Savings by Using LED Lights: Cost, Payback, and Long-Term Benefits
LED lighting has become one of the most effective ways to reduce electricity bills at home and in industries. While the upfront cost of LED lights is slightly higher compared to conventional tube lights, the annual savings, longer lifespan, and reduced maintenance costs make them a far superior choice. Let’s break down the numbers and see why LEDs are a smart investment.
Conventional Tube Light vs LED Tube Light – Power Consumption
1. Conventional Tube Light (with choke)
Tube Wattage: 36 W
Choke Wattage: 36 W
Total Consumption per Hour: 72 W (0.072 kWh)
Daily Usage (10 hours): 720 Wh (0.72 kWh)
Monthly Usage (30 days): 21.6 kWh
Annual Usage: 262.8 kWh
Electricity Tariff (avg.): ₹8 per unit
Annual Cost: ₹2,102
2. LED Tube Light
Wattage: 20 W
Total Consumption per Hour: 20 W (0.02 kWh)
Daily Usage (10 hours): 200 Wh (0.20 kWh)
Monthly Usage (30 days): 6 kWh
Annual Usage: 72 kWh
Electricity Tariff (avg.): ₹8 per unit
Annual Cost: ₹576
Annual Savings with LED Lights
Annual Power Cost (Conventional): ₹2,102
Annual Power Cost (LED): ₹576
Savings in Power Consumption: ₹1,526
Now, consider initial replacement cost of LED tube: ₹300.
Net Annual Savings: ₹1,226
Payback Period:~1.5 months (after which all savings are profit)
LED Lights vs Conventional Tube Lights – Life Expectancy
Feature
Conventional Tube Light
LED Tube Light
Wattage
(for same brightness)
72 W
(incl. choke)
20 W
Annual
Cost (10 hrs/day)
₹2,102
₹576
Life
Span
10,000
– 15,000 hrs
25,000
– 50,000 hrs
Maintenance
Frequent
choke/starter failure
No
choke required
Warranty
Rarely
offered
2–3
years standard
Payback
Period
–
1.5
months
Why LEDs Are the Future of Lighting
Energy Efficiency: LEDs consume up to 70% less electricity than conventional tube lights.
Longer Life: With up to 50,000 hours of lifespan, LEDs last 2–3 times longer.
Low Maintenance: No chokes or starters, hence fewer breakdowns.
Falling Prices: With mass production, LED costs are dropping rapidly.
Warranty Assurance: Most manufacturers offer 2–3 years warranty, ensuring peace of mind.
Eco-Friendly: Reduced carbon footprint and lower e-waste due to longer life.
Practical Tip
You don’t need to replace the entire fixture. Modern LED tube rods are designed to fit into existing fittings – you just remove the choke and starter. This makes the switch to LEDs easier and cost-effective.
Conclusion
Switching to LED lights is not just an eco-friendly choice but also a financially rewarding decision. For every tube light replaced, you save ₹1,200+ per year. Multiply this by all the tube lights in your home or workplace, and the savings run into thousands of rupees annually.
With short payback, reduced maintenance, long lifespan, and lower electricity bills, LEDs are the smarter, greener, and more economical option for the future.
✅ Standard Disclaimer:
The calculations provided are based on average power tariffs (₹8/unit) and 10 hours of daily usage. Actual savings may vary depending on local electricity rates, usage hours, and LED product quality.
Circuit breakers are essential protective devices in electrical systems. They not only interrupt fault currents but also ensure selective coordination with other protective devices. To understand their performance and applications, we need to study their utilization categories, types of releases, rated values, tripping characteristics, and marking requirements.
1. Utilization Categories of Circuit Breakers
The utilization category of a circuit breaker specifies whether it is designed for selectivity under short-circuit conditions. There are two main categories:
(i) Category A
Not designed for selectivity under short-circuit conditions.
Do not have intentional short-time delay.
No short-time withstand current rating.
Commonly used for final distribution protection (e.g., MCCBs in feeders).
(ii) Category B
Designed for selectivity under short-circuit conditions.
Have an intentional short-time delay (may be adjustable).
Must have a short-time withstand current rating specified by the manufacturer.
Typically used in main breakers and upstream protection.
2. Releases in Circuit Breakers
A release in a circuit breaker refers to the tripping mechanism that operates under fault or abnormal conditions. The main types are:
(i) Shunt Release
Trips the breaker when an external voltage signal is applied.
Used for remote tripping (e.g., emergency shutdown).
(ii) Overcurrent Release
Protects against overloads and short circuits.
Instantaneous Release → trips immediately at preset fault current.
Definite Time Delay → trips after a fixed delay, independent of fault current magnitude.
Inverse Time Delay → tripping time decreases as fault current increases.
Independent of previous load
Dependent on previous load
Terminology:
Overload release → for overload protection.
Short-circuit release → for high fault current protection.
(iii) Under-voltage Release
Trips the breaker when supply voltage drops below a threshold.
Ensures breaker does not reclose automatically on power restoration.
(iv) Other Releases
Special releases based on application (e.g., earth fault release, combined protections).
3. Characteristics of Releases
(i) Shunt Release & Under-voltage Release
Rated control circuit voltage
Type of current (AC/DC)
Frequency (for AC)
(ii) Overcurrent Release
Rated current setting
Current type (AC/DC)
Frequency (for AC)
Adjustable current and time settings (on front of MCCB/CB)
4. Rated Current of Circuit Breaker
Defined as the RMS value of current at the maximum setting, which the breaker can carry continuously without exceeding permissible temperature-rise limits.
For adjustable releases → current setting range must be marked (in amperes or multiples of rated current).
For non-adjustable releases → breaker is marked with rated current only.
👉 In case of indirect releases via CTs, marking can be based on CT primary current or overload release setting, with CT ratio clearly indicated.
Temperature Considerations:
Non-thermal releases → unaffected by -5 °C to +40 °C ambient.
Thermal releases → values given at reference temperature of 30 °C ± 2 °C.
5. Tripping Time Settings
1) Definite Time Delay Overcurrent Release
Time delay is independent of fault current.
Marked as fixed or adjustable time in seconds.
2) Inverse Time Delay Overcurrent Release
Time delay is dependent on fault current magnitude.
Tripping characteristics given as time-current curves by manufacturers.
Curves provided for extreme current settings and, if adjustable, for extreme time settings as well.
6. Marking on Circuit Breakers
Circuit breakers must be durably marked for identification and safe operation.
(a) Mandatory Markings (visible when installed)
Rated current (In)
Suitability for isolation (symbol if applicable)
Position indicators (O = Open, I = Closed)
(b) External Markings (may not be visible when installed)
Rated insulation voltage (if > operational voltage)
Pollution degree (if ≠ 3)
Conventional enclosed thermal current
IP Code
Minimum enclosure/ventilation requirements
Distance to earthed parts (for unenclosed use)
Suitability for environment A/B
RMS sensing (if applicable)
(d) Markings on Operating/Tripping Devices
Control circuit voltage & frequency (closing devices)
Shunt/Under-voltage release ratings
Indirect overcurrent release rating
Auxiliary contacts details & ratings
Terminal marking
✅ Summary:
Circuit breakers are classified into Category A and B based on selectivity requirements. They use different releases (shunt, under-voltage, overcurrent, etc.) for protection and control. Proper understanding of rated current, tripping characteristics, and marking requirements (IEC 60947-2) is essential for correct selection, application, and maintenance of circuit breakers in electrical systems.
The rated
short-circuit making capacity of a circuit-breaker is the value of
short-circuit capacity assigned to that circuit-breaker by the manufacturer for
the rated operational making voltage at rated frequency and at a specified
power factor for A.C., or time constant for D.C. It is expressed as the maximum
prospective peak current. For a c the rated short-circuit making capacity of a
circuit-breaker shall be not less than its rated ultimate short-circuit breaking
capacity, multiplied by the factor n of table as below .
For d c the
rated short-circuit making capacity of a circuit-breaker shall be not less than
its rated ultimate short-circuit breaking capacity. A rated short-circuit
making capacity implies that the circuit-breaker shall be able to make the current
corresponding to that rated capacity at the appropriate applied voltage related
to the rated operational voltage.
Rated short-circuit breaking capacities
In
case of circuit breakers rated Short-Circuit capacity is the values of
short-circuit breaking capacity of that circuit-breaker assigned by the
manufacturer for the rated operational voltage, under specified conditions.
A
rated short-circuit breaking capacity requires that the circuit-breaker shall
be able to break any value of short-circuit current up to and including the
value corresponding to the rated capacity at a power-frequency recovery voltage
corresponding to the prescribed test voltage values and:
a) For alternating current at any power factor
not less than as per table below;
b)For
direct current, with any time constant not greater than as per table given
above.
For
power-frequency recovery voltages in excess of the prescribed test voltage
values , no short-circuit breaking capacity is guaranteed
Now what are Power frequency recovery
voltages?
All
tests shall be made at the rated frequency of the circuit-breaker. For all
short-circuit tests, if the rated breaking capacity is essentially dependent on
the value of the frequency, the tolerance shall not exceed +-5%. If the manufacturer declares the rated
breaking capacity to be substantially unaffected by the
value
of the frequency, the tolerance shall not exceed +-25 %.
For
alternating current the circuit-breaker shall be capable of breaking a
prospective current corresponding to its rated short-circuit breaking capacity
and the related power factor given in table above, irrespective of the value of
the inherent D.C. component, on the assumption that the AC, component is
constant.
Definitions:-
(a)Rated service short-circuit breaking
capacity of a circuit-breaker
A breaking
capacity for which the prescribed conditions according to a specified test
sequence include the capability of the circuit-breaker to carry its rated
current continuously
(b)Ultimate
short circuit breaking capacity of circuit breaker:-
A breaking
capacity for which the prescribed conditions according to a specified test
sequence do not include the capability of the circuit-breaker to carry its
rated current continuously
The rated short-circuit breaking
capacities are stated
as
The
rated ultimate short-circuit breaking capacity of a circuit-breaker is the value
of ultimate short-circuit breaking capacity assigned to that circuit-breaker by
the manufacturer for the corresponding rated operational voltage. It is
expressed as the value of the prospective breaking current, in kA (RMS. value
of the a.c. component in the case of a,c. ),
(ii)Rated service short-circuit breaking
capacity (Ics.)
The rated service short-circuit breaking capacity of
a circuit-breaker is the value of service short-circuit
breaking capacity assigned to that circuit-breaker by the manufacturer for the
corresponding rated operational voltage. It is expressed as a value of prospective
breaking current, in kA, corresponding to one of the specified percentages of
the rated ultimate short-circuit breaking capacity, in accordance with table as
given below, and rounded up to the nearest whole number. It may be expressed as
a % of Icu (for example Ics = 25 % Icu).
Alternatively,
when the rated service short-circuit breaking capacity is equal to the rated
short-time withstand current , it may be stated as that value, in kA, provided
that it is not less than the relevant minimum value of table as below.
Where
Icu exceeds 200 kA for utilization
category A, or 1000 kA for utilization category B, the manufacturer may declare
a value Ics of 50 kA.
Standard
relationship between short-circuit making and breaking capacities and related
power factor, for a.c. circuit-breakers
The standard relationship between short-circuit
breaking capacity and short-circuit making capacity is as given in table below.
The
rated short-circuit making and breaking capacities are only valid when the
circuit-breaker is operated in accordance with the requirements as given below
in Operating conditions of circuit breakers. For special
requirements, the manufacturer may assign a value of rated short-circuit making
capacity higher than that required by table above. Tests to verify these rated
values shall be the subject of agreement between manufacturer and user.
Rated
short-time withstand current (Icw)
The
rated short-time withstand current of a circuit-breaker is the value of
short-time withstand
current
assigned to that circuit-breaker by the manufacturer under the test conditions
For
A.C., the value of this current is the R.M.S value of the A.C. component of the
prospective short-circuit current, assumed constant during the short-time
delay.
The
short-time delay associated with the rated short-time withstand current shall
be at least 0.05 s, preferred values being as follows:
0.05
–0.1 –0.25–0.5–1 S
The
rated short-time withstand current shall be not less than the appropriate
values shown in table above
Operating
Conditions of Circuit breakers
(a)Closing
For a
circuit-breaker to be closed safely on to the making current as a neutral pole,
then all corresponding to its rated short-circuit
making capacity, it is essential that it should be operated with the same speed
and the same firmness as during the type test for proving the short-circuit
making capacity.
(i)Dependent manual closing
For a
circuit-breaker having a dependent manual closing mechanism, it is not possible
to assign a short- circuit making capacity rating irrespective of the
conditions of mechanical operation.
Such a
circuit-breaker should not be used in circuits having a prospective peak making
current exceeding 10 kA. However, this does not apply in the case of a
circuit-breaker having a dependent manual closing mechanism and incorporating
an integral fast-acting opening release which causes the circuit-breaker to
break safely, irrespective of the speed and firmness with which it is closed on
to prospective peak currents exceeding 10 kA; in this case, a rated
short-circuit making capacity can be assigned,
(ii)Independent manual closing
A
circuit-breaker having an independent manual closing mechanism can be assigned
a short-circuit making capacity rating irrespective of the conditions of
mechanical operation.
(iii)Dependent power closing
The
power-operated closing mechanism, including intermediate control relays where necessary,
shall be capable of securing the closing of the circuit-breaker in any
condition between no-load and Its rated making capacity, when the supply
voltage, measured during the closing operation, remains between the limits of
110 “A and 85 ‘A of the rated control supply voltage, and, when a c., at the
rated frequency.
At 110 % of
the rated control supply voltage, the closing operation performed on no-load
shall not cause any damage to the circuit-breaker.
At 85 “A of
the rated control supply voltage, the closing operation shall be performed when
the current established by the circuit-breaker is equal to its rated making
capacity within the limits allowed by the operation of its relays or releases
and, if a maximum time limit is stated for the closing operation, !n a time not
exceeding this maximum time limit.
(iv)Independent
power closing
A circuit-breaker
having an independent power closing operation can be assigned a rated short-circuit
making capacity irrespective of the conditions of power closing. Means for
charging the operating mechanism, as well as the closing control components,
shall be capable of operating In accordance with the manufacturer’s
specification.
(v) Stored energy closing
This type of
closing mechanism shall be capable of ensuring closing of the circuit-breaker
in any condition between no-load and its rated making capacity. When the stored
energy is retained within the circuit-breaker, a device shall be provided which
Indicates when the storing mechanism is fully charged, Means for charging the
operating mechanism, as well as the closing control components, shall be
capable of operating when the auxiliary supply voltage is between 85%.
and 110 % of
the rated control supply voltage. It shall not be possible for the moving
contacts to move from the open position unless the charge is sufficient for
satisfactory completion of the closing operation. When the energy storing
mechanism is manually operated, the direction of operation shall be Indicated This
last requirement does not apply to circuit-breakers with an independent manual
closing operation.
(b)
Opening
(i)
General
Circuit-breakers
which open automatically shall be trip-free and, unless otherwise agreed between
manufacturer and user, shall have their energy for the tripping operation
stored prior
to the
completion of the closing operation,
(ii)
Opening by over-current releases
Opening under
short-circuit conditions The short-circuit release shall cause tripping of the
circuit-breaker with an accuracy of +-20% of the tripping current value of the
current setting for all values of the current setting of the short-circuit
current release. Where necessary for over-current co-ordination , the manufacturer
shall provide Information (usually curves) showing
àmaximum cut-off
(let-through) peak current as a function
of prospective current (r, m.s. symmetrical); à /2t characteristics for
circuit-breakers of utilization category A and, if applicable, B for
circuit-breakers with instantaneous override.
Conformity with this information may be
checked during the relevant type tests in test sequences
II and Ill
(iii) Opening under overload conditions
1) Instantaneous or definite time-delay operation
The release
shall cause tripping of the circuit-breaker with an accuracy of+-10%of the tripping current value of the current setting for
all values of current setting of the overload release.
2) Inverse time-delay operation
Conventional
values for inverse time-delay operation are given in table below.
At the reference
temperature and at 1.05 times the current setting, i.e. with the conventional
non-tripping current, the opening release being energized on all phase poles,
tripping shall not occur in less than the conventional time from the cold
state, i.e. with the circuit-breaker at the reference temperature. Moreover,
when at the end of the conventional time the value of current is immediately
raised to 1.30 times the current setting, i.e. with the conventional tripping
current, tripping shall then occur in less than the conventional time later.
If a release
is declared by the manufacturer as substantially independent of ambient temperature,
the current values of table 6 shall apply within the temperature band declared
by the manufacturer, within a tolerance of 0.3%/K.
The
width of the temperature band shall be at least 10K on either side of reference
temperature.
Alternators are used in cars to generate current for running of cars. We
quite often get confused that why alternator is required when there is battery
available in cars.
Battery in cars is only used for starting the cars, but for lights
operation and functioning of other parts current is required now from where
that power will come???
For fulfilling the above purpose alternator is required, alternator has
following functions in cars:-
(i)Running of lights, heater, Air conditioners and operation of other
electrical accessories
(ii)Recharging of battery as it get discharged during starting.
Now how this alternator works in cars and who provides mechanical power
to alternator so that power output can be generated at alternator output??
When you switched off your car engine than radio of car will work on car
battery. For engines running following are required:-
(i)Air
(ii)Fuel
(iii)Spark
Last part is supplied by alternator because spark is generated through
electricity, although battery is
availablefor supplying the spark but not for keep running the car. Battery
electricity is sufficient for keep running the vehicle for few KMs but vehicle required much more than that , so to serve the purpose
alternator will comes into picture.
Alternator in vehicle has output of 13.5 - 14.8 volts.
In past generators were used in cars, these generators are very
inefficient in comparison to alternators, also at that time charging of battery
and keeping accessories lighting up was different from present scenario. There
are following components of alternators:-
(i)Stator
(ii)Rotor
(iii)Voltage regulator you can also say automatic voltage regulator
(iv)Direct current circuitry consisting of diodes
Now with rotation of rotor electricity get generated and output is used
for charging batteries and keeping the auxiliaries ON.
DC circuitry is used to convert the alternating current generated by
alternator to DC. Voltage regulator is used to keeping the voltage generated by
alternator within limits. Feedback is
received by voltage regulator and accordingly output gets controlled. Now day’s voltage regulators are integral
part of alternators. But in past voltage regulators were big boxes and they
were kept in hood and wired into the system. Voltage regulator functions are as
below:-
(a)Cut off the power to battery when
battery get fully charged i.e. when battery voltage reached certain level
around 14.0-14.5 volts
(b)To keep voltage level within limits as
per requirement of auxiliaries.
How to get noticed that
Alternator is faulty??
It can be easily detected as you will observe reduced illumination from
head lights , sometimes reduced illumination may not get detected while driving
as during that time battery will provide necessary electricity . But as battery
power get used for illumination of headlights now when you tried again to restart
the vehicle then vehicle doesn’t start as battery get drained up.
Starting current of a car:-
When you tried to start a car your battery should be strong enough to
provide crank to engines so that car get started easily. You may often see that
very heavy leads are connected at battery terminals as starting current is very
heavy for starting the car. By Ohms law we know that Voltage = Current X
Resistance and now Voltage of battery is 12 V and starter motor resistance is
approximately 0.12 Ohm so
Current = 12/ (0.12 + Internal resistance of battery)
Now lower is the resistance of battery higher will be the starting
current. Now it is general practice that more expensive is the battery lower
will be the resistance.
So higher will be the current and faster will be the starting of vehicle.
From above equation we will also find that if we neglect battery
resistance then starting current will be 100A. So staring current will be also
less than 100A always. If your battery is fully charged then it will be good
enough to overcome the problem of poor internal resistance of battery. Battery
is considered to be fully charged at 12.6 volt levels and low at 12.6 Volts and
completely discharged at 11.9 Volts. Good quality batteries will able to
start vehicle even when it is completely discharged so much but a poor quality battery
may not be able to start vehicle even at 80% charged position.
In general when your car is new then you can buy any battery and don’t
worry about anything but when your get older always buy a high quality battery,
as resistance of older wires may get increased which may leads to lower
starting current. So we have also seen that during starting current is very
high approx. 100 A so it is always advisable to use strong leads capable of
taking that 100A load.
