STATIC DRIVES
At present, the world runs on the basis of electricity. The
electricity is the necessity source for employment of Industries and domestic
applications. Among all of these we maintain a constant regularity in the power
supply. Motion control is required in many types of equipment such as rolling
mills, paper machines, machine tools, fans, pumps, robots, washing machines etc...
For implementing the motion to a particular machine, drivers are used.
Generally, drivers are defined as a mechanism to employ the machine y set into
motion. These drivers are employed with prime movers such as steam turbines,
hydraulic motors. Drivers employing for electric motors are known as electric
drives.
Definition: Electric drive is defined as
machine equipment designed to convert electric energy to mechanical energy and
provide electric control of process.
Static drive: The static drive is defined
as an electric drive which gives motion control to a machine by remaining
stable (or) fixed.
Advantages:
1.It is simple to operate and obtain flexibility in speed
control.
2.It is easy to maintain and environmental free.
3.There is a availability in wide range of torque, speed, and
power characteristics
4. Comparing with prime mover, drivers have longer life,
lower maintenance requirements, and lower noise.
5. Occupies less space and very compact and also remote
controlled.
6. They are adaptable to critical operating conditions like
explosive, radioactive, submerged liquids, vertical mountains etc.
7.Good efficiency and economical in use with low losses.
Disadvantages:
1.The production decreases if the failure occurs in any event
of supply.
Parts of Electric drives:
For every
mechanism, the parts (or) components are required to express the system
efficient. An electric drive has following major parts.
1. Load: The required output is named as
load. A load can comprises machinery designed to accomplish a given task.
Examples:
Transformer`s from substations, locomotives, drills, fans and pumps.
2. Motor: Based on the requirement operation
the different motors are selected, the different electric motors are listed
below:
DC MOTORS:
Shunt, series, compound and permanent magnet.
AC MOTORS: Squirrel cage, wound rotor and
linear brushless dc motor, wound field and permanent magnet.
3. Power Modulator:
The power
modulator modulates the flow of power from source to the motor. The power
modulates satisfactory classification is
a) Converters
b) Variable
impedances
c) Switching circuits.
Functions of Power Modulator:
1.The speed and torque characteristics are obtained by the
power modulator.
2.Limits the power values of transient state.
3.The requirement of electric energy conversion takes place.
4.There is a possibility for Select the operating modes of motor
such as motoring and breaking.
4. Source:
The source is simplified as power supply. We know electric
power supply has two categories i.e. single phase and three phases. By improving
the ranges of supply three phase to be considered and for low single phase are
enough, by keeping the frequency constant.
*Based on applications the frequency and voltage may changes.
For example aircraft and space applications require 400HZ supply.
5. Control unit:
The power
modulator is controlled by control unit. The function of control unit is to
provide sequencing and interfacing. The control unit consists of semiconductor
converters such as digital Integrated circuits, transistors and also a microprocessor.
ELECTRIC
DRIVE CHOICE
There are many types of choices are present which we can
operate the system based on the requirement. Some of the choices are listed
below:
1. Steady state operation
2. Transient operation
3. Requirement related to source
4. Location and environment
5. Reliability
Steady state operation:
In steady state operation the nature of torque and speed
characteristics are obtained, good speed regulation and efficiency, better duty
cycle, quadrants of operation and also speed fluctuations are remind in this
operation state.
Transient operation:
Values of acceleration, deceleration, starting, breaking and
reversing performance are remind in this operation state.
Requirement related to source:
Types of source, capacity, magnitude of voltage, voltage
fluctuations, power factor, harmonics and their effects, space and weight
restrictions, capital and running cost, these are requirements which are
related to source.
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