Application of Frequency Converter on Conveyor Belt of Production Line

I. Overview

There are many kinds of conveyor belts for transportation, such as chain type, belt type, spiral type, drum type, vibration type, bucket type, etc. Due to the different physical and chemical properties, shapes, handling routes and transportation methods of the transporting materials, people put forward different requirements for the function of the transducer. In addition, economic factors should also be considered. The same speed regulation can be mechanical or electrical. Because conveyor belt is an indispensable labor-saving machine in industrial automation. Therefore, when choosing the frequency converter, we need to consider the factors of control performance, economy and maintenance convenience comprehensively.

2. Requirements of Conveyor Belt for Frequency Conversion Speed Regulation

(1) Selection of cage asynchronous motor

(2) Increasing productivity

After frequency conversion speed regulation, the speed regulation range can achieve at least 1:10 (up to 1:20), which basically meets the needs of general engineering. Vector control frequency converter can also be used in situations requiring wide speed regulation. If the speed range of speed sensorless vector control frequency converter can reach 1:100, the speed sensor vector control frequency converter can even reach 1:1000.

(3) Soft start and brake

Conveying bottled objects with conveyor belts requires the strictest smoothness of starting and braking, as shown in Fig. 11-1. Only by adjusting the best starting and braking time can we prevent the goods from shaking or breaking. The starting and braking time of the latest type of converter can be independently adjusted to 0.1-6000s, and the lowest output frequency can be reduced to 0.5-1Hz.

(4) Frequent starting, parking and reversible operation

Because the frequency converter starts slowly at low frequency and low voltage, the starting current impact is small, the starting torque is high, and the motor heating is low, so it can start and stop frequently and save energy.

(2) Frequency converter uses power transistor to change the phase sequence to make the motor reverse and forward, which is different from the movable and friction parts of contactor in reverse, and can ensure that the motor fever is low in reversible operation.

(3) It has electric braking function, as shown in Figure 11-2. When the frequency converter is in the process of deceleration, for example, from F1 to f2, it can be seen from the figure that the motor's torque immediately changes from positive towing torque T1 to negative braking torque T2. The principle is that the synchronous speed decreases with the frequency reduction process, and the motor is in the state of power generation. The electric energy is absorbed by the capacitor parallel to the DC power supply of the frequency converter, which increases the voltage at both ends of the capacitor. For large capacity motors, because of the high braking energy, energy consumption braking resistance must be connected in parallel to consume energy, or the rectifier should be changed into a switching rectifier composed of switching devices, which can feed the energy back to the power grid.