The production machinery driven by motor, sometimes according to the requirements of processing technology, needs to run at different speeds, that is, multi-stage speed. Traditional technology is to use gear shift method, but this method makes the equipment structure complex, large volume, high failure rate, maintenance difficult. It is much more convenient to use the frequency converter, and the multi speed operation can be realized without adding or modifying the hardware equipment.
1、 Two methods to realize multi speed operation of frequency converter
The first method is called terminal control method. In this method, firstly, through parameter setting, the frequency converter works in the multi-stage speed operation state controlled by the terminal, and several input terminals of the frequency converter become the multi-stage speed frequency control terminal. Then, the relevant functional parameters are set, and the working frequency corresponding to each speed, as well as the acceleration time or deceleration time are preset. After that, the frequency selection command can be given by logic control circuit, PLC or upper computer to realize multi-stage speed frequency operation.
The other method does not use the multi-function input terminal, and only sets the relevant function parameters. Although there are many parameters involved, the operation mode is flexible and can be repeated. In order to distinguish the former control method, this method is called program control method.
2、 Terminal controlled multi speed operation
In the external input multi-function control terminal of frequency converter, several (usually 2-4) input terminals are designated as multi gear (3-15 gear) speed control terminals through function preset. The speed switching is realized by changing the state and combination of input terminals by external switching devices. The speed grades are arranged in binary order, so the two input terminals can be combined into the 4th speed at most, the three input terminals can be combined into the 8th speed at most, and the four input terminals can be combined into the 16th speed at most. When the external switch contacts are in the off state (equivalent to binary 0), it is impossible to judge whether there is no input command (all input is 0) or all input commands are 0. Therefore, the inverter usually regards the all 0 state as invalid. In this way, the 4-bit binary command can only be used as a multi speed command of up to 15 gears.
Next, take cvf-g3 series inverter as an example to introduce the specific operation method. Firstly, the function parameter B-1 (frequency input channel selection) is preset to “9”, that is, the control of operation frequency and mode is given to “external multi-function input terminal”. Then, l-63 is preset as “1”, L-64 is preset as “2”, l-65 is preset as “3”, l-66 is preset as “4”; the significance of these parameter presets is: firstly, it is determined that the frequency converter operates in multi speed mode; secondly, the external input terminals x1, X2, X3 and X4 become multi speed input control terminals; moreover, it is determined that X1 corresponds to the lowest bit of 4-bit binary number, and X4 corresponds to 4-bit binary number The highest bit of a decimal number. The speed switching is realized by the on-off state and its combination of external switches on the specified control terminal. Figure 1 is a schematic diagram of four multi speed control terminals. The on-off status of each relay or PLC contact corresponds to one of the four binary numbers. The corresponding bit of switch on is 1, and the corresponding bit of switch off is 0. diangon.com In Figure 1, all four switches are off, that is, the binary number is 0000. It should be noted that the definition of “0” and “1” is opposite to the corresponding relationship between the switch state when some frequency converters are set with multi speed operation level, and the specific application should be subject to the introduction of the manual. See Table 1 for the on-off state of the switch and the frequency (speed) grade corresponding to its combination.
Table 1 corresponding relationship between terminal switch status and speed grade
Then preset the working frequency corresponding to the speed of each gear and the acceleration time or deceleration time.
For example, cvf-g3 frequency converter can respectively set multi-stage speed frequency 1 ~ multi-stage speed frequency 15 through the 15 function parameters of L-18 ~ L-32. The frequency setting range is 0.00hz ~ upper limit frequency. The operating frequency of each section speed can be the same or different from each other.
The acceleration and deceleration time parameters of cvf-g3 frequency converter are shown in Table 2.
Table 2cvf-g3 inverter speed acceleration and deceleration time parameter settings
Description of acceleration and deceleration time setting in Table 2. The acceleration and deceleration time of multi-stage speed 1 to multi-stage speed 7 are set with one parameter respectively, and the acceleration time and deceleration time can only be equal, for example, 28 seconds. The acceleration and deceleration time of multi-stage speed 8 and multi-stage speed 12 ~ multi-stage speed 15 are set with parameters B-7 and B-8. Therefore, the acceleration and deceleration time of these five stages are the same, but the acceleration and deceleration time of each stage can be different. The acceleration and deceleration time of multi-stage speed 9 ~ multi-stage speed 11 can be set separately by parameters, but they are different from each other.
In the specific operation, which segment speed runs first and which segment speed runs later is completely determined by the contact state connected on terminals x1-x4 in Figure 1, and it does not necessarily run in the order of segment speed 1-15.
In the above cvf-g3 series inverters, we determined that the operation mode of the inverter was controlled by the external multi-function input terminal through the setting of function parameter code B-1; the multi-function input terminals x1-x4 were set as the multi speed control terminal through l-63-l-66; the operation frequency of the 15 speed was preset through the 15 function parameter codes l-18-l-32; the operation frequency of the 15 speed was preset through the function parameter codes in Table 2 After the acceleration and deceleration time of each speed, the logic control circuit, PLC or upper computer can give the frequency selection command to control the on-off state and combination of contacts KA1 ~ ka4 in Figure 1, so as to realize multi-stage speed frequency operation. The running time of each segment speed is determined by the state of contact ka1-ka4. Once the state changes, it means that the last segment speed is ended and a new segment speed is started.