When one talks about the basic necessities of life, primarily three
commodities come to mind - food (including water), shelter and clothing.
However, a modern definition of the basic necessities would see a new entrant,
perhaps, a continuous electricity supply to power one’s home.
Not just on a personalized scale, availability of continuous electricity
propels the prosperity and growth of a nation and has a direct impact on the
performance of states as industrial development requires continuous and
reliable power supply that helps in enhancing the scale of production.
Apparently, one often finds oneself out of luck when a power outage occurs in
one’s locality, and the issue becomes all the way more accentuated in the
sweltering humid summer months.
Now, some might debate on the fact that
they reside in one of the metropolitan cities where power outage is a term
unheard of. However, what they might not be taking into account are the
occurrences such as power grid maintenance, torrential rains, dust storms,
earthquakes and other unforeseen instances that might dilapidate the power
lines which might take several days to repair.
Under such circumstances what alternative does one have to resurrect the
optimal standards of living?
Perhaps, a ‘power inverter’, or more commonly inverter.
You might be glad to know that my father works at a company that manufactures
home appliances like water geysers, power inverters, voltage stabilizers, fans
etc. So, at home, we frequently have a conversation about these appliances,
what goes into making them, how some brands try to cut manufacturing costs to
increase their profit margin etc.
Today, I will try my best to pass on the knowledge that I have acquired from my
father over the years, to you so as to help you make a good buying
decision.
So without further a do, let’s begin…
THE BASICS
All the electronic appliances in one’s home require electric current to
operate, and electric current is produced by flowing electrons. In India, the
supply of voltage that one receives in one’s home from the power grid is
a 220–240 volt AC. For different countries, the supply voltage might
be different. Most of the electronic appliances in one’s home are designed to
operate on alternating current (AC). However, in times of power outages, the
power grid doesn’t provide voltage to make the electrons flow in order to
produce electric current. This is when the second type of voltage supply called
as DC supply, majorly produced by batteries and photovoltaic cells comes into
play.
A major drawback of DC power is that it can not be used to power electronic
appliances, therefore, to power the appliances by the means of a DC supply, a
need to convert DC power into AC arises, and the device that converts DC power
produced by batteries into AC is called as inverter. It is used to
produce an uninterrupted 220–240V AC supply in the absence of supply from
mains.
In case of battery powered inverters, DC power is produced by the means of a
chemical reaction that occurs in the battery, whereas, when solar inverters are
placed in consideration, sunlight falling on the photovoltaic cells (arranged
in rectangular panels) is harnessed by the semiconductor layers of photovoltaic
cells. Semiconductor layers, usually made of silicon absorb sunlight, and this
light energy sets loose the electrons in the silicon, hence DC power is
generated.
(Image of a solar inverter setup depicting solar panels, DC batteries
for alternate power backup and a solar inverter)
Now, having learnt the basics of how an inverter works, let us now proceed to
discuss the various factors that help determine the specifications of the
inverter and its battery that would accommodate one’s energy requirements:-
- Power requirement of various
appliances
This is one of the most crucial factors that heavily influences the
Volt-Ampere (VA) rating one should opt an inverter with. Power requirement is the sum
total of the individual power consumption of all the electronic
appliances one wishes to operate on the inverter in times of outages.
Typically, the most essential appliances such as few fans and lights, a
refrigerator and a television are a few devices one would require running at
all times.
Now, for illustration, we would keep into consideration these few devices that
one would require to be in constant operation even in times of power outages
and we would analyse the sum total of power consumption and correspondingly
determine the VA rating one should aim to choose an inverter with -
4 Ceiling Fans - 75W x 4 = 300W
5 Fluorescent Tube - 50W x 5 = 250W
1 Double Door (3 Star Energy Rating) Refrigerator - 175W (approx.)
1 LED television (42 inches) - 75W (approx.)
Total power consumption = 300 + 250 + 175 + 75 = 800W
Now, if inverters, or any electronic appliance for that matter, operated on
100% efficiency then power supplied by the source and power consumed by the
appliances would be equal. However, in reality 100% efficiency does not exist,
primarily due to heat losses, and thus inverters operate on about 75–80%
efficiency. An extension to the efficiency of an electrical appliance is a term
called power factor and is the ratio of power required by an appliance to
operate to the power supplied in the circuit.
Thus corresponding to 80% efficiency, the power factor would be
approximately 0.8. The final Volt-Ampere (VA) rating one should consider buying
an inverter with is found by dividing the Total Power Consumed by the Power
Factor.
In our illustration, total power consumption is 800W, thus, dividing it by 0.8
would yield 1000VA. Therefore, the optimal inverter to pick for such kind of
load requirement would be the one that has rating of at least 1100 VA.
Now, depending upon the requirement and usage, one can run large appliances
such as air conditioners and water geysers on inverter power as well, by
deciding on an inverter that has a significantly higher Volt-Ampere (VA)
rating.
- Types of inverter technologies
Inverters are primarily classified into two types based on the output
characteristic - Pure Sine Wave and Square Wave
Pure Sine wave inverter technology delivers output voltage waveform
that is a complete replica of sine wave, and since in most cases, voltage
supply from the power companies has the waveform of a pure sine wave as well,
the appliances operating on pure sine wave inverters run with higher
efficiency, produce lesser heat and noise and chances of crashes in gadgets
like computers and occurrences of glitches/noise in display screens such as
televisions and monitors are almost nil.
Square Wave inverter technology does a satisfactory job running
appliances such as fluorescent tubes and fans, however, when it comes to
powering sophisticated devices such as laptops, electric motors, refrigerators,
microwave ovens, televisions etc. the square wave inverter technology is not as
efficient as pure sine wave one. Though, using a square wave inverter for
powering the above stated appliances would not necessarily damage them, one
might experience the devices getting warmer than usual which indicates
efficiency loss is higher in case of square wave inverters than their pure sine
wave counterparts. In some cases, when operating appliances like televisions
and refrigerators on square wave inverter, one might encounter audible
buzz/noise.
(Waveforms of Pure Sine Wave and Square Wave Inverters)
- Battery capacity
Battery backup is one of the pivotal aspects of owning an inverter. The
time period for which a battery can provide power to the electronic appliances
in absence of power outages depends on three factors - battery capacity,
voltage of the battery and total power consumption.
Majority of the inverter batteries have a nominal voltage rating of 12V. Now,
to illustrate, we would consider the power consumption of 800 W which we
calculated before. Typically, power outages can last from about few minutes to
several hours, and again, this depends highly on the locality as well.
Therefore, for proceeding with the analysis, we would assume that a typical
power outage lasts for approximately 4 hours.
So, to calculate what capacity of battery one would require under the given
circumstances, there is a rule of thumb -
(Power consumption) x (Battery backup) / (Voltage of the battery)
i.e. (800W x 4 hours) / 12 volts = 266.67 Ampere-hours
For the considered power consumption and duration of power outage, a 266.67
Ah battery would be required, which can be easily constructed by connecting two
150 Ah batteries in parallel.
For various power consumption requirements, batteries of numerous Ampere-hour
ratings are available in the market. Depending upon requirement, one may use
the battery individually or connect two or more of them in parallel to increase
the power backup times.
Now, having examined the several factors that assist in determining the
specifications of the inverter and its battery, let us proceed to understanding
the ways in which some manufacturers (names not taken) try to cut manufacturing
costs in order to maximize their own profits and in turn deliver a sub-standard product
to the customers, the components of which have a very short shelf life and may
require frequent repairs/replacements.
COST CUTTING TECHNIQUES
- Low-grade cooling fan. As discussed previously,
electronic appliances do not operate on 100% efficiency. Most appliances
function at 80% efficiency, the remaining 20% is lost to heat. In case of
inverters, a high quality and potent fan is required to keep the inverter
circuitry from overheating and keep functioning at optimal temperature.
Unfortunately, most buyers do not pay attention to the cooling fan
deployed in the inverter, and this gives some manufacturers a perfect
opportunity to increase their profit margin and make use of an inferior
cooling fan that is very inept in keeping the temperatures within the
inverter casing in permissible range. As a result, over a period of few
months, the excessive heat causes the components of the inverter to
malfunction and finally melt, causing the entire unit to be
non-operational. Cost of repairing the inverter might range from a few
hundred bucks to more than a thousand bucks and this process is recurring.
- Overstated Voltage-Ampere rating. In order to reduce manufacturing costs further, some manufacturers resort to exaggerating the VA capacity of the inverters they manufacture so as to lure innocent customers. However, obtaining near absolute power output from the inverter requires use of high quality components that have near ideal resistance and impedance, which again add to the initial cost. So, in order to keep the initial cost of the product low so as to attract buyers, those manufacturers make use of components that have higher impedance values which leads to loss of efficiency to heat. As a result of which, the inverter tends to beep continuously, displaying overload warning and trips just when the load reaches slightly higher than 65-70% of the stated Volt-Ampere rating.
Note: In our constant endeavour to
assist you in making an informed buying decision, we test the new launches of
the products on multiple parameters, and if they stand tall in our analysis we
periodically add them to the below mentioned list of our recommended products.
So, if you plan to make the purchase at a later time, you may visit the links
once again at the very time of buying to ensure that the purchase turns out to
be a very fruitful one.
Inverter
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