Comparison of UPS and EPS emergency power system
One. When the mains power is normal, the backup UPS is directly supplied by the mains to the load. When the mains is out of its working range or there is a power failure, it will be converted to battery inverter power supply through the transfer switch. Its characteristics are: simple structure, small size, low cost, but the input voltage range is narrow, the output voltage is stable and the accuracy is poor, there is a switching time, and the output waveform is generally a square wave.
2. When the mains power is normal, the online interactive UPS will directly supply power to the load from the mains. When the mains power is low or high, it will output through the UPS's internal voltage stabilizing circuit after voltage stabilization. , When the mains power is abnormal or out of power, it is switched to battery inverter power supply through the transfer switch. Its characteristics are: a wide input voltage range, low noise, small size, etc., but there is also a switching time.
3. When the mains power is normal, the online UPS is rectified by the mains to provide DC voltage for the inverter to work, and the inverter provides AC power to the load. When the electricity is abnormal, the inverter is powered by the battery, and the inverter is always in working condition to ensure uninterrupted output. Its characteristics are that it has a very wide input voltage range, basically no switching time and high output voltage stability and precision, which is especially suitable for occasions with higher power requirements, but the cost is higher. At present, almost all UPSs with power greater than 3KVA are online UPSs.
UPS also has functions such as voltage stabilization, filtering, etc. Some UPSs can be powered by the mains bypass in the event of a failure or overload.
The backup voltage output has large fluctuations. Between 170V-260V, high-speed relays are used to realize the conversion between the mains and the battery, and the conversion time is less than 10 milliseconds . The online type always uses the inverter circuit to work, and its voltage stability is high, basically within the range of 220V±5%, and there is basically no conversion time for the battery; the static switch is used for the mains bypass conversion, and the conversion time can reach microseconds. level.
UPS has high output accuracy, fast conversion time, high cost (about twice that of EPS), high energy consumption (online), and short mainframe life ( 8-10 years).
EPS emergency power supply is actually similar to the backup UPS power supply. Usually the inverter is in a non-working state, and it turns to the storage battery when the mains power is cut off. Generally, constant current and constant voltage processing are not performed on the power supply. Usually use contactor conversion, the switching time is 0.1 ~ 0.25S. Its advantages are simple structure, low cost, low energy consumption and no noise, long service life of the main machine (15-20 years), suitable for inductive, capacitive and comprehensive loads, and can realize variable frequency soft start when needed.
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