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SD Engineering Sdn BhdElectrical Calculation

Ac and DC UPS complete with Battery sizing

Battery and load specification

Batery type Nickel-Cadmium alkaline

Nominal (operational) Voltage 24 Volt

Maximum Voltage 26.4 Volt

(24V + 10%)

Minimum Voltage 21.6 Volt

(24V - 10%)

Nominal Voltage/cell V/cell 1.2

Recommended Battery float charge V/cell 1.4

( Based on Saft-Nife thr value is 1.4V/cell )

Quantity of cell required (N) 19 (round-up figure)

(Maximum voltage/Float voltage)

End voltage(per cell) 1.15 (nearest figure is 1.14)

(Min voltage/number of cell)

Continous load (Acont.) 35.1 Ampere (refer to load tabulation)

Design criteria

Temperature correction factor @25oC 1

Design Margin or spare capacity 1.10 ( 10% additional)

Ageing factor due to the battery deteriorate 1.25 ( 25% additional)

Computation

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SD Engineering Sdn BhdElectrical Calculation

Ac and DC UPS complete with Battery sizing

Battery sizing S=N

Uncorrected cell size (AH) = Max

S=2

N = number of period in load profile

p = period being analysed

Ap = Ampere required for period "P"

T = time (minute/hour or second)

KT = AH capacity at standard rating/Amp that cell supply in time T

From the graph compute the uncorrected battery size in Ampere hour

A0 0 ampere

A1 100.1 ampere

A2 35.1 ampere

KT1=128/102 1.2549

T1 at 45 minute and A1

KT2= 8.3/45.2 0.1836

T2 at (T1-next time duration) minute

& A2 .

Therefore computed uncorrected cell size 113.68 Ampere-Hour

Corrected battery size(AHcorrect) = 156.31 Ampere-Hour

AHcorrect = AH max. uncorrect x temperature correction factor x design margin x ageing factor

Manufacturer's Data

Based on Saft-Nife battery is SBH157 157 AH

Physical battery cell sizing 349mm(H) x 195mm(W) x 252mm(L)-(2 cell per block)

Number of cell 19

Proposed battery rack 3 tiers

Propose battery arrangement

Charger sizing

1000

800

t

1

)1p(p }{ KAAsp

p

=

=

--

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SD Engineering Sdn BhdElectrical Calculation

Ac and DC UPS complete with Battery sizing

Calculation Procedure

Maximum system voltage per cell( V1max) = Maximum system voltage/ number of cell

V1max = 1.4 volt

This is the maximum volt, the battery are allowed to be charged during high rate or float charge

Based on Saft-Nife battery high the rate charge voltage level is between 1.45 to 1.75V/cell

It assumed that battery banks are allowed for the high rate charge it is assumed that the charger shall

be size to cater for the short duration of charging.

Recommended high rate charge (Ahr) 94.2 Ampere

0.4 C5A for 2.5Hr and 0.2C5A for 2.5Hr

Charger size( AC )=Ahr+ Cont.load (Acont.) 129 Ampere

Manufacturer's Standard size 150 Ampere

Input Power (P)=KxVnxIn 4752 watt @ 3 phase 415V source

Vn = nominal charger output voltage

In = max charger output current

K = Constant factor @ 24V 1phase 2.64

K = Constant factor @ 24V 3 phase 1.32

Battery Charger physical sizing

(all dimension in mm unless specified)

H=1630

D=490

W=670

9323-RPT-EL-002

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SD Engineering Sdn BhdElectrical Calculation

Ac and DC UPS complete with Battery sizing

9323-RPT-EL-002