HOMEWORK # 6 MACHINES AND EQUIPMENT
1. What a machine is?
A machine (or mechanical device) is a mechanical structure that uses power to apply forces
and control movement to perform an intended action.
Machines can be driven by animals and people, by natural forces such as wind and water, and
by chemical, thermal, or electrical power, and include a system of mechanisms that shape the
actuator input to achieve a specific application of output forces and movement.
Examples include: a wide range of vehicles, such as automobiles, boats and airplanes;
appliances in the home and office, including computers, building air handling and water
handling systems; as well as farm machinery, machine tools and factory automation systems
and robots.
2. Electric machine
In electrical engineering, electric machine is a general term for machines using electromagnetic
forces, such as electric motors, electric generators, and others.
They are electromechanical energy converters: an electric motor converts electricity to
mechanical power while an electric generator converts mechanical power to electricity.
The moving parts in a machine can be rotating (rotating machines) or linear (linear machines).
Besides motors and generators, a third category often included is transformers, which
although they do not have any moving parts are also energy converters, changing the
voltage level of an alternating current.
3. Electric generator.
An electric generator is a device that converts mechanical energy to electrical energy.
A generator forces electrons to flow through an external electrical circuit. It is somewhat
analogous to a water pump, which creates a flow of water but does not create the water
inside.
The two main parts of an electrical machine can be described in either mechanical or electrical
terms.
In mechanical terms, the rotor is the rotating part, and the stator is the stationary part of an
electrical machine. In electrical terms, the armature is the power-producing component and
the field is the magnetic field component of an electrical machine.
The armature can be on either the rotor or the stator.
The magnetic field can be provided by either electromagnets or permanent magnets
mounted on either the rotor or the stator.
Generators are classified into two types, AC generators and DC generators.6
AC generator
An AC generator converts mechanical energy into alternating current electricity. Because
power transferred into the field circuit is much less than power transferred into the armature
