This document contains FAQs (Frequently Asked Questions) on solar inverters. The reader will get a very good idea about solar inverters, the different types, and where they are used.
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FAQs on Solar Inverters
Q. What is an inverter?
A. An inverter is a device which a DC (Direct Current) input and produces an AC
(Alternating Current) output.
More often than not, the DC input is taken from a battery. However it can also be
from solar PV modules in the case of solar applications.
The AC output is for running household appliances like tubes, fans, air
conditioners, refrigerators, TVs, computers, etc. and also for industrial
appliances.
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FAQs on Solar Inverters
Q. Why is an inverter so called?
A. The inverter has got its name from a commutator which originally were large
rotating electromechanical devices. They combined a synchronous ac motor with
a commutator so that the commutator reversed its connections to the ac line
exactly twice per cycle resulting in “AC-in DC-out”. However, if one inverted
the connections to a converter, one could put DC in and get AC out. Hence an
inverter was an “inverted” converter and that is how it got its name.
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FAQs on Solar Inverters
Q. What are the two types of inverters?
A. The two main types of inverters are: pure sine wave inverters and modified sine wave
inverters.
Pure sine wave inverters, as their name suggests, produce a pure sine wave output which is
identical to the power that we get from the grid. Many household appliances like digital clocks,
battery chargers, light dimmers, variable speed motors, and audio/visual equipment require a pure
sine wave, and therefore it is advisable to power them with pure sine wave inverters. If you do
that, it will ensure that all these “sensitive” loads will work properly and last a long time.
Modified sine wave inverters, as their name suggests, do not produce a pure sine wave output;
their output is a “stepped wave” which is obviously not as smooth as a pure sine wave. They
achieve voltage regulation by varying the pulse width according to the battery voltage and the
load. The stepped wave output is not good for “sensitive” loads and can damage them. It also
causes a buzzing sound in stereos and ceiling fans. However, modified sine wave inverters should
not be underestimated; they are highly capable and by narrowing the waveform they save energy
when running only small loads, as happens during most of the day in a typical home. Modified
sine wave inverters were successful at one point, and still are to a large extent. However, more
and more companies are not coming out with only pure sine wave inverters as the incremental
cost to produce pure sine wave inverters reduces with advances in technology.
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FAQs on Solar Inverters
Q. What is a solar inverter?
A. A solar inverter is a device that converts the (constantly varying) DC output of
a solar PV module – the input to the solar inverter – into AC. A solar inverter is a
necessary part of a solar PV installation or a solar PV power plant.
Q. What are the types of solar inverters?
A. There are three main types of solar inverters: off-grid solar inverters, grid-tied
solar inverters, and hybrid solar inverters.
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FAQs on Solar Inverters
Q. What are off-grid solar inverters?
A. Off-grid solar inverters, as their name suggests, work “off the grid”, which means that they are
not connected to the grid. Off-grid solar inverters are also called standalone solar inverters.
Q. Where are off-grid solar inverters used?
Off-grid solar inverters are used in places where the grid is either unavailable or is very
unreliable. Examples of good applications of off-grid solar inverters are farmhouses, telecom
towers at remote locations, or street lights at remote locations.
One other very important application is local, smart, mini-grids in rural areas for the purpose of
electrification. There are many villages in rural India where the grid is not available. Such villages
can be electrified using self-contained mini-grids. Off-grid solar inverters play a very important
part in this application.
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FAQs on Solar Inverters
Q. What are grid-tied solar inverters?
A. Grid-tied solar inverters, as their name suggests, are those that are connected or “tied” to the
grid.
Q. Where are grid-tied solar inverters used?
A. Grid-tied solar inverters are used in places where the grid is fairly stable. So big cities and
urban areas is where grid-tied solar inverters will be used.
In the case of residential properties, most of the electricity will be fed into the grid since
residential properties do not consume a whole lot of energy during the sunshine hours.
In the case of commercial properties, a lot of electricity is required during the day for powering
lights, fans, A/Cs, computers, etc. Therefore, most of the generated electricity will be used for
self-consumption, and only very little will be fed into the grid, if at all.
Utility-scale solar PV power plants are special in the sense that they could be (and in all
probability are) located in remote areas but feed electricity into the grid. A transmission line is
constructed from the solar PV power plant to the nearest sub-station to feed electricity into the
grid.
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FAQs on Solar Inverters
Q. What are hybrid solar inverters?
A. Hybrid solar inverters, as their name suggests, are those that can work in grid-
tied mode when the grid is available, and in off-grid mode when the grid is
unavailable.
Q. Where are hybrid solar inverters used?
A. Hybrid solar inverters are used in places where the grid is unreliable. Many
Tier-II and Tier-III cities in India have an unreliable grid, and that is where
hybrid solar inverters will be very useful.
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FAQs on Solar Inverters
Q. What are the capacities of off-grid solar inverters?
A. Typically, off-grid solar inverters in come small capacities, say 1
kW to 20 kW. The main reason for this is that solar PV is still quite
expensive. So nobody goes for big off-grid solar PV systems. When
the requirement is high, people usually rely on the grid for electricity.
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FAQs on Solar Inverters
Q. What are the capacities of grid-tied solar inverters?
A. Grid-tied solar inverters come in all capacities, from 1 kW all the
way up to 1 MW and even more. The smaller capacity inverters are
called string inverters, while the larger capacity inverters are called
central inverters. String inverters in small rooftop installations, while
central inverters are used in large rooftop installations and in utility-
scale solar PV power plants.
