TABLE OF CONTENTS
CHAPTER PAGE
1. Concepts of Alternating Current
2. Inductance
3. Capacitance
4. Inductive and Capacitive Reactance
5. Transformers .
APPENDIX
Glossary. Alphabet.
III. Square and Square Roots.
IV. Useful AC Formulas
V. Trigonometric Functions
VI. Trigonometric Tables
AIR-CORE TRANSFORMER—A transformer composed of two or more coils, which are wound around a non-metallic core.
ALTERNATING CURRENT—An electrical current which constantly changes amplitude and changes polarity at regular intervals.
APPARENT POWER—That power apparently available for use in an ac circuit containing a reactive element. It is the product of effective voltage times effective current expressed in voltamperes. It must be multiplied by the power factor to obtain true power available.
AVERAGE VALUE OF AC—The average of all the instantaneous values of one-half cycle of alternating current.
CAPACITANCE—The property of an electrical circuit that opposes changes in voltage.
CAPACITOR—An electrical device capable of storing electrical energy in an electrostatic field.
CAPACITIVE REACTANCE—The opposition offered to the flow of an alternating current by capacitance, expressed in ohms. The symbol for capacitive reactance is Xc.
CHARGE CYCLE—The period of time that a capacitor in an electrical circuit is storing a charge.
COIL—An inductive device created by looping turns of wire around a core.
COPPER LOSS (I2
R LOSS)—
The power lost due to the resistance of the conductors. In transformers the power lost due to heating because of current flow (I) through the resistance (R) of the windings.
CORE—Any material that affords a path for magnetic flux lines in a coil.
COUNTER EMF—Counter electromotive force; an electromotive force (voltage) induced in a coil that opposes the applied voltage.
COUPLING, COEFFICIENT OF—An expression of the extent to which two inductors are coupled by magnetic lines of force. This is expressed as a decimal or percentage of maximum possible coupling and represented by the letter K.
CYCLE—One complete positive and one complete negative alternation of a current or voltage.
DIELECTRIC—An insulator; a term applied to the insulating material between the plates of a capacitor.
DIELECTRIC CONSTANT—The ratio of the capacitance of a capacitor with a dielectric between the electrodes to the capacitance of a capacitor with air between the electrodes.
DIELECTRIC HYSTERESIS LOSS—Power loss of a capacitor due to the changes in orientation of electron orbits in the dielectric caused by rapid reversal in polarity of line voltage. The higher the frequency, the greater the loss.
DIELECTRIC LEAKAGE—Power loss of a capacitor due to the leakage of current through the dielectric. Also relates to leakage resistance, the higher the leakage resistance, the lower the dielectric leakage.
DISPLACEMENT CURRENT—The current which appears to flow through a capacitor.
EDDY CURRENT—Induced circulating currents in a conducting material that are caused by a varying magnetic field.
EDDY CURRENT LOSS—Losses caused by random current flowing in the core of a transformer.Power is lost in the form of heat.
EFFECTIVE VALUE—Same as root-mean-square.
ELECTROMAGNETIC INDUCTION—The production of a voltage in a coil due to the change in the number of magnetic lines of force (flux linkage) passing through the coil.
ELECTROMAGNETISM—The generation of a magnetic field around a current carrying conductor.
ELECTROMOTIVE FORCE (emf)—The force (voltage) that produces an electric current in a circuit
ELECTROSTATIC FIELD—The field of influence between two charged bodies.
EXCITING CURRENT—The current that flows in the primary winding of a transformer, which produces a magnetic flux field. Also called magnetizing current.
FARAD—The basic unit of capacitance. A capacitor has a capacitance of 1 farad when a voltage change of 1 volt per second across it produces a current of 1 ampere.
FLUX—Electrostatic or magnetic lines of force.
FREQUENCY (f)—The number of complete cycles per second existing in any form of wave motion;such as the number of cycles per second of an alternating current.
HENRY (H)—The electromagnetic unit of inductance or mutual inductance. The inductance of a circuitis 1 henry when a current variation of 1 ampere per second induces 1 volt.
It is the PEAK VALUE—The maximum instantaneous value of a varying current, voltage, or power. It is equal to 1.414 times the effective value of a sine wave. to the flow of an alternating current by the inductance,capacitance, or both, in any circuit.
