Ahmet Gökay Öztürk 030050143 (8th week)

AC motors

Electric motors designed to operate with alternating current (AC)
supplies are themselves broadly categorized into two classes: induction
and synchronous. There are many variations of synchronous machines.
AC motors work by setting up a magnetic field pattern that rotates
with respect to the stator and then employing electromagnetic forces to
entrain the rotor in the rotating magnetic field pattern. Synchronous
machines typically have a magnetic field which is stationary with respect
to the rotor and which therefore rotate at the same speed as the stator
magnetic field. In induction motors, the magnetic field is, as the name
implies, induced by motion of the rotor through the stator magnetic
field.
(J.Kirtley, Electric Motor Handbook, pg.3)


DC motors

DC motors, as the name implies, operate with terminal voltage and
current that is “direct”, or substantially constant. While it is possible to
produce a “true DC” machine in a form usually called “acyclic”, with
homopolar geometry, such machines have very low terminal voltage
and consequently high terminal current relative to their power rating.
Thus all application of DC motors have employed a mechanical switch
or commutator to turn the terminal current, which is constant or DC,
into alternating current in the armature of the machine.DC motors have usually been applied in two broad types of application.
One of these categories is when the power source is itself DC. This is
why motors in automobiles are all DC, from the motors that drive fans
for engine cooling and passenger compartment ventilation to the engine
starter motor.
A second reason for using DC motors is that their torque-speed
characteristic has, historically, been easier to tailor than that of all AC
motor categories. This is why most traction and servo motors have been
DC machines. For example, motors for driving rail vehicles were, until
recently, exclusively DC machines.
(J.Kirtley, Electric Motor Handbook, pg.2-3)


Pneumatics

Pneumatics is the discipline that deals with mechanical properties of gases
such as pressure and density, and applies the principles to use compressed
gas as a source of power to solve engineering problems. The most widely
used compressed gas is air, and thus its use has become synonymous with
the term pneumatics. Hydraulics is the discipline that deals with the mechanical
properties of liquids, and applies the principles to solve engineering
problems. Gases and liquids are both fluids as opposed to solids.
Pneumatics and hydraulics are similar in many respects and often described
by the generic term fluid power.
(Peter Beater, Pneumatic Drives System Design, Modelling and Control, pg.1)



Lever Mechanism

Levers are the simplest of mechanisms; there is evidence that
Stone Age humans used levers to extend their reach or power;
they made them from logs or branches to move heavy loads such
as rocks. It has also been reported that primates and certain birds
use twigs or sticks to extend their reach and act as tools to assist
them in obtaining food.
A lever is a rigid beam that can rotate about a fixed point
along its length called the fulcrum. Physical effort applied to one
end of the beam will move a load at the other end. The act of
moving the fulcrum of a long beam nearer to the load permits a
large load to be lifted with minimal effort. This is another way to
obtain mechanical advantage.
(N. SCLATER, N. P. CHIRONIS, MECHANISMS AND MECHANICAL DEVICES SOURCEBOOK 4th ed., pg 4)