Several methods of frequency converter frequency setting - Database & Sql Blog Articles

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An inverter is a modern energy-saving device that has gained popularity in recent years. It combines power electronics and computer control technologies, offering high-speed regulation, ease of use, and energy efficiency—especially when the output frequency is below 50Hz. As a result, it is widely used across industries such as machinery, chemicals, metallurgy, and light manufacturing. Depending on application requirements, there are multiple methods to set the frequency of an inverter. This text will take the FR-500 series inverter from Mitsubishi as an example to explain different frequency-setting techniques.
There are generally two main approaches to setting the frequency of an inverter: one involves using the built-in operation panel, while the other uses external control terminals. The first method allows users to adjust the frequency directly through the panel by pressing up and down buttons. This approach requires no external wiring, is simple to operate, and offers high precision. It’s ideal for single inverter setups where digital control is needed.
The second method involves using the control terminals of the inverter. There are two common ways to do this. One is to connect an external potentiometer, and the other is to use the internal electric potentiometer function of the inverter.
When using an external potentiometer, the FR-500 series provides a standard 10V DC supply at terminal 10, a frequency input at terminal 2, and a common analog input at terminal 5. By adjusting the voltage between the two ends of the external potentiometer, the input voltage at terminal 2 changes, thus altering the inverter's frequency setting. This method is popular due to its simplicity, but it also has some drawbacks. For instance, temperature fluctuations can cause resistance drift, affecting accuracy. Additionally, electromagnetic interference may distort the signal, and long cable runs can lead to voltage drops, limiting the maximum frequency achievable.
On the other hand, using the inverter’s internal control functions, such as the RH and RM terminals, allows for more precise and stable frequency control. These terminals can act like an electric potentiometer, with RH increasing the frequency and RM decreasing it. This method offers better accuracy (within ±0.01% of the maximum output), stronger immunity to interference, and no temperature drift. It also allows for flexible installation of control buttons and synchronized operation across multiple inverters.
In conclusion, choosing the right frequency-setting method depends on specific application needs, including precision, environmental conditions, and system complexity. Selecting the appropriate technique ensures optimal performance and reliability in real-world applications.