Application of the hottest frequency converter in

2022-08-13
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Application of frequency converter in DK760 carding machine

after long-term operation, some important components of DK760 carding machine have been damaged, and the servo transmission that drives the doffer of the carding machine is one of them. In the late 1980s and early 1990s, servo transmissions were mostly used for high-end equipment that needed precise speed regulation. The whole speed regulation system is composed of three parts: servo power supply device, servo transmission and AC synchronous motor. The server power supply provides 300V DC and the servo transmission outputs three groups of 200V AC with adjustable frequency, which are used together with the 2.8KW AC synchronous motor. The speed measuring motor installed at the end of the AC synchronous motor outputs the speed and other signals of the motor, which are fed back to the servo transmission, and then the pulse signal generated by the servo transmission is transmitted to the computer of DK760 carding machine to monitor the doffer drive. Although this control method has high control accuracy and large starting torque of the motor, the structure of the device is complex, and the damage of any part of the speed regulation system will cause the DK760 carding machine to stop production and look for new traders and terminals. DK760 carding machine is a high-yield carding machine with less tables. Once doffer drives servo speed change 3 The damage of the thermocouple in the furnace, the thermocouple in the center of the sample and the thermocouple on the surface of the sample will affect the shutdown of equipment with more subsequent processes. Contact Germany trutschler company to import servo transmission, which is time-consuming and expensive. On the other hand, servo 14 Data sampling frequency: the high-speed sampling frequency transmission can be selected according to the user's experimental requirements. It was a technology before the widespread application of frequency converters. Some manufacturers that used to produce servo transmission have stopped producing this kind of product for various reasons. The later the servo transmission is replaced, the less the supply is. Therefore, we apply the frequency converter to the doffer drive of DK760 carding machine. The specific conditions are as follows

1. Control requirements for doffer drive of DK760 carding machine

dk760 carding machine completes the control of doffer drive through the computer on the machine. The application of frequency converter instead of servo transmission should meet the following requirements for doffer drive:

(1) start doffer after the cylinder of carding machine is started to the set speed. The initial speed of doffer can be set in the range of 20m/min ~ 60m/min and start slowly

(2) according to the different number and weight of cotton slivers and the requirements for product output. The doffer speed during the operation of the carding machine can be set in the speed range of 80m/min ~ 160m/min, or even higher

(3) the doffer can drive alone at a line speed of 300m/min for doffer needle grinding

2. The changes in the control circuit of frequency converter replacing servo transmission are sketchy. Remove the servo transmission and AC synchronous motor, and install the up converter and AC asynchronous motor. Connect the frequency converter and three-phase AC asynchronous motor according to the requirements of the frequency converter. The model of frequency converter is LG sv037i-4u, 3.7KW; AC asynchronous motor is Y-type, 3KW, 4 poles

connect the d10v carding machine doffer speed control voltage originally connected to servo transmission ports X and X to the 10V speed control port of the frequency converter (refer to DK760 carding machine circuit diagram 760-e2.900.004). Connect a small DC 24V relay in series to the controller release signal line originally connected to the X end of the servo transmission, and then connect the signal line to the 0V end of the +24v power supply. The normally open contact of DC 24V small relay is connected to the COM and FWD ends of the frequency converter to control the start and stop of the frequency converter. A DC24V proximity switch is installed at the end of the AC motor to generate the pulse signal of the speed of the AC asynchronous motor. Originally, the terminal X of the module on the servo transmission inputs the synchronous motor speed pulse to the carding machine computer. The signal line of the proximity switch is passed through X, and the pulse signal of the proximity switch is transmitted to the carding machine computer to replace the pulse output by the servo transmission

3. commissioning and parameter determination of frequency converter speed regulation system

(1) determine speed regulation input parameters. The maximum speed of the synchronous motor that originally drove the doffer of the DK760 carding machine was 2400r/min, which corresponds to the linear speed of 300m/min when the doffer of the carding machine drives the grinding needle alone. At this time, the input voltage of the X and X ports of the servo transmission corresponds to dc10v. That is, for every dc1v input, the doff linear speed is 30m/min. This correspondence is also true in actual production. For example, when the computer shows that the doffer coiling speed is 123m/min, the input voltage of ports X and X of the test servo transmission is 4.1V. After replacing the frequency converter and AC asynchronous motor, first determine the maximum output frequency of the frequency converter as 50Hz. First, under the condition that the AC asynchronous motor does not carry any load, test the motor speed as 1500r/rain under the condition that the carding machine computer controls the doffer to drive alone. At this time, the doffer output speed should be: 300 × 1500/2400=187.5(m/min)。 Then, according to the calculation and test, the number of teeth of the serrated disc installed on the tail shaft of the AC motor is determined as 9 teeth, so that each revolution of the motor shaft DC24V proximity switch sends 9 pulses. The carding machine computer shows that the actual speed of doffer will flash back and forth between 187m/min and 188m/min

(2) determine the magnification of the input voltage of the frequency converter. Because the asynchronous AC motor is used to replace the synchronous AC motor, the frequency of the asynchronous AC motor under long-term operation should not exceed 50. The average value of the experiment must be 5 consecutive Hz, otherwise the motor is easy to heat and burn. The maximum output frequency is 50Hz when the input voltage of speed regulation set by the frequency converter is dcl0v by default. It does not match the output when the speed regulation input voltage of the original carding machine servo transmission is dcl0v. The magnification of the input voltage of the frequency converter must be adjusted. According to the above input-output relationship, when the frequency converter outputs 50Hz, the doffer speed should be 187.5m/min, and the corresponding speed regulation input voltage should be 187.5 × 1/30=6.25(V)。 That is to say, when the input voltage of speed regulation reaches 6.25v, the frequency converter should output 50Hz AC. This is a theoretical value. There is a slip relationship after the AC asynchronous motor is loaded. In practical use, we adjust the analog input gain of the speed control input voltage of the frequency converter to 60%. That is, when the input voltage reaches 6V, the frequency converter outputs 50Hz. Because the starting torque of the AC asynchronous motor is small, the minimum starting frequency of the frequency converter is determined to be 5.9hz corresponding to the minimum speed of 20m/min when the doffer starts

4. use of frequency converter

carding machine doffer drive has been using frequency converter for 8 months, and the operation fully meets the production requirements. According to the previous production situation, the maximum operating speed of our DK760 carding machine is 150m/min, and the maximum output frequency of the frequency converter is determined as 50Hz. The maximum operating speed of the carding machine doffer is completely beyond the actual range of use. If doffer wants to sharpen the needle, he can temporarily change the maximum output frequency of the frequency converter to 80Hz. It doesn't matter that the AC asynchronous motor operates for less time under light load and high frequency. In practical use, for example, if the output speed of the doffer of the carding machine is set to 122m/min, the actual speed displayed by the computer of the carding machine is stable at 122m/min for most of the time, sometimes it will jump to 121m/min, but it will soon jump back to 122m/min. this also shows that using the frequency converter to control the AC asynchronous motor can completely replace the expensive synchronous motor servo speed change system in speed accuracy. (end)

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