Apply frequency converter for motor speed control, it can vary the motor speed based on actual applications, and save energies. It is mainly based on the following factors:
- Frequency Control System should have low self-loss and high efficiency;
- The motor is always kept at a low slip running, reduce the rotor losses;
- It can achieve a soft start and brake function, reduce the starting current impact.
When using frequency converter control, it should be consider from the process requirements, efficiency savings, payback period and other prospects. If only consider the benefits of technical requirements and energy savings, the following situations will be more favorable to use frequency converter control:
According to process requirements, the production line or single piece equipment is required by the program or motor speed. Such as: packing machine conveyor system, according to different kinds of products, you need to change the system transmission rate, and can use the converter speed control system to realize implement process control.
Use frequency control instead of mechanical transmission, such as: machine tools, not only can save the complex gearbox, but also precision progress to meet the process control requirements.
Use frequency control instead of the gate or barrier to adjust the flow. This is suitable for fans, pumps, compressors. For example: boiler pump, blower and fan. frequency control not only can save the servo amplifier, power steering, electric actuator and the water supply valve (or the windshield), and makes the whole boiler control system has a faster dynamic response, high control accuracy and stability.
After the 1970s, the development of large scale integrated circuits, computer control technology and the application of modern control theory, made the AC electric drive system gradually have a wide speed range, high-speed stability range, high precision steady speed fast dynamic response as well as a four-quadrant reversible operation. It has good technical performance and is comparable with the DC electric drive. In AC variable speed technology, frequency converter has absolute advantages: Speed performance and reliability continue to improve, prices continue to be lower, especially has obvious frequency saving effect, and easy to implement process automation. It has enormous benefits for lots of industries.
Advantages of frequency converter for speed controls
- Smooth speed controlling and high efficiency. At low speeds, the static characteristics of high clearance rate, relative stability;
- Greater speed range, high accuracy;
- Low starting current, no impact on the frequency converter system and the power grid, energy saving effect is obvious;
- Small size, easy installation, commissioning and maintenance;
- Easy to implement process automation;
- There must be a dedicated frequency converter;
- At constant torque speed, low speed motor overload can be greatly reduced.
Comparison to other speed control methods
AC motor speed control has three types: pole-changing speed, changing the slip speed and frequency control. Among them, the best is frequency control. Here is a comparison for AC variable speed system and DC speed control system.
In the AC motor speed control system, often leaving some margin in selecting a motor, the motor not always run at maximum load condition. If the use of variable frequency power conversion technology, under light load, by controlling the rotational speed of the motor can achieve energy-saving purpose. Industrial fans, pumps, compressors and other equipment consume about 50% of electricity power. If use frequency converter, it can greatly improve the efficiency and reduce electricity consumption by 10%.