mạch điện ac trang bị điện

Ho Chi Minh City National University
Ho Chi Minh City University of Technology
Faculty of Mechanics Engineering
Department of Mechatronics Engineering

Subject:
Electrical & Electronic Equipment for Industrial Machinery

AC Electric Circuit & Theory

PhD. Ngô Hà Quang Thịnh,


Contents
▪ Introduction
▪ Definition
▪ How to perform AC current
▪ Power of AC current
▪ Transformer
▪ Natural Response of a Parallel RLC circuit
▪ Natural Response of a Series RLC circuit
PhD. Ngô Hà Quang Thịnh,


Introduction


What are SI units ?
► Abbreviation from French “Système international d'unités”,
established in 1960.
► The SI Units are based on 7 defined quantities: length (m), mass (kg),

time (s), current (A), temperature (K), amount (mol), luminous intensity
(cd).
► SI units enable engineers to communicate in a meaningful way about
quantitative results.

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Derived units in SI

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Prefixes to Signify Powers of 10
► Engineers often use powers divisible by 3, and base numbers between
1 and 1,000

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Prefixes to Signify Powers of 10

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Passive Sign Convention
► If the reference current through the element is in the direction of the
reference voltage drop across the element, we can use a positive sign in
the i-v relation of the element.
► E.g. Let the reference current and voltage of the resistor satisfy the

passive sign convention, → we have v = +R x i, though the values of v, i
can be >0 or <0.

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Generation & Distribution of AC Power

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Residential Wiring

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Single Phase Three-Wire Residential Wiring

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Ground Fault Circuit Interrupter (GFCI)

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What is a Complex Number

► A complex number z is a point (or vector) on a two-dimensional plane,
known as the complex plane and represented by C.

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Cartesian Coordinates

► The Cartesian coordinates of z are
- x = Re{z}: the real part of z
- y = Im{z}: the imaginary part of z
► The corresponding axes are known as the real and imaginary axes,
respectively

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Polar Coordinates

► The polar coordinates of z are
- r = |z|: the modulus or magnitude of z
- θ = z: the angle of z

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Converting Between Coordinates

► The Cartesian coordinate pair (x, y) is also equivalent to the polar
coordinate pair (r, θ) where r is the (non-negative) length of the vector
corresponding to (x, y) and θ is the angle of the vector relative to positive
real time

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Definition


What is Alternating Current

► Consider that a machine is constructed to rotate a set of wire coils with
the turning of a shaft in the magnetic field.
► In accordance with Faraday’s Law of electromagnetic induction, AC
voltage will be produced across the wire coils when shaft is rotated.
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AC Waveform
► Voltage, current or flux signal and
so on are related to time in sine
function:

where
Vm: amplitude of voltage [V]
ω: angular frequency
[rad/s]
Ф: initial phase when t = 0 [rad]
► Period T or frequency f of current, voltage are determined in the following:

► Units :

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AC Measurements

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