Hello, fellows, I hope all of you are having fun in your life. In today’s tutorial, we will have a look at Introduction to DC Machines. Like alternating current machines, there are 2 types of DC machines. The first one is a DC motor that converts electrical power into mechanical power, and the second one is a DC generator that converts mechanical power into electrical. As AC machines are further divided into subcategories like induction motors, induction generators, synchronous motors, and synchronous generators, and DC machines also have different types like shunt motors, shunt generators, series motors, series generators, etc.
In DC machines like AC machines, alternating current and voltage are produced, that convert to DC current and voltage by a process called commutation. Due to that, DC machines are also known as commutating machines. In today’s post, we will have a look at different types of DC machines, their working, structure, applications, and some other related parameters. So let’s get started with an introduction to DC Machines.
Introduction to DC Machines
DC machines are types of electrical machines that use DC current in the case of DC motors and generate DC voltages in the case of DC generators.
• The DC motor transforms electrical power into mechanical power, and the generator converts mechanical power into electrical.
As in power generation systems and industries, mostly AC machines like induction motors, synchronous motors, and generators are employed, but the use of DC machines cannot be denied due to their constant speed-providing capability.
The physical construction and design of both DC motors and generators are alike to each other. The DC generator is used in a safe environment where there is no need for special protection and circuitry for the generator.
While the motor is employed in such an environment where it can be easily affected by environmental conditions like moisture and dust, it needs a special structure that can provide resistance to dust, fire, and some other related effects.
We are familiar with the common use of DC batteries that are used only for some limited applications where a smaller amount of energy is required, but in such applications where a large amount of DC power is needed, DC machines are the best replacement for the battery.
Working Principle of DC Machines
Any type of electrical machine, whether AC or DC, works on the phenomenon of Faraday’s law of electromagnetic induction.
This law states that if any conductor through which current is passing is placed in a magnetic field, a force acts on this conductor due to its rotation in the field.
The direction of rotation of this conductor in the field can be found by using the very famous Left-Hand Rule of Fleming.
Faraday’s law also states that if we put any conductive loop in the field, the voltage will be induced in that conductive device. The direction of the induced voltage can be found by the right-hand rule.
EMF= dø/dt
Types of DC Machines
- There are 2 main types of DC machines. The first one is a generator, and the second one is a DC motor. A DC motor uses DC current and provides mechanical power, and a DC generator generates DC voltage.
- As we discussed, when a current-carrying conductor is placed in a field, an induced force acts on it.
- There are two main categories by which the DC machine gets excited. The first one is self-excited, and the second one is separately excited.
- In self-excited machines, field current is produced by the machines themselves, while in separately excited machines the field current is provided by the separated source.
- Due to these two excitation methods, the DC machines are further divided into different types that are described here.
Compound DC machine
Shunt DC machine
Separately excited DC machine
Series DC machine
- Let’s friends now we discuss all these types with the detailed.
Separately Excited DC Machine
- If there is no internal voltage induced at the field windings and there is no field current so external power source is connected at the field winding to produce current and voltage; these windings are known as separate windings.
- In the given figure, you see the detailed circuit of separately excited machines.
Shunt DC Machine
In this type of DC machine, the field winding (it is located at the stator of a machine) is linked with the armature winding (wound rotor) in parallel.
Due to a parallel connection, the voltage across the field windings is equal to the supply voltage in the case of a motor and equals the generated voltage in the case of a generator.
So these windings have a large number of turns. In a given diagram, you can see the circuit of shunt DC machines.
Series Wound DC Machine
- In these DC machines, the field windings are connected with the armature windings in series connection schemes.
- As this winding is in series so the armature current also passes through it. To have less power loss, the turns of the field windings are fewer in this machine.
- In the given figure, you can see the circuit diagram of these machines.
Compound DC Machine
- This motor consists of series and shunt windings in its circuitry. 2 windings are placed at every pole of the machine.
- The number of turns in the series winding is less due to the large value of armature current flowing through it, and the shunt windings have a large no of turns.
- There are 2 methods by which these two windings are connected in these machines. If the field windings are in parallel with the armature windings, then the machines are known as the short shunt compound. In the given figure, you can see these arrangements.
- If the field windings is in parallel with the armature and series windings, the machines are known as the long shunt compound machines. In the given figure, you can see the resultant circuitry.
Applications of DC Machines
- DC machines are used for supplying excitation of an alternator and it also used for the welding process, electrolytic, and electroplating processes.
- Small DC machines are used for controlling different devices like speed sensing, tracking, and position.
FAQs
What are types of DC machines?
- There are two types of dc machines: one is a DC generator, and the other is a DC motor. The DC generator transforms mechanical power into DC power, and the DC motor converts electrical power into mechanical power.
What is the importance of DC machines?
- DC machines are used for providing high starting torque applications and correct speed control for different ranges. It also used for elevators, steel mills, and excavators.
That is a complete post on the dc machines if you have any questions about this post ask in the comments. See you in the next tutorial.
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