become a battery sizing guru
TRANSCRIPT
UPS 101
What is a UPS?Per Wikipedia:An uninterruptible power supply, also uninterruptible power source, or UPS is an electrical apparatus that provides emergency power to a load when the input power source fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide instantaneous protection from input power interruptions, by supplying energy stored in batteries. The on-battery runtime of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment.
This is a UPS
Why is a UPS Needed?
• A UPS is needed for Critical Computer Systems that CANNOT lose power.• Power loss to a computer can be catastrophic.• Lost billing• Lost sales• Lost productivity• Equipment damage
Simplified Diagram of UPS
Normal UPS Power Flow
Loss of Utility - Power Flow
Battery
Sizing
Batteries Are Fun!
Rules for Battery Sizing
Battery Sizing Rules1. UPS battery systems CANNOT be sized for less
than (5) minutes of run-time. NO EXCEPTIONS!
2. The Battery End Cell Voltage is 1.67VPC (volts per cell) when sizing VRLA batteries for 5 to 15 minutes of run-time.
Coup De Fouet EffectUPS battery systems CANNOT be sized for less
than (5) minutes of run-time. Why?
* If you size the battery system for less than (5) minutes, there’s a very good possibility the UPS will shutdown prematurely at this point.
End Cell Voltage Rules UPS systems are TYPICALLY designed to provide 15
minutes of battery run-time at full load. For applications needing run-times in excess of
15 minutes, the “RULES” change. For 15+ minutes of run-time, the end cell
voltage raises to 1.75VPC.
What You Need to Know to Properly Size a UPS Battery System
1. Output kVA rating of the UPS
2. Output power factor of the UPS
3. DC link voltage of the UPS
4. Number of battery strings on the UPS
5. Minutes of battery run-time needed
Customer Supplied Information
1. Battery Manufacturer’s Run-Time Chart(s)
2. Formula to Calculate Battery Run-Time
3. A Calculator
Have These Handy
Battery Run-Time Chart
UPS kVA * power factor = kWB
“The Magic FORMULA”
# of battery cells in 1 string kWB * 1000 = WPC
WPC# of battery strings
= WPC per String
UPS inverter efficiency (90%)
40kVA * 0.8 power factor = 35.6 kWB
Small UPS Example
240 # of battery cells in 1 string 35.6 kWB * 1000 = 148.3 WPC
148.3 WPC(1) # of battery strings
= 148.3 WPC per string
UPS inverter efficiency (90%)
C&D High Rate Max Battery Run-Time
Chart
1.67VPC UP TO 15 MINUTES148.3 WPC per string(1) # of battery string
500kVA * 0.8 power factor = 444.4 kWB
Large* UPS Example
240 # of battery cells in 1 string 444.4 kWB * 1000 = 1,851.9 WPC
1,851.9 WPC(4) # of battery strings
= 463 WPC per string
UPS inverter efficiency (90%)Yep! The Form
ula is the SAME!
* 150kVA and larger
C&D High Rate Max Battery Run-Time Chart
1.67VPC UP TO 15 MINUTES1.75VPC OVER 15 MINUTES
463 WPC per string(4) # of battery strings
C&D High Rate Max Battery Run-Time Chart
1.75VPC OVER 15 MINUTES463 WPC per string
(4) # of battery strings
You Are Now Officially a
Battery Sizing Guru!