An uninterruptible power supply (UPS) provides emergency backup power to critical loads when utility power fails. It works by filtering incoming utility power and using an inverter to convert stored battery power to AC power for connected devices. UPS systems are commonly used to power servers, networking equipment, security systems, and other devices that require continuous uptime. Dual conversion online UPS systems provide especially clean backup power by constantly converting incoming AC to DC then back to AC again using an inverter. Proper inspection and maintenance of UPS systems and their batteries is important for safety and optimal performance.

1. By: Engr. Salman Hameed Yousafzai

2. UPS
 An uninterruptible power supply, also
uninterruptible power source, UPS or battery/flywheel
backup, is an electrical apparatus that provides
emergency power to a load when the input power
source or mains power fails.

3. Working Principal

4. Commercial Series UPS’s
Square Wave (PWM) Output
 Small Office / Home users
 Personal Computers
 Servers
 Point of Sale Equipment

5. PWM Sine Wave Output (when
on battery)
Filtered AC utility to the loads until a blackout condition occurs. At this point
the inverter converts the DC voltage to AC power which, in turn, is supplied to
the loads.

6. Commercial & Light Industrial
Applications
 LAN File Servers,
 Personal Computers,
 Workstations,
 Network Routers,
 Hubs and Switches
Security Systems
Test Equipment,
Automated Teller Machines,
Telecommunications,
Commercial & Light Industrial Applications

7. Dual Conversion On-Line UPS

8.  Modes of Operation
Online Mode
Back-Up Mode
Static Bypass
Maintenance/Manual Bypass
External Maintenance Bypass
Dual Conversion On-Line UPS

9.  Modes of Operation
Online Mode
Back-Up Mode
Static Bypass
Maintenance/Manual Bypass
External Maintenance Bypass
Dual Conversion On-Line UPS

10.  Modes of Operation
Online Mode
Back-Up Mode
Static Bypass
Maintenance/Manual Bypass
External Maintenance Bypass
Dual Conversion On-Line UPS

11.  Modes of Operation
Online Mode
Back-Up Mode
Static Bypass
Maintenance/Manual Bypass
External Maintenance Bypass
Dual Conversion On-Line UPS

12.  Modes of Operation
Online Mode
Back-Up Mode
• Static Bypass
Maintenance/Manual Bypass
External Maintenance Bypass
Dual Conversion On-Line UPS

13.  Modes of Operation
Online Mode
Back-Up Mode
Static Bypass
Maintenance/Manual Bypass
External Maintenance Bypass
Dual Conversion On-Line UPS

14. Dual Conversion On-Line UPS
 Supplied AC Utility converted to DC, inverted to AC via
inverter providing clean, noise free power.
 Due to this conversion AC supplied from the Inverter, the
connected Loads are “Always” isolated from the dirty AC
supply!
 Available from 700VA single phase configurations up to
250kVA three phase configurations.
 Isolation Transformers are standard for systems 5kVA and
up.
 LCD Display.

15. Inspection
 Inspection:
 weekly inspection
 Check voltage level
 Charging current
 Cleaning
 Physical condition of batteries
 Temperature of batteries
 Alarms
 Test on load with main supply off for at least one hour

16. Maintenance
 Safety:
 Be careful before maintenance
 Use H.T gloves while opening connection/ tightening and
gogles.
 Incase of +ve –ve short circuit there could be a blast.
 Maintenance:
 Cleaning with blower and cotton waste
 Connection tightening
 Replace weak/faulty batteries
 Connection must be made as per drawing drawn and verified
by competent person before installation of new batteries.