Top ten functions of VFD (Variable-frequency Drive)

Top ten functions of VFD (Variable-frequency Drive)

(1) Adjustable torque limit.

After frequency control, the corresponding torque limit can be set to protect the machinery from damage, thereby ensuring the continuity of the process and the reliability of the product. The current frequency conversion technology makes not only the torque limit adjustable, but also the torque control accuracy reaching about 3% to 5%. Under the power frequency state, the motor can only be controlled by detecting the current value or thermal protection, but cannot set the precise torque value to operate like in variable frequency control.

(2) Controlled stopping method.

Just like controllable acceleration, in variable frequency speed regulation, the stopping method can be controlled, and there are different stopping methods to choose from (deceleration stop, free stop, deceleration stop + DC braking), which can also reduce the impact on mechanical components and The impact of the motor makes the entire system more reliable and the life span will be increased accordingly.

(3) Energy saving

Centrifugal fans or water pumps can significantly reduce energy consumption after using VFD (Variable-frequency Drive), which has been reflected in more than ten years of engineering experience. Since the final energy consumption is cubically proportional to the motor's speed, the return on investment will be faster after using frequency conversion.

(4) Reversible operation control

In VFD (Variable-frequency Drive) control, no additional reversible control device is required to achieve reversible operation control. It only needs to change the phase sequence of the output voltage, which can reduce maintenance costs and save installation space.

(5) Reduce mechanical transmission parts

Since the current vector control VFD (Variable-frequency Drive) plus synchronous motor can achieve efficient torque output, thereby saving mechanical transmission components such as gearboxes, ultimately forming a direct frequency conversion transmission system. This reduces cost and space and improves stability.

(6) Lower power is required during startup.

Motor power is proportional to the product of current and voltage, so the power consumed by a motor started directly through power frequency will be much higher than the power required for variable frequency start. Under some working conditions, its power distribution system has reached its highest limit, and the surge generated by its direct power-frequency starting motor will have a serious impact on other users on the same network, which will result in warnings and even fines from the power grid operator. . If VFD (Variable-frequency Drive) is used to start and stop the motor, similar problems will not occur.

(7) Controllable acceleration function.

The variable frequency speed regulation can start at zero speed and accelerate evenly according to the user's needs, and its acceleration curve can also be selected (linear acceleration, S-shaped acceleration or automatic acceleration). When started by power frequency, severe vibration will occur to the motor or connected mechanical parts, shafts or gears. This vibration will further increase mechanical wear and tear and reduce the life of mechanical components and motors. In addition, variable frequency start can also be used in similar filling lines to prevent bottles from tipping over or being damaged.

(8) Adjustable running speed.

The use of variable frequency speed regulation can optimize the process and quickly change it according to the process. Speed changes can also be achieved through remote control PLC or other controllers.

(9) Control the starting current of the motor.

When the motor is started directly through the power frequency, it will produce 7 to 8 times the rated current of the motor. This current value will greatly increase the electrical stress on the motor windings and generate heat, thereby reducing the life of the motor. The variable frequency speed regulation can start at zero speed and zero voltage (torque boost can also be added appropriately). Once the relationship between frequency and voltage is established, VFD (Variable-frequency Drive) can drive the load to work in V/F or vector control mode. Using variable frequency speed regulation can fully reduce the starting current and improve the winding endurance. The most direct benefit to the user is that the maintenance cost of the motor will be further reduced and the life of the motor will be increased accordingly.

(10) Reduce power line voltage fluctuations.

When the motor is started at power frequency, while the current increases sharply, the voltage will also fluctuate significantly. The magnitude of the voltage drop will depend on the power of the starting motor and the capacity of the distribution network. Voltage drops will cause voltage-sensitive equipment in the same power supply network to malfunction, trip or work abnormally, such as PCs, sensors, proximity switches and contactors, etc., which will all operate incorrectly. After adopting variable frequency speed regulation, since it can gradually start at zero frequency and zero voltage, the voltage drop can be eliminated to the greatest extent.