Electrical Machines: Types, Composition, and Operation
1.1. Electrical Machines
Electrical machines are devices capable of converting electrical power to create or use mechanical energy, or vice-versa.
Rating
Generators
Generators convert mechanical energy into electrical power.
Types:
- Dynamo: Generates direct current (DC) power.
- Alternator: Generates alternating current (AC) power.
The induced electromotive force (EMF) is calculated to determine the power generated.
Transformers
Transformers convert alternating electrical current at one voltage and current level (V1, I1) to another voltage and current level (V2, I2).
Motors
Motors convert electrical power into mechanical energy (movement).
Types:
- DC Motors
- AC Motors
- Three-phase alternating current motors
- Universal motors
- Single-phase motors
3. DC Motors
Definition
A direct current (DC) motor is an electric motor that converts direct current electrical energy into mechanical energy, resulting in the rotation of its movable parts.
3.1. Composition
These motors have specific components to create a magnetic field and an electric field inside the coil. These components are the stator and the rotor.
Stator
The stator is the stationary part of the motor, containing the inductor coil, electromagnets, and poles. It includes:
- Inductor coil
- Excitation coil
Rotor
The rotor is the rotating part of the motor. It includes:
- Delgas
- Induced coil
- Axis
- Brushes
3.2. Operation
When the motor is connected to a power source, electric currents circulate through the inductor coil, creating a magnetic field in the electromagnet. This induces a current in the coil through the brushes and the collector. Once the magnetic field is established, forces act on the induced coil, causing it to rotate along with the rotor.
5. Three-Phase Asynchronous Motors
Three-phase asynchronous motors are widely used in industrial applications due to their simple construction, ease of maintenance, and relatively low cost. They convert three-phase alternating current into mechanical energy.
5.1. Composition
Stator
The stator is the fixed part of the motor, consisting of a steel sheet crown housed within a shell. Three inductor coils are placed in the crown’s slots, and their ends are connected to a plate, allowing the motor to be connected to the power source.
Rotor
The rotor is the rotating part of the motor, consisting of a metal crown with several conductors mounted between two ends. The rotor is mounted on an axis.
5.2. Operation
The operation of a three-phase asynchronous motor is based on the electromagnetic force acting on a current-carrying conductor or coil in a magnetic field. When the motor is connected to a three-phase alternating current power source, a rotating magnetic field is generated by the inductor coils. Unlike DC motors, the rotor conductors are not directly connected to the power source. Instead, the rotating magnetic field induces currents in the rotor conductors. These induced currents interact with the magnetic field, creating electromagnetic forces that cause the rotor to rotate.