The forwards and backwards which ensure that large

The Construction and Operation of an AC Servo motor


A Servo motor is a very widely
used variable speed drive system linear/ rotary actuator which is able to
deliver precision position control for a closed-loop position control

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Servo motors are able to
withstand high rates of acceleration and deceleration and are able to move
quickly forwards and backwards which ensure that large ac servo motors are
capable of bringing a heavy load to a complete stop within a very accurate



The following describes the operation
of an ac servo motor;

The laminated rotor bar (which
is manufactured out of conducting materials such as aluminium or copper) is
short circuited at both ends. The stator is also manufactured out of laminated
materials and is equipped with slots, within these slots a number of windings
are connected, these windings are connected to a power supply, which, when a
voltage in induced in the bars located inside the rotor bar, a current flows through
the bars. An electromotive torque is generated as a direct result of the
current flow and this accelerates the speed of the rotor. As the speed of the
rotor increases, the induced voltage decreases because the rotor reaches the
coexistent speed. At coexistent speed, the torque becomes zero. Consequently,
ac motors will always turn at a speed lower than the coexistent speed. The
coexistent speed is determined by the frequency of the power supply and a large
number of poles which are located in the stator.





Performance check between an AC Servo motor and a DC
Stepper motor

Although both AC and DC
motors, perform the same function, turning electrical energy into mechanical
movement, they are controlled, constructed and are both powered very

While, AC motors are powered
using alternating current, and DC motors are powered using direct current, DC
motors usually require more maintenance than an equivalent AC motor over the
period of its lifetime as it is constructed with materials and parts which
would most likely hinder the length of its working life. Within a DC motor, one
would find brushes and a commutator which will not only require more maintenance
but will also limit the operating speed and reduce the working life of the motor.
AC motors are built using fewer parts and are very rugged and durable; increasing
the working life of the motor.

DC motors are also differentiated
by the speed control, as the speed is controlled by varying and adjusting the
armature winding’s current, whilst the speed is controlled by adjusting the
frequency in an AC motor which can be done by using an adjustable frequency
drive control.
















The Construction and Operation of an AC Generator

An AC generator is an electric
generator which is able to convert mechanical movement into electrical energy.








In most cases, industrial AC generators
are manufactured out of the following materials and items.

–       Laminated Steel Stator Core w/ Case

–       Armature Winding

–       End Turns

–       Seals

–       Bearings

–       Slip Rings

–       Steel Rotor

–       Couplings

–       Coils




The working of an AC generator
is based on electromagnetic induction

An electrical generator is a
mechanical device which produces an electromotive force by changing the number
of magnetic flux lines.

The generator produces
electricity by having mechanical movement turn one side of the coil inside of
the generator one half turn upwards and then down during the next half turn, because
of this mechanical movement, it means that as a coil is rotated in a magnetic
field, the induced current reverses the direction of the coil every half turn.

This can be shown by the
diagram below.











The size of the induced
voltage can be increased by carrying out the following;

–       Having a larger iron core inside the coil

–       Using a magnet with a larger and stronger magnetic field

–       Increasing the number of wires within the coil

–       Rotating the coil faster

–       Rotating the magnet faster


The Effectiveness of an AC Generator


–       Losses

Within an AC generator, there
is some amount of resistance and inductive reactance. These cause an effect
called ‘internal resistance’ which causes a loss in an AC generator. When the
current flows, a voltage drop can develop across the internal resistance
therefore causing a loss.


–       Maintenance

Over the working life of an AC
generator, there can be mechanical loss which can affect the efficiency of the generator
output. The following should be considered to increase efficiency of the generator;

–       Bearing friction

–       Good lubrication of internal components

–       A clean commutator

–       Brush friction

–       Air friction

–       Proper brush seating

–       Brush tensioning


–       Lifespan

There are many factors which
exist which could affect the lifespan and the length of an AC generators
working life such as:

–       Input power problems

–       Incorrect mechanical installations

–       Load malfunctions

–       Working environment

According to ‘’
an AC generator (if used correctly, and in the correct environment) can last
anywhere up to 15 years or more.


–       Limitations

AC electric power can be prone
to sparks and overheating due to the generators production of high currents these
issues could lead to serious health and safety risks such as fires and electric
shock which could be very dangerous and could put employees lives at risk. Due
to the high currents which AC generators produce, a greater amount of
insulation is required which could pose health and safety risks.