In early telecommunications rooms, it was common to use a rectified 220V AC power supply to charge a 48V battery pack, which directly supplied power to the program-controlled switch. With the application of computer networks and communication networks in telecommunications rooms, it is necessary to provide high-quality 220V AC power for them. Due to the existing 48V battery pack, the method of battery pack+inverter is usually used to convert 48V DC into 220V AC power for network power supply. This method has many drawbacks.
1.The most important function of UPS (uninterruptible power supply system) is to provide uninterrupted power supply. When the power grid meets the input range, it is transformed into AC/DC and DC/AC to supply power to the load. When the power grid exceeds the limit, the battery supplies power to the load. When the UPS fails or overloads, the bypass power supply supplies power to the load. During maintenance, the UPS can also be maintained online by manually repairing the bypass switch. The power supply method of battery pack+inverter, when the battery pack fails and needs to be replaced, must interrupt the system, which will cause huge losses to the system. The uninterrupted function of UPS cannot be replaced by battery pack and inverter.
2.The function of UPS is to achieve uninterrupted switching between dual power sources, provide a certain amount of backup time, stabilize voltage, frequency, isolate interference, etc. It can block power grid interference such as momentary interruptions, harmonic interference, voltage fluctuations, frequency fluctuations, surges, etc. before the load. Due to the fact that the input DC bus of the UPS inverter and the external battery pack are not directly connected to the user’s existing 48V communication power supply, there will be no conducted interference to the programmable controller. In addition, UPS usually adopts a steel plate frame structure to prevent external radiation interference, which eliminates radiation interference to other equipment while maintaining a beautiful appearance. RFI filters are used at its input and output terminals to provide purified AC power to the load.
For a 48V battery pack+inverter, since the inverter power supply and the DC power supply used in the programmable control room are the same battery pack, and the inverter adopts a high-frequency pulse width modulation working mode, its backflow noise interference will inevitably enter the input end of the programmable telephone, which will greatly affect the quality of communication.
3. Because the inverter is powered by a fixed 48V and the battery voltage is low, when the output power requirement is high, the production process requirements for the power module are higher, making it difficult to achieve high-power inverters. At present, the inverter of * * * is about 15KVA. However, the built-in battery pack of UPS itself can have a DC voltage as high as several hundred volts, so the single machine power can be very high.