Inductance & Inductive Reactance

Two factors affecting inductive reactance

- Inductance - frequency

Factors that affect the inductance of a coil

- number of turns - permeability - length of magnetic path - area

Three factors that affect the rate of change of flux

- rotational frequency - flux density - the angle of cutting

Factors that affect counter EMF

- the inductance of the coil - the rate of change of current

Discharge resistor

A resistor connected across the coil to reduce the inductive kick. Reduces arcing at the switch when inductive circuit is opened

Faraday's law

The amount of induced EMF is directly proportional to the rate of change of flux

Inductive kick

The collapsing magnetic field of a conductor can induce a very high voltage into the circuit. It is dangerous

Self induction

The generation of an EMF in a conductor or circuit by a change of flux in the same circuit Coils (motors, relay coils), transformers

Mutual induction

The generation of an EMF in one conductor or circuit by a change of flux around a separate conductor or circuit. Transformers

RL time constant

The inductance of the circuit divided by the resistance. Requires approximately five time constants to reach the maximum or steady-state value. Each time constant will change the current by 63.2% Formula: t=L/R

Inductive reactance

The opposition created by inductance in an AC circuit

Lenz's law

The polarity of an induced voltage must be such that any current resulting from it will develop a flux that tends to oppose any change in the original flux And induced voltage will oppose the change that produced it. CEMF

Induction

The process by which a voltage is produced by the interaction of a conductor and a magnetic field.

Inductance

The property of a circuit that opposes a change in current. Symbol: L Unit of measure: Henry U.O.M. Symbol: H

Reactive power

The rate at which energy is stored and then returned to the circuit. The product of the reactive voltage and the reactive current Measured in volt-ampere reactive Unit of measure: VAR Symbol: Q

Inductor with DC source

When current is increasing (rate of change of current is maximum)the induced voltage is maximum. When current is zero (starting to increase so rate of change is maximum) the induced voltage is maximum. When the current is maximum the induced voltage is zero

Inductor with AC source

When current is zero the induced voltage is maximum. When current is maximum the induced voltage is zero. Current lags voltage by 90°