The object of protection of frequency converters in overload protection - Reynolds

Inverters are mainly divided into two categories according to the frequency conversion method: communication/DC/communication and communication/communication inverters. Here we take the widely used general "communication/DC/communication" as an example to briefly talk about its structure and operating principle. From the above figure, it can be clearly known that the communication/DC/communication inverter is also known as the indirect inverter, which refers to the operation, the 50Hz power frequency communication power is first converted into pulsating DC through the rectifier module unit, and then through the capacitor in the intermediate circuit circuit, filtered into a relatively smooth DC power supply, and supplies power supply energy for the IGBT inverter module. The turn-on and cut-off frequencies of these IGBT modules are controlled by the IC main control board chip system, and the inverter module circuit converts the high-voltage DC power supply into adjustable frequency and variable voltage communication electricity, and then supplies it to the three-phase asynchronous motor of the communication load for inverter control.

The object of protection of frequency converters in overload protection - Reynolds

The object of protection of frequency converters in overload protection - Reynolds

Because the primary component used internally is semiconductor equipment, and these components inevitably present many artificial and other elements in the process of use, simply forming the damage of the inverter, and the damage of the three-phase motor for the second time, so the engineers plan a simple signal detection and sampling circuit in the electronic circuit to monitor the operation status of the inverter in real timeThe operation will be stopped, and the fault phenomenon and fault location will be displayed on the LED display, and people will check and repair according to the fault code, and start the inverter again after eliminating the fault. In the internal control of the general inverter, the parking and braking methods can be controlled by the inverter, and the general inverter has a variety of shutdown methods and braking methods to set or select, such as deceleration stop, free stop, deceleration shutdown + braking, etc., so as to avoid reducing the impact of the inverter on the motor and mechanical components, so that the whole system is more safe and reliable operation.

In fact, there are many maintenance circuits set up inside the inverter, but because the user is not involved in some phenomena, there is no specific research on it. The internal maintenance of the inverter can complete the maintenance function of various abnormal phenomena of the inverter itself and the load motor, which mainly includes overheating (overload) maintenance and stall avoidance maintenance.

(1) Overheating (overload) maintenance function: The overheating (overload) maintenance of the inverter is overcurrent maintenance or overheating maintenance, and all inverters are equipped with electronic thermal maintenance functions or thermal relays for maintenance. When the load inertia controlled by the inverter is too large or the motor stalls due to excessive load, the output current exceeds the rated value or communicates that the motor is overheated, and the maintenance circuit action is to stop the motor and avoid damage to the inverter and the load motor.

(2) Avoid stall maintenance: Stall means that when the acceleration time of a given motor of the inverter is too short, and the acceleration of the motor is far from keeping up with the output frequency of the inverter, the inverter will trip and stop operation due to excessive current. In order to avoid the above-mentioned stall phenomenon and make the motor run normally, the inverter is provided with a stall avoidance maintenance circuit, which can detect the size of its output current, and carry out comparison operation to carry out the active adjustment and control of the frequency. When the acceleration current is too large, the acceleration frequency is appropriately slowed down, and when the deceleration current is too large, the acceleration frequency is also appropriately slowed down to avoid stalling.

Now the vector inverter can also adjust the torque of the motor, so that it can be set inside the inverter to maintain the motor and mechanical equipment from damage, so as to ensure the continuity of the normal operation of the mechanical equipment driven by the inverter and the reliability of the product.

The object of protection of frequency converters in overload protection - Reynolds

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