Tuesday, June 30, 2009

Dc Motor Speed Control Lecture Video

DC MOTOR DRIVE FUNDAMENTALS
UNDERSTANDING DC MOTOR DRIVES
DC motors have been available for nearly 100 years. In fact the first electric motors were designed and built for operation from direct current power.
AC motors are Now and will of course remain the basic prime movers for the fixed speed requirements of industry. Their basic simplicity, dependability and ruggedness make AC motors the natural choice for the vast majority of industrial drive applications.

Then where do DC drives fit into the industrial drive picture of the future?
In order to supply the answer, it is necessary to examine some of the basic characteristics obtainable from DC motors and their associated solid state controls. more

Precision DC motor speed controller
Optical tachometers that produce a frequency proportional to RPM are popular feedback sources for precision analog motor speed control. This usually involves a frequency-to-voltage converter (FVC) to convert the tachometer output to a voltage that’s then input to a conventional servo. Though it typically works fine, it’s unnecessarily complicated and requires a tachometer with a relatively high pulse/revolution characteristic to allow for both a reasonably fast loop response and adequate ripple filtering in the FVC. more


DC Motor Speed Control PWM



The user may feel that the RC PWM signal may be an awesome resource to control the speed of a DC motor. And this is of course true, except that the RC PWM signal itself is pretty much useless as a direct means of controlling the DC motor speed. What needs to be done is to have an intermediate circuit to decode the position information (RC Pulse width) and generate a speed magnitude signal. In other words, if the input pulse is 1 ms, move the DC motor on reverse at maximum speed, if 1.5 ms wide stop the DC motor and if 2.0 ms, move the DC motor forward at maximum speed. Any other pulse width is then decoded to partial speed on the corresponding direction. more


Dc Motor Speed Control - Introduction Lecture Video



Dc Motor Speed Control - Block Diagram Lecture Video



Dc Motor Speed Control Current Control & S C L Lecture Video




Dc-Motor Speed Control Controller Design-1 Lecture Video



Dc Motor Speed Control Controller Design-2 Lecture Video
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Monday, June 22, 2009

Dc Motor Lecture Video

Basic DC Motor theory
The DC motor has two basic parts: the rotating part that is called the armature and the stationary part that includes coils of wire called the field coils. The stationary part is also called the stator. The armature is made of coils of wire wrapped around the core, and the core has an extended shaft that rotates on bearings. You should also notice that the ends of each coil of wire on the armature are terminated at one end of the armature. The termination points are called the commutator, and this is where the brushes make electrical contact to bring electrical current from the stationary part to the rotating part of the machine.

The coils that are mounted inside the stator are called field coils and they may be connected in series or parallel with each other to create changes of torque in the motor. You will find the size of wire in these coils and the number of turns of wire in the coil will depend on the effect that is trying to be achieved.
more


Basic DC Motors
Principles of operation
In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.



more



D C Motors Lecture Video


DC Motor 2 Lecture Video


DC Motor 3 Lecture Video
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Saturday, June 13, 2009

Induction Motor Drives and Speed Control Lecture Video

Lecture - Induction Motor Drives Video



Lecture - Speed Control of Induction Motor Part - 1 Video



Lecture - Speed Control of Induction Motor Part-2 Video



Implementing Embedded Speed Control for AC Induction Motors

Topices
•Induction Motor principles
–Physics of induction motors
–Induction motor construction
•Control hardware –typical layout
•Modulation techniques
–Sinusoidal, Quasi-sinusoidal & Space Vector
•Control methods
–Open loop algorithms
–Closed loop algorithms
•MCU performance benchmark
•Summary



Induction Motors
•Motors operate on principle of Induction and hence the name “Induction Motors”is used
•Motors also known as AC motors because Alternating Current (AC) is required
•All AC motors are “brushless”
–No mechanical contacts to wear
–Requires AC source
–If used, inverter creates desired freq and magnitude of AC
•AC induction motors for lower cost applications
–Single speed applications: fan, blower, pump, compressor
–No control, just start the AC power source
–Relays are used for ON/OFF
more


Speed control of three phase AC induction motor using single phase supply along with active power factor correction
Abstract
Majority of industrial drives use electric motors, since
they are controllable and readily available. In practice,
most of these drives are based on ac induction motor
because these motors are rugged, reliable, and relatively
inexpensive. The proposed technique of single phase to
three phase conversion has a wide range of applications in
rural areas and also in industries where three phase
equipment or motors are to be operated from the easily
available single phase supply. These converters are
excellent choice for situations where three phase power
supply is not available. The added advantage is that the
three phase motor is more efficient and economical than
the single phase motor. Also the starting current in three
phase motor is less severe than in single phase motor.
This needs a strong, efficient cost effective and high
quality single phase to three phase conversion. Advanced
PWM techniques are employed to guarantee high quality
output voltage with reduced harmonics and sinusoidal
input current irrespective of the load. To obtain sinusoidal
input current at the terminal of single phase source a high
performance active input power factor correction
technique for single phase boost switch mode rectifier
operating with discontinuous current conduction is used.
The operation is based on variable turn-on time. Equal
Area Criteria (EAC) is applied to the discontinuous
current operation. To obtain high quality output voltage,
double edge modulated sine wave PWM technique is
implemented for three phase inverter. From experimental
results obtained on a laboratory prototype it can be
concluded that input power factor remains nearly unity for
any variations in the load or speed. Thus three phase ac
drives using single phase supply with improved power
factor is an approach to implement high frequency
induction boosting along with the three phase PWM
inverter for controlling the speed of three phase induction
motor by maintaining v/f ratio at constant value. This
scheme can be used in lathe machines, small cranes, lifts
etc, which are frequently switched ON and OFF1.
more
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