A dc motor is capable for converting electrical energy into mechanical energy. The most common type of dc motor is operated by the generated magnetic fields. Most of the types of DC motors work with the principle of electromechanical or electronic, to produce changes of current in the motor. As the name implies, this motor is operated by DC voltage.
Parts of a DC Motor
If you have read about DC motor explanation, you may find a different number of the parts of a DC motor. The most common mentioned parts are rotor, stator, brush, commutator, and armature. They are not wrong but it is not completely true. The complete explanation about parts of a DC motor can be read below:
Rotor comes from the “rotate” meaning it is the electrical rotating part of a dc motor. Rotor is the moving parts of a dc motor. It dynamically moves when the voltage is applied to the armature winding. This will produce mechanical movement for a dc motor.
This one is the important parts of a dc motor. Rotor is built from:
- Armature core
- Armature windings
Stator comes from the “stationary” meaning it is the electrical stationary parts of a dc motor. Stator does not move and only produces a magnetic field around the rotor to make the rotor rotating when the voltage is applied to it.
Stator is built from:
- Yoke or frame
- Field windings
Brushes are attached to the commutator as a bridge to deliver the electrical energy from the supply circuit to the rotor. Brushes are usually made from Carbon or Graphite material.
Commutator has the form of a split ring. The ring is made from copper and split in 2 or more depending on the number of armature windings. The split segment is connected to the armature winding.
The main purpose of the commutator is to deliver the electric current to the armature windings. The main idea of how a dc motor works is the interaction between North and South poles produced by armature windings and field windings. The generated north pole from the armature will be attracted to the south pole from the field winding and vice versa, producing rotating movement from the rotor. The constant torque produced by this rotor movement in one direction is called commutation.
Thus, the commutator is the part connected to the armature to do current switching for the armature windings. Each split ring segment is insulated each other with insulator material like a Mica. Summary, we deliver electric current from the supply to the brushes through to the commutator and then the armature windings.
Armature winding is used to energize the static magnetic field in the rotor. We install the armature winding around the slot of the armature core.
Armature windings can be made with:
- Lap winding construction
- Wave winding construction
Further in from the armature windings we will find the armature core made from low hysterisis silicon steel lamination to reduce the magnetic losses. These laminated steel sheets will be assembled together to create the armature core with cylindrical shape. There are also slots inside the core with the same material as the core.
The field windings are made from copper wire and circle around the Pole Shoes. Field winding is used to energize the static magnetic field in the stator. We install the field windings around the slot of the Pole Shoes. We do not need field windings if we use permanent magnets like in a Permanent Magnet Motor or PMDC motor.
Yoke or Frame
Yoke is an iron frame as a protective cover for both rotor and stator. This part protects everything inside it, supports the armature, and the house of the magnetic poles, field windings, and the pole to provide magnetic fields for the rotor.
Poles in the stator are used to energize a specific sequence of magnetic poles to make sure the rotor is rotating. It is divided into Pole Core and Pole Shoes.
For a dc motor we need the magnetic fields to make the rotor start rotating. In order to generate magnetic fields, we put field windings around the Pole Shoe which is attached to the Pole Core in the Yoke inner part. These Pole Shoe and Pole Core parts are attached to each other using hydraulic pressure. The structure is the yoke holding the Pole Core which carries the Pole Shoes carrying field windings. This pole unit generates flux spread out into the air gap between rotor and stator.