Figure 1 shows the principles of operation of an electronic UPS. Single- or three-phase power is obtained from the power system and is rectified to DC. Floating on the DC bus is a battery bank that provides energy storage to keep the system operating during an interruption. Clearly, the. Figure 2(a) shows a so-called standby UPS. In this scheme, the computer actually receives utility power during normal operation. The reason for this is that to cut cost, the inverter is not rated. Figure 2(b) shows another type of UPS, called the line-interactive UPS. The operation is similar to the standby UPS in that utility power is delivered during normal operation. The reader. Another alternative for uninterruptible power is a motor-generator set, as shown in Figure 3. In this case, the utility power runs the motor, which turns the generator to supply power to the load. Usually, a flywheel is added to provide enough energy storage to continue running the generator through brief interruptions. Another alternative is to ha.
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