Working principles, Advantages and disadvantages of Backup Uninterruptible Power Supply and Online U

At present, the common classification of uninterruptible power supplies on the market is: online Uninterruptible Power Supply and backup Uninterruptible Power Supply. When we load low-power equipment, if the equipment itself does not have high requirements for power, we generally use backup Uninterruptible Power Supply to load. If you load very precise equipment or equipment with important data, it is recommended to buy online Uninterruptible Power Supply.

1. Backup Uninterruptible Power Supply:

When the mains power is normal, the mains power is supplied to the power-consuming equipment through simple voltage stabilization and filtering output, and the battery is in a charging state. When the power is off, the inverter works to convert the DC power provided by the battery into stable AC power output to the power-consuming equipment. Since the inverter does not work when the mains power is normal, it only starts to work when the battery is discharged when the mains power is off, so this Uninterruptible Power Supply is called a backup Uninterruptible Power Supply.

The backup Uninterruptible Power Supply is mainly suitable for occasions where the mains power fluctuation is not large and the power supply quality requirements are not high. The switching time of the backup Uninterruptible Power Supply is generally less than 10 milliseconds, so it is not suitable for use in critical places where the power supply cannot be interrupted. However, in reality, the switching time is very short, and the switching power supply of a general computer or electrical equipment should be able to maintain about 10 milliseconds when the power is off, and the electrical equipment generally will not have problems due to this switching time.

Advantages and disadvantages of backup Uninterruptible Power Supply:

Advantages: small size, high efficiency, low price, and low operating cost. Since the inverter is in a non-working state under normal circumstances, the grid power directly supplies the load, so the backup Uninterruptible Power Supply has a high power conversion efficiency. The service life of the battery is generally 3 to 5 years.

Disadvantages: The load is not truly isolated from the online power supply system; the long conversion time and the lack of a real static switch mean that it takes a relatively long time to convert the load to the inverter. Although this conversion time is acceptable in some applications, this performance cannot meet the requirements of large or complex sensitive loads; the output voltage cannot be adjusted; the output frequency depends on the frequency of the AC input power supply and cannot be adjusted.

When the grid power supply fails, there is a long conversion time from the grid power supply to the inverter power supply. For those devices that require high power quality, the length of this conversion time is crucial. Furthermore, since the inverter of the backup Uninterruptible Power Supply does not work frequently, it is not easy to grasp the dynamic status of the inverter, which is easy to form hidden faults. The backup Uninterruptible Power Supply is generally used in some non-critical low-power devices.

2. Working principle of online Uninterruptible Power Supply:

Whether the online Uninterruptible Power Supply is powered by the mains or the battery, its output power is always provided by the inverter. When the mains is interrupted or the power is supplied, there is no conversion time. Normally, the mains is converted into direct current by the rectifier, and then the inverter converts the direct current into a pure sinusoidal voltage to supply the load. On the other hand, the mains is rectified to charge the battery. Once the mains is interrupted, it is switched to battery power supply, and the inverter converts the direct current into sinusoidal alternating current to supply the load.

When the mains power is normal, the online Uninterruptible Power Supply first converts AC power into DC power, then performs pulse width modulation and filtering, and then converts DC power back into AC power to supply power to the load. Once the power system detects that the mains power is interrupted, it immediately switches to the battery inverter to supply power to the load. Therefore, the online Uninterruptible Power Supply outputs a pure sine wave power supply that is completely isolated from the mains power grid, which can greatly improve the quality of power supply and protect the load from working safely and effectively.

Advantages and disadvantages of online Uninterruptible Power Supply:

Advantages: Since the online Uninterruptible Power Supply supplies power to the load by the inverter of the Uninterruptible Power Supply, whether it is when the mains power is normal or when the mains power is interrupted and the battery in the system supplies power to the inverter, the power supply to the load is provided by the inverter of the Uninterruptible Power Supply. Simple circuit and low cost. High reliability. High efficiency, the efficiency can reach more than 95%. Strong overload capacity, when the mains power is supplied, the overload capacity can reach 100%.

Compared with the backup Uninterruptible Power Supply, the online Uninterruptible Power Supply has excellent output voltage transient characteristics. Generally, when the load is loaded at 100% or unloaded at 100%, its output voltage changes within a range of about 1%, and the duration of this change is generally 1 to 3 cycles.

Online uninterruptible power supplies generally use PWM technology above 20kHz, and their noise is relatively low, about 50dB.

Most uninterruptible power supplies have strong software functions, which can easily access the Internet for remote control and intelligent management of uninterruptible power supplies.

Disadvantages: Expensive.

3. The difference between online uninterruptible power supplies and backup uninterruptible power supplies:

The main difference between the two is that the output of online uninterruptible power supplies is through inverters, which have functions such as isolation and shaping, while the backup Uninterruptible Power Supply directly outputs when the mains is present, and inverts when the mains is off, and the output waveform is generally a square wave.

One of the major advantages of online uninterruptible power supplies is that they have a long power supply time, generally several hours, and some are more than ten hours. Its main function is to restore the power outage to the same level as usual. Due to its special function, the price is also significantly more expensive. Online uninterruptible power supplies are mainly suitable for important industries such as computers, transportation, banking, securities, and medical care.

Backup uninterruptible power supplies can generally only provide power for a few minutes to tens of minutes, mainly to give you time to back up data and finish the work at hand as soon as possible, and their prices are also relatively low. For less critical applications, such as individual home users, a low-power backup Uninterruptible Power Supply can be equipped.

4. Summary:

Compared with backup uninterruptible power supplies, online uninterruptible power supplies have significantly better power supply quality than backup uninterruptible power supplies, because they can achieve voltage and frequency stabilization, suppress surges, spikes, electrical noise, compensate for voltage sags and long-term low voltages, and when switching from city power supply to battery power supply, the conversion time is zero.