حسابات ال UPS

كيفية حسابات UPS  مع مكوناته
هنآخد مثال عشان نفهم
أحسب سعة وحدة UPS للأحمال التالية
DCS Cabinet =200 VA     Autonomy = 4 H
ESD Cabinet =200 VA      Autonomy=4 H
Telecommunication Cabinet =150 VA    Autonomy =6 H 
Computer Console= 90 VA   Autonomy =2 H

الحل

أولا:- حسابات Design Load
Sd=Sp(1+Kg)(1+Kc)
Sd (Apparent power ) VA
Kg(Future Load )=5 to 20%
Kc(Design Margin)=10 to 15%

Peak Load (Sp)=150+200+200+90=640 VA
Design Load(Sd)=640(1+0.1)(1+0.1)=774.4 VA

ثانيا :- حسابات Energy Demand
Ed=Et(1+Kg)(1+Kc)
Ed (Energy Demand )=Vah
Et (Total Load Energy)=Vah   وده حسابه من الجدول الملحق
Kg(Future Load  %)
Kc(Design contingency %)
Et=150 x 6 +200 x 4+200 x 4+90 x 2=2680 V ah
Design Energy Demand= 2680(1+0.1)(1+0.1)=3242.3 V ah
ثالثا :- حسابات البطاريات

N max=Vdc(1+Vi max)/Vc
N min= Vdc(1-Vi min)/V dch

على فرض ان البطارية Vdc=120 DC 
وفرض Max Voltage tolerancess  =20% 
وفرض Min Voltage tolerancess  =10% 
V c=Cell Charging Voltage  =2.25 Vdc/Cell
V d ch= Cell discharging Voltage  =1.8 Vdc/Cell
بالتعويض فى المعادلة السابقة
N max=120(1+0.2)/2.25=64 Cell
N min=120(1-0.2)/1.8=60 Cell
بعدين نعوض فى المعادله دى
C min=Ed(Ka x Kt x Kc)/Vdc x K dod
C min هى اصغر قيمة لسعة البطارية
Ed هى القيمة اللى حسبناها فوق
Ka معامل البطارية %               suggest =25%
Kt معامل درجة الحرارة %         suggest= at 30 C =0.965
Kc معامل سعة البطارية %          Suggest =10%
K dch=معامل اعلى قيمة تفريغ للبطارية   from example =80%
بالتعويض فى المعادلة السابقة
C min=3242(1.25 x 1 x 0.965)/120 x 0.8=44.4 Ah
رابعا:-حسابات سعة UPS
As per design load=774.4 VA we will select UPS=1 KVA
خامسا :- حسابات Rectifier , Charger 
من المعادلة
I  load current =S/Vdc = 1000/120=8.33 A
Ic=Cxki/tc 
Ic Max DC charger
c = select battery capacity Ah we will select 50
Ki  Battery charger  eff=1.1
Tc=min battery recharge time  we will select for this ex=2 hours
Ic=50x1.1/2=27.5 A

اذا المجموع الإجمالى لكلا من Rectifier & Charger
I min DC=Ic+I ldc
I min DC= 27.5+8.33=35.8 A
اذا هيكون سعة Rectifier =40A
سادسا :- حسابات Inverter & static Switch

فى معادلة بتقول
Ic=S/1.732 x V
Ic=1000/1.732 x 240 =2.4 A

هنختار اقرب قيمة ولتكن 5 امبير

منقول م احمد عيسى

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