Development and History of the component that made electricity first
and Generators convert mechanical rotation into electric power.
- a device that makes direct current electric power using electromagnetism.
It is also known as a generator, however the term generator normally
refers to an "alternator" which creates AC power.
- normally this term is used to describe an alternator which
creates AC power using electromagnetism.
Dynamos, and Batteries are the three tools necessary to create/store
substantial amounts of electricity for human use. Batteries
may have been discovered as early as 248 BC. They simply use chemical
reaction to make and store electricity. Scientists experimented with
the battery to invent the early incandescent lamp, electric motors and
trains, and scientific tests. However batteries were not reliable or
cost effective for any regular electrical use, it was the dynamo that
radically changed electricity from a curiosity into a profitable, reliable
First you need
a mechanical power source like a turbine(powered by water falling),
wind turbine, gas turbine or steam turbine. A shaft from one of these
devices is connected to a generator to make power.
generators work using the wild complex phenomena of electromagnetism.
Understanding the behavior of electromagnetism, its fields and its effects
is a large subject of study. There is a reason why it took 60 years
AFTER Volta's first battery to get a good powerful dynamo working.
We will keep things simple
to help introduce you to the interesting subject of power generation.
In the most
basic sense a generator/dynamo is one magnet rotating while inside
the influence of another magnet's magnetic field. You cannot see a magnetic
field, but it is often illustrated using lines of flux. In the illustration
above lines of magnetic flux would follow the lines created by the iron
is made up of stationary magnets (stator) which create a powerful magnetic
field, and a rotating magnet (rotor) which distorts and cuts through
the magnetic lines of flux of the stator. When the rotor cuts through
lines of magnetic flux it makes electricity.
Due to Faraday's
Law of Induction if you take a wire and move it back and forth in a
magnetic field, the field pushes on electrons in the metal. Copper has
27 electrons, the last two in the orbit are easily pushed on to the
next atom. This movement of electrons is electrical flow.
See the video
below showing how current is induced in a wire:
If you take
a lot of wire such as in a coil and move it in the field, you create
a more powerful "flow" of electrons. The strength of your
generator depends on:
of the conductor in the magnetic field
"v"-Velocity of the conductor (speed of the rotor)
"B"-Strength of the electromagnetic field
You can do calculations
using this formula: e = B x l x v
See the video
to see all of this demonstrated:
a simple electromagnet referred to as a solenoid. The term "solenoid"
actually describes the tubular shape created by the coiled wire.
are usually not made of natural magnetite or a permanent
magnet (unless it is a small generator), but they are copper or
aluminum wire coiled around an iron core. Each coil must be energized
with some power to make it into a magnet. This coil around iron is called
a solenoid. Solenoids are used instead of natural magnetite because
the solenoid is MUCH more powerful. A small solenoid can create a very
strong magnetic field.
The coils of wire in the generators must be insulated. Generator failure
is caused by temperatures rising too high which results in a breakdown
of insulation and a short between to parallel wires.
Terms: Electromagnetism - study of forces that
happen between electrically charged particles Rotor - part of the generator of dynamo that rotates Armature - same as a rotor Flux - the lines of strength in a magnetic field, it is
measured in density, SI unit of weber Stator - magnets in a generator/dynamo that do not move,
they establish the stationary magnetic field Solenoid - a magnet created by a wire coil around an iron/ferris
core (solenoid technically means the shape of this magnet, but
engineers refer to solenoid and electromagnet interchangeably. Commutator - Learn more detail about them here Torque
- force in a rotational motion
is an older term used to describe a generator that makes direct current
power. DC power sends electrons in only one direction. The problem
with a simple generator is that when the rotor rotates it eventually
turns completely around, reversing the current. Early inventors didn't
know what to do with this alternating current, alternating current is
more complex to control and design motors and lights for. Early inventors
had to figure a way to only capture the positive energy of the generator,
so they invented a commutator. The commutator is a switch that allows
current to only flow in one direction.
the video below to see how the commutator works:
The Dynamo consists of 3 major components: the stator, the armature,
and the commutator.
Brushes are part of
the commutator, the brushes must conduct electricity as the keep
contact with the rotating armature. The first brushes were actual
wire "brushes" made of small wires. These wore out easily
and they developed graphic blocks to do the same job.
statoris a fixed structure that makes magnetic
field, you can do this in a small dynamo using a permanent magnet.
Large dynamos require an electromagnet.
The armature is made of coiled copper windings which
rotate inside the magnetic field made by the stator. When the
windings move, they cut through the lines of magnetic field. This
creates pulses of electric power.
is needed to produce direct current. In direct current power flows
in only one direction through a wire, the problem is that the
rotating armature in a dynamo reverses current each half turn,
so the commutator is a rotary switch that disconnects the power
during the reversed current part of the cycle.
Since the magnets in an dynamo
are solenoids, they must be powered to work. So in addition to brushes
which tap power to go out to the main circuit, there is another set
of brushes to take power from from the armature to power the stator's
magnets. That's fine if the dynamo is running, but how do you start
a dynamo if you have no power to start?
Sometimes the armature retains
some magnetism in the iron core, and and when it begins to turn it makes
a small amount of power, enough to excite the solenoids in the stator.
Voltage then begins to rise until the dynamo is at full power.
If there is no magnetism
left in the armature's iron, than often a battery is used to excite
the solenoids in the dynamo to get it started. This is called "field
Below in the discussion of
wiring the dynamo you will notice how power is routed through the solenoids
video of a small simple dynamo similar to the diagrams above (built
in the 1890s):
differs from the dynamo in that it produces AC power. Electrons
flow in in both directions in AC power. It wasn't until the 1890s that
engineers had figured out how to design powerful motors, transformers
and other devices which could use AC power in a way that could compete
with DC power.
While the alternator
uses commutators, the generator uses a slip ring with brushes to tap
the power off of the rotor. Attached to the slip ring are graphite or
carbon "brushes" which are spring loaded to push the brush
onto the ring. This keeps power consistently flowing. Brushes get worn
down over time and need to be replaced.
of slip rings and brushes, many examples from old to new:
the time of Gramme in the 1860s it was figured out that the best way
to build a dynamo/generator was to arrange magnetic coils around a wide
circle, with a wide spinning armature. This looks different than the
simple small dynamo examples you see used in teaching how the devices
In the photo
below you will see clearly one coil on the armature (the rest were removed
for servicing) and other coils built into the stator.
From the 1890s until today
3 phase AC power has been the standard form of power. Three phases is
made through the design of the generator.
To make a three phase generator
you have to place a certain number of magnets on your stator and armature,
all with proper spacing. Electromagnetism is as complex as dealing with
waves and water, so you need to know how to control the field through
your design. Problems include having your magnet unevenly attracted
to the iron core, improper calculations of the distortion of the magnetic
field (the faster it spins, the more the field is distorted), spurious
resistance in the armature coils, and a myriad of other potential problems.
generator evolved from work by Michael Faraday and Joseph
Henry in the 1820s. Once these two inventors discovered and documented
the phenomena of electromagnetic induction, it lead to experimentation
by others in both Europe and North America.
Hippolyte Pixii (France) built the first dynamo using a commutator,
his model created pulses of electricity separated by no current. He
also by accident created the first alternator. He did not know what
to do with the changing current, he concentrated on trying to eliminate
the alternating current to get DC power, this led him to create the
1830s-1860s - The battery is still the most powerful way to supply
electricity for the various experimentation going on in that period.
Electricity was still not commercially viable. A battery powered electric
train from Washington DC to Baltimore failed, proving a gross embarrassment
to the new field of electricity. After millions of dollars wasted steam
still proved to be a better power source. Electricity still needed to
prove to be reliable and commercially viable.
1860 - Antonio Pacinotti- Created a dynamo that provided continuous
1867 - Werner Von Siemens and Charles Wheatstone create a more
powerful, more useful dynamo which used a self powered electromagnet
in the stator instead of the weak permanent magnet.
1871 - Zenobe Gramme sparked the
commercial revolution of electricity. He filled the magnetic field with
an iron core which made a better path for magnetic flux. This increased
the power of the dynamo to the point were it was usable for many commercial
1870s - There was an explosion of new designs in dynamos, designs
ranged a wild assortment, only a few stood out as being superior in
1876 - Charles F. Brush
(Ohio) developed the most efficient and reliable dynamo design ever
to that point. His inventions was sold through the Telegraph Supply
1877 - The Franklin
Institute (Philadelphia) conducts test on dynamos from around the world.
Publicity from this event spurs development by others like Elihu
Thomson, Lord Kelvin, and Thomas
Edison's Long Legged Mary, a commercially successful dynamo for
his DC systems 1884
1878 - The
Ganz Company begins to use AC generators in small commercial
installations in Budapest.
1880 - Charles
F. Brush had over 5000 arc lights in operation, representing
80 percent of all lamps world wide. The economic power of electrical
age had begun.
- Alternating Current systems develop in Europe with Siemens,
Sabastian Ferranti, Lucien Gaulard, and others. DC dynamos reign
supreme in the lucrative American market, many are skeptical
to invest in AC. AC generators were powerful, however the generator
alone was not the biggest problem. Systems for control and distribution
of AC power needed to be improved before it could compete with
DC on a market.
1886 - In
the North American Market inventors like William
Stanley, George Westinghouse, Nikola Tesla, and Elihu
Thomson develop their own AC
systems and generator designs. Most of them used Siemens
and Ferranti generators as their basis of study. William Stanley
was quickly able to invent a better generator after being unsatisfied
with the Siemens generator he used in his first
Siemens AC generators used in London in 1885, in the US Edison was reluctant
to jump into the AC power field while in Europe the technology was developing
1886-1891 - Polyphase
AC generators are developed by C.S. Bradly (US), August Haselwander
(Germany), Mikhail Dolivo-Dobrovsky (Germany/Russia), Galileo Ferraris
(Italy), and others. AC systems which include better control and powerful
electric motors allow AC to compete.
generator designed by Mikhail Dolivo-Dobrovsky used at the exhibition
is seen at left.
1892 - Charles P. Steinmetz
presents his paper to the AIEE on hysteresis. Steinmetz's understanding
of the mathematics of AC power is published and helps revolutionize
AC power system design, including large AC Generators.
1890s - Generator
design is improved rapidly thanks to commercial sales and
available money for research. Westinghouse, Siemens, Oerlikon,
and General Electric develop the world's most powerful generators.
Some generators still operate 115
years later. (Mechanicville, NY)
1894 Elihu Thomson developed many
AC generators for General Electric
A later Westinghouse 2000 kW 270 Volt generator from after
Generators with history explained (1897), designed by AC mastermind
Charles P. Steinmetz
Generator being constructed and tested (1905), designed by Oliver Shallenberger,
Tesla and others at Westinghouse.
powerful generators used at Folsom, CA (designed by Elihu Thompson,
Dr. Louis Bell, and others at GE)
produced by Oerlikon for the International Electro-technical Exhibition
(designed by Dobrovolsky in Germany)
General Electric Story - by The Hall of History, Schenectady, NY
1989 Second Edition
-Wikipedia (Generators, Charles Brush)
-Principals of Electricity - by General Electric
-History of AC Power - Edison Tech Center
-Hawkins Electrical Guide
/ Video: -Copyright 2011 The Edison Tech Center.
Shot on location at the Deutsches Museum, Munich
-Some generators photographed at the Edison Tech Center, Schenectady,
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