Contents

POWER. 1

POWER IN AC CIRCUITS. 1

Average, MAX and min PoweR. 1

Complex Power. 1

Power factor correction. 2

Trigonometric identites Frequently used in complex power calculations. 2

INDUCTORS. 2

TRANSFORMERS. 3

DOT convention. 3

Bridge Circuits. 4

Millman’s Theorem.. 5

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

INDUCTORS

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

TRANSFORMERS

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 Circuits

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

Millman’s Theorem