I. Automatic voltage regulator
This regulator has simple structure and low price, but its reliability is poor. Because it is stabilized by the movement (sliding or rolling) of the carbon brush, as shown in Figure 2. The control circuit controls the M point to move up and down according to the output setting, so that the output voltage meets the requirements of the load. The disadvantages of this circuit are low reliability, slow dynamic response and no isolated interference. The carbon brush will gradually become thinner when it is constantly moving until it is damaged, and its life will be shortened faster under the condition of high humidity. Because it is a mechanical movement, the dynamic response is slow, which will lead to the sudden rise and fall of instantaneous voltage and damage the equipment behind it.
For example, when the input voltage drops by 15%, that is, 220V drops to 187V, in order to ensure that the output is still 220V, m must slide up to N point, and the change at this time is 220:187 =1.18. At this time, if a large inductive load is suddenly downloaded, on the other hand, if a large inductive load is suddenly loaded, there will also be a voltage drop of 100V, which will also lead to the battery discharge of UPS.
Second, the AC voltage regulator of the purified power supply
The appearance of this AC voltage regulator mainly replaces the original electromagnetic compensation 6 14 voltage regulator. The principle of this voltage regulator is to form different equivalent inductances according to the different conduction angles of the bidirectional thyristor, so that the output can compensate the change of the input. The principle is shown in Figure 3.
The power supply has high stability, up to 0.65438 0%, high efficiency, up to 97%, and low distortion of output voltage waveform, up to 0.2%. The regulator has high reliability and the ability to isolate interference. It can also be seen from the figure that there is no power tube in the main circuit, but passive devices such as inductors and capacitors, and the only semiconductor device is a highly reliable bidirectional thyristor. However, the disadvantage of this circuit is that its regulating range is narrow, and it is generally only suitable for the rated grid voltage of 10%, and its power is not easy to increase. Obviously, it can't meet the requirements of the telecommunications sector, so it is generally not considered.
I hope it helps you.
Third, the parameter regulator.
1, working principle of parameter regulator
Parametric regulator is a widely used regulator in the early days, and it is a circuit for stabilizing voltage according to the principle of ferromagnetic resonance. Its advantage is that the whole circuit is composed of transformer and capacitor, and there are no semiconductor components, so the reliability is relatively high. Because the parameter regulator works in a resonant state, it has a strong ability to isolate interference. Fig. 4 shows the working principle of the parameter regulator. Because this circuit is used more, there are many problems, so here is a detailed introduction. The purpose is to understand its advantages and disadvantages in order to use it more reasonably. As shown in Figure 4, the circuit schematic diagram of the parameter regulator is shown, and its equivalent circuit is an inductor and a capacitor in series.
The capacitive reactance of the capacitor is xc =1/(2fc); The reactance of the inductor is XL=2fL.
Where: f- power frequency, HZ
Capacitance, f
L- inductance of transformer, h
According to the circuit, UC is the voltage on the capacitor, UL is the voltage on the inductor, and I is the current passing through the resistor and capacitor. The voltage difference between the inductive reactance and the capacitive reactance is 180, so the voltages when they are connected in series are subtracted. When resonance is reached, UC=UL, and XC+XL = O. Therefore, it is concluded that:
f= 〈 1〉
This is the resonance point of LC series circuit. From the above analysis, we can see three problems:
When the input voltage reaches a certain value, the impedance in the LC series circuit reaches the minimum value, or the current reaches the maximum value, that is, the transformer enters the saturation state, at this time, the voltage on the transformer is basically unchanged, and the output enters the voltage stabilizing region.
At the resonance point, LC has a fixed relationship with the mains frequency, and the formula < 1 > can also be expressed by the angular frequency, namely
ω= 〈2〉
After the resonance point, if the input voltage continues to rise, all the rising parts are added to the capacitor.
2. Advantages of parameter regulator:
A. Because the parametric regulator works in a saturated state at resonance, the external interference will not cause the change of saturated current, so the interference is isolated.
B, because all the increased input voltage is added to the capacitor, the allowable input voltage conversion range is larger.
C, because there are no electronic components in the circuit, the reliability is high.
3. Disadvantages of parameter regulator:
A, because it works in a saturated state, it consumes a lot of power and is inefficient.
B, because resonance is at the mains frequency, it is very sensitive to the change of frequency. Once the power frequency changes, it will cause the vibration to stop. Once the vibration stops, the reactive power stored in the inductor for more than three times will be released instantly, forming thousands of volts of high-voltage pulses to be transmitted to the outside, destroying nearby equipment. This led to many UPS fires in a domestic telecommunications department.
C, because the resonance is at the mains frequency, if the rectifier load is behind it, the harmonic generated by rectification will also cause the circuit to stop vibrating. According to the test of relevant scientific research institutions, the capacity of the parameter regulator is several times that of the following load (typical experiment is 10 times). Many UPS fires in the above-mentioned telecommunications departments are caused by the small capacity of parameter regulators: for example, a parameter regulator of 15KVA, a parameter regulator of 16KVA and a parameter regulator of 30KVA and 40KVA, almost none of them are spared from dozens of supporting equipment.
D, due to the large amount of reactive power stored in the circuit, the input power factor is low, and the input commercial power cannot be fully utilized, occupying valuable electric energy resources.
The places where parameter regulators are successfully used are mostly places with large capacity or good conditions. Therefore, this kind of power supply should be used with caution, especially in places with high requirements such as telecommunications departments.
4.NPS intelligent regulated power supply
This is a new technology, which is a patented product developed after summarizing the advantages and disadvantages of the above voltage regulator and absorbing the experience of Delta conversion technology. The circuit not only adopts the mature PWM technology at present, but also combines the Delta conversion technology of UPS.
NPS intelligent regulated power supply effectively solves the problems existing in the above voltage regulator:
1, because it absorbs the experience of Delta transform technology, it has some advantages, such as the input power factor is as high as 0.95 or above, which is much higher than that of parametric regulator.
2. High efficiency. It is not difficult to see from the circuit structure that it concentrates the advantages of automatic voltage regulator. And the response speed is fast, which is incomparable to automatic voltage regulator.
3, the input and output isolation performance is good, and the advantages of the parameter regulator and the purified power supply are concentrated. Because there is no storage of reactive power in the work, there is no problem of destroying other equipment.
4. High reliability. Because of the combination principle of PWM circuit and magnetic circuit, the structure is light, not as heavy as parameter regulator.
5. Because of high working efficiency, low loss and low temperature in the machine, the reliability of the machine is improved.
6, can be intelligently monitored. The machine has RS232 serial port, which can be used for remote monitoring.
7, the capacity can be made very large, unlike the purified power supply and parameter regulator, which can only achieve tens of KVA.
It is with the above advantages that it should be the first choice for power distribution.