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Apr-02, 2020 News

Hi, we are Must , the top brand UPS manufacturer from China . today , we’ll talk about how to select the right UPS ,and how to match the right batteries.

First, determine the power segment first

In short, the first step is to confirm the power of the equipment we want to load on the UPS, and then we can confirm the power of the UPS. In general, we recommend that the load power account for 30% to 80% of the UPS power. If the load is too large, such as when starting up at the same time, the UPS power supply may be overloaded, and the load is too small, which not only causes waste, but also is not good for the performance of the battery.

Second, UPS working methods

At present, the most common working methods on the market are backup, online interactive, online , online double conversion , as follows:

(1) Backup UPS, without voltage regulation, has conversion time when mains and battery are converted, generally used for personal computer protection, or used when UPS power performance is not high. This type of UPS power segment is generally used. Smaller
(2) Online interactive, without voltage regulation, there is conversion time when mains and battery are converted, but there is voltage regulation function, generally used in wiring closet or micro computer room, protection server and network equipment, etc. This type of UPS power section Generally below 5KVA.
(3) Online double-conversion UPS, no conversion time when mains and battery conversion, no switching time is generally used to protect servers or network equipment and other equipment in the equipment room. This type of UPS power segment is from small to large, span comparison Large 1KVA ~ 1000KVA, currently more common on the market.

The performance of the above UPS power supplies from high to low is: online double conversion, online interactive, backup. Prices are generally proportional to performance. Is that we must choose your expensive UPS? the answer is negative. As our title, we have to choose the UPS that suits you. If it is for personal computers, then you can choose a backup UPS. If it is for the server, you should choose between online interactive and online double conversion. The choice should be made according to the following conditions:

1. Equipment requirements

To see if your equipment requires a very high-precision power supply, check the label on the nameplate of the load equipment or ask the equipment manufacturer. For high-precision power supply, you need to choose an online double-conversion UPS. The second is to look at the type of load, some loads are not allowed to have power supply flashing, such as: relay type equipment or switch signal equipment, if you have online interactive UPS for this type of equipment, then it is possible to UPS When the mains and the battery are switched, the load has power failure or malfunction, so for this type of equipment, the online double conversion UPS should be selected. If your device does not have the above two requirements, you can continue with the steps below.

2. Local power grid

If the quality of the local power grid is relatively good, that is to say, the voltage fluctuations are usually small, then you can consider the online interactive UPS. However, if the local power grid is of poor quality and the voltage fluctuates greatly, then we recommend using an online double-conversion UPS. This is because this type of UPS has better adaptability to the mains than the online interactive.

3. UPS transfer battery follow-up time

If you require a longer time delay, consider choosing a dual-use machine or a UPS without a built-in battery. Both UPSs can be equipped with an original battery or a third-party battery to achieve a longer time delay. the goal of.

4. the installation method

Generally speaking, UPS power supply has two installation methods, one is tower installation, the other is rack installation, which can be selected according to your equipment room environment or on-site environment, and also need to pay attention, not all UPS power supply Both installations are supported at the same time. In most cases, the rack-mounted UPS can also be installed in a tower, but the tower-type UPS may not be rack-mounted, because the tower UPS may not be able to install the rails. Therefore, after confirming the UPS power section and working mode, be sure to confirm whether the UPS power supply can meet your installation requirements.

Third, the advantages and disadvantages of different types of UPS batteries

One: the types of batteries commonly used in UPS, the factors affecting battery life, the advantages and disadvantages of different types of batteries:

There are three types of batteries in UPS applications: open liquid lead-acid batteries, maintenance-free batteries, and nickel-chromium batteries. The batteries provided by UPS manufacturers are generally maintenance-free batteries. The following three types of batteries are mainly introduced with maintenance-free batteries:

1: Open liquid lead-acid batteries: These batteries can be divided into 8-10 years according to structure and 15-20 years of life. Since this battery sulfuric acid electrolysis produces corrosive gases, such batteries must be installed in a room that is ventilated and away from precision electronic equipment, and the battery room should be lined with anti-corrosion tiles.
Due to evaporation, the open battery needs to measure the specific gravity regularly, adding acid and adding water. This battery can withstand high temperature and high pressure and deep discharge. The battery room should be non-smoking and open battery racks.
This battery cannot be transported after being charged, so it must be 55-90 hours after initial charging. The normal voltage per section is 2V, and the initial charging voltage is 2.6-2.7v.

2: Maintenance-free battery: Also known as valve-regulated sealed lead-acid battery, the following principles should be followed in use and maintenance:
a: The allowable operating range of the sealed battery is 15 degrees – 50 degrees, but the use within 5 degrees – 35 degrees can extend battery life. The battery chemistry will change below minus 15 degrees and will not charge. Use in the range of 20 degrees to 25 degrees will achieve the highest life. The battery will achieve long life but low capacity when operating at low temperature, and will achieve higher capacity but short life at high temperature.
b: The relationship between battery life and temperature can be referred to the following rules. After the temperature exceeds 25 degrees Celsius, the battery life will be reduced by half for every 8.3 degrees.
c: Maintenance-free battery design float voltage is 2.3V / knot. The 12V battery is 13.8V. CSB recommends 2.25-2.3V per section. In the case of 120 cells in series, after the temperature is higher than 25 degrees Celsius, the float voltage should be lowered by 3 MV for each degree of temperature increase. The same temperature should be raised by 3 MV to avoid overcharging voltage. The discharge termination voltage is 1.67V per section at full load (<30 minutes). At low discharge rate (small current for a long time discharge) to rise to 1.7V-1.8V per section, APC SYMMETRA can adjust the charging voltage according to the load.d: The battery is not recharged within 72 hours after the end of discharge. Sulfate will adhere to the plate for insulation charging and damage the battery.e: When the battery is floated or evenly charged, the gas generated inside the battery is electrolyzed into water on the negative plate, thereby maintaining the capacity of the battery without adding water. However, corrosion of the battery plates will reduce battery capacity.f: Battery separator life is only 5-6 months at an ambient temperature of 30-40 degrees. The battery stored for a long time must be charged once every 6 months. The battery must be stored in a cool, dry environment. The self-discharge rate of the maintenance-free battery in a 20 degree environment is 3-4% per month and varies with temperature.g: Maintenance-free batteries are equipped with safety valves. When the internal air pressure of the battery rises to a certain level, the safety valve can automatically remove excess gas, and the safety valve will automatically recover when the internal air pressure is restored.h: The cycle life of the battery (the number of charge and discharge cycles) depends on the discharge rate, the depth of discharge, and the manner of restorative charging, the most important of which is the depth of discharge. When the discharge rate and time are constant, the shallower the discharge depth, the longer the battery cycle life. The maintenance-free battery has a cycle life of approximately 200 cycles at 25 degrees 100% deep discharge.i: The battery exhibits capacity decay when it reaches the end of its life, internal short circuit, deformation of the casing, corrosion of the plates, and reduction of the open circuit voltage.j: IEEE defines the end of battery life to be 80% of the capacity shortage nominal capacity AH. The non-linear relationship between the nominal capacity and the actual backup time, the capacity reduction of 20% corresponding to the backup time will be much reduced. Some UPS manufacturers define the end of life of the battery as the capacity drops to 50-60% of the nominal capacity.Fourth, how to calculate the number of batteries equipped with UPS4.1. battery calculation method:For example, a 40KVAUPS, DC voltage is 384V, each group is 32V for 12V battery. If the backup time requires 2 hours, calculate the battery capacity as:40000VA*2H/(0.7*384V)=297AHSo choose 3 sets of 100AH batteries, a total of 96 sections.The battery pack current is 40KVA/384V=104A, so the battery cable is 50mm2.Total number of batteries = (power / DC voltage * hours) / each block of security * number of blocks per blockThe power is the power of the UPS, the DC voltage is the voltage required for the UPS battery power supply, and the UPS DC voltage of different powers is different. The number of blocks in each group is the minimum number of blocks required. When the battery is generally configured, it must be the number of blocks per group. Integer multiple, the common UPS DC voltage and the number of blocks per group are as follows (the battery is calculated based on 12V per block):For example, configure a 5K 8-hour delay UPS with a power of 5000 and a DC voltage of 96V. Each battery pack has 8 blocks and 100AH batteries. The total number of batteries required is: (5000/96*8)/100. *8=32 blocks

UPS—Uninterruptible Power System is the abbreviation for Uninterruptible Power System. The function is to provide uninterrupted and reliable AC power supply, and the UPS can supply power continuously during the interruption of power (power failure). It is the result of battery storage. The length of time that can be supplied is determined by the capacity of the battery. The calculation method of 4.2 and UPS battery configuration is introduced as follows:

A. The following factors affect the standby time

1. the total load power P (W), taking into account the power factor of the UPS, in the calculation can be directly in the P total volt-amperes (VA)
2. V low is the termination voltage (V) after battery discharge, 2V battery V is low = 1.7V; 12V battery V is low = 10.2V
3, V float is the floating charge voltage (V) of the battery, 2V battery V float = 2.3V; 12V battery V float = 13.8V
4. Kh is the battery capacity conversion coefficient (Ct/C10), 10Hr discharge rate is 1, 5Hr discharge rate is 0.9, 3Hr discharge rate is 0.75, and 1Hr discharge rate is 0.6.
5. I is the battery operating current (A), T is the continuous discharge time (H), and V is the DC supply voltage of the external battery of the UPS (V)

B. Calculation method

1. the number of 12V single cells N: N = V ÷ 122V the number of single cells is 6N
2. battery operating current I: I = P total ÷ V
3. Actual battery capacity C: C=I×T÷Kh
For example, the power backup time of 1KVA is 4 hours, and the model of KST UPS is HP9101H, V=36V.
1N=36V÷12V=3 knots
4. battery can be selected with 100AH group 3 sections, or 65AH 2 group 6 sections, the results of the selection are deviated, depending on the user’s needs and cost considerations.

Note: The common capacity specifications for 12V batteries are 7Ah, 17Ah, 24Ah, 38Ah, 65Ah, 100Ah, 200Ah,250AH etc.

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