This ppt gives a small introduction to vector speed control of induction motor. In my uploads another pdf is there which completely explains about vector control method

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Vector Speed Control of Induction motor
Presented by
Ranjith Samala--------------16311A0240
Rajinikanth S-----------------16311A0241
Karunakar Reddy S----------16311A0242
EEE department
Internal Guide
K V V P CHARI
EEE Department

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Contents:-
1.Introduction
2.Speed control methods
3.Vector speed control
4.Working
5.Advantages
6.Conclusion

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Introduction:-
Induction Motors are the most commonly used motors in many applications. These are
also called as Asynchronous Motors, because an induction motor always runs at a
speed lower than synchronous speed.
An induction motor is the most modest electrical machine from constructional point
of view, in the majority of the cases. Induction motor works on the principle of
induction where electro-magnetic field is induced into the rotor when rotating
magnetic field of stator cuts the stationary rotor. Induction machines are by far the
most common type of motor used in industrial, commercial or residential settings

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Various speed control methods:-
1. Pole Changing
2. . Variable rotor resistance control
3. Variable supply voltage control
4. Variable Supply Frequency
5. Constant V/f control
6. Vector Control

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Pole changing speed control :-
As the no of poles increasing the speed of the motor decreases vice versa.
Frequency control method
The frequency is directly proportional to speed
of the motor

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Variable supply voltage :-
The voltage is directly proportional to the speed
Consider rotor resistance is constant and motor is
running at nearer to synchonous speed then the slip is
neglible ...,
With above considerations the torque is directly
proportional to the square of the voltage

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Constant v/f control method;-
Mainly this method we are maintaining flux constant by
keeping v/f ratio constant. This is the most popular
method for controlling the speed of an induction motor.

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Vector Speed Control Method:-
Vector control, also called field-oriented control (FOC), is a variable-
frequency drive (VFD) control in which the stator currents of a three-phase AC
electric motor are identified as two orthogonal components that can be
visualized with a vector.
-It was developed for high performance motors
- We can get full torque at zero speed

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Block diagram:-

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Working:-
-In this method the stator currents of a three-phase AC
electric motor are identified as two orthogonal components
that can be visualized with a vector
-One is current component of flux and another one is current
component of torque
- The control system of the drive calculates the corresponding
current component references from the flux and torque
references given by the drive's speed control.

11. Matlab simulatiobs:-
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Working:-

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Obesrvation(OUTPUT):-

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Clarke transformation:-
The Clarke or
αβ0 transform is a space vector transformation of time-domain signals
(e.g. voltage, current, flux, etc) from a natural three-phase coordinate
system (ABC) into a stationary two-phase reference frame . It is named
after electrical engineer Edith Clark

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Clarke transformation:-

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Parks transformation
This transformation converts vectors in balanced two-phase
orthogonal stationary system into orthogonal rotating
reference frame.

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Parks transformation

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Advantages:-
Speed or position measurement or some sort of estimation is needed.
• Torque and flux can be changed reasonably fast, in less than 5-10
milliseconds, by
changing the references.
• The accuracy of the torque depends on the accuracy of the motor parameters
used in the
control. Thus large errors due to for example rotor temperature changes often
are
encountered.

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Conclusion:-
By using FOC scheme with induction motor, high starting torque can be
obtained like in DCmotor. The benefits of FOC are that all the advantages of DC
motor can be obtained in FOC-induction motor drive, with the default
advantages of IM over DC motor, which makes the induction motor the most
suitable drive for the applications where variable speed operations are necessary
with fast response.

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