Classification and characteristics of UPS

UPS power supply can be divided into two categories based on its working mode: backup and online. According to its output waveform, it can also be divided into two types: square wave output and sine wave output. When the backup UPS power supply is in normal power supply, the mains supply directly provides power to the load through the AC bypass channel and then through the conversion switch, and the inverter inside the machine is in a stopped working state. This UPS power supply is essentially equivalent to a commercial voltage regulator with extremely poor voltage stability. Apart from improving the amplitude fluctuation of the mains voltage, it has basically not improved any adverse effects such as frequency instability, waveform distortion, and thousands of disturbances connected from the power grid. Only when the mains power supply is interrupted or below 170V, the battery will supply power to the UPS inverter and provide stable and frequency stable AC power to the load. The advantages of backup UPS power supply are high operating efficiency, low noise, and relatively cheap price. It is mainly suitable for situations where there is little fluctuation in the market and there is no high demand for power supply quality. When the online UPS power supply is powered normally by mains power, it first converts the mains AC power supply into a DC power supply, then undergoes pulse modulation and filtering, and then converts the DC power supply back into an AC power supply. This means that it usually supplies AC power to the load through an inverter after rectification of the AC power supply. Once the mains power is interrupted, the AC power supply to the load will be immediately provided by the battery through an inverter. Therefore, for online UPS power supply, under normal circumstances, regardless of the presence or absence of mains power, it is always powered by the inverter of the UPS power supply to the load, thus avoiding all impacts caused by voltage fluctuations and disturbances in the mains power grid. It is obvious that the power supply quality of online UPS power supply is significantly better than that of backup UPS power supply, as it can achieve stable frequency and voltage supply to the load, and the conversion time from mains power supply to battery power supply is zero. The UPS power supply with square wave output has poor load capacity (the load capacity is only 40-60% of the rated load) and cannot be charged with inductive loads. If the load carried is too large, the third harmonic component contained in the square wave output voltage will increase the capacitive current in the load, and in severe cases, it will damage the power filter capacitor of the load. The relationship between the waveform distortion of the output voltage of a sine wave output UPS power supply and the load is not as obvious as that of a square wave output UPS power supply. The load capacity is relatively strong and can carry micro inductive loads. Regardless of the type of UPS power supply, when they are in the inverter power supply state, unless it is unavoidable, it is generally not allowed to operate at full load or overload, otherwise the failure rate of the UPS power supply will significantly increase.