UPS can be divided into three categories according to its working principle: standby, online and online interaction.
1, standby UPS
When the commercial power is normal, it directly supplies power to the load, and when the commercial power exceeds its working range or power is cut off, it is converted into battery inverter power supply through the changeover switch. Its characteristics are simple structure, small volume and low cost, but the input voltage range is narrow, the output voltage stability accuracy is poor, there is switching time, and the output waveform is generally square wave.
2. Online interactive UPS
When the commercial power is normal, it directly supplies power to the load. When the commercial power is low or high, it is output after being stabilized by the internal voltage stabilizing circuit of UPS. When the commercial power is abnormal or power is cut off, it is converted into battery inverter power supply through the changeover switch. Its characteristics are: wide input voltage range, low noise, small size, but also switching time.
3. Online UPS
When the commercial power is normal, the commercial power is rectified to provide DC voltage for the inverter to work, and the inverter provides AC power for the load. When the commercial power is abnormal, the inverter is powered by the battery, and the inverter is always in working state to ensure uninterrupted output. Its characteristics are extremely wide input voltage range, no switching time and high output voltage stability precision, which is especially suitable for occasions with high requirements for power supply but high cost. At present, almost all UPS with power greater than 3KVA are on-line UPS.