Speed regulation method for frequency converter of press machine

Abstract

A press machine frequency converter speed regulation method comprises the following steps that the value of Us is calculated according to the relational expression between the analog quantity voltage Us at the VS position and the output frequency f of a frequency converter, and the total resistance value in a required potentiometer set is calculated in combination with the total current; the combined switch SA1 is rotated, the corresponding gears are switched on, the combined switch SA1 is provided with a plurality of gears, and each gear is connected to the corresponding intermediate relay and potentiometer group; knobs of all potentiometers in the potentiometer group are adjusted to enable the sum of the knobs to be equal to the total resistance value, and the potentiometer group is formed by connecting one to two potentiometers in series. According to the invention, the potentiometer group composed of a plurality of potentiometers is accessed to replace the existing single potentiometer, so that the purpose of adjusting more accurate resistance value is achieved; through cooperative adjustment of the two potentiometers, the target resistance value can be maintained after reaching the target resistance value, equivalently, the resistance value of the gear is stored, when the frequency of the speed section is needed next time, the combination switch can be directly selected to the gear, and operation is saved.

Description

Technical Field

[0001] The invention relates to the technical field of presses, and in particular to a speed regulation method of a frequency converter for a press. Background Art

[0002] The variable frequency speed regulation of the press is a mainstream speed regulation method at present, which has the advantages of convenient speed regulation, energy saving, soft start, overload, overvoltage and other measures, and motor protection. When the press speed is regulated, the analog input potentiometer is rotated to change the analog potential to adjust the motor input voltage frequency to achieve the purpose of speed regulation. Figure 1 It is a commonly used variable frequency speed regulation circuit. The access part at the lower left corner is the existing frequency converter speed regulation structure, which is adjusted by a single potentiometer. Please refer to the patent number ZL201710377070.2 and the patent name "A speed regulation device and speed regulation method for a frequency converter suitable for a press".

[0003] Because some press dies, workpieces, and stamping processes have high requirements for the speed of the press, ordinary speed potentiometers cannot smoothly adjust the speed due to the resistance material itself, including factors such as the resistance value span. Although a single potentiometer has a wider resistance range, it may not be adjusted to the ideal resistance due to its lack of accuracy. For example, a single potentiometer adjusts 5.5KΩ and then adjusts it to 5.65KΩ, with a span in between. After adjusting the resistance value during this use, the next time it is used for another workpiece, it needs to readjust the resistance value to meet the corresponding speed requirements. It does not have the function of storing multiple gears of target resistance values, so it can only be adjusted again and again during use, which does not save operations. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a method for speed regulation of a frequency converter of a press machine, which solves the technical problem that a single potentiometer cannot adjust a more accurate resistance value and cannot store the gears corresponding to multiple target resistance values ​​to save operations.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for speed regulation of a frequency converter of a press machine comprises the following steps:

[0007] S1: Calculate the value of Us according to the relationship between the analog voltage Us at VS and the output frequency f of the inverter, and calculate the total resistance value in the required potentiometer group in combination with the total current;

[0008] S2: Rotate the combination switch SA1 to connect the corresponding gear. The combination switch SA1 is provided with multiple gears, and each gear is connected to the corresponding intermediate relay and potentiometer group;

[0009] S3: Adjust the knob of each potentiometer in the potentiometer group so that the sum of the knobs is equal to the above-mentioned total resistance value. The potentiometer group is composed of one or two potentiometers connected in series.

[0010] Preferably, the multiple gears are set to 4, namely, fixed speed gear 1 SA1-1, fixed speed gear 2 SA1-2, fixed speed gear 3 SA1-3 and stepless speed regulation gear SA1-4, wherein the fixed speed gear 1 SA1-1 is connected to the intermediate relay KA1 and the potentiometer group composed of potentiometer R1 and potentiometer R2, the fixed speed gear 2 SA1-2 is connected to the intermediate relay KA2 and the potentiometer group composed of potentiometer R1 and potentiometer R2, the fixed speed gear 3 SA1-3 is connected to the intermediate relay KA3 and the potentiometer group composed of potentiometer R1 and potentiometer R2, and the stepless speed regulation gear SA1-4 is connected to the intermediate relay KA4 and the potentiometer R4.

[0011] More preferably, the potentiometer R1 adopts a single-turn carbon film resistor, and its resistance value adjustment range is 0-10KΩ, and the potentiometers R2, R3, R4, R5, R6, and R7 all adopt plastic-sealed precision adjustable resistors, and their resistance value adjustment range is 0-5KΩ.

[0012] Preferably, under the condition that the output frequency f of the frequency converter is within the range of 25HZ-50HZ, the relationship between the output frequency f of the frequency converter and the analog voltage Us is: f=2.5Us+25.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The present invention adopts a potentiometer group composed of multiple potentiometers to replace the existing single potentiometer to adjust the analog voltage on the inverter. By operating the combination switch, the gear is selected to select the set fixed speed 1, 2, 3 or stepless speed adjustment gear to achieve the purpose of adjusting the resistance value more accurately;

[0015] 2. The present invention achieves the target resistance value through the coordinated adjustment of two potentiometers, and can maintain this resistance value, which is equivalent to storing the resistance value of this gear. When the frequency of this speed range is needed next time, the combination switch can be directly selected to this gear. Since three commonly used frequencies can be stored, it can be used for three commonly used sets of molds with speed requirements. Of course, if more precise frequency ranges are needed, it can also be expanded for use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of a main motor connected to a frequency converter and a potentiometer structure (lower left) in an existing variable frequency speed regulation circuit;

[0018] Figure 2 It is a schematic diagram of the appearance of the combination switch of the present invention;

[0019] Figure 3 The relationship between each gear position and contact point of the present invention;

[0020] Figure 4 The connection diagram of the potentiometer group of the present invention is shown in FIG. Figure 1 Connected in the lower left corner to replace the analog given resistance);

[0021] Figure 5 For the control of the present invention Figure 4 A separate control loop in which a certain potentiometer group is connected;

[0022] Figure 6 4 is a diagram showing the relationship between the analog voltage Us at VS of the present invention and the output frequency f of the frequency converter. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0024] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0025] Figure 1-6 A method for speed regulation of a press machine frequency converter is shown, comprising the following steps:

[0026] S1: Calculate the value of Us according to the relationship between the analog voltage Us at VS and the output frequency f of the inverter, and calculate the total resistance value in the required potentiometer group in combination with the total current;

[0027] S2: Rotate the combination switch SA1 to connect the corresponding gear. The combination switch SA1 is provided with multiple gears, and each gear is connected to the corresponding intermediate relay and potentiometer group;

[0028] S3: Adjust the knob of each potentiometer in the potentiometer group so that the sum of the knobs is equal to the above-mentioned total resistance value. The potentiometer group is composed of one or two potentiometers connected in series.

[0029] As the analog voltage Us at VS changes, the output frequency f of the inverter changes, which ultimately changes the speed of the main motor of the press.

[0030] As an embodiment of the present invention, the plurality of gears are set to 4, such as Figure 2 and Figure 3 The gear positions on the combination switch are gear 1 (fixed speed 1 gear SA1-1), gear 2 (fixed speed 2 gear SA1-2), gear 3 (fixed speed 3 gear SA1-3) and gear 4 (stepless speed adjustment gear SA1-4). Figure 4 and Figure 5 The fixed speed 1 gear SA1-1 is connected to the intermediate relay KA1 and the potentiometer group composed of potentiometers R1 and R2, the fixed speed 2 gear SA1-2 is connected to the intermediate relay KA2 and the potentiometer group composed of potentiometers R1 and R2, the fixed speed 3 gear SA1-3 is connected to the intermediate relay KA3 and the potentiometer group composed of potentiometers R1 and R2, and the stepless speed adjustment gear SA1-4 is connected to the intermediate relay KA4 and the potentiometer

[0031] R4. Since some press molds, workpieces, peripheral equipment (machine arms, feeders), and stamping processes have high requirements for press speed, ordinary speed regulating potentiometers cannot smoothly adjust speed (some resistance values ​​may not be adjustable) due to the resistance material itself, including the resistance span and other factors. Therefore, the present invention combines the two corresponding potentiometers in gears 1, 2, and 3 into a potentiometer group, so that the adjustment span is larger and the adjustment resistance value is more accurate.

[0032] It can be seen that the present invention is equivalent to storing three commonly used frequencies for use with three commonly used sets of molds that require speed. Of course, more precise frequency bands are required and can be expanded for use. Gears 1, 2, and 3 can adjust the required resistance value to match the corresponding mold. After the resistance value is adjusted, it is not often adjusted. Gear 4 is a stepless speed gear, which is suitable for daily press adjustment. The target resistance value is achieved through the coordinated adjustment of two potentiometers, and this resistance value can be maintained, which is equivalent to storing the resistance value of this gear. When the frequency of this speed segment is required next time, the combination switch can directly select this gear.

[0033] Preferably, potentiometer R1 adopts a single-turn carbon film resistor with a resistance adjustment range of 0-10KΩ, which is conducive to constructing a larger resistance value. Potentiometers R2, R3, R4, R5, R6, and R7 all adopt plastic-sealed precision adjustable resistors with a resistance adjustment range of 0-5KΩ, which is conducive to reducing the span of the synthetic resistance value and obtaining an accurate resistance value.

[0034] Under the condition that the output frequency f of the inverter is within the range of 25HZ-50HZ, Figure 6The relationship between the output frequency f of the inverter and the analog voltage Us is: f=2.5Us+25.

[0035] The following are implementation examples of the present invention:

[0036] The process of adjusting the resistance value is equivalent to adjusting the analog voltage of the inverter and dividing the analog voltage of the inverter. Figure 1 , analog 10V given, by rotating the potentiometer to change the analog voltage at the inverter VS, change the inverter output frequency, VS analog voltage range 10V-0V, for the inverter output set upper and lower frequency limits (50HZ-25HZ), (the inverter upper and lower frequency limits are adjustable) and frequency range 25-50HZ, take the commonly used 4-pole AC asynchronous motor as an example, the speed is adjusted between 1440-720 rpm.

[0037] Taking the adjustment of gear position 1 as an example, select the combination switch SA1 to gear position 1. Figure 4 and Figure 5 , the contact of the combination switch SA1-1 is connected, the coil of the KA1 intermediate relay is energized, the corresponding KA1 normally open contact is closed, and the combined resistance of R2 and R5 is connected to the inverter output DC10V analog voltage terminal ( Figure 5 The 24V in the figure is the external control voltage, which is used in a separate control loop and has nothing to do with the analog voltage 10V of the inverter.) Assuming that the current resistance value of R2 is 5KΩ, the current resistance value of R5 is 0.5KΩ, and the current voltage divider resistance value is 5.5KΩ.

[0038] Calculate the analog voltage Us at VS (units omitted below):

[0039] According to Ohm's law, the total current I = U / R, I = 10 / (10K+0.5K), I = 1 / 1050

[0040] The analog voltage at VS is obtained from Us=IR, Us=1 / 1050*(0.5K+5K)=5500 / 1050=110 / 21. The current frequency can be calculated according to the inverter voltage-frequency linear equation. See attached. Figure 5 :

[0041] From the linear equation f=2.5Us+25, since Us is a voltage of 110 / 21V, it is calculated that the current frequency f is 2.5*110 / 21+25=38.1HZ.

[0042] It is worth mentioning that the above calculation is an ideal case, which is calculated without considering the internal resistance value of the analog voltage. The specific frequency should be based on the actual debugging frequency.

[0043] The above process shows the advantages of the combination of two potentiometers. The same resistance value can be achieved through different combinations: for example, if the lower resistance is adjusted to 5.6KΩ, it can be 5KΩ+0.6KΩ, 4KΩ+1.6KΩ, 2KΩ+3.6KΩ, etc. There are many combinations. Using a single potentiometer to adjust may not necessarily adjust to the ideal resistance. A single potentiometer adjusts 5.5KΩ, and then adjusts it to 5.65KΩ, with a span in between.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for speed regulation of a frequency converter of a press machine, characterized in that: The following steps are involved: S1: According to V S The value of Us is calculated by the relationship between the analog voltage Us at and the output frequency f of the inverter, and the total resistance value in the required potentiometer group is calculated in combination with the total current; S2: Rotate the combination switch SA1 to connect the corresponding gear. The combination switch SA1 is provided with multiple gears, and each gear is connected to the corresponding intermediate relay and potentiometer group; S3: Adjust the knob of each potentiometer in the potentiometer group so that the sum of the knobs is equal to the above-mentioned total resistance value. The potentiometer group is composed of one or two potentiometers connected in series.

2. The method for speed regulation of a press machine frequency converter according to claim 1, characterized in that: The multiple gears are set to 4, namely, fixed speed gear 1 SA1-1, fixed speed gear 2 SA1-2, fixed speed gear 3 SA1-3 and stepless speed regulation gear SA1-4, wherein the fixed speed gear 1 SA1-1 is connected to the intermediate relay KA1 and the potentiometer group composed of potentiometer R1 and potentiometer R2, the fixed speed gear 2 SA1-2 is connected to the intermediate relay KA2 and the potentiometer group composed of potentiometer R1 and potentiometer R2, the fixed speed gear 3 SA1-3 is connected to the intermediate relay KA3 and the potentiometer group composed of potentiometer R1 and potentiometer R2, and the stepless speed regulation gear SA1-4 is connected to the intermediate relay KA4 and the potentiometer R4.

3. The method for speed regulation of a press machine frequency converter according to claim 2, characterized in that: The potentiometer R1 adopts a single-turn carbon film resistor, and its resistance value adjustment range is 0-10KΩ. The potentiometers R2, R3, R4, R5, R6, and R7 all adopt plastic-sealed precision adjustable resistors, and their resistance value adjustment range is 0-5KΩ.

4. The method for speed regulation of a press machine frequency converter according to claim 1, characterized in that: When the output frequency f of the frequency converter is within the range of 25 Hz to 50 Hz, the relationship between the output frequency f and the analog voltage Us is: f=2.5Us+25.

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