Frequency setting method of the hottest frequency

Frequency setting method of frequency converter

frequency converter is a new speed regulation and energy-saving product rising in recent years. It is a perfect combination of power electronics technology and computer application technology. Because of its high speed regulation accuracy, convenient operation, and energy saving (when the output frequency is less than 50Hz), it has been widely used in machinery, chemical industry, metallurgy, light industry and other fields. According to the needs of practical application, there are different types of frequency setting methods of frequency bender. Now take the fr-500 series frequency converter of Mitsubishi Corporation of Japan as an example to illustrate the characteristics of several frequency settings

the frequency setting method of the frequency converter can be divided into two categories. The first is to use the frequency converter operation panel to set the frequency, and the second is to use the frequency converter control terminal to set the frequency for the reaction with epichlorohydrin. The first type uses the frequency converter operation panel to set the frequency. Only the up and down keys on the operation panel can set the frequency. This method does not need external wiring. It is simple and has high frequency setting accuracy. It belongs to digital frequency setting and is suitable for the frequency setting of a single frequency converter. The second is to use the frequency converter control terminal to set the frequency, which is divided into two methods. The first is to use the external potentiometer to set the frequency; The second is to use the close-up function of the frequency converter control terminal to set the frequency with an electric potentiometer

the first method uses an external potentiometer to set the frequency, as shown in Figure 1. The 10 terminal of fr-500 series frequency converter provides a standard 10V DC voltage, the 2 terminal is the frequency setting input terminal, and the 5 terminal is the analog input common terminal. By adjusting the output voltage of the 2 terminals of the external potentiometer R, the input voltage value of the 2 terminals of the frequency converter is changed, which also changes the frequency setting value of the frequency converter (pay attention to the prominent part of the machine). The purpose of frequency setting is achieved. This method has the following advantages:

(1) the wiring is simple. Only three terminals of the potentiometer need to be connected to the voltage input terminal, voltage output terminal and common terminal of the frequency converter

(2) the frequency setting is simple and easy to operate. You can set the frequency by gently turning the knob of the external potentiometer

(3) the installation is flexible. According to the actual needs, the external potentiometer can be installed at any position for remote operation

however, this method also has the following disadvantages:

(1) there is a temperature drift phenomenon. Because the resistance value is affected by temperature, when the external temperature changes, the resistance value will change, and the frequency setting value will also change

(2) low anti-interference ability. When there is strong electromagnetic interference around, the induced voltage will be generated in the connecting cable between the frequency converter and the external potentiometer, which will change the voltage value input to the end 2 of the frequency converter, which will also change the set value of the frequency and affect the stability of the set frequency

(3) the installation distance of potentiometer is limited. Theoretically, the voltage variation range at the end of the frequency converter 2 is 0. Our company is very grateful for -10v. However, if the external potentiometer is installed too far away, the connecting cable will produce a voltage drop, and the voltage at the end of the frequency converter 2 will not reach 10V, so that the output frequency cannot reach the maximum set value

therefore, the frequency setting method of the frequency converter is generally used in occasions with low speed regulation accuracy, small surrounding interference and small environmental temperature change, which belongs to analog quantity regulation

the second method is to use the specific function of the frequency converter control terminal. By setting the internal parameters of the frequency converter, terminals RH and RM can become electric potentiometers, that is, when RH is connected with the common end SD, the output frequency of the frequency converter increases, and when RM is connected with SD, the output frequency of the frequency converter decreases to achieve the purpose of frequency setting, as shown in Figure 2. Compared with the first rich and colorful method of friction phenomenon, This method has the following advantages:

(1) the frequency setting accuracy is high. The external potentiometer method belongs to the analog setting method, and the frequency variation range is within 0.2% of the maximum output frequency, while the electric potentiometer is used to set the frequency, and the frequency variation range is within 0.01% of the maximum output frequency

(2) strong anti-interference ability. Because it is only a switch signal input, it is not disturbed by the surrounding electromagnetic field

(3) no temperature drift. Since the external potentiometer is cancelled, it is not affected by the change of ambient temperature

(4) the installation is flexible, and the buttons SB1 and SB2 can be installed in any position

(5) good synchronization performance, which can increase and decrease the frequency of multiple inverters at the same time

in short, we should reasonably select the frequency setting method according to the actual needs to achieve the application effect