Electrical Transformers and Rotating Machines Explained

Transformers

• Transformer: A device that converts static electricity of specific voltage and current characteristics into others without varying the frequency.
• Magnetic circuit: Its mission is to provide a path attractive enough so that all the flux generated by a coil concentrates inside.
• Short-circuit test: Consists of increasing the voltage value in the primary until the current reaches the nominal value. It measures circuit voltage and Joule effect losses.
• Power transformer efficiency: The relationship between the power delivered to the load and the power absorbed from the network.
• Voltage drop in a transformer: The difference in tension between the no-load state and the tension under secondary load.
• Connection index: An integer indicating the phase shift between the low-voltage side and the high-voltage side (e.g., /30).

Advantages and Disadvantages of Autotransformers

• Advantages: Conductor savings, smaller magnetic circuit, better cooling, and minor voltage drop.
• Disadvantages: Loss of isolation and higher short-circuit current.

Rotating Electrical Machines

• Generator: Transforms mechanical energy into electricity.
• Engine: Converts electrical energy into mechanical energy.
• Rotor: The rotating part of the machine.
• Stator: The fixed part of the machine that houses the rotor.

Types of Rotating Machines

• DC: Excitation via winding or permanent magnets.
• AC: Asynchronous and synchronous.
• Other types: Stepper, switched reluctance, and universal.

Electrical Machine Components

• Inducer: The electrical circuit of the rotor.
• Inductor: The electrical circuit of the stator.
• Collectors: Collect all beginnings and ends of the induction coil.
• Brushes: Allow connection of the machine to an external circuit via the stator.
• Axis: Transmits or receives mechanical energy during machine operation.

Motor Characteristics

Asynchronous Motors

• Simple construction
• High starting torque
• Relatively constant speed with varying loads
• High connection current

Synchronous Motors

• Creation of a rotating magnetic field in the air gap
• Speed does not depend on the load on the shaft
• The difference between rotor speed and synchronism is called slip.