of times of the current carrying capacity of the circuit conductor, which can produce abnormal high temperature or huge mechanical stress and cause various disasters.

Second, the cause of overvoltage.

The sudden change of circuit state and electromagnetic state in the power system is the root cause of overvoltage. Overvoltage is divided into two categories: external overvoltage and internal overvoltage. It is the premise of determining the insulation coordination of the power system to study the causes of various overvoltages in the power system and take measures to limit them, which is of great significance for the manufacture of electrical equipment and the operation of the power system.

It is a protection method that makes the protection device act when the current exceeds the predetermined maximum value. When the current flowing through the protected element exceeds a certain value set in advance, the Qingwei protection device is activated, and the selectivity of the action is guaranteed by the time limit, so that the circuit breaker trips or gives an alarm signal.

1. In order to realize the correctness of the action selection of overcurrent protection, the action time of each protection is generally set according to the ladder principle. That is, the action time of adjacent protection, the self-load increases step by step to the direction of the power supply, and the action time of each set of protection is constant, regardless of the size of the short-circuit electric clearing current.

2. Inverse time overcurrent protection feature: the larger the current flowing through the fuse, the shorter the fusing time.

3. The anti-time overcurrent protection refers to the protection that the action time automatically decreases with the increase of the short-circuit current.

4. The anti-time overcurrent protection used on the transmission line can cut off the fault at the head of the protected line faster.