Simple calculation of UPS battery configuration and discharge

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UPS—Uninterruptible PowerSystem 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 the mains (blackout). 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 UPS battery configuration is introduced as follows:

First, UPS battery configuration calculation method

1. The following factors affect the standby time:

(1) Total load power P (W), taking into account the power factor of the UPS, can be calculated directly in units of 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 low is the termination voltage (V) after battery discharge, 2V battery V is low = 1.7V; 12V battery V is low = 10.2V

(4) Kh is the battery capacity conversion factor (Ct/C10), 10Hr discharge rate is 1, 5Hr discharge rate is 0.9, 3Hr discharge rate is 0.75, and 1Hr discharge rate is 0.62.

(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)

2, UPS battery configuration 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.

1 N=36V÷12V=3 knots

2 I=1000VA÷36V=28A

3 C=24A×4H÷0.9=124AH

4 The 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, etc.

According to the above calculation method, the list can be calculated. The following table is for reference:

Backup time total power (kVA) number of batteries (number) time number discharge coefficient K theoretical battery capacity (Ah) actual battery capacity (Ah)

30 minutes 130.50.53021

1 hour 1310.624834

2 hours 103220.688358

3 hours 103230.7511379

4 hours 1340.8151106

5 hours 103250.9157110

6 hours 103260.92185130

8 hours 13809.6252176

10 hours 2020101909636

Description:

1. The discharge rate is calculated by the battery at room temperature. The discharge rate of different brands of batteries is also different, and its value should also be changed.

2. Fill in the corresponding parameters in the blue area and move the cursor to the corresponding red cell.

3. Theoretical battery capacity = total power * number of hours / (11 * number of batteries * discharge coefficient).

4. The actual battery capacity is N times the theoretical battery capacity (N can be selected from 0.6, 0.7, 0.8, 0.9, etc.)

Second, the discharge current calculation of the UPS battery pack

In fact, because the discharge characteristics of the battery are nonlinear, the discharge calculation of the battery becomes more complicated, and the smart is roughly estimated. This is especially difficult for non-professional end users or general dealers. In the calculation of battery discharge, the commonly used method is to estimate according to the 哼 current discharge curve (if any) provided by the battery manufacturer. As long as the discharge current of the battery and the capacity specification of the battery are determined, the corresponding discharge time can be detected. . For small capacity UPS, the following formula can be directly used for calculation.

Discharge current I(A) = [UPS power (P) × power factor (PF)] / [DC terminal voltage (U) of the battery pack after discharge × Inverter efficiency (η)]

I=(P.PF)/U.η

Here are a few common data:

(1) PF: The high frequency machine is 0.7, the power frequency machine is 0.8, or based on the PF provided by each UPS manufacturer.

(2) U: DC voltage of the battery pack after discharge = number of battery packs (N) × voltage (V) after discharge of a single battery.

(3) η=0.92

The following examples illustrate:

Example 1. A 576V10KVAUPSN=576/12=48, PF=0.8, and the termination voltage is 6×1.67/single block

Calculate I=[(10×1000)×0.8]/[(48×6×1.67)×0.92]=18.1A

In this way, the backup time of the UPS is used to find the matching battery model according to the discharge curve characteristics of the battery.

summary

The calculation of the discharge configuration of the battery is relatively common and complicated, and there is no standard for agreeing to the specification. This undoubtedly brings a lot of trouble to the user's application. The establishment of the new calculation publicity and the continuous improvement in the future will make the battery discharge calculation method more reasonable, standardized, convenient and practical. At the same time, the introduction of computer computing will bring new ideas to the calculation and management of battery applications.

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