Contents

POWER

POWER IN AC CIRCUITS

Average, MAX and min PoweR

Complex Power

Power factor correction

Trigonometric identites Frequently used in complex power calculations

INDUCTORS

TRANSFORMERS

DOT convention

Bridge Circuits

Millman’s Theorem

# POWER

## POWER IN AC CIRCUITS

### Average, MAX and min PoweR

 Signal Instantaneous Power Average , Maximum and Minimum power in terms of power factor (PF)

### Complex Power

 Complex Power 1.       Apparent Power is the magnitude of the complex power.   2.       Average/Real Power and Reactive Power is the real part and imaginary part of the complex power respectively.   3.       Unit of reactive power is VARS Reactive Power (VARS) Average Power/Real Power Complex Power 1.       Apparent Power =   2.       The unit of apparent power is VA   3.       Apparent power is the magnitude of the complex power. 1.       Complex Power 2.       Real Power 3.       Reactive Power 4.       Apparent Power

### Power factor correction

 (Lagging power factor)    (Leading power factor)    is the impedance angle, or power factor angle

### Trigonometric identites Frequently used in complex power calculations

 Average value of Average value of

 Inductance of a coil with N turns, cross section area A, length L and core permeability Voltage induced across an inductor Voltage induced across a coil (w.r.t flux linkage ) Flux linkage  and current relation Energy stored in an inductor Magnetic equivalent of electric current Source of EMF is battery Source of MMF is current coil

## DOT convention

 A current entering the dotted terminal of one coil produces voltage with a positive voltage reference at the dotted terminal of the second coil. A current entering the dotted terminal of one coil produces voltage with a positive voltage reference at the dotted terminal of the second coil. Voltages and currents in terms of phasors Coefficient of mutual coupling Dot convention and current / voltage polarity reference Reflection of secondary into primary Reflection of primary into secondary Current and flux direction using right hand rule LENZ’S LAW   The direction of the induced voltage( in other words the current direction)will be such that it will oppose the change in the flux General Transformer Equation primary or secondary RMS Voltage  Frequency of RMS Voltage  turns of primary or secondary  Peak value of flux Impedance Matching If the transformer is acting as an impedance matching device than

 Bridge circuit can be used to determine the value of an unknown resistance. The bridge is balanced if  or.   When the bridge is balanced then