CARACTERISTICAS de las MAQUINAS ELECTRICAS ➤ POTENCIA, CORRIENTE, RENDIMIENTO, FRECUENCIA⚡ (PARTE 2)

Introduction to Magnitudes and Characteristics of Electric Machines

In this section, the instructor introduces the topic of magnitudes and characteristics of electric machines. The focus is on motors, transformers, and generators. The previous class covered the first part of this topic, defining important characteristics such as power and voltage.

Magnitudes and Characteristics of Electric Machines

• Magnitudes and characteristics are typically found on the machine's characteristic plate.

• Power, voltage, current, power factor, frequency, and efficiency are important magnitudes for electric machines.

• The next class will cover magnetic fields and circuits in relation to transformers.

• Generalities about electric machines were discussed in previous classes, including their importance in power systems.

• Classification of electric machines was also covered.

Power and Voltage

This section focuses on power and voltage in electric machines.

Power

• Nominal power is the maximum power a machine can handle under normal operating conditions.

• Nominal power can be calculated using nominal voltage and nominal apparent power.

• Active power (in watts) can be used if apparent power is not available.

Voltage

• Nominal voltage refers to the rated voltage for a machine.

• Other terms related to voltage include service voltage, maximum allowable service voltage, and test voltage.

Current Basics

This section covers basic concepts related to current in electric circuits.

Current Basics

• Current is the flow of electrons or charges through a conductor within a closed circuit.

• Basic concepts about current were covered in the Circuit Theory course.

• The instructor recommends referring to his YouTube channel for more information on circuit theory courses.

Nominal Current Calculation

This section explains how to calculate the nominal current for electric machines.

Nominal Current Calculation

• Nominal current is the maximum current a machine can handle under normal operating conditions.

• Nominal current can be calculated using formulas that involve nominal voltage and nominal power.

• For single-phase systems, a specific formula is used. For three-phase systems, another formula is used.

Design Current and Overload

This section discusses design current and overload in electric machines.

Design Current and Overload

• Design current is derived from the nominal current and may include safety factors or corrections.

• In some cases, machines may exceed their nominal values, which is known as overload or overcurrent.

Starting Current

This section introduces starting current in electric machines.

Starting Current

• Starting current refers to the initial surge of current when a machine starts operating.

• Calculating design currents helps in selecting appropriate conductors and protection equipment.

Understanding Overload and Starting Current

This section discusses the concept of overload and starting current in electrical machines. It explains that a machine can tolerate a 10-20% overload for a short period, but prolonged overload can damage the machine. Protections are in place to prevent such damage. The starting current refers specifically to motors, which typically have high values ranging from 2 to 8 times their nominal current. Various methods, such as star-delta starting, autotransformer starting, variable frequency drives, and solid-state starters, are used to limit the high starting currents and protect the motor.

Overload and Starting Current

• An electrical machine can handle a 10-20% overload of its nominal value for a short duration.

• Prolonged overload can cause damage to the machine.

• Protections are implemented to safeguard against excessive overload.

• Starting current refers specifically to motors.

• Motor starting currents are generally 2 to 8 times their nominal current.

• Different techniques like star-delta starting, autotransformer starting, variable frequency drives, and solid-state starters are used to limit high starting currents and protect the motor.

Understanding Power Factor

This section explains power factor in electrical circuits. Power factor is defined as the ratio between active power and apparent power when voltages and currents have phase differences. In AC systems, power factor can be either unity or less than unity depending on the relationship between active power and apparent power.

Power Factor

• Power factor is the ratio of active power to apparent power in AC circuits.

• Power factor depends on whether voltages and currents have phase differences.

• In DC systems, power factor is always equal to one (unity).

• In AC systems:

• If active power and apparent power have the same sign, power factor is unity.

• If active power and apparent power have opposite signs, power factor is less than unity.

Power Factor in DC Systems

This section focuses on power factor in DC systems. In DC circuits, there are no phase differences between voltage and current, resulting in a power factor of unity.

Power Factor in DC Systems

• In DC systems, there are no phase differences between voltage and current.

• Therefore, the power factor in DC circuits is always equal to one (unity).

Calculating Power Factor in AC Systems

This section explains how to calculate power factor in AC systems. The formula for calculating power factor involves dividing active power by apparent power. The angle of the phase difference between voltage and current (angle phi) is used to determine the cosine value required for the calculation.

Calculating Power Factor in AC Systems

• Power factor can be calculated using the formula: Power Factor = Active Power / Apparent Power.

• The angle phi represents the phase difference between voltage and current.

• The cosine of angle phi is used as a multiplier to calculate the power factor.

Power Factor in DC Machines

This section discusses power factor specifically related to DC machines. In DC machines, where there are no phase differences between voltage and current, the power factor is always equal to one (unity).

Power Factor in DC Machines

• In DC machines, there are no phase differences between voltage and current.

• Therefore, the power factor in DC machines is always equal to one (unity).

[t=0:13:44s] Factor de Potencia

En esta sección se define el factor de potencia y su importancia en las máquinas eléctricas.

Definición del factor de potencia

• El factor de potencia es la relación entre la potencia activa y la potencia aparente en un sistema eléctrico.

• Se expresa como un valor entre 0 y 1, donde 1 indica un factor de potencia óptimo.

• El factor de potencia puede ser especificado en la placa característica de las máquinas eléctricas.

Frecuencia en corriente alterna

• La frecuencia representa el número de ciclos periódicos completos de la onda fundamental en un segundo.

• Se expresa en ciclos por segundo o hertz (Hz).

• En corriente continua, la frecuencia es igual a cero.

Importancia de conocer la frecuencia

• La frecuencia nominal para máquinas de corriente alterna es generalmente 60 Hz en países como Perú, Colombia, Brasil y Ecuador.

• Sin embargo, en Europa la frecuencia es de 50 Hz.

• Es importante tener en cuenta esta diferencia al importar o exportar máquinas eléctricas entre regiones con diferentes frecuencias.

[t=0:17:11s] Rendimiento

En esta sección se aborda el concepto de rendimiento y su relación con el factor de potencia.

Definición del rendimiento

• El rendimiento es la relación entre la potencia suministrada y la potencia absorbida por una máquina eléctrica.

• Se calcula como la potencia suministrada dividida por la potencia absorbida.

Influencia del factor de potencia en el rendimiento

• El factor de potencia influye en el rendimiento de las máquinas eléctricas.

• Un factor de potencia bajo resulta en una mayor corriente para producir una determinada potencia activa, lo que aumenta las pérdidas en los devanados y disminuye la eficiencia.

• A medida que el factor de potencia se acerca a 1, la corriente disminuye y las pérdidas también se reducen, mejorando así el rendimiento.

Cálculo del rendimiento

• El rendimiento se puede calcular como la potencia de salida dividida por la potencia de entrada.

• También se puede expresar como 1 menos las pérdidas de potencia dividido por la potencia absorbida o de entrada.

[t=0:19:45s] Eficiencia

En esta sección se explica cómo calcular la eficiencia y su relación con la potencia de entrada y salida.

Definición de eficiencia

• La eficiencia es otra forma de medir el rendimiento de una máquina eléctrica.

• Se calcula como la relación entre la potencia suministrada (salida) y la potencia absorbida (entrada).

Cálculo alternativo para obtener la eficienca

• La eficiencia también se puede calcular como 1 menos las pérdidas de potencias dividido por la potenica absorbida o entrada.

Conclusion

New Section

In this section, the speaker discusses important characteristics of electric machines such as speed, torque, and starting torque. However, these topics will be covered in detail when focusing on specific types of electric machines like motors, transformers, and generators. For now, the focus has been on power, voltage, current, and power factor.

Characteristics of Electric Machines

• The speaker mentions that important characteristics of electric machines include speed, torque, and starting torque.

• These characteristics will be discussed in more detail when specifically studying motors, transformers, and generators.

• Currently, the focus has been on understanding concepts related to power (potencia), voltage (tensión), current (corriente), and power factor.