Speed Control of Induction Motor – AC Motor Speed Control Methods

Speed Control of Induction Motor – AC Motor Speed Control Methods


An induction motor is basically a constant
speed motor, that means, for the entire loading range, change in speed of the motor is quite
small. Speed of a DC shunt motor can be varied very
easily with good efficiency, but in case of Induction motors, speed reduction is accompanied
by a corresponding loss of efficiency and poor power factor. As induction motors are widely being used,
their speed control may be required in many applications. In this video I will go to brief you Different
speed control methods of induction motor. If you want to learn about Speed Control of
DC Motor, checkout my another video in description Below. Different speed control methods of induction
motor are explained below. Following are the May two type of controlling
arrangement which need to consider by controlling Induction motors. Speed control with respect to stator side
of the induction motor. Speed control with respect to rotor side of
the induction motor. The speed control of induction motor by considering
to control on stator side can also subdivide into several speed controlling methods such
as. By changing the supply voltage of the motor. Changing the stator pole numbers of the motor. Changing the frequency of the supply side
of the motor. By changing the supply voltage of the motor. As can be seen from Equation, the torque developed
by an induction motor varies as square of the voltage applied to its stator terminals. Thus by varying the applied voltage, the electromagnetic
torque developed by the motor can be varied. This method is generally used for small squirrel-cage
motors where cost is an important criterion and efficiency is not. However, this method has rather limited range
of speed control. Changing the stator pole numbers of the motor. The primary factor in determining the speed
of an induction motor is the number of poles, given by the below formula; Ns=Synchronous speed, in revolutions per
minute. f=AC power frequency. p=Number of poles per phase winding. From the above formula, Pole changing in induction
machine can be done using a Dahlander motor also known as a pole changing motor. Pole changing can be used to achieve different
speeds in induction machine by switching the configuration of the electrical stator windings
in the ratio of 2:1, indirectly adding or removing poles and thus varying the rotor
speed. The number of stator poles can be changed
by, multiple stator winding, method of consequent poles, pole amplitude modulation. Changing the frequency of the supply side
of the motor. By changing the supply frequency, the motor
synchronous speed can be altered and thus the torque-speed of a three- phase induction
motor can be controlled. The synchronous speed of the motor at rated
conditions is known as the base speed. By using variable frequency control, it is
possible to adjust the speed of the motor either above or below the base speed. Increase in frequency increases the torque-speed
relation and a decrease in frequency decreases the torque-speed relation of the motor. The speed control of induction motor by considering
to control on rotor side can subdivide into several speed controlling methods such as. Adding an external resistant into rotor side
circuit. Applying cascade connection. Injecting emf into rotor side circuit of the
motor. Adding an external resistant into rotor side
circuit. This method is applicable only the wound rotor
induction motors. Speed variation can be obtained by inserting
external resistance in the rotor circuit. External resistances are placed in series
with the rotor windings during starting to limit the starting current. Without the external resistances, the starting
currents are many times the rated currents. Depending on the size of the machine, it can
draw 300% to over 900% of the full-load current. Once the motor is started, the external resistance
can be cut out to obtain high torque throughout the accelerating range. Applying cascade connection. In this cascade operation method of induction
motor speed controlling there are two motors are mount on the same shaft of the motor and
run at same speed. One motor is connected to three-phase supply
and other is work from the feed induced emf of the first motor through slip rings. By using this method different speed can apply
for induction motor and speed can control. Injecting emf into rotor side circuit of the
motor. In this induction, motor speed control method
external voltages add into the rotor circuit of the motor and the frequency must be same
as slip frequency. So injecting emf in opposite phase of the
rotor increase the rotor resistance. By that, this method can use to speed controlling
of the induction motor. Dear viewers Thanks for watching the video,
any question write in the comment box. Don’t forget to like and share. More update please subscribes our channel
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28 Replies to “Speed Control of Induction Motor – AC Motor Speed Control Methods”

  1. Hi,
    Do you have a Controller Board with following specifications (RPM Controller via IR)?
    1- Controller board should run on 12V DC.
    2- Controller board should READ/DETECT RPM of an already running Motor-A via Infrared as its input.
    3- Based on RPM of Motor-A, Controller board should run/turn another Motor-B on same RPM as of Motor-A PLUS 0% to 10% greater (should be adjustable).
    4- Controller board should only give output to Motor-B, when Motor-A’s RPM will be within range from 1 to 3500 RPM.
    5- If RPM of Motor-A increased from 3,500 (should be 500+- RPM adjustable) then input to Motor-B should be stopped immediately.
    6- If RPM of Motor-A becomes <= 0 (should be 500+ RPM adjustable) then input to Motor-B should be stopped immediately.
    7- Features of Motor-B will be 11v to 14v DC, 1 to 2 Horse Power, Maximum 4,000 RPM.
    8- Controller Board should have display:
    A- Actual RPM of Motor-A
    B- Actual RPM of Motor-B
    C- Actual difference between RPM of Motor-B and Motor-A
    D- Set difference between RPM of Motor-B and Motor-A
    E- Set Highest RPM of Motor-A to cut-off input to Motor-B
    F- Set Lowest RPM of Motor-A to cut-off input to Motor-B

    Thanks

  2. For one your not going to rewind a motor to just change the poles you would just buy the right motor for the proper application much more cost effective and 2 you could double the voltage to a motor even triple it, it will not change your speed because that motor is wound for one speed unless and high and low voltage so if you double it your more than likely just going to burn your motor up. VFD is the only safe sane way to speed up your motor or slow it down and even VFD's have problems with rotor currents destroying bearings because of high frequency currents travelling through the shaft arching between the balls and the race. I would add a Common mode choke to filter out Eddy currents ageis rings suck!

  3. hello, what do you mean by increase decrease of the "torque-speed relation"? higher frequency results higher speed and higher torque, while lower frequency results lower speed and lower orque, I guess. The question is: frequency has more effect on spped than on torque, is it correct?

  4. Solid state relay with variable resister that is VR .How to control the AC motor .With 100 mfd starting current.Running capacitor is 25mfd.Please give me the detials vedio

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