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Single chip microcomputer STM32L151CCU6
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Mobile phone crystal 3.2*2.5mm 3225 26M (26.000MHZ)
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Photocoupler
1. Given frequency
The output frequency of the inverter set by the user according to the requirements of the production process is called a given frequency. For example, the fan motor of the original power frequency supply is now changed to the variable frequency speed regulation power supply, the set frequency can be set to 50Hz, and there are two setting methods: 1 use the operation panel of the inverter to input the digital quantity of the frequency 50; The control terminal is regulated with an external reference (voltage or current) signal, the most common form being done by an external potentiometer.
2. Output frequency
The output frequency refers to the frequency of the actual output of the inverter. When the load on the motor changes, in order to stabilize the drag system, the output frequency of the inverter will be continuously adjusted according to the system conditions. Therefore, the output frequency often changes around a given frequency.
3. Reference frequency
The reference frequency is also called the fundamental frequency. Generally, the rated frequency of the motor is used as a reference value of the reference frequency.
The reference voltage refers to the output voltage of the inverter when the output frequency reaches the reference frequency. The reference voltage is usually taken from the rated voltage of the motor. The relationship between the reference voltage and the reference frequency is shown in Figure 3-3.
4. Upper and lower frequency
The upper limit frequency and lower limit frequency refer to the highest and lowest frequency of the inverter output, respectively, and are usually expressed by f H and f L . Depending on the load carried by the drag system, it is sometimes necessary to limit the maximum and minimum speed of the motor to ensure the safety of the drag system and the quality of the product. In addition, if the frequency caused by the erroneous operation of the operation panel and the malfunction of the external command signal is too high or too low, the upper limit frequency and the lower limit frequency can be set to protect. A common method is to assign the upper and lower frequency of the inverter. When the given frequency of the inverter is higher than the upper limit frequency or lower than the lower limit frequency, the output frequency of the inverter will be limited to the upper limit frequency or lower limit frequency, as shown in Figure 3-4. For example, set f H = 60 Hz, f L = 10 Hz. If the given frequency is 50Hz or 20Hz, the output frequency is consistent with the given frequency; if the given frequency is 70Hz or 5Hz, the output frequency is limited to 60Hz or 1OHz.
5. Jog frequency
Jog frequency refers to the given frequency of the inverter when it is jogging. The production machinery is often commissioned before commissioning and each new machining process begins to see if the entire part of the drive system is operating well. To prevent accidents, most jogs operate at a lower frequency. If it is cumbersome to change the given frequency to the jog frequency before each jog, the general inverter provides the function of preset jog frequency. If the jog frequency is preset, it is only necessary to switch the operating mode of the inverter to the jog mode every time it is jogged, and it is not necessary to change the given frequency.
6. Carrier frequency (PWM frequency)
The output voltage of the PWM inverter is a series of pulses. The width and interval of the pulse are not equal. The size depends on the intersection of the modulated wave (fundamental wave) and the carrier (triangle wave). The higher the carrier frequency, the more the number of pulses in a cycle, that is, the higher the frequency of the pulse, the better the smoothness of the current waveform, but the greater the interference to other devices. If the carrier frequency preset is not suitable, it will also cause the vibration of the motor core to generate noise. Therefore, the general inverter provides the PWM frequency adjustment function, so that the user can adjust the frequency within a certain range, thereby making the system noise. The smallest, the smoothest waveform, and the least interference. The relationship between frequency conversion carrier frequency and performance is shown in Table 3-5.
Table 3-5 Relationship between carrier frequency and performance of the inverter
Carrier frequency (kHz)
Electromagnetic noise
Noise, leakage current
Current waveform
1
Big
small
8
in
in
Between the two
15
small
Big
Carrier frequency (kHz)
Electromagnetic noise
Noise, leakage current
Current waveform
1
Big
small
8
in
in
Between the two
15
small
Big
7. Starting frequency
The starting frequency refers to the frequency at which the motor starts to start. This frequency can start from 0, but for loads with large inertia or large friction torque, it is necessary to increase the starting torque. At this time, the frequency can be increased to the starting frequency, and the starting current is also large. The general frequency converter can preset the starting frequency. Once the frequency is preset, the frequency converter will ignore the operating frequency less than the starting frequency.
The principle of giving the starting frequency is: the driving system can be started smoothly if the starting current does not exceed the allowable value.
8. Multi-speed speed
Due to different process requirements, many production machines need to operate at different speeds at different stages. To facilitate this load, most drives offer multi-speed frequency control. That is, different operating frequencies are selected by the combination of on and off of several switches. A common form is to use four inputs to select the 16-speed frequency.
Four switches DINI, DIN2, DIN3, and DIN4 are provided in the control terminal of the inverter. The combination of the switching states is used to select the frequency of each gear, and a total of 16 frequency blocks can be selected. The correspondence between them is shown in Table 3-6.
Table 3-6 Correspondence between DIN state combination and speed frequency
frequency
status
DIN4 status
DIN3 status
DIN2 status
DIN1 support state
OFF
0
0
0
0
FF-I
0
0
0
1
FF2
0
0
1
0
FF3
0
0
1
1
FF4
0
1
0
0
FF5
0
1
0
1
FF6
0
1
1
0
FF7
0
1
1
1
FF8
1
0
0
0
FF9
1
0
0
1
FF10
1
0
1
0
FF11
1
0
1
1
FF12
1
1
0
0
FFl3
1
1
0
1
FFl4
1
1
1
0
FF15
1
1
1
1
9. Jump frequency
The jump frequency is also called the avoidance frequency, which refers to the frequency that does not allow the inverter to continuously output. It is usually expressed by f J. Due to the vibration and speed of the production machinery, when the motor is adjusted to a certain speed (the inverter outputs a certain frequency), the frequency of the mechanical vibration will coincide with its natural frequency, and resonance will occur. The damage is very large. In order to avoid the occurrence of mechanical resonance, the drag system should skip the speed corresponding to the resonance, so the output frequency of the inverter should skip the frequency corresponding to the resonant speed.
When the inverter presets the hopping frequency, it usually presets a jump interval. The lower limit of the interval is f J1 and the upper limit is f J2 . If the given frequency is between f J1 and f J2 , the output frequency of the inverter will be limited to f. J1 . For the convenience of users, most inverters provide 2 to 3 jump intervals. The working range of the skip frequency is shown in Figure 3-6.
For example, if f J1 = 30 Hz, f J2 = 35 Hz; when the given frequency is 32 Hz, the output frequency of the inverter is 30 Hz. If f J1 = 35Hz, f J2 = 30Hz; when the given frequency is 32Hz, the output frequency of the inverter is 35Hz.