Inductive Reactance Electronics. Inductors in AC Circuits.

Inductive Reactance

Electronics

Inductors in AC Circuits

Inductance

Inductance opposes a change in current.

Inductors create a voltage that opposes the current.

Counter EMF(voltage)

Lv

Inductance

The Henry (symbol: H) is the SI unit of inductance.

It is named after the American physicist Joseph Henry..

Current

Voltage

Capacitor in DC

ELI

E L IVoltage InductanceInductance CurrenCurren

tt

Voltage leads CurrentVoltage leads Current

in anin an

Inductive CircuitInductive Circuit

Current

Voltage

Inductance in AC

Current Voltage

I = Ipsin(2πft) Ip-Peak Current

2π-Cycle

f-frequency(Hz)

t-time(seconds)

V = L di/dt

V = L Ip(2πf)cos(2πft)

Vp = Ip(2πf)L

V = L d(Ipsin(2πft))/dt

Vp = Ip2πfL

R = 2πfL

Inductive Reactance

XL = 2πfL

L is an Active Component

Vp/Ip= 2πfL

Calculate the maximum current in a coil which has an inductance of 3 mH. The frequency is 60Hz. The maximum voltage across the coil is 6 V.

XL = 2πfL

L=3mH E=6Vf=60Hz

XL = 2π(60Hz)(.003H)

XL = 1.13Ω

I = E/XL

I = 6V/1.13Ω

I = 5.3A

Inductive/Resistive Circuit 90° Phase Shift caused by Inductor Impedance, Z, is calculated by

adding XL and R vectorially.

XL

R

Z

What is the impedance of a 100mH choke in series with a 470Ω resistor with a 12V, 60Hz applied across them? What is the phase angle between voltage and current?

XL = 2πfL

L=100mH E=12Vf=60Hz

XL = 2π(60Hz)(.1H)

XL = 37.7Ω

R=470Ω

XL

R

Z

Current

Voltage

Inductance in AC 4.6°

Inductance in AC Circuits

1mF = 1 X 10-3F

1μF = 1 X 10-6F

1nF = 1 X 10-9F

1pF = 1 X 10-12F

Capacitor Values

RLC Circuits

RLC Circuits 90° Phase Shift caused by Inductor

XL

R

Z

XC

-90° Phase Shift caused by Capacitor

Xc = 1/(2πfC)

Xc = 1/(2π(60)(1.5X10-6)

Xc = 1768Ω

XL = 2πfL

XL = 2π(60)(0.65)

XL = 245Ω

XL

RZXC

𝚹 = -81°ICE – Current leads Voltage by 81°

Resonance The frequency where XL = XC

The Circuit becomes a purely resistive circuit

Xc = 1/(2πfC) XL = 2πfL

1/(2πfC) = 2πfL

Xc = XL

1/(4π2CL) = f2

= f

= f

161 Hz= f

Worksheet Lab 2-6

Capacitors In

AC CircuitsProblems

Reactance Test Classwork Lab 7, Book 2 – Capacitive Reactance Worksheets

Lab 2-5 Lab 2-6 Lab 2-8 Lab 2-9 Lab 2-11 Lab 2-12 Lab 2-13Due the

day of the test!!