Inductance and Inductive ReactanceInductance and Inductive Reactance

Inductance- the characteristic of an electrical ckt that oppose any change in current

Symbol is “L” measured in a Henry (H)

Inductors – Coils, inductors, reactors or chokes

Faraday’s Law Faraday’s Law

States that the induced voltage depends on:

the number of turns in the coil,

The strength of the magnetic field

How fast the conductor cuts across the magnetic field

Lenz’s LawLenz’s Law

Inductance Inductance

All ckts have conductors Has its greatest impact when there is a change in

current Does not oppose current only the change in current AC ckt current always changes do to the sine wave

Coil InductanceCoil Inductance

Four factors Number of turns in the coil

Diameter of the coil and length

Type of material

Number of layers of the windings

Power Loss in an InductorPower Loss in an Inductor

Copper losses I2R

Iron – core inductors Hysteresis loss Eddy-current loss

Transformer Action Transformer Action Mutual Inductance

Inductive ReactanceInductive Reactance

the reactance of an inductor is called inductive reactance. In other words, an inductors resistance in an AC circuit is called Inductive Reactance

Inductive ReactanceInductive Reactance

Reactance (x) is expressed in Ohms and Ohms law applies to inductive reactive circuits

Inductive Reactance represented by XL

Depends on: Frequency usually 60 hz Inductance of the coil (H) - henry

Inductive ReactanceInductive Reactance

As a Formula

XL = 2пfL

XL = inductive reactance Ω

П = 3.14

f = Frequency in Hz

L = inductance in henrys

Voltage, Current and InductanceVoltage, Current and Inductance

Ohms Law

LX

E Inow or

R

E I ==

Sine Wave Pure ResistanceSine Wave Pure Resistance

Sine Wave With ReactanceSine Wave With Reactance

Phase DiagramPhase Diagram

CCWRotation

90

+y

-y

+xE

= 1

20

V

I = 12A

Power in an Inductive CircuitPower in an Inductive Circuit

Purely resistive

Inductive Reactance

Vars (Q) – volt amps of reactance

VA (S) - Volt amps

Power (P) – Power of load