Provide knowledge of UPS uninterruptible power supply, understand the classification of UPS uninterruptible power supply and UPS electrica Circuit, etc.
Comparison of Fixed Switching Frequency and Variable Switching Frequency PFC RectifiersFor convenience, the input current at fixed switching frequency is also represented by phase voltage, that is, M ‘=√ 3M instead of M, as shown in Figure 1-1 From the average value equation of current ia at constant switching frequency and variable switching frequency, the…
In 1993, Ucecla et al. studied the three-phase single switch Boost PFC rectifier controlled by DCM mode variable frequency PWM with variable switching frequency fs. Its circuit is shown in Fig1-1. This is a single switch three-phase PFC rectifier circuit with Boost input inductance L. For the convenience of analysis, it is assumed that: ①…
For the constant switching frequency and constant on-time (Ton) SPWMPFC rectifier introduced earlier, the 5th harmonic content of the mains input current is still on the high side. In 1995, Q. Huang proposed a variable control method of Ton. The method is to inject the 6th harmonic to change the duty cycle d, so as…
In order to reduce input current harmonics and improve input power factor, a.r.prasad proposed a three-phase boost single switch SPWM PFC rectifier circuit in 1987, as shown in Figure 1-1. S in the figure is a single tube control switch, l is the input boost energy storage inductance, CD is the DC filter capacitor, and…
In the power frequency UPS, the commonly used SCR polyphase phase-controlled rectifier is a 12-phase two-phase superimposed rectifier, and the 18-phase three-phase superimposed rectifier and the 24-phase four-phase superimposed rectifier may be used. Their characteristic values are compared in Table 1. It can be seen from this table that when the UPS is working at…
Most of the SCR polyphase phase-controlled rectifiers used in three-phase high-power power frequency UPS use 12-phase rectifiers or 12-phase rectification + 11th harmonic passive filters, which have become a typical power frequency UPS circuit mode, which can Meet the requirements of the national standard GB/T 7260.3 for the harmonic content of the mains input current….
The variable amplitude 12-phase two-superimposed rectifier is the most widely used in UPS. When the harmonic injection technology is adopted, its application will be wider. For this reason, we will briefly introduce the influence of the input transformer on the harmonic current. Provide time reference. There are two ways to connect the main circuit of…
This time, we introduce a 12-phase diode rectifier technology that uses transformers to inject harmonics, which can make 12-phase diode rectifiers become 24-phase diode rectifiers to improve the input power factor of mains power. The harmonic injection circuit is composed of an injection transformer and a single-phase rectifier bridge. The circuit utilizes the characteristic that…
In order to further improve the mains input power factor of the SCR polyphase phase-controlled power frequency rectifier, reduce the waveform distortion rate THDi of the mains input current to less than 10%, and make the mains input current and the mains input voltage in the same phase, there is a A simple and effective…
There are two ways to shift the phase of the mains input polyphase rectifier transformer to obtain the polyphase output: one is to use the star and delta connection (Y/△ or △/Y) between the primary and secondary to shift the phase by 30°; One is to use the series connection (zigzag connection) between the secondary…