Transcript Motors

ENGINEERING
Electric Motors
Engineering
MVRT
10-21-2006
WHAT IS A MOTOR?
A motor generates rotational
motion.
Conventional motors use
chemical or electromagnetic
and electric PE.
ie: Car engines (motors) burn
gasoline to turn wheels.
THE ELECTRIC MOTOR
An electric motor uses electric
Electromagnets
energy.
Magnet
Magnet
Armature
Once
A
The
simple
armature
it has
DCreached
motor.
continues
Current
theto
zero
flow
generates
rotate.
position,
the
ancurrent
EMF around
is reversed
the
armature.
and
the process repeats.
ROTATIONAL MOTION
Rotational motion has two
components.
TORQUE
SPEED
Torque is the force of the rotation.
Speed is the rate of rotation.
POWER
Power describes energy over
time in Watts (W).
There are two power equations
that deal with electric motors:
ELECTRIC
ROTATIONAL
P=IV
P=TV
Power = Current
times Voltage
Power = Torque
times Speed
ELECTRIC POWER
Power = Current times Voltage
P=IV
V
Voltage is difference in
charge, or potential.
Volts V
I
Current is the quantity of
electrons moving over time.
Amps A
ROTATIONAL POWER
Power = Torque times Speed
P=TV
T
Torque is the force of the
rotation.
Newton-meters Nm
Speed is the rotations per
V unit of time.
Rotations per Minute RPM
MOTOR CHARACTERISTICS
Electric motors behave with
certain characteristics.
P
T
V
V P
As
the
armature
of
the
motor
With
The
Thus,
Even
At
these
graph
no
maximum
the
as
load
you
high
faster
of
put
and
the
power
the
load
in
relationship
constant
a
motor
and
huge
inputs,
turns,
most
the
maximum
speed
of
Here
At
To
We
This
The
And
find
low
those
take
is
torque
speed
find
is
always
speed,
the
points,
our
when
at
graph
best
at
real
halfway
this
this
you
their
power
you
torque
point
of
point
either
power
have
product
between
output
is
is
vs.
have
called
called
either
vs.
isof
Ideally,
any
the
point,
the
maximum
graph
graph
the
of
product
should
speed
torque
look
versus
of
at
T
However,
At
this
point,
in
reality,
the
motor
the
is
power
most
is
turns,
it
generates
backward
This
is
called
the
free
load
rpm.
voltage,
constant
between
the
amount
of
the
greater
energy
of
motors
voltage,
torque
power,
its
isresistance
converted
output
and
the
the
rpm
motor
graph
a to
certain
looks
to
This
is
called
the
stall
torque.
the
motor
at
this
voltage.
speed.
low
a
speed
greatest.
motor...
two
max
power
torque
graph...
extremes.
power
or
or
high
high
torque.
rpm.
power.
torque.
this
like
and
power.
voltage.
this.
V is the same.
not
efficient.
constant.
current.
rpm.this.to
outputs
like
current
begins
heat.
flow.
a flatten
certainout.
torque.
THE CIM
Power Output: 343 Watts
Free RPM:
5310
Stall Torque:
343.4 oz-in
Ideal for long
running times.
THE FISHER PRICE
Power Output: 387.5 Watts
Free RPM:
126
Stall Torque:
51.79 Nm
Hi power, but
suited for
medium loads
due to plastic
gears.
THE WINDOW
Power Output: 22 Watts
Free RPM:
84
Stall Torque:
10.6 Nm
Useful for preventing backdrive.
THE GLOBE
Power Output: 55 Watts
Free RPM:
81
Stall Torque:
150 in-lb
Low power motor for low-medium
load applications.
THE MABUCHI
Power Output: 16.8 Watts
Free RPM:
4700
Stall Torque:
60.8 mNm
Counterclockwise rotation with
additional spur gear.
Sadly, the Mabuchi was not around
when motor photos were being
taken.
Nobody missed it.
ENGINEERING
Electric Motors
By Humphrey Hu
Photographs from Wikipedia, USFIRST
You may not modify this Powerpoint
without permission