What is the function of UPS uninterrupted power supply?
Time:2022-03-12
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UPS (Uninterruptible Power System), also known as Uninterruptible Power Supply, is a constant voltage and frequency uninterruptible power supply that contains energy storage devices and is mainly composed of inverters. Mainly used to provide uninterrupted power supply to a single computer, computer network system, or other power electronic devices. When the mains power input is normal, the UPS stabilizes the mains power and supplies it to the load for use. At this time, the UPS is an AC mains power stabilizer, and it also charges the internal battery; When the mains power is interrupted (due to an accident power outage), UPS immediately supplies 220V AC power to the load by inverting the power from the battery inside the machine, ensuring that the load maintains normal operation and protects the load‘s software and hardware from damage.
The functions and functions of UPS
UPS is an abbreviation for Uninterruptible Power System, which emerged with the birth of computers and is one of the commonly used peripheral devices in computers. In fact, UPS is a constant voltage and rated uninterruptible power supply that includes energy storage devices and is mainly composed of inverters. In its early stages of development, UPS was only considered as a backup power source. Later, due to power grid quality issues such as voltage surges, voltage spikes, voltage transients, voltage drops, continuous overvoltage or undervoltage, and even voltage interruptions, the electronic systems of computers and other equipment were disrupted, causing serious consequences such as damage to sensitive components, loss of information, and flushing of disk programs, resulting in huge economic losses. Therefore, UPS is increasingly valued and has gradually developed into a power protection system with functions such as voltage stabilization, frequency stabilization, filtering, resistance to electromagnetic and radio frequency interference, and protection against voltage surges.
At present, a wide variety of UPS power supply equipment can be purchased in the market, with output power ranging from 500VA to 3000kVA. When there is mains power supply to UPS, the UPS stabilizes the mains power (220V ± 5%) and supplies power to the computer. At this time, the UPS is an AC mains voltage stabilizer, and it also charges the internal battery. Due to the different designs of UPS, the range of UPS adaptation also varies. A variation of ± 10-15% in UPS output voltage is generally considered normal for computer use. When the mains power is abnormal or interrupted, UPS immediately converts the electrical energy from the battery inside the computer into inverter to supply the computer system, in order to maintain the normal operation of the computer system and protect the software and hardware of the computer from loss.
Classification and Characteristics of UPS
UPS power can be divided into two categories based on its working mode: backup and online. According to its output waveform, it can be further divided into square wave output and sine wave output. When the backup UPS power supply is under normal power supply from the mains, the mains 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 type of UPS power supply is essentially equivalent to a city power regulator with extremely poor voltage regulation performance. It not only improves the amplitude fluctuation of the mains voltage, but also has basically no improvement on the frequency instability, waveform distortion, and interference 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 a stable and frequency stable AC power supply 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 not much fluctuation in the market electricity and there is no high demand for power supply quality.
When the online UPS power supply is powered by mains power normally, it first converts the mains AC power supply into a DC power supply, then performs pulse width modulation and filtering, and then converts the DC power supply back into an AC power supply. That is, it usually rectifies the AC power supply and then provides AC power to the load through an inverter. Once the mains power is interrupted, the battery will immediately provide AC power to the load 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 effects caused by voltage fluctuations and interference from 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, because it can achieve stable frequency and voltage supply to the load, and its 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 capacity 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 inverter power supply mode, unless absolutely necessary, it is generally not allowed to operate at full load or overload, otherwise the failure rate of UPS power supply will significantly increase.
Matching UPS with load
Some UPS use watts (W) or kilowatts (kw) to represent their output power, such as 500W, 1kw, etc; Some UPS use volt ampere (VA) or kilovolt ampere (kVA) to represent their output power, such as 3000VA, 5kVA, etc. The general conversion relationship between VA and W is: watts are 0.8 times the volt ampere, for example, 3kVA=2.4kw. UPS is used for line load power supply, and each type of UPS has a specific output power capacity. If a 3kVA UPS has a maximum output power of 3kVA or 2.4kw, it is required that the total power consumption of the devices connected to this UPS cannot exceed 2.4kW. Usually, devices are labeled with their power consumption (or rated power). In this case, it is necessary to ensure that the combined rated power of all devices connected to the UPS does not exceed the output power of the UPS. This method is usually called matching the output power of the UPS with the power consumption of the load. But for some devices, the startup power is 3-5 times the rated power (for example, if the rated power of a printer is 200W, then when calculating load matching, it should be calculated based on 5 × Convert 200W to 1000W. Other computer external devices, except for printers, usually have a startup power slightly higher than the rated power. Therefore, when considering matching, it is best to match the load at 80% of the UPS output power.
Before adding an external battery, a standard UPS can generally provide power for about 6-10 minutes from the moment of mains power interruption when its output power matches the load power consumption (i.e. full load) (specific values are recorded in the UPS manual for each model). If the power consumption of the load is only half of the output power of the UPS (commonly known as half load or 50% load rate, such as when a 1000W UPS is connected to a 500W load), it can provide power for 12-25 minutes. The UPS power supply time for different load quantities can be calculated approximately by doubling the load reduction time. Proper use of UPS power supply can not only reduce the chance of UPS failure, but also effectively extend its service life.
When using a USP power supply, the following points should be noted:
(1) When using UPS power supply, it is necessary to strictly follow the relevant regulations in the manufacturer‘s product manual to ensure that the sequence of the live and neutral wires connected to the UPS meets the requirements.
(2) The main purpose of equipping UPS is to prevent computer loss of information and damage to hard drives due to sudden power outages, but some devices are not afraid of sudden power outages during operation (such as printers). To save energy from UPS, printers can be considered to be directly connected to the mains without going through UPS. If it is a network system, it can be considered that UPS only supplies power to the host (or server) and its related parts. This ensures that UPS can be used on the most important equipment while saving investment.
(3) Do not overload UPS. The maximum load capacity of a UPS power supply should be 80% of its nominal load capacity (for example, for a 1000W UPS, match the load with an 80% load rate of 800W; for a 1000VA UPS, convert 80% to 800W and then match the load with an 80% load rate of 640W). If used under overload, it often causes breakdown of the inverter transistor in the inverter state. In addition, when using UPS, it is strictly prohibited to connect inductive loads such as fluorescent lamps, and only pure electrical or smaller capacitive loads can be connected.
(4) When turning on and off the machine, attention should be paid to the order of turning on and off: turn on the UPS first, and then turn on the power switch of the load later (preferably with a delay of 1-2 minutes to allow the UPS to fully enter the working state), and turn on the power switch of the load one by one. The power switch of the load should be turned on one by one: when turning off the machine, the order is exactly the opposite, turn off the power switch of the load one by one, and then turn off the UPS. UPS needs to be turned on for a long time, while computers and other loads need to be used before turning on. After use, simply turn off the power switch of the computer and other loads.
(5) Do not frequently turn off and on the UPS power.
It is generally required to wait at least 6 seconds after turning off the UPS power before turning it on again. Otherwise, the UPS power may be in a "startup failure" state, which means the UPS power is in an abnormal state with neither mains nor inverter output.
(6) The electrical energy inside the UPS battery may be depleted or almost depleted for some reason. In order to compensate for battery energy and improve battery life, UPS needs to conduct timely and long-term continuous charging (usually no less than 48 hours, with or without load) to avoid faults caused by battery failure. Newly purchased or stored UPS should be charged for 12 hours before use. UPS that is not used for a long time should be charged every 3 months for 12 hours. If it is in a high-temperature area, it should be charged every 2 months. Using UPS without charging will damage the battery.
