How to reduce the speed of DC motor by keeping constant.
The evolution of DC motors took place in the 18th century.DC motors are widely applied in multiple industries.The British researcher Sturgeon developed the first DC motor in the early 1800s.The initial commutator type of DC motor was invented by him.One might wonder what the function of the DC motor is and why it's important to know about it.The article explains its operation and various speed controlling techniques.
A Dc motor uses direct current to convert the electrical energy into mechanical energy.The power to operate various applications in multiple domains is delivered by this change in the device itself.
DC motor speed control is one of the most useful features.You can vary the speed of the motor according to the requirements if you control it.
The speed control mechanism can be used to control the movement of robotic vehicles, motors in paper mills, and elevators where different types of DC motors are used.
A simple DC motor works on the principle that when a conductor is placed in a magnetic field, it experiences a mechanical force.The field provides a magnetic field in a practical DC motor.
The conductor produces its own magnetic flux when it is supplied with a current.The magnetic flux can either be added or subtracted by the field windings in one direction.The conductor is forced to start rotating by the force of the magnetic flux in one direction compared to the other.
The rotating action of the conductor produces an electric field.The supplied voltage is the cause that this EMF tends to oppose.DC motor has a special characteristic of adjusting its Torque in case of different load due to the back EMF.
The impact of speed control on the speed of rotation of the motor is important for the performance and outcome of performance.At the time of drilling, every kind of material has its own rotation speed and can change based on drill size.
In the case of pump installations, there will be a change in the throughput rate and so a conveyor belt needs to be in sync with the functional speed of the device.The factors come from the speed of the motor.One should observe various types of speed control methods because of this.
DC Motor speed control can either be done manually by the worker or using an automatic controlling tool.In contrast to speed limitation, there has to be speed regulation opposing the variation in the speed because of the shaft load.
The supplied voltage is V, the back EMF is Ia, and the armature resistance is Ra.
We will discuss the speed controlling methods of both DC series and shunt motors.
The regulating resistance has a series connection with the motor supply.This is explained by the below picture.
The power loss that happens in the DC series motor's controlling resistance can be ignored because this regulating technique is mostly used for a long period in order to decrease the speed at the time of light loading scenarios.It is a cost-effective technique that is used in cranes, trains, and other vehicles.
The rheostat will be connected to the armature in both series.The series rheostat will have a change in the voltage level applied to it.The change in current takes place by changing the rheostat.Significant power losses in speed regulation resistances make this technique of controlling speed in DC motor not so costly.The normal level of speed can be regulated.
The speed of a DC series motor can be done through power supply to the motor, but this approach is costly and not extensively implemented.
A diverter is used in this technique.Some part of the motor current can be moved across the field to decrease the flux rate.The field current is less than the resistance of the diverter.This technique is used for more than the normal range of speeds and is implemented across electric drives when there is a decrease in load.
Reducing the field winding turns from where the flow of current takes place will increase the speed.This technique is used in electric tractions when the number of tappings in the field is taken out.
The magnetic flux is varied in order to vary the speed of the motor.
The magnetic flux can be varied by the current flowing through the field winding.There is a way to achieve this by using a variable resistor in a series.
When the variable resistor is kept at its minimum position, the rated current flows through the field winding and the speed stays the same.The current through the field winding decreases when the resistance is increased gradually.The flux is decreased by this.The speed of the motor increases.
This method can be used to control the speed of the DC motor.The method also uses a variable Resistor.
The armature resistance is normal when the variable resistor is at its minimum value.When the resistance value goes up, the voltage goes down.This leads to a decrease in the speed of the motor.
In the above picture, M is the main motor where its speed is to be regulated and G corresponds to an individually excited DC generator where this is driven by using a three-phase motor.The M-G set is a pattern of DC generator and AC motor combination.
The generator's field current can affect the generator voltage.When the DC motor's armature section is provided, the voltage level is varied.The motor field current needs to be constant in order to keep the flux constant.When the motor speed is regulated, the armature current is the same as the rated level.
The delivered field current will have a different level of voltage than the rated level.The rated current and the field flux of the motor are related to the speed regulation.There is a direct proportion to the speed of the power.The speed increases when there is an increase in power.
Speed control can't be provided in the desirable range.The flux control method can affect commutation due to its use of a resistors in series with the armature.A different way to control the motor speed is desirable.
The Ward Leonard technique allows for the acquisition of the power drive and the constant value of Torque from the speed level to the base speed.When the speed level is more than the base speed, the field flux regulation technique is used.
The armature current is kept constant at the specified value and the generator's value is constant as well.The field winding gets a fixed and variable voltage.
The Ward-Leonard System uses an AC motor-driven Generator to provide variable voltage to the armature while the other uses a switchgear mechanism.
The Ward Leonard method is used to control the speed of the DC motor.Some examples are mine hoists, paper mills, lifts, and cranes.
The most widely used technique is the speed control of the DC motor using the PWM method.Variable width pulse is used to control the voltage applied to the motor.This method is very efficient as the power loss is kept at a minimum, and it doesn't involve the use of any complex equipment.
A simple electric motor speed controller is depicted in the above block diagram.As shown in the above diagram, a microcontroller is used to feed signals to the motor driver.The motor driver has H-bridge circuits to drive the motor.
The motor driver IC is used to control the applied voltage of the motor.The input signal from the pushbuttons is used for the variation of the pulse.Two pushbuttons are provided for decreasing and increasing the duty cycle.
A detailed explanation of various techniques of DC motor speed control has been given in this article.It's a good idea to know about the 12v dc motor speed controller.
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