I. INTRODUCTION
As an important device in the field of modern industrial control, whether the output of frequency converter can be directly connected to the contactor has been the focus of attention in the industry. In practical application, the contactor connected to the output of the inverter may lead to a series of problems, thus affecting the normal operation of the equipment. In this paper, we will discuss in depth the reasons why the output of the inverter can not be connected to the contactor, and analyze it with relevant data and information.
II. The basic principle of inverter and contactor
Inverter is a kind of electrical equipment that can change the frequency of the power supply, and control the speed of the motor by adjusting the frequency of the power supply. The contactor, on the other hand, is an electrical component used to connect or disconnect the circuit, which is widely used in various electrical control systems. Under normal circumstances, the inverter and contactor work independently to complete their specific functions.
III. Potential Problems of Connecting Contactors to the Output of Inverters
Overload current and equipment damage
When the contactor at the output of the inverter is not absorbed, the inverter starts and reaches a certain frequency before the contactor is absorbed. At this point, an additional inrush current is generated by the contactor's engagement because the frequency converter is already outputting a certain amount of current. This inrush current may be much larger than the rated current of the contactor, leading to overloading of the contactor, which may damage the inverter or the contactor itself. In addition, this inrush current may also cause an impact on the power grid, affecting its stability.
Electromagnetic interference and equipment failure
The high-frequency voltage output from the inverter generates electromagnetic waves, which may interfere with the normal operation of other equipment. When the inverter output is connected to the contactor, this electromagnetic interference may be more serious. This is because the suction and disconnection of the contactor generates additional electromagnetic noise, further increasing the intensity of the electromagnetic interference. This electromagnetic interference may cause other equipment to operate incorrectly or malfunction, and even affect the stability of the entire electrical control system.
Reduced life span of the contactor
Due to the high-frequency voltage and inrush current of the inverter output, the metal contacts of the contactor are prone to ablation. This ablation phenomenon will lead to an increase in the contact resistance of the contactor, which in turn affects the performance and service life of the contactor. In addition, high-frequency voltage may also cause the internal components of the contactor to heat up, further accelerating the aging process of the contactor. Therefore, connecting the inverter output to the contactor may significantly reduce the service life of the contactor.
Decrease in control accuracy
Inverters usually have high control accuracy and response speed. However, when a contactor is connected to the output of the inverter, this may result in a decrease in the control accuracy of the inverter because it takes some time for the contactor to be engaged and disengaged. For example, where precise control of the motor speed is required, the suction and disconnection of the contactor may introduce additional errors, affecting the control accuracy of the entire system.
Safety Hazards
The contactor connected to the output of the inverter may also have safety hazards. Due to the impact of inrush current and electromagnetic interference, it may lead to equipment overheating, fire and other safety accidents. In addition, the false operation or failure of the contactor may also lead to equipment shutdown, damage and other serious consequences. Therefore, in practical applications should try to avoid the inverter output connected to the contactor.
IV. Alternatives to connecting the output of the inverter to the contactor
Although the output of the inverter can not be directly connected to the contactor, but through other ways to achieve a similar function. For example, a soft starter can be added between the output of the inverter and the motor or the built-in soft start function of the inverter to realize the smooth start and stop of the motor. In addition, PLC and other controllers can be used to control the action sequence and logical relationship between the inverter and the contactor to ensure the stable operation of the whole system.
V. Conclusion
In summary, the reasons why the output of the inverter can not be connected to the contactor mainly include overload current and equipment damage, electromagnetic interference and equipment failure, reduced life of the contactor, reduced control accuracy and safety hazards. In order to avoid these problems, the contactor should be avoided as much as possible on the output of the inverter, and corresponding alternative solutions should be taken to realize similar functions. At the same time, the monitoring and maintenance of the electrical control system should be strengthened in the actual application to ensure the stable operation of the whole system.