The two main differences between vector-specific and general-purpose inverters are the high precision of the control and the high output torque at low speeds.
Vector-specific inverters.
Vector-specific models work on the principle of rectification and then inversion to get the frequency and voltage you want.
Vector control technology transforms a three-phase system into an M-T two-phase system through coordinate transformation, decomposing the stator current vector of an AC motor into two DC components (i.e. magnetic chain component and torque component), thus achieving the purpose of controlling the magnetic chain and torque of an AC motor separately, thus achieving the same good control effect as a DC speed control system.
Vector control is also called 'speed control', literally.
V/F control mode:Just like when driving a car with a constant throttle opening on your foot, the speed must be changing! Because the car is on an uneven road and the resistance of the road is changing, the speed slows down when going uphill and speeds up when going downhill, right? With inverters, your frequency setting is equivalent to the throttle opening of your foot when you drive, and the throttle opening is fixed when controlling V/F.
Vector control mode:It can control the vehicle to maintain a constant speed and improve speed control accuracy under changing conditions such as road conditions, resistance, uphill and downhill.
General inverter.
Frequency converters, suitable for all loads, are general purpose frequency converters. However, if there are special types of frequency converters, it is recommended to use special types of frequency converters, special types of frequency converters, optimised according to the characteristics of the load, with simple parameter settings, better speed regulation performance and energy saving.
The correct choice of frequency converter is essential for the normal operation of the control system. When choosing a frequency converter, it is important to fully understand the load characteristics of the frequency converter drive. In practice, people often divide production machinery into three types: constant torque loads, constant power loads and fan and pump loads.
Constant torque loads .
The load torque TL is independent of the speed n. The TL always remains constant or essentially constant at any speed. For example, friction loads such as conveyors, mixers and extruders, as well as potential loads such as cranes and hoists, are constant torque loads.
The frequency converter, when towing a load at constant torque, should have a sufficiently high torque at low speeds and a sufficient overload capacity. If low and steady speed operation is required, the heat dissipation capacity of standard asynchronous motors should be taken into account to avoid excessive motor temperature rise.
Constant power loads.
The torque required for machine tool spindles, rolling mills, paper machines, winders and unwinders in plastic film production lines is roughly inversely proportional to the speed and is known as a constant power load. The constant power characteristics of the load should be expressed in terms of a certain range of speed variations. When the speed is very low, the TL cannot be increased indefinitely due to mechanical strength limitations and becomes constant torque in nature at low speeds. The constant power and constant torque zones of the load have a great influence on the choice of drive solution. When the motor is in constant flux speed regulation, the maximum permissible output torque remains unchanged and belongs to constant torque speed regulation; however, in weak magnetic speed regulation, the maximum permissible output torque is inversely proportional to the speed and belongs to constant power speed regulation. If the constant torque and constant power range of the motor is the same as the constant torque and constant power range of the load, i.e. in the case of "matching", the capacity of the motor and the capacity of the inverter are minimised.
Fan and pump loads.
In various fans, pumps and oil pumps, as the impeller rotates, the resistance of the air or liquid in a certain speed range is roughly proportional to the second power of the speed n. As the speed decreases, the speed decreases to the second power of the speed. The power required for this load is proportional to the third power of speed. When the required air volume and flow rate are reduced, the inverter can adjust the air volume and flow rate by speed regulation, which can result in significant power savings. As the power required at high speeds increases too quickly with speed and is proportional to the third power of speed, fan and pump loads should not normally exceed the supply frequency.