In modern industrial automation control, frequency converters play a crucial role. It can not only achieve precise control of motor speed, but also improve the energy efficiency of the system. However, when facing the problem of excessive speed of frequency converters, engineers need to understand the reasons and master the corresponding speed control methods. This article will reveal the reasons for the speed changes of the frequency converter and introduce several effective speed control techniques. Motor driver
##The reasons for the excessively fast speed of the frequency converter
###1 Parameter setting issue
Improper setting of the speed parameters of the frequency converter may lead to excessive speed. The maximum output frequency, upper limit of operating frequency, and lower limit of operating frequency in the basic parameter group are key factors. The correct setting should be that the maximum output frequency is greater than or equal to the upper limit frequency, and the upper limit frequency is also greater than or equal to the lower limit frequency. If it is found that the frequency is difficult to reduce, the set value of the lower limit frequency should be checked if it is too high.
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###2 Controller and wiring issues
When the parameter settings are correct, it is necessary to check the controller and circuit. The commonly used frequency modulation methods include analog control and communication control. Analog control can be achieved through potentiometers or DA modules. For the potentiometer, use a multimeter to check if its output voltage is normal and ensure that the output of the potentiometer is consistent with the analog input of the frequency converter. The DA module also needs to check the output voltage and monitor the DA conversion program in the programming software to ensure that the input digital quantity matches the set frequency.
##Variable frequency drive speed regulation method
###1 Variable pole logarithmic speed regulation
Variable pole logarithmic speed regulation adjusts the synchronous speed of an electric motor by changing the wiring method of the stator winding. This method has the advantages of hard mechanical properties, good stability, no slip loss, and high efficiency. Suitable for production machinery that does not require stepless speed regulation, such as machine tools, elevators, lifting equipment, etc.
###2 frequency control
Variable frequency speed regulation is to adjust the synchronous speed by changing the frequency of the stator power supply of the motor. The core of a variable frequency speed control system is a frequency converter, which can be an AC-DC-AC frequency converter or an AC-AC frequency converter. Variable frequency speed regulation has the characteristics of high efficiency, wide speed regulation range, and high accuracy, which is suitable for occasions with high precision requirements and good speed regulation performance. Variable frequency speed regulation is divided into speed regulation below the fundamental frequency and speed regulation above the fundamental frequency. The former is constant torque speed regulation, while the latter is constant power speed regulation.
###3 Cascade speed regulation
Cascade speed regulation is the process of introducing adjustable additional electromotive force into the rotor circuit of a wound motor to change the slip and achieve speed regulation. This method can feed back the slip loss to the power grid or convert energy for utilization, with high efficiency. Suitable for production machinery with a speed range of 70% -90% of rated speed, such as fans, water pumps, etc.
##Conclusion
Mastering the speed regulation method of frequency converters is crucial for improving production efficiency and energy utilization efficiency. By understanding the causes of speed changes in frequency converters and applying appropriate speed control techniques, engineers can ensure that mechanical equipment operates at its optimal state. Whether it is variable pole logarithmic speed regulation, variable frequency speed regulation, or cascade speed regulation, choosing the appropriate method will help achieve accurate speed regulation
