Fundamental Electronics

1. BACK UP SYSTEMS
CHAPTER 16.5
UPS
By
Dinesh Kumar Sarda

2. Uninterrupted Power Supply
( UPS )

3. WHAT IS A UPS??
UPS is the Mid-Point Between
Utility & Critical Load
POWER
STATION
UTILITY
NETWORK UPS
CRITICAL
LOAD

4. WHY IS UPS REQUIRED ??
TO FIGHT
THE
POWER
FAILURES

5. CAUSES OF POWER FAILURES
TRANSIENT
Voltage
Surge
NOISE
NOTCHES
VOLTAGE
DISTORTION
FREQUENCY
VARIATION
SAG
SWELL
UNDER
VOLTAGE
OVER
VOLTAGE
MOMENTARY
INTERRUPTION
LONG-TERM
INTERRUPTION
3% of failures are related to direct power failures.
The rest is mainly due to fluctuations

6. ROLE OF UPS
 UPS maintains a continuous supply of electric
power to connected equipment by supplying
power from a separate source when utility power
is not available
 It differs from an auxiliary power supply or
standby generator, which does not provide
instant protection from a momentary power
interruption

7. DIFFERENCE BETWEEN UPS AND INVERTER
Two widely known solutions to battery based
power back-up are UPS and inverter.
Lets find out what is the basic difference
between the two…

8. UPS INVERTERS
UPS, standing for Uninterruptable Power
Supply, is an electric circuit (device) which
instantly backs up power supply for a
gadget. The gadgets works continues to
work on smoothly and there is no damage
to it.
inverter is circuitry which converts AC to DC
and stores in the battery. When power
supply goes off, that DC power is converted
back to AC and is transmitted to the
respective electronic gadget.
UPS does the similar task of power supply
and is quite similar to inverter’s working in
order to supply power. However, UPS
monitors the input voltage level and
processes it in terms of voltage regulations
Inverter converts DC power (stored in its
battery) to fulfill respective requirements of
the devices. It uses relays and sensors to
detect when to use DC power, otherwise it
charges the battery for DC power.
UPS takes around 10 to 15 milliseconds for
the change over time.
inverter takes up to 500microseconds for
the change over time.
UPS works at 240-270V AC Inverter takes up around 170-270V of AC
inverter can be divided into three types:
(a) Square Wave, (b) Quasi Wave, (c) Sine
Wave inverters.
As the name suggests, these types are on
the basis of the type of the wave generated.
UPS are of three types, basically:
(a) Offline UPS, (b) Online UPS and
(b) (c) Line-interactive UPS

9. A highly sophisticated circuit along with
swift working makes a UPS more
expensive than an inverter, which restricts
its widespread usage for gadgets
Inverter’s major drawbacks include more
fluctuations in power output, higher
delay, and a less quality circuitry.
Inverters are preferred more for general
electric gadgets whose working doesn’t
get affected by extended delays in power
supply.
UPS are used for gadgets such as
computer, servers, workstations which
perform critical task and cannot tolerate
delays in power supply.

10. INVERTERRECTIFIER
BATTERY
POWER
IN
POWER
OUT
INVERTER

12. OFF LINE UPS
What is a UPS ?
Off-line definition:
• The UPS is “sleeping” in normal mode
• At power failures, power will drop out in
5-20 msec, until the UPS “wakes up”.
Input voltage
Output voltage
UPS

14. ON LINE UPS
Input voltage
Output voltage
On-line definition:
• The UPS is active in normal mode.
• The UPS is constantly regulating the
output voltage without any
interruption or variations.
UPS

16. LINE INTERACTIVE UPS

17. How to choose the right inverter & battery for your home?

18. First understand your Power Requirement
One of the most important factor that you must know before
buying an inverter is your “Power requirement”. In simple words-
what all electrical appliances (like fan, tube lights, television, CFL
etc.) you want to run at the time of power failure. The power
requirement is addition of the power consumed by various
electrical equipments.
Suppose you want 3 Fans, 3 Tube lights, 1 CFL & 1 television to
operate at the time of power failure. Below is the power consumed
by these items:
• 1 Fan – 70 Watts
• 1 tube light – 60 watts
• 1 CFL – 25 watts
• 1 Television – 120 watts
Therefore your total power requirement is ( 3*70 +3*60 + 25 + 120)
= 535 watts

19. Find the VA rating of the inverter you need
 It stands for the Volt ampere rating. It is the voltage and current supplied
by the inverter to the equipments. If an inverter operates with 100%
efficiency, then the power requirement of the electrical items and power
supplied by inverter is same. But we all know that 100% or ideal
conditions don’t exist in real. Most inverters have the efficiency range
from 60 % to 80%. This efficiency is also called power factor of an inverter
and is simply the ratio of power required by the appliances to power
supplied by an inverter. Power factor of most inverters ranges from 0.6 to
0.8.
 Hence Power supplied (or VA rating of inverter) = Power requirement (
power consumed by equipments in watts) / Power factor( efficiency).
 Here average value of power factor or efficiency is considered i.e. 0.7
 Power of inverter (VA) = 535/0.7 = 765 VA
 In the market 800 VA inverters are available. So an inverter with 800 VA
will be the right choice for your home.

20. Know the battery your inverter needs
 Battery is the backbone of an inverter system. The performance and life of
an inverter largely depend upon the battery quality. The next big question is “how
much back up will an inverter provide?” or for “how many hours it can run all of
your equipments?”. This is what is called the battery capacity. It is the battery
capacity that decides the back up hours. It is expressed in Ah (Ampere Hours).
 In the market batteries with capacity of 100 Ah,150 Ah, 180 Ah etc. are readily
available. So how to decide which one do you need? To find this out lets do a
reverse calculation. Consider that you need a battery that provides back up for 3
hours.
 Battery capacity = Power requirement (in watts) * Back up hours ( in hrs) / Battery
Voltage (in volts)
 Battery Capacity = (535 * 3) / 12 = 133 Ah
 ** Value of Battery voltage is taken 12V
 Therefore a battery with a capacity of 130 Ah will work for you.
 So if you want to run 3 fans, 3 tube lights , 1 CFL and 1 TV for 3 hours during power
failure you would need 800VA inverter and 130 Ah battery.

21. Wiring of a household UPS
UPS
WIRING.mp4