Summary of the essential knowledge of UPS uninterruptible power supply for weak current engineering

1. UPS power supply selection

According to the equipment situation, the power environment and the power protection purpose you want to achieve, you can choose the appropriate UPS; For example, for low-power devices with built-in switching power supplies, backup UPSs can generally be used. In places where the power environment is poor, online interactive or online UPSs should be used, and for those that do not allow intermittent time or require sine wave AC power For equipment, only online UPS can be used.

First of all, you must determine how powerful your device is. Generally speaking, the power of an ordinary PC or industrial computer is about 200W, that of a Mac machine is about 300W, and that of a server is about 300W. Between 600W, the power value of other equipment can refer to the manual of the equipment.

Secondly, it should be understood that there are two ways to express the rated power of UPS: apparent power (in VA) and actual output power (in W). Due to the existence of reactive power, This difference is caused. The conversion relationship between the two is: apparent power*power factoru003dactual output power

The power factor of the backup type and the online interactive type is between 0.5 and 0.7 In between, the online power factor is generally 0.8.

When equip equipment with UPS, the actual output power of UPS should be used as the basis for matching. Some dealers intentionally or unintentionally confuse the difference between (VA) and (W). Point to draw the user's attention.

According to the choice of use environment, it can be divided into industrial-grade UPS and commercial-grade UPS. Industrial-grade UPS is suitable for places with harsh environment. Commercial-grade UPS has higher environmental requirements. .

UPS is usually divided into two types: industrial frequency machine and high frequency machine. The power frequency machine is composed of a silicon controlled SCR rectifier, an IGBT inverter, a bypass and a power frequency step-up isolation transformer. Because the working frequency of its rectifier and transformer is 50Hz, it is called a power frequency UPS as the name suggests.

The high-frequency machine is usually composed of IGBT high-frequency rectifier, battery converter, inverter and bypass. IGBT can control the IGBT by controlling the drive added to its gate. The switching frequency of the IGBT rectifier is usually from several K to tens of KHz, even as high as hundreds of KHz. Compared with the 50Hz power frequency, it is called a high-frequency UPS.

Second, UPS capacity unit W and KVA

Any power equipment has capacity regulations, mostly in W and KVA Is the unit, W (watt) is the effective power, KVA (kilovolt-ampere) is the apparent power; the current nominal capacity of UPS power supply is KVA, the general technical parameters will give the W value, which is obtained by the power factor of 0.8 Out, 1KVAu003d800W, and so on.

3. What is the unit of AH?

AH is the unit of electrical equipment capacity. A.hu003dampere-hour, which can be simply understood as: 1A.h means that the power storage device can continue to work for 1 hour when the power supply current intensity is 1A.

Battery capacity unit

The capacity unit of lithium battery is milliampere hour, ampere hour, watt hour.

Expressed by conformity: milliampere hour mah (MAH); ampere hour ah (AH); watt hour Wh.

In layman's terms, the physical meaning of battery capacity refers to how much charge the battery can hold or release. We often use Ah (ampere hour) or mAh (milliampere hour) to express.

According to the definition of current: Iu003dQ/t, we can see that Qu003dIt, the unit of current I is mA (milliamps), t represents time, the unit is hour (hour), so our The battery capacity unit is mAh.

In other words, if the capacity of a battery is 1000mAh, if the current when it is working is 100mA, it can theoretically supply power for 10 hours.

However, we can see from the formula that Qu003dIt, and no voltage is involved, so this unit can only indicate how many coulombs of charge can be accommodated inside the battery. But it cannot tell how much work this battery can do, and what the maximum power the battery can provide. The working voltage of different types of products is different.

So we often see a number in Wh next to mAh. The work that the battery can do Wu003dUItu003dUQ, and the unit of voltage U*current I is W (watts), so W in the battery is represented by Wh, which indicates how much work the battery can do.

Four, UPS uninterruptible power supply function

1. Uninterrupted mutual switching between the two power supplies;

2. Isolation. Block the grid disturbances such as instantaneous discontinuities, harmonics, voltage fluctuations, frequency fluctuations and voltage noise before the load. Even if the load does not interfere with the grid, the interference in the grid will not affect the load;

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3. Voltage transformation function: input voltage is equal to or not equal to output voltage, such as 380V1380V, 380V/220V, including voltage stabilization;

4. Frequency Conversion function: the input frequency is equal to or not equal to the output frequency, such as 50Hz/50Hz, 50Hz/60Hz, including frequency stabilization;

5. Provide a certain backup time: UPS The battery stores a certain amount of energy and continues to supply power for a period of time to protect the load in the event of a power outage or interruption in the power grid