Do you want to know the Working and Speed Control of the DC motors? If the answer is yes! then check this blog post which covers the basics of DC motors, their working mechanism, and why speed control is essential. The article covers various speed control methods, including armature voltage control and field flux control, along with practical ways of regulating the speed of a DC motor. Whether you are an engineering enthusiast or simply curious about the topic, this blog is a must-read for everyone interested in understanding DC motors.
DC motor is an electrical machine that converts electrical energy to mechanical energy. It's called a DC motor because the power supply used is DC (direct current).
DC motor works on the principle that when a current-carrying conductor is placed in a magnetic field it experiences a force which is given by Flemming’s Left-hand rule ( When you keep your forefinger, middle finger, and thumb perpendicular to each other and forefinger represent the direction of the magnetic field, the middle finger represents the current flowing through the armature then the thumb represents the direction of the force generated on the armature coil.)
As the armature coil rotates it cuts the magnetic flux lines which results in a change in the magnetic field giving rise to back emf according to Faraday's law of electromagnetic induction. This induced emf is in the opposite direction of the applied voltage. This back emf makes the DC motor self-regulating. Example: When you increase the load on the motor, the speed of the motor gets reduced. This decreases the back emf and increases the current through armature thereby
increasing the torque to compensate for the applied load. Likewise, when you decrease the load, the speed of the motor increases. This increases the back emf and decreases the current through the armature by which the torque is reduced to make up for the load.
Also, read our blog on DC Motor Applications explaining DC motor applications in different industries, products, and types of DC motors.
In various applications, such as robotics and electronics, precise speed control of the DC motor is essential for optimal performance.
Imagine you are in a car. To get a comfy ride in traffic, you will need to control the speed of the vehicle. Similarly in electronics, to control the movements of robots or drones so that they won't crash speed control is used. For drones, you get
ready-made Electronic Speed Controllers(ESC) to do this. In this article, we will see how this can be achieved.
The difference between speed control and speed regulation is that speed control is done automatically or manually whereas speed regulation is the measure of the regulation(maintaining) of the constant speed on changing load conditions at the motor shaft.
The speed of a dc motor is given by the following equation
N is the speed of the DC motor
V is the voltage across the armature
Ra is the armature resistance
Ia is the current through the armature
K is constant and ϕ is the flux
From the equation we can see that speed control of the dc motor can be achieved by changing flux which is done by changing field current (Flux control method), changing armature resistance(Armature control method) or voltage supply(Voltage control method). Let's see each one of them one by one
Here we change the magnetic flux to control the speed of the motor. To achieve this, we change the current through the field winding. So to do this we place a resistor in series with the field winding and vary this resistor to control the current through
which we control the field and then finally the speed of the dc motor. When resistance is set to a minimum, the current through the field winding increases, and thus flux also increases and speed decreases from the equation of speed and below equation.
ϕ =
