1.6 Voltaje, Corriente Y Potencia Electrica En Un Circuito Balanceado 3e2t43

Tema: 1.6_Voltaje, Corriente y Potencia Eléctrica en un Circuito Trifásico Balanceado.

 Integrantes:  Marco Antonio Salto Molina.

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 Armando Daniel Becerril Valdovinos.

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BALANCED THREE-PHASE CIRCUITS The generation, transmission and distribition of eletric power is accomplished by means of theree-phase cirtuits. at the generating station, three sinusoidal voltages are gererated having the same amplitude but displaced in phase by 120°. this is called a balanced source. if the renerated voltages reach their peak values in the sequential order ABC, the generator is said to have a positive phase sequence, shown in Figure 2.11 (a). if the phase order is ABC, the generator is said to have a negative phase sequence, as shown in Figure 2.11(B)

La generación, transmisión y distribución de energía eléctrica se lleva a cabo por medio de circuito trifásicos en la estación generadora, tres tensiones sinusoidales se generan, que tienen la misma amplitud, pero desfasadas en fase en 120°. esto se llama una fuente equilibrada. si los voltajes Generados alcanzan sus valores máximos en el orden secuencial ACB, se dice que el generador tiene una secuencia de fase positiva, que se muestra en la Figura 2.11 (a). si el orden de las fases es ABC, se dice que el generador tiene una secuencia de fase inversa, como se muestra en la figura 2.11(B)

 In a three-phase system, the instantaneous power delivered to the external loads is constant rather than pulsaung as it is In a single-phase circuit, Also. three-phase motors, having constant torque, start and run much better than single-phase motors. This feature of three-phase power, coupled with the inherent efficiency of its transmission compared to single-phase (less wire for the same delivered power), s for its universal use.  En un sistema de trifásico, la potencia instantánea entregada a las cargas externas es constante en lugar de pulsante como lo es en un circuito monofásico, Además. Los motores trifásicos, con par constante, iniciar y ejecutar mucho mejor que los motores de una sola fase. Esta característica de potencia trifásica, junto con la eficiencia inherente de su transmisión en comparación con el de una sola fase (menos alambre para la misma potencia de salida), cuenta con uso universal.

 A power system has Y-connected generators and usually includes both ∆ - and Y-connected loads Generators are rarely ∆ -connected, because if the voltages are not perfectly balanced, there will be a net voltage, and consequently a circulat-ing current, around the ∆. Also, the phase voltages are tower in the Y-connected generator, and thus less insulation is required.

 Un sistema de energía de generadores Y-conectado y por lo general incluye tanto ∆ - y cargas conectadas ∆-generadores son raramente Una conectado, ya que si los voltajes no son perfectamente equilibrado, habrá una tensión de red, y en consecuencia una circulante ing actual, alrededor del ∆. Además, las tensiones de fase que están en la torre y conectado en estrella se requiere generador, y por lo tanto menos aislamiento.

 In power systems, great care is taken to ensure that the loads of transmission lines are balanced. For balanced loads, the terminal voltages of the generator V An , V Bn and V Cn and the phase voltages

V an ,

V bn

and

V cn

at the load terminals are balanced For

"phase A," these are given by.

 En los sistemas de energía, se tiene mucho cuidado para asegurar que las cargas de las líneas de transmisión están equilibrados. Para cargas equilibradas, las tensiones en los terminales del generador de V An , V Bn

y

V Cn

y las tensiones de fase

V an ,

V bn

y

V cn

en los

terminales de carga están equilibradas Por "fase A", estos se dan por:

BALANCED THREE-PHASE POWER consider a balanced three-phase source supplying a balanced Y-connected load with the following instantaneous voltages.

for a balanced load the phase currents are

where

¿ V P ∨¿

and

¿ I P∨¿

are the magnitudes of the rms phase voltage

and current, respectively. the total instantaneous power is the sum of the instantaneous power of each phase, given by

substituting for the instantaneous voltage and currents from (2.40) and (2.41) into (2.42)

using the trigonometric identity

the three double frequency cosine in (2.43) are out of phase with each other by 120° and add up to zero, and the three-phase instantaneous power is

note that although the power in each phase is pulsating, the total instantaneous power is constant and equal to three times the real power in each phase. indeed, this constant power is the main advantage of the three-phase system over the single-phase system. since the power in each phase is pulsating, the power, then, is made up of the real power and the reactive power. in order to obtain formula symmetry between real and reactive powers, the concept of complex or apparent power (S) is extended to three-phase systems by defining the three-phase reactive power as

thus, the complex three-phase power is

equation (2.44) and (2.45) are sometimes expressed in of the rms magnitude of the line voltage and the rms magnitude of the line current. in a Y|V L| connected load the phase voltage |V P|= √ 3 and the phase current

|I P|=|I L| in the delta-connection

|V P|=|V L|

y

|I L| |I P|= √ 3

. substituting for the phase

voltage and phase currents in (2.44 ) and (2.45) the real and reactive powers for either connection are given by