Intro to AC

AC Alternating Current

Flows in two directions. It can reverse many times per second.

Intro to AC

This is a picture of a Sine Wave.

Intro to AC

The part of the wave above the line is the Positive Alternation.The part of the wave below the line in the Negative Alternation.

Intro to AC

A wave with a positive alternation and a negative alternation is called one Cycle.

The amount of time it takes for one cycle is called the wave’s Period.

The number of cycles in one second is called Frequency.

The length of one cycle is called Wavelength.

Intro to AC

Induction is the production of an electric current in a conductor by varying the magnetic field applied to the conductor.

High Flux Variation produces a high current flow.

Low Flux Variation produces a low current flow.

Intro to AC

Three things are required to induce current flow:

A conductor A magnetic field Relative Motion

Intro to AC

When generating AC power the faster the relative motion the higher the frequency.

Intro to AC

A Sine wave is also called a Sinusoidal Wave.

All other wave shapes are called Non-sinusoidal Waves.

Intro to AC

Formulas

Frequency = 1 / Period Period = 1 / Frequency RT in series = R1 + R2 RT in Parallel = R1 * R2 / R1 + R2 I = V / R V = I * R

Intro to AC

Inductanceand

RL Circuits

Inductance

An Inductor is an electronic component that has the ability to concentrate a magnetic field.

Inductance

The letter symbol for an Inductor is “L” The schematic symbol for an Inductor

Inductance

There are three main classifications of inductors: Air Core Iron Core Variable

Inductance

Inductance is the ability of a conductor to induce voltage when cut by a magnetic field.

Inductance

There are several factors that can determine the amount of inductance:

Number of turns of wire on coil Distance between windings Cross-sectional area of core Permeability of core

Inductance

The henry (H) is the basic unit of inductance. One henry is very large. Millihenry (mH) and microhenry (µH) are more common units of inductance.

Inductance

An RL filter is a circuit constructed from inductors and resistors that will block certain frequencies and pass others.

Inductance

One configuration, called a low pass filter, passes low frequencies while blocking high frequencies.

The other configuration, called a high pass filter, passes high frequencies while blocking low frequencies.

Inductanceand

RL Circuits

Inductance

An Inductor is an electronic component that has the ability to concentrate a magnetic field.

Inductance

The letter symbol for an Inductor is “L” The schematic symbol for an Inductor

Inductance

There are three main classifications of inductors: Air Core Iron Core Variable

Inductance

Inductance is the ability of a conductor to induce voltage when cut by a magnetic field.

Inductance

There are several factors that can determine the amount of inductance:

Number of turns of wire on coil Distance between windings Cross-sectional area of core Permeability of core

Inductance

The henry (H) is the basic unit of inductance. One henry is very large. Millihenry (mH) and microhenry (µH) are more common units of inductance.

Inductance

An RL filter is a circuit constructed from inductors and resistors that will block certain frequencies and pass others.

Inductance

One configuration, called a low pass filter, passes low frequencies while blocking high frequencies.

The other configuration, called a high pass filter, passes high frequencies while blocking low frequencies.

Time Constants

RC time constants are a measure of the time it takes to charge or discharge of a capacitor.

RL time constants are a measure of the time it takes for an inductor to charge to a certain value.

TIME CONSTANTS

It takes 5 time constants to fully charge or discharge a capacitor.

TIME CONSTANTS

The values of ea for each time constant are:

Charging dischargingtc1 = 63% 37%tc2 = 86% 14%tc3 = 95% 5%tc4 = 98% 2%Tc5 = 99% 1%

TIME CONSTANTS

The formula used to determine the time for one time constant is for rc circuits:

tc= c*r

The formula used to determine the time for one time constant is for rl circuits:

tc= l/r

TIME CONSTANTS

The formula used to determine the time for one time constant is:

tc= r * c

TIME CONSTANTS

The formula used to determine the Total time for a Capacitor to charge or an inductor current to raise to maximum is:

time = tc * 5

TIME CONSTANTS

Resonance

LCR circuits have inductors, capacitors, and resistors in series or in parallel.

Resonance

The currents through the capacitor and inductor are 180 degrees out of phase.  Capacitors and inductors oppose each other.

Resonance

In a series LCR circuit, the circuit is:

Resistive when: xc = xlCapacitive when: xc > xlInductive when: xc < xl

Resonance

In a Parallel LCR circuit, the circuit is:

Resistive when: xc = xlCapacitive when: xL > xc

Inductive when: xl < xc

Resonance

Resonance is the condition in an LCR circuit where inductive reactance equals capacitive reactance.

Resonance

A resonant series circuit is a series LCR circuit with an applied frequency that causes XL to equal XC.

Resonance

The frequency where XL equals XC is called the resonant frequency.

Resonance

In a series LCR circuit at resonance:

zt is minimumit is maximum

Resonance

A resonant parallel circuit is a parallel LCR circuit with an applied frequency that causes XL to equal XC.

Resonance

In a parallel LCR circuit at resonance:

ZT is maximumit is minimum

Resonance

Transformers

Transformers are electronic components that match a voltage source to a load.

Transformers

The transformer increases or decreases voltage, depending on the requirements of the load.

Transformers

The purpose of a transformer is to transfer power. Power IN always equals power OUT.

Transformers

Transformers have two coils, theprimary and the secondary coil.

Transformers

The PRIMARY coil receives the input voltage.

The SECONDARY coil receives the induced voltage.

Transformers

Transformers operate on the principle of mutual inductance.

Transformers

Step up transformers increase the applied voltage.

Step down transformers decrease the applied voltage.

Transformers

Transformers have three important circuit values.

1. Turns Ratio 2. Voltage 3. Current

Transformers

Turns ratio formula:

Transformers

To find secondary voltage (Es): =

To find secondary current (Is):

Transformers

The formula for secondary power:

To find primary power:

Transformers

To calculate primary current:

Remember the ratio relationship: = =

Transformers

IILT107 Concepts of Alternating Current by Tony Newton, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

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