This article mainly explains what is the reason why the reactor should be used before the servo amplifier. First of all, it introduces the function and principle of the servo amplifier. Secondly, it explains why the servo amplifier must use the reactor to answer the following questions.
The role and principle of servo amplifierThe function of the servo amplifier is to synthesize and amplify a plurality of input signals and feedback signals. According to the difference in the polarity of the integrated signals, the corresponding signals are output to control the forward rotation or reverse rotation of the servo motor. When the input signal and the feedback signal are balanced, the servo motor stops rotating and the output shaft of the actuator is stabilized at a certain position.
The servo amplifier group consists of a pre-amplifier, a flip-flop, a thyristor main circuit, and a power supply. Its composition is shown in the figure below.
To meet the needs of complex multi-parameter adjustments, the servo amplifier is set up with three input signal channels and one position feedback signal channel. Therefore, it can input three input signals and one position feedback signal at the same time. In a single-parameter simple adjustment system, only one of the input channels and feedback channels is used.
In the servo amplifier, the pre-amplifier combines the three input signals and a feedback signal into a deviation signal and amplifies the voltage signal U22-21 output. This output voltage is converted into a trigger pulse at the same time through the flip-flop 1 (or 2) to control the thyristor of the thyristor main circuit 1 (or 2) to be turned on, thereby adding the AC 220V power to the two-phase servo motor windings to drive the two-phase servo motor. Turn it. When â–³1 â€0â€, U22-21â€0, trigger 2 and main circuit 2 work, two-phase servo motor rotates forward; when â–³1 †0, trigger 1 and main circuit 1 work, two-phase servo motor Reverse; two groups of flip-flops and two thyristor main circuit circuit components and parameters are the same, so when the input signal and the position feedback current If balance, pre-amplifier output U22-21 ≈ 0, both flip-flops are Without trigger output, the thyristors in the main circuit 1 and 2 are blocked, the power of the two-phase servomotor is disconnected, and the motor stops rotating.
This shows that the servo amplifier is equivalent to a three-position contactless relay and has a large power amplification capability.
Analysis of Reasons for Using Reactor before Servo AmplifierServo amplifier is an important part of the motion control system. It can provide servo motor with adjustable frequency power and achieve high-precision drive system positioning. Currently, it is a high-end product of transmission technology. The use of servo amplifiers ranging from a few thousand to more than 10,000 yuan should be very careful and try to extend its useful life
The current surge caused by sudden changes in the grid voltage and overvoltage, harmonic interference, spikes in the voltage, etc., damage the sensitive components in the loop of the servo amplifier. A reactor (called a line reactor) is installed in front of the servo amplifier to protect the drive from the above shock, as shown in Figure 1.
Figure 1 Line reactor
1. Reactor and its function
A reactor, as its name suggests, is a device that can act as an impedance in a circuit. The wire is wound into a solenoid form, and the core is inserted into the solenoid, so that the inductance is large and becomes a reactor, which is actually an inductor.
The ratio of the voltage drop of the reactor to the line voltage is called the reactance rate to characterize the parameters of the reactor. The impedance and reactance of the reactor are shown in Figure 2. The typical reactance rate is 3% or 5%.
Figure 2 Impedance Calculation and Reactance Formula
It can be seen that the larger the current frequency through the reactor, the greater the impedance. This is the principle that the reactor can smooth the peak voltage and suppress the harmonics (see the blue word for harmonics).
Moreover, after learning harmonics, you know that servo amplifiers and frequency converters are important sources of harmonics and are the main culprit of power grid pollution. After installing the reactor, it can not only prevent the interference from the grid, protect the servo amplifier, but also reduce the pollution of the grid caused by the harmonic current generated by the rectifier unit of the servo amplifier.
2. Reactor symbol
The sign of the reactor in the electrical diagram is the same as that of the inductor. Figure 3 shows the main power input circuit of the FANUC βi SVSP servo amplifier. L1 is the line reactor.
Figure 3 The main power input circuit of a servo amplifier
3, output reactor
The reactor is installed between the inverter and the motor and is called a load reactor or an output reactor to protect the motor, as shown in Figure 4.
Figure 4 Output reactor
The detailed principle is shown in Figure 5.
Fig. 5 Principle of connection between reactor and drive system
How much does the reactor and the reactor have no effect on the smooth current? As shown in FIG. 6, the reactor can smooth a transient voltage and suppress harmonics.
Fig. 6 Comparison of effect with/without reactor
4, power filter
Electromagnetic interference (EMI) is also a major problem in servo drive systems. Therefore, line reactors (line reactors) are equipped with a line filter at the input of the power module to suppress electromagnetic interference. Figure 7 shows.
Figure 7 Power Filter Use
FANUC servo amplifier specifications often refer to AC reactor, AC line filter, now you understand the role of these things? Why install a reactor in front of the servo amplifier in order to suppress the harmonic interference from the power supply grid and smooth out the spikes contained in the power supply voltage, improve the power quality of the servo amplifier and protect the sensitive components in the loop.
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