<s>
A	O
dynamo	B-Library
is	O
an	O
electrical	O
generator	O
that	O
creates	O
direct	O
current	O
using	O
a	O
commutator	O
.	O
</s>
<s>
Dynamos	B-Library
were	O
the	O
first	O
electrical	O
generators	O
capable	O
of	O
delivering	O
power	O
for	O
industry	O
,	O
and	O
the	O
foundation	O
upon	O
which	O
many	O
other	O
later	O
electric-power	O
conversion	O
devices	O
were	O
based	O
,	O
including	O
the	O
electric	O
motor	O
,	O
the	O
alternating-current	O
alternator	B-Algorithm
,	O
and	O
the	O
rotary	O
converter	O
.	O
</s>
<s>
Today	O
,	O
the	O
simpler	O
alternator	B-Algorithm
dominates	O
large	O
scale	O
power	O
generation	O
,	O
for	O
efficiency	O
,	O
reliability	O
and	O
cost	O
reasons	O
.	O
</s>
<s>
A	O
dynamo	B-Library
has	O
the	O
disadvantages	O
of	O
a	O
mechanical	O
commutator	O
.	O
</s>
<s>
Also	O
,	O
converting	O
alternating	O
to	O
direct	O
current	O
using	O
rectifiers	B-Algorithm
(	O
such	O
as	O
vacuum	O
tubes	O
or	O
more	O
recently	O
via	O
solid	O
state	O
technology	O
)	O
is	O
effective	O
and	O
usually	O
economical	O
.	O
</s>
<s>
[ [ 	O
file:Faraday	O
disk	O
generator.jpg	O
|thumb|The	O
Faraday	B-Algorithm
disk	I-Algorithm
was	O
the	O
first	O
electric	O
generator	O
.	O
</s>
<s>
He	O
also	O
built	O
the	O
first	O
electromagnetic	O
generator	O
,	O
called	O
the	O
Faraday	B-Algorithm
disk	I-Algorithm
,	O
a	O
type	O
of	O
homopolar	B-Algorithm
generator	I-Algorithm
,	O
using	O
a	O
copper	O
disc	O
rotating	O
between	O
the	O
poles	O
of	O
a	O
horseshoe	O
magnet	O
.	O
</s>
<s>
This	O
was	O
not	O
a	O
dynamo	B-Library
in	O
the	O
current	O
sense	O
,	O
because	O
it	O
did	O
not	O
use	O
a	O
commutator	O
.	O
</s>
<s>
Later	O
homopolar	B-Algorithm
generators	I-Algorithm
would	O
solve	O
this	O
problem	O
by	O
using	O
an	O
array	O
of	O
magnets	O
arranged	O
around	O
the	O
disc	O
perimeter	O
to	O
maintain	O
a	O
steady	O
field	O
effect	O
in	O
one	O
current-flow	O
direction	O
.	O
</s>
<s>
thumb|200px|right|Hippolyte	O
Pixii	O
's	O
dynamo	B-Library
.	O
</s>
<s>
The	O
first	O
commutated	O
dynamo	B-Library
was	O
built	O
in	O
1832	O
by	O
Hippolyte	O
Pixii	O
,	O
a	O
French	O
instrument	O
maker	O
.	O
</s>
<s>
About	O
1856	O
he	O
formulated	O
the	O
concept	O
of	O
the	O
dynamo	B-Library
about	O
six	O
years	O
before	O
Siemens	O
and	O
Wheatstone	O
but	O
did	O
not	O
patent	O
it	O
as	O
he	O
thought	O
he	O
was	O
not	O
the	O
first	O
to	O
realize	O
this	O
.	O
</s>
<s>
His	O
dynamo	B-Library
used	O
,	O
instead	O
of	O
permanent	O
magnets	O
,	O
two	O
electromagnets	O
placed	O
opposite	O
to	O
each	O
other	O
to	O
induce	O
the	O
magnetic	O
field	O
around	O
the	O
rotor	O
.	O
</s>
<s>
It	O
was	O
also	O
the	O
discovery	O
of	O
the	O
principle	O
of	O
dynamo	B-Library
self-excitation	B-Algorithm
,	O
which	O
replaced	O
permanent	O
magnet	O
designs	O
.	O
</s>
<s>
The	O
dynamo	B-Library
was	O
the	O
first	O
electrical	O
generator	O
capable	O
of	O
delivering	O
power	O
for	O
industry	O
.	O
</s>
<s>
The	O
modern	O
dynamo	B-Library
,	O
fit	O
for	O
use	O
in	O
industrial	O
applications	O
,	O
was	O
invented	O
independently	O
by	O
Sir	O
Charles	O
Wheatstone	O
,	O
Werner	O
von	O
Siemens	O
and	O
Samuel	O
Alfred	O
Varley	O
.	O
</s>
<s>
The	O
"	O
dynamo-electric	B-Library
machine	I-Library
"	O
employed	O
self-powering	O
electromagnetic	O
field	O
coils	O
rather	O
than	O
permanent	O
magnets	O
to	O
create	O
the	O
stator	O
field	O
.	O
</s>
<s>
The	O
use	O
of	O
electromagnets	O
rather	O
than	O
permanent	O
magnets	O
greatly	O
increased	O
the	O
power	O
output	O
of	O
a	O
dynamo	B-Library
and	O
enabled	O
high	O
power	O
generation	O
for	O
the	O
first	O
time	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
1870s	O
Siemens	O
used	O
electromagnetic	O
dynamos	B-Library
to	O
power	O
electric	O
arc	O
furnaces	O
for	O
the	O
production	O
of	O
metals	O
and	O
other	O
materials	O
.	O
</s>
<s>
The	O
dynamo	B-Library
machine	O
that	O
was	O
developed	O
consisted	O
of	O
a	O
stationary	O
structure	O
,	O
which	O
provides	O
the	O
magnetic	O
field	O
,	O
and	O
a	O
set	O
of	O
rotating	O
windings	O
which	O
turn	O
within	O
that	O
field	O
.	O
</s>
<s>
The	O
Gramme	B-Algorithm
dynamo	I-Algorithm
was	O
one	O
of	O
the	O
first	O
machines	O
to	O
generate	O
commercial	O
quantities	O
of	O
power	O
for	O
industry.Fink	O
,	O
Donald	O
G	O
.	O
and	O
H	O
.	O
Wayne	O
Beaty	O
(	O
2007	O
)	O
,	O
Standard	O
Handbook	O
for	O
Electrical	O
Engineers	O
,	O
Fifteenth	O
Edition	O
.	O
</s>
<s>
Further	O
improvements	O
were	O
made	O
on	O
the	O
Gramme	B-Algorithm
ring	I-Algorithm
,	O
but	O
the	O
basic	O
concept	O
of	O
a	O
spinning	O
endless	O
loop	O
of	O
wire	O
remains	O
at	O
the	O
heart	O
of	O
all	O
modern	O
dynamos	B-Library
.	O
</s>
<s>
Thompson	O
,	O
Sylvanus	O
P	O
.	O
(	O
1888	O
)	O
,	O
Dynamo-electric	O
machinery	O
:	O
a	O
manual	O
for	O
students	O
of	O
electrotechnics	O
.	O
</s>
<s>
Charles	O
F	O
.	O
Brush	O
assembled	O
his	O
first	O
dynamo	B-Library
in	O
the	O
summer	O
of	O
1876	O
using	O
a	O
horse-drawn	O
treadmill	O
to	O
power	O
it	O
.	O
</s>
<s>
Brush	O
's	O
design	O
modified	O
the	O
Gramme	B-Algorithm
dynamo	I-Algorithm
by	O
shaping	O
the	O
ring	B-Algorithm
armature	I-Algorithm
like	O
a	O
disc	O
rather	O
than	O
a	O
cylinder	O
shape	O
.	O
</s>
<s>
After	O
dynamos	B-Library
and	O
motors	O
were	O
found	O
to	O
allow	O
easy	O
conversion	O
back	O
and	O
forth	O
between	O
mechanical	O
or	O
electrical	O
power	O
,	O
they	O
were	O
combined	O
in	O
devices	O
called	O
rotary	O
converters	O
,	O
rotating	O
machines	O
whose	O
purpose	O
was	O
not	O
to	O
provide	O
mechanical	O
power	O
to	O
loads	O
but	O
to	O
convert	O
one	O
type	O
of	O
electric	O
current	O
into	O
another	O
,	O
for	O
example	O
DC	O
into	O
AC	O
.	O
</s>
<s>
The	O
technology	O
of	O
rotary	O
converters	O
was	O
replaced	O
in	O
the	O
early	O
20th	O
century	O
by	O
mercury-vapor	O
rectifiers	B-Algorithm
,	O
which	O
were	O
smaller	O
,	O
did	O
not	O
produce	O
vibration	O
and	O
noise	O
,	O
and	O
required	O
less	O
maintenance	O
.	O
</s>
<s>
thumb|upright	O
=	O
1.3	O
|Low	O
voltage	O
dynamo	B-Library
for	O
electroplating	O
from	O
the	O
turn	O
of	O
the	O
century	O
.	O
</s>
<s>
Direct	O
current	O
machines	O
like	O
dynamos	B-Library
and	O
commutated	O
DC	O
motors	O
have	O
higher	O
maintenance	O
costs	O
and	O
power	O
limitations	O
than	O
alternating	O
current	O
(	O
AC	O
)	O
machines	O
due	O
to	O
their	O
use	O
of	O
the	O
commutator	O
.	O
</s>
<s>
The	O
sliding	O
friction	O
between	O
the	O
brushes	O
and	O
commutator	O
consumes	O
power	O
,	O
which	O
can	O
be	O
significant	O
in	O
a	O
low	O
power	O
dynamo	B-Library
.	O
</s>
<s>
This	O
may	O
be	O
several	O
volts	O
,	O
so	O
it	O
can	O
cause	O
large	O
power	O
losses	O
in	O
low	O
voltage	O
,	O
high	O
current	O
machines	O
(	O
see	O
the	O
huge	O
commutator	O
of	O
the	O
7	O
volt	O
electroplating	O
dynamo	B-Library
in	O
the	O
adjacent	O
picture	O
)	O
.	O
</s>
<s>
Although	O
direct	O
current	O
dynamos	B-Library
were	O
the	O
first	O
source	O
of	O
electric	O
power	O
for	O
industry	O
,	O
they	O
had	O
to	O
be	O
located	O
close	O
to	O
the	O
factories	O
that	O
used	O
their	O
power	O
.	O
</s>
<s>
Electricity	O
could	O
only	O
be	O
distributed	O
over	O
distances	O
economically	O
as	O
alternating	O
current	O
(	O
AC	O
)	O
,	O
through	O
the	O
use	O
of	O
the	O
transformer	B-Algorithm
.	O
</s>
<s>
With	O
the	O
1890s	O
conversion	O
of	O
electric	O
power	O
systems	O
to	O
alternating	O
current	O
,	O
during	O
the	O
20th	O
century	O
dynamos	B-Library
were	O
replaced	O
by	O
alternators	B-Algorithm
,	O
and	O
are	O
now	O
almost	O
obsolete	O
.	O
</s>
<s>
The	O
word	O
'	O
dynamo	B-Library
 '	O
(	O
from	O
the	O
Greek	O
word	O
dynamis	O
( δύναμις	O
)	O
,	O
meaning	O
force	O
or	O
power	O
)	O
was	O
originally	O
another	O
name	O
for	O
an	O
electrical	O
generator	O
,	O
and	O
still	O
has	O
some	O
regional	O
usage	O
as	O
a	O
replacement	O
for	O
the	O
word	O
generator	O
.	O
</s>
<s>
The	O
original	O
"	O
dynamo	B-Library
principle	O
"	O
of	O
Werner	O
von	O
Siemens	O
referred	O
only	O
to	O
the	O
direct	O
current	O
generators	O
which	O
use	O
exclusively	O
the	O
self-excitation	B-Algorithm
(	O
self-induction	O
)	O
principle	O
to	O
generate	O
DC	O
power	O
.	O
</s>
<s>
The	O
earlier	O
DC	O
generators	O
which	O
used	O
permanent	O
magnets	O
were	O
not	O
considered	O
"	O
dynamo	B-Library
electric	O
machines	O
"	O
.Volker	O
Leiste	O
:	O
1867	O
–	O
Fundamental	O
report	O
on	O
dynamo-electric	O
principle	O
before	O
the	O
Prussian	O
Academy	O
of	O
Sciences	O
siemens.com	O
The	O
invention	O
of	O
the	O
dynamo	B-Library
principle	O
(	O
self-induction	O
)	O
was	O
a	O
major	O
technological	O
leap	O
over	O
the	O
old	O
traditional	O
permanent	O
magnet	O
based	O
DC	O
generators	O
.	O
</s>
<s>
The	O
discovery	O
of	O
the	O
dynamo	B-Library
principle	O
made	O
industrial	O
scale	O
electric	O
power	O
generation	O
technically	O
and	O
economically	O
feasible	O
.	O
</s>
<s>
After	O
the	O
invention	O
of	O
the	O
alternator	B-Algorithm
and	O
that	O
alternating	O
current	O
can	O
be	O
used	O
as	O
a	O
power	O
supply	O
,	O
the	O
word	O
dynamo	B-Library
became	O
associated	O
exclusively	O
with	O
the	O
'	O
commutated	O
direct	O
current	O
electric	O
generator	O
 '	O
,	O
while	O
an	O
AC	O
electrical	O
generator	O
using	O
either	O
slip	O
rings	O
or	O
rotor	O
magnets	O
would	O
become	O
known	O
as	O
an	O
alternator	B-Algorithm
.	O
</s>
<s>
A	O
small	O
electrical	O
generator	O
built	O
into	O
the	O
hub	O
of	O
a	O
bicycle	O
wheel	O
to	O
power	O
lights	O
is	O
called	O
a	O
hub	O
dynamo	B-Library
,	O
although	O
these	O
are	O
invariably	O
AC	O
devices	O
,	O
and	O
are	O
actually	O
magnetos	B-Algorithm
.	O
</s>
<s>
The	O
electric	O
dynamo	B-Library
uses	O
rotating	O
coils	O
of	O
wire	O
and	O
magnetic	O
fields	O
to	O
convert	O
mechanical	O
rotation	O
into	O
a	O
pulsing	O
direct	O
electric	O
current	O
through	O
Faraday	O
's	O
law	O
of	O
induction	O
.	O
</s>
<s>
A	O
dynamo	B-Library
machine	O
consists	O
of	O
a	O
stationary	O
structure	O
,	O
called	O
the	O
stator	O
,	O
which	O
provides	O
a	O
constant	O
magnetic	O
field	O
,	O
and	O
a	O
set	O
of	O
rotating	O
windings	O
called	O
the	O
armature	O
which	O
turn	O
within	O
that	O
field	O
.	O
</s>
<s>
The	O
few	O
uses	O
for	O
electricity	O
,	O
such	O
as	O
electroplating	O
,	O
used	O
direct	O
current	O
provided	O
by	O
messy	O
liquid	O
batteries	B-Architecture
.	O
</s>
<s>
Dynamos	B-Library
were	O
invented	O
as	O
a	O
replacement	O
for	O
batteries	B-Architecture
.	O
</s>
<s>
The	O
earliest	O
dynamos	B-Library
used	O
permanent	O
magnets	O
to	O
create	O
the	O
magnetic	O
field	O
.	O
</s>
<s>
These	O
were	O
referred	O
to	O
as	O
"	O
magneto-electric	O
machines	O
"	O
or	O
magnetos	B-Algorithm
.	O
</s>
<s>
However	O
,	O
researchers	O
found	O
that	O
stronger	O
magnetic	O
fields	O
—	O
and	O
thus	O
more	O
power	O
—	O
could	O
be	O
produced	O
by	O
using	O
electromagnets	O
(	O
field	O
coils	O
)	O
on	O
the	O
stator.	O
,	O
translated	O
from	O
German	O
by	O
Nathaniel	O
Keith	O
These	O
were	O
called	O
"	O
dynamo-electric	B-Library
machines	I-Library
"	O
or	O
dynamos	B-Library
.	O
</s>
<s>
The	O
field	O
coils	O
of	O
the	O
stator	O
were	O
originally	O
separately	B-Algorithm
excited	I-Algorithm
by	O
a	O
separate	O
,	O
smaller	O
,	O
dynamo	B-Library
or	O
magneto	B-Algorithm
.	O
</s>
<s>
An	O
important	O
development	O
by	O
Wilde	O
and	O
Siemens	O
was	O
the	O
discovery	O
(	O
by	O
1866	O
)	O
that	O
a	O
dynamo	B-Library
could	O
also	O
bootstrap	B-Application
itself	O
to	O
be	O
self-excited	B-Algorithm
,	O
using	O
current	O
generated	O
by	O
the	O
dynamo	B-Library
itself	O
.	O
</s>
<s>
Self-excited	B-Algorithm
direct	O
current	O
dynamos	B-Library
commonly	O
have	O
a	O
combination	O
of	O
series	O
and	O
parallel	O
(	O
shunt	O
)	O
field	O
windings	O
,	O
which	O
are	O
directly	O
supplied	O
power	O
by	O
the	O
rotor	O
through	O
the	O
commutator	O
in	O
a	O
regenerative	O
manner	O
.	O
</s>
<s>
The	O
dynamo	B-Library
begins	O
rotating	O
while	O
not	O
connected	O
to	O
an	O
external	O
load	O
.	O
</s>
<s>
In	O
this	O
manner	O
,	O
the	O
self-exciting	O
dynamo	B-Library
builds	O
up	O
its	O
internal	O
magnetic	O
fields	O
until	O
it	O
reaches	O
its	O
normal	O
operating	O
voltage	O
.	O
</s>
<s>
A	O
self-excited	B-Algorithm
dynamo	B-Library
with	O
insufficient	O
residual	O
magnetic	O
field	O
in	O
the	O
metal	O
frame	O
will	O
not	O
be	O
able	O
to	O
produce	O
any	O
current	O
in	O
the	O
rotor	O
,	O
regardless	O
of	O
what	O
speed	O
the	O
rotor	O
spins	O
.	O
</s>
<s>
This	O
situation	O
can	O
also	O
occur	O
in	O
modern	O
self-excited	B-Algorithm
portable	O
generators	O
,	O
and	O
is	O
resolved	O
for	O
both	O
types	O
of	O
generators	O
in	O
a	O
similar	O
manner	O
,	O
by	O
applying	O
a	O
brief	O
direct	O
current	O
battery	O
charge	O
to	O
the	O
output	O
terminals	O
of	O
the	O
stopped	O
generator	O
.	O
</s>
<s>
Both	O
types	O
of	O
self-excited	B-Algorithm
generator	O
,	O
which	O
have	O
been	O
attached	O
to	O
a	O
large	O
external	O
load	O
while	O
it	O
was	O
stationary	O
,	O
will	O
not	O
be	O
able	O
to	O
build	O
up	O
voltage	O
even	O
if	O
the	O
residual	O
field	O
is	O
present	O
.	O
</s>
<s>
Dynamos	B-Library
,	O
usually	O
driven	O
by	O
steam	O
engines	O
,	O
were	O
widely	O
used	O
in	O
power	O
stations	O
to	O
generate	O
electricity	O
for	O
industrial	O
and	O
domestic	O
purposes	O
.	O
</s>
<s>
They	O
have	O
since	O
been	O
replaced	O
by	O
alternators	B-Algorithm
.	O
</s>
<s>
Large	O
industrial	O
dynamos	B-Library
with	O
series	O
and	O
parallel	O
(	O
shunt	O
)	O
windings	O
can	O
be	O
difficult	O
to	O
use	O
together	O
in	O
a	O
power	O
plant	O
,	O
unless	O
either	O
the	O
rotor	O
or	O
field	O
wiring	O
or	O
the	O
mechanical	O
drive	O
systems	O
are	O
coupled	O
together	O
in	O
certain	O
special	O
combinations	O
.	O
</s>
<s>
It	O
seems	O
theoretically	O
possible	O
to	O
run	O
dynamos	B-Library
in	O
parallel	O
to	O
create	O
induction	O
and	O
self	O
sustaining	O
system	O
for	O
electrical	O
power.Dynamo-Electric	O
Machinery	O
:	O
A	O
Manual	O
for	O
Students	O
of	O
Electrotechnics	O
,	O
by	O
Silvanus	O
P	O
.	O
Thompson	O
,	O
1901	O
,	O
8th	O
American	O
Edition	O
,	O
Ch	O
.	O
</s>
<s>
31	O
,	O
Management	O
of	O
Dynamos	B-Library
,	O
pp	O
.	O
</s>
<s>
Dynamos	B-Library
were	O
used	O
in	O
motor	O
vehicles	O
to	O
generate	O
electricity	O
for	O
battery	O
charging	O
.	O
</s>
<s>
An	O
early	O
type	O
was	O
the	O
third-brush	O
dynamo	B-Library
.	O
</s>
<s>
They	O
have	O
,	O
again	O
,	O
been	O
replaced	O
by	O
alternators	B-Algorithm
.	O
</s>
<s>
Dynamos	B-Library
still	O
have	O
some	O
uses	O
in	O
low	O
power	O
applications	O
,	O
particularly	O
where	O
low	O
voltage	O
DC	O
is	O
required	O
,	O
since	O
an	O
alternator	B-Algorithm
with	O
a	O
semiconductor	O
rectifier	B-Algorithm
can	O
be	O
inefficient	O
in	O
these	O
applications	O
.	O
</s>
<s>
Hand	O
cranked	O
dynamos	B-Library
are	O
used	O
in	O
clockwork	O
radios	O
,	O
hand	O
powered	O
flashlights	O
and	O
other	O
human	O
powered	O
equipment	O
to	O
recharge	B-Architecture
batteries	B-Architecture
.	O
</s>
<s>
Dynamos	B-Library
are	O
used	O
on	O
bicycles	O
to	O
power	O
their	O
lights	O
.	O
</s>
