The frequency conversion speed control system is widely used in the industrial production of all kinds of small and medium enterprises. This is due to our variable-frequency speed control scheme can provide accurate speed control to achieve stepless speed. Therefore, it can easily control the rising, falling and transversal movement of the mechanical transmission, improve the efficiency of the process (the change of speed does not depend on the mechanical part) , and save more energy than the traditional motor running at the same speed. The following are 10 reasons for the use of frequency control in production activities:
(1) the starting current of the motor is controlled to realize soft starting.
When the motor starts directly with power frequency, the starting current is 4 ~ 7 times of the rated current of the motor. Too much current will increase electrical stress in the motor windings and generate heat, thereby shortening the life of the motor. Frequency converter (hereinafter referred to AS-VFD) uses frequency conversion speed control technology, can be in accordance with the V/F or vector control mode to drive the load. Using frequency conversion speed regulation can fully reduce the starting current, improve the bearing capacity of winding, reduce the impact of mechanical equipment, failure rate and equipment maintenance costs.
(2) to reduce voltage fluctuation and pollution of power grid.
When the motor is started at power frequency, the current will increase sharply and the voltage will fluctuate greatly. The magnitude of the voltage drop will depend on the power of the starter motor and the capacity of the distribution network. Voltage drop can cause voltage sensitive devices in the same power supply network to trip or work abnormally, such as PC, sensor, Proximity Switch, contactor, etc. . However, after adopting the frequency conversion drive scheme, the voltage fluctuation can be eliminated to a great extent because it can be started step by step at zero frequency and zero voltage.
(3) the power required for start-up is lower, which reduces the capacity requirement of power grid.
The power of the motor is proportional to the product of current and voltage, so the power consumption of the motor started directly by power frequency will be much higher than the power required by frequency conversion. In some cases, the power distribution system has reached the good limit, and the surge generated by the direct power frequency starting motor will cause serious impact on other users in the same power grid, and will be warned and even fined by the power grid operators. This can be improved by using VFD to start and stop the motor.
(4) controllable acceleration function to improve the working condition of the equipment.
Frequency control can start from zero speed, according to user needs uniform acceleration, the acceleration curve can also choose (linear acceleration, s-shaped acceleration or automatic acceleration) . If the shaft or gear of the motor or the connected mechanical part vibrates violently when the power frequency starts, the vibration will further aggravate the mechanical wear and loss and reduce the service life of the mechanical part and the motor.
(5) the running speed can be adjusted to improve the product quality.
The frequency conversion speed regulation scheme can optimize the process flow, and can change quickly according to the process flow. It can also realize intelligent speed control by remote control PLC or other controller to achieve optimized processing effect.
(6) adjustable torque limit to provide equipment protection.
After frequency conversion speed regulation, the corresponding torque limit can be set to protect the machinery from damage, thus ensuring the continuity of the process and product reliability. At present, frequency conversion technology not only makes the torque limit adjustable, but also the torque control accuracy can reach about 3% ~ 5% . Under the power frequency condition, the motor can only be controlled by detecting the current value or the thermal protection device, and the torque value can not be set exactly like the frequency conversion control.
(7) controllable shutdown mode to achieve precise control.
Just like the controllable acceleration, in the frequency control, you can control the stop mode, there are different stop mode to choose from (slow down, free stop, slow down + DC brake) . Similarly, it reduces the impact on mechanical components and motors, making the entire system more reliable and correspondingly extending its life.
(8) reduce energy consumption and realize energy-saving operation.
The use of VFD for secondary loads such as centrifugal fans or pumps can greatly reduce energy consumption, which has been reflected in more than ten years of engineering experience. Because the ultimate energy consumption is the square ratio of the motor speed, the return on investment after frequency conversion will be faster. . .
(9) the running direction of the equipment is reversible and it is easy to realize positive and negative operation.
In VFD control, to realize reversible operation control, only changing the phase sequence of output voltage is needed, which can reduce the maintenance cost and save installation space. (10) reduce mechanical transmission components and optimize system structure.
At present, the old drive motor of vector control inverter can achieve high-efficiency torque output, thus omitting mechanical transmission components such as gearbox, and finally forming direct frequency conversion transmission system.
