3 Significant Ways For DC Motor Speed Control
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One of the most useful features of DC motor control is the speed control. If you control the speeds of the motor, you need to vary the speed of the motor according to the requirements for getting the required operation. There are many applications like the movement of the robotic vehicles, motors in paper mills, and elevators use the speed control mechanism.
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DC Motor’s working principle
When a conductor carrying current is placed in a magnetic field it is controlled by a mechanical force and this is the simple working of the DC motor. The current carrying conductor and the field is the armature in a DC motor.
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The magnetic flux is produced on its own with a supply of the current to the conductor (armature). Due to field windings it either adds up to the magnetic flux at one direction or rejects the magnetic flux due to field windings. The rotation is because of the accumulation of magnetic flux at one direction compared to the other. Faraday’s law of electromagnetic induction shows that the rotating action of the conductor generates an EMF. The supplied voltage or the cause is opposed by the EMF according to Lenz’ law. In case of varying load due to the EMF, the torque is adjusted and this is the speciality of DC motor. CRBTech.Electrical-Training
3 ways of controlling DC motor speed control
1 Flux Control Method
The magnetic flux of the winding is varied for varying the speed of the motor. By changing the current flowing through the field windings the magnetic flux can be changed as it depends on the current flowing through the windings. This is achievable with the help of a variable resistor in a series with the field winding resistor. The variable resistor kept at the minimum position flows through the windings due to the speed voltage keeps the speed normal. The current through the field winding is reduced when the resistance increases slowly. Thus the flux voltage produced is reduced in turn. Beyond a particular normal value the speed of the motor increases. CRBTech.Electrical-Training
2
Control Method of the Armature
By controlling the resistance of the armature the speed of the DC motor is controlled leading to voltage drop across the armature. A changeable resistor in series with the armature is used in this method. The armature resistance is at normal one when the changeable resistor reaches to a minimum value thus the armature voltage drops. The voltage across the armature decreases as the resistance value is increased gradually. The speed of the motor is decreased because of this. CRBTech.Electrical-Training
3
Voltage Control Method
Speed control cannot be provided at a required range from the above mentioned methods. The armature control leads to huge power loss because of the usage of the transistor in series with the armature. Commutations happen because of magnetic flux control. It is always good to have an alternative method for controlling the speed of the motor.
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The field winding receives a fixed voltage and the armature receives a variable voltage in the new method. The switch gear system is used for such purposes for the provision of changing voltage to the armature. And the other one has a provision of AC motor driven Generator for providing variable voltage to the armature. This method is very efficient as it keeps the power loss at its minimum. It does not include the use of complex equipment. The electrical engineering course in Pune will help you to make your profession as an electrical designer in this field.
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