Advantages and applications of variable frequency power supply

AC variable frequency power supply speed regulation technology has been widely used in industrially developed countries. In the United States, 60% - 65% of electricity is used for motor drive. Due to the effective use of variable frequency speed regulation technology, 15% - 20% of electricity is saved in industrial transmission alone.

The use of variable frequency power supply speed regulation is to adjust the speed according to the requirements and save energy. It is mainly based on the following factors:

1) The variable frequency speed regulation system has low loss and high working efficiency.

2) The motor always maintains a low slip operating state to reduce rotor losses.

3) It can realize soft start and braking functions and reduce the starting current impact.

When using variable frequency power supply for speed regulation, it is necessary to consider various aspects such as process requirements, savings benefits, and investment payback period. If only considering process requirements and savings benefits, variable frequency speed regulation is more advantageous in the following situations:

F According to the process requirements, the production line or a single device needs to adjust the motor speed according to the program or requirements. For example, the conveying system of the packaging machine needs to change the system conveying speed according to different types of products. The use of variable frequency speed regulation can make the speed control system simple in structure, accurate in control, and easy to implement program control.

F Use frequency conversion speed regulation instead of mechanical speed change. For example: machine tools, not only can save complex gear transmission, but also improve accuracy and meet program control requirements.

F. Using variable frequency speed regulation instead of gates or dampers to adjust the flow is suitable for fans, water pumps, compressors, etc. For example, variable frequency speed regulation is implemented on the boiler water pump, blower, and induced draft fan, which not only saves the servo amplifier, electric operator, electric actuator, and water supply valve (or wind shield), but also enables the entire boiler control system to obtain fast dynamic response, high control accuracy and stability.

After the 1970s, the development of large-scale integrated circuits and computer control technology, as well as the application of modern control theory, has gradually enabled AC electric drive systems to have good technical performances such as a wide speed regulation range, a high speed stability range, high speed stability accuracy, fast dynamic response, and reversible operation in four quadrants, which can be comparable to DC electric drive in terms of speed regulation performance. In AC speed regulation technology, variable frequency speed regulation has an absolute advantage, and its speed regulation performance and reliability are constantly improving, and its price is constantly decreasing. In particular, variable frequency speed regulation has obvious power saving effects, and it is easy to realize process automation, which is deeply favored by the industrial industry.

1. Excellent characteristics of AC variable frequency speed regulation

1) Good smoothness and high efficiency during speed regulation. At low speed, the characteristic static closing rate is high and the relative stability is good.

2) The speed regulation range is large and the precision is high.

3) The starting current is low, with no impact on the system and power grid, and the power saving effect is obvious.

4) The variable frequency power supply is small in size and easy to install, debug and maintain.

5) Easy to automate the process.

6) A dedicated variable frequency power supply | voltage stabilizer is required, which is currently very expensive.

7) During constant torque speed regulation, the overload capacity of the motor in the low speed range is greatly reduced.

2. Comparison with other speed control methods

There are three methods for regulating the speed of AC motors: pole-changing speed regulation, slip-changing speed regulation, and variable frequency speed regulation. Among them, variable frequency speed regulation has the most advantages. Here we only compare the AC variable frequency speed regulation system with the DC speed regulation system.

AC traction itself has the potential for power saving that can be tapped. In the AC speed control system, a certain margin is often left when selecting the motor, and the motor does not always run under the maximum load; if the variable frequency power supply speed control technology is used, the motor speed can be controlled when the load is light, and the purpose of power saving can be achieved. Fans, water pumps, compressors, etc. are widely used in industry, and their electricity consumption accounts for about 50% of industrial electricity consumption; if the variable frequency power supply speed control technology is used, its efficiency can be greatly improved, and the power consumption can be reduced by 10%.