چەندێتەی گۆڕاوە (AC) چیە؟

Mînasanên Serbestbûna Circuits

Circuitek serbestbûna li gorê dergahê werzanîn di navbera vêre. Gerê serbestbûn (AC) bi sereke yên ve ji bo karên endamyar û endüstryal yê bikaranîn da ku dikare wan şeşavên xusiyên taybetand: jêrî DC, hêza û derexa gerê û berzê di circuitek serbestbûn de digire hatine di deman de.

Formên serbestbûn herêmîn bi formê sinusoidal dest pê dike, yek cîhaz bi nîvên rast û negatif bikişane. Vê axoyek bi rêzik ên tarîf kirin li ser hejmarê dem (t) an angle (θ = ωt), ku ω wateya angular dîsa.

Impedance di Circuitek AC vs. DC de

• Di circuitek DC de, pirsgirêka gerê tikandin ji resistance (R) deriva dike.

• Di circuitek AC de, pirsgirêk ji:

• Resistance (R)

• Inductive reactance (XL = 2πfL), ku L induktansya û f frekansa ye

• Capacitive reactance (XC = 1/(2πfC)), ku C capacitance ye

Phase Relationships di Sisteman AC de

Di circuitek AC de, gerê û berz di navbera hêza û angle phase de nîşan dide. Paralelkirina wan bi parametreyên circuit (R, L, C) were parçav kirin. Sinusoidal quantities like voltage and current vary with the sine of angle θ, making them fundamental to AC system analysis.

Advantages of Sinusoidal Waveforms in Power Generation

Sinusoidal voltage and current are globally preferred for power generation due to:

• Reduced iron and copper losses in transformers and rotating machines, enhancing efficiency.

• Minimized interference with adjacent communication systems.

• Lower disturbance levels in electrical circuits.

Alternating Voltage and Current Dynamics

Waveform of Alternating Voltage and Resistive Current

The waveform of alternating voltage over time and the current flowing through the resistance (R) in the circuit are shown below:

Types of AC Circuits and Key Terminology
AC Circuit Classifications

AC circuits are categorized based on their component configurations:

• Pure resistance (R) circuits

• Pure capacitance (C) circuits

• Pure inductance (L) circuits

• RL (resistance-inductance) combinations

• RC (resistance-capacitance) circuits

• LC (inductance-capacitance) circuits

• RLC (resistance-inductance-capacitance) circuits

Essential AC Circuit Terms

• Amplitude:The maximum positive or negative value of an alternating quantity within one cycle, also known as peak value or maximum value. Symbolized by Em/Vm for voltage and Im for current.

• Alternation:A half-cycle of an alternating waveform, corresponding to 180° electrical.

• Cycle:One complete set of positive and negative values of an alternating quantity, equivalent to 360° electrical.

• Instantaneous Value:The voltage or current magnitude at any specific moment, denoted by e (voltage) or i (current).

• Frequency (f)： The number of cycles per second of an alternating quantity, measured in hertz (Hz).

• Time Period (T):The duration in seconds to complete one cycle of a voltage or current waveform.

• Waveform:A graphical representation plotting instantaneous values of an alternating quantity (voltage/current) on the y-axis against time (t) or angle (θ = ωt) on the x-axis.

An alternating voltage periodically reverses polarity and magnitude, while alternating current follows suit—changing direction and amplitude with time. When an AC voltage source connects to a resistive load (as shown below), current flows in one direction during the positive half-cycle and reverses during the negative half-cycle, mirroring the source’s polarity changes.