Glossary

A | B | C | D | E | F | G | H | I | L | M | O | P | R | S | T | V | W

 

A

 “A” Stage (of Resin) The condition of low molecular weight of a resin polymer during which the resin is readily soluble and fusible.

Abrasion Resistance – Ability to resist surface wear.

Accelerator – An additive which hastens a chemical reaction under specific conditions.  Another term is Promoter.

Adhesive – A material capable of holding other materials together by surface attachment.

Aging – The change in properties of a material with time under specific conditions.

Alternating Current – Current in which the charge-flow periodically reverses and is represented by:  I – I.cos (2π f t + Ø) where, I is the current, I. is the amplitude, f the frequency, Ø the phase angle.

Ambient Temperature – The temperature of the surrounding cooling medium, such as gas or liquid, which comes into contact with the heated parts of the apparatus.

American Wire Gauge (AWG) – The standard system used for designating wire diameter.  Also referred to as the Brown and Sharpe (B&S) wire gauge.

Ampere – A unit of current.  It is the current flowing through one ohm of resistance at 1 volt potential.

Anneal – To heat and then gradually cool in order to relieve mechanical stresses.

Arc Resistance – The time required for an arc to establish a conductive path in a material.

Armature – The part of a machine which includes the main current-carrying winding.  In direct-current machines and in alternating-current conmutator machines, the armature winding is connected to the commutator and the armature is the rotating member.  In alternating current machines without commutators, the armature may be either the rotating member of the stationary member.

“B” Stage – The condition of a resin polymer when it is more viscous, with high molecular weight, being insoluble but plastic and fusible.

Barrier – A partition for the insulation or isolation of electric circuits or electric arcs.

Bond Strength – The amount of adhesion between bonded surfaces.

Breakdown (Puncture) – A disruptive electrical discharge through insulation. 

Breakdown Voltage – The voltage at which the insulation between two conductors will break down.

British Thermal Unit – Quantity of heat required to raise the temperature of one pound of water 1º F at its point of maximum density.

Brush – A metal or carbon block used to make contact with a rotating part, such as the armature, of a generator or motor.

Busbar – A heavy copper (or other metal such as aluminum) strip or bar used on switchboards and in power plants to carry heavy currents.

Butt Wrap – Tape wrapped around an object in an edge-to-edge condition.

“C” Stage – The condition of a resin polymer when it is in the solid state, with high molecular weight, being insoluble and infusible.

Calender – To prepare sheets by pressure between two or more counter-rotating rolls.

Cambric – Fine weave linen or cotton fabric used for insulating purposes.  Available in straight and bias weave styles.

Canvas – A cotton fabric weighing more than four ounces per square yard.

Capacitance (Capacity) – That property of a system of conductors and dielectrics which permits the storage of electricity when potential difference exists between the conductors.

Capacitor (Condenser) – A device, the primary purpose of which is to introduce capacitance into an electric circuit.

Cast – a)  To form plastic objects, film, or sheets by pouring a fluid monomerpolymer solution into an open mold, onto a moving belt, or by precipitation in a chemical bath, b)  To form objects by pouring molten metal into molds.

Catalyst – A substance which initiates and/or accelerates a chemical reaction but normally does not enter into the reaction.

Circuit – A complete path over which electrons can flow from the negative terminals of a voltage source through parts and wires to the positive terminals of the same voltage source.

Circular Mil – A unit of area equal to the area of a circle whose diameter is 1 mil (0.001 inch); equal to square mil x 0.78540.  Used chiefly in specifying cross-sectional areas of round conductors.

Coat – To cover with a finishing, protecting, or enclosing layer of any compound (such as varnish).

Coefficient of Expansion – The fractional change in dimension of a material for a unit change in temperature.

Coil, Electric – Successive turns of insulated wire which create a magnetic field when an electric current is passed through them.  It may also consist of a number of separately insulated sections which lie side by side around the same magnetic circuit.

Collector Rings (Slip Rings) – Metal rings suitably mounted on an electric machine, serving, through stationary brushes bearing thereon, to conduct current into or out of the rotating member.

Commutator – A cylindrical ring or disk assembly of conducting members, individually insulated in a supporting structure with an exposed surface for contact with current-collecting brushes.

Condensation – A chemical reaction in which two or more molecules combine with a resulting separation of water or some other simple substance.

Conductor – An electrical path which offers comparatively little resistance.  A wire or combination of wires not insulated from one another, suitable for carrying a single current.

Contaminant – An impurity or foreign substance present in a material which affects one or more properties of the material.

Corona – A luminous discharge due to ionization of the gas surrounding a conductor around which exists a voltage gradient exceeding a certain critical value.  A type of discharge, sometimes visible, in the dielectric of an insulation system caused by an electric field and characterized by the rapid development of an ionized channel which does not completely bridge the electrode.  May be continuous or intermittent.  Not a material property, but related to the system, including electrodes.

CoronaResistance – The time that insulation will withstand a specified level field-intensified ionization that does not result in the immediate complete breakdown of the insulation.

Corrosion – Chemical action which causes destruction of the surface of a metal by oxidation or chemical combination.  Also caused by reduction of the electrical efficiency between the metal and a contiguous substance or the disintegrating effect of strong electrical currents or ground return currents in electrical systems.  The latter is known as electrolytic corrosion. 

Crazing – Minute cracks on or near the surface of materials such as ceramics and plastics.

Creep – The dimensional change with time of a material under load.

Creepage – Electrical leakage on a solid dielectric surface.

Cross-Linking – The setting–up of chemical links between the molecular chains.

Cure – To change the physical properties of a material by chemical reaction, by the action of heat and catalysts, alone or in combination, with or without pressure.

Curing Temperature – Temperature at which a material is subjected to curing.

Curing Time – In the molding of thermosetting plastics, the time it takes for the material to be properly cured.

Current – The rate of transfer of electricity.  Practical unit is the ampere which represents the transfer of one coulomb per second.

Cut-Through – Resistance of solid material to penetration by an object under conditions of pressure, temperature, etc.

Delamination – The separation of layers in a laminate through failure of the adhesive.

Density – Weight per unit volume of a substance.

Dielectric – a) Any insulating medium which intervenes between two conductors and permits electrostatic attraction and repulsion to take place across it.  b) A non-conductor of direct electric current.

Dielectric Strength – The voltage which an insulating material can withstand before breakdown occurs, usually expressed as a voltage gradient (such as volts per mil).

Dimensional Stability – Ability to retain precise shape and size.

Dipping – The process of impregnating or coating insulating materials or windings by the simple method of immersion in the liquid insulating material.

Direct Current – An electric current which flows in only one direction.

Drier – A material (usually a metallic oxide) which aids in the drying of oils and resins employed in varnishes.

Elastomer – A material which at room temperature stretches under low stress to at least twice its length and snaps back to original length upon release of stress.

Electrolysis – The production of chemical changes by passing current through an electrolyte.

Electromagnet – A coil of wire, usually wound on an iron core, which produces a strong magnetic field when current is sent through the coil both to the electric lines of force and to their direction of motion.

Electromagnetic Field – A rapidly moving electric field and its associated moving magnetic field, located at right angles.

Electromagnetic Induction – The production of a voltage in a coil due to a change in the number of magnetic lines of force (flux linkages) passing through the coil.

Elongation – The fractional increase in length of a material stressed in tension.

Encapsulating – Enclosing an article in plastic.

Exothermic – Chemical reaction in which heat is given off.

Extractables – Outgasing due to decomposition of materials.

Extrusion – Compacting a plastic material and forcing it through an orifice in a more-or-less continuous fashion.

Filament Winding – Impregnated roving or single strands of glass or other reinforcement wound in a predetermined pattern on to a suitable form or mandrel which is then cured.

Fishpaper – type of paper treated chemically to increase mechanical and electrical properties.

Flame Resistance – Ability of the material to extinguish flame once the source is removed.

Flammability – Measure of the material’s ability to support combustion.

Flash Point – The temperature at which a flammable material will produce enough vapor to flash in air.

Flexural Strength – The strength of a material in bending.

Form Wound – A coil or winding prewound on a form of a predetermined shape.

Frequency – The number of complete cycles or vibrations per unit of time.

Gel – A semi-solid system consisting of a solid held in a liquid.

Generator – A rotating machine which converts mechanical energy into electrical energy.

Ground Insulation – The major insulation used between a winding and the magnetic core or other structural parts, usually at ground potential.

Heat Sink – Any device that absorbs and draws off heat from a hot object, reradiating it into the surrounding atmosphere.

Horsepower – A unit of power equal to 550 ft.-lbs.  per second, electrically equivalent to 746 watts.

Hydrolysis – Chemical decomposition of a substance involving the addition of water.

Hygroscopic – Tending to absorb moisture.

Impregnate – To fill the voids and interstices of a material with a compound.

Infra-red – Part of the electromagnetic spectrum between the visible light range and the radar range.

Inhibitor – A chemical compound added to a mixture to restrain its chemical reaction until a desired condition exists.

Inorganic – Designating, or composed of, matter other than animal or vegetable, such as earthy or mineral matter.

Insulation – Material having a high resistance to the flow of electric current, to prevent leakage of current from a conductor.

Insulation System – All of the insulation materials used to insulate a particular electrical or electronic product.

Insulator – A material of such low electrical conductivity that the flow of current through it can usually be neglected.

Laminated Plastics – Layers of a synthetic resin-impregnated or coated base material bonded together by means of heat and pressure to form a single piece.

Lamination – The process of preparing a laminate.  Also any layer in a laminate.

Layer – Consecutive turns of a coil lying in a single plane.

Lead – The conductor brought out from a coil or winding.

Magnet – Specifically, a body possessing the property of attracting to itself particles of iron.  More generally, a material capable of maintaining within and about itself a field of magnetic force.

Magnetic Core – In an armature or a transformer, etc., the iron stampings or laminates which, when assembled, form a metallic path for the magnetic circuit.

Magnetic Field – The region surrounding a magnet, through which magnetic forces act.  Composed of lines of force.

Moisture Resistance – The ability of a material to resist absorbing moisture from the air or water.

Motor – A machine that converts electric energy into mechanical energy.

Organic – Designating or composed of matter originating in plant or animal life or composed of chemicals of hydrocarbon origin, either natural or synthetic.

Phenolic Resin – A synthetic resin produced by the condensation of phenol with formaldehyde.

Plastic – High polymeric substances, including both natural and synthetic products, but excluding the rubbers, that are capable of flowing under heat and pressure.

Plasticizer – Chemical agent added to plastics to make them softer and more flexible.

Polarity – An electrical condition determining the direction in which current tends to flow.

Pole – One end of a magnet.  One electrode of a battery.

Polyamide – A polymer in which the structural units are linked by amide or thioamide groupings.

Polyester – A resin formed by the reaction between a dibasic acid and a dihydroxy alcohol.

Polymer – A compound formed by uniting smaller molecules into a repeating structural unit.

Polymerize – To unite chemically two or more monomers or polymers of the same kind to form a molecule with higher molecular weight.

Polyvinyl Acetate – A thermoplastic material composed of polymers of vinyl acetage.

Polyvinyl Chloride (PVC) – A thermoplastic material composed of polymers of vinyl chloride.

Polyvinylidene Chloride – A thermoplastic material composed of polymers of vinylidene chloride (1, 1-dichloroethylene).

Potting – Similar to encapsulating, except that steps are taken to insure complete penetration of all the voids in the object before the resin polymerizes.

Random Winding – A winding wherein the wires do not lie in an even pattern.

Reinforcement – A material used to reinforce, strengthen, or give dimensional stability to another material.

Resin – An organic substance of natural or synthetic origin characterized by being polymeric in structure and predominately amorphous.  Most resins, though not all, are of high molecular weight and consists or long chain or network molecular structure.  Usually resins are more soluble in their lower molecular weight forms.

Rotor – The rotating member of a machine.

Rubber – An elastomer capable of rapid elastic recovery.  Specifically, natural rubber, the standard of comparison for elastomers.

Shaded Pole Motor – A single phase induction motor having one or more auxiliary short-circuited windings acting on only a portion of the magnetic circuit.

Shelf Life – Length of time under specified conditions that a material retains its usability.

Silicone – Polymeric materials in which the recurring chemical group contains silicon and oxygen atoms as links in the main chain.

Sleeving – A braided, knitted, or woven tube.

Slot – One of the grooves formed in the iron core of a motor or generator armature for the conductors forming the armature winding.

Slot Cell – A formed sheet of insulation placed within the slot of a magnetic core.  This separate from the coil.

Solvent – A liquid substance which dissolves other substances.

Squirrel-cage Induction Motor – An induction motor in which the secondary circuit, usually the rotor, consists of a squirrel-cage winding (two disks connected along their circumference with copper bars) arranged in slots in the iron core.

Stator – The portion of a machine which contains the stationary parts of the magnetic circuit with their associated windings.

Storage Life – The period of time during which a liquid resin or adhesive can be stored and remain suitable for use.  Also called Shelf Life.

Substrate – A material on whose surface an adhesive substance is spread for bonding or coating.  Any material which provides a supporting surface for another material, especially materials used to support printed circuit patterns.

Tap – A special lead brought out from an intermediate point of a coil or winding.

Tape – A relatively narrow, woven or cut, strip of fabric, paper, or film material.

Tear Strength – Force required to initiate or continue a tear in a material under specified conditions.

Temperature Class - Representative Products
Class A  -  105ºC  (221ºF) - Cotton, silk, paper (rag & kraft) fibre-board & press- board
Class B  -  130ºC  (226ºF) - Polyester film (mylar), dacron, & glass fiber
Class F   -  155ºC  (311ºF) - Duroid, D-M-D, & acrylic resins
Class H  -  180ºC  (356ºF) - Silicones & polyester resins
Class C  -  over 220ºC  (428ºF) - Nomex, Kapton, Teflon, mica, porcelain & fiberglass

Tensile Strength – The pulling stress required to break a given specimen.

Thermal Conductivity – Ability of a material to conduct heat.

Thermal Endurance – The time at a selected temperature for an insulating material or system of materials to deteriorate to some predetermined level of electrical, mechanical, or chemical performance under prescribed conditions of test.

Thermal Expansion (Coefficient of) – The fractional change in length (sometimes volume) of a material for a unit change in temperature.

Thermocouple – A device for measuring temperature where two electrical conductors of dissimilar metals are joined at the point of heat application and a resulting voltage difference directly proportional to the temperature, is developed across the free ends and is measured potentiometrically.

Thermoplastic – A classification of resin that can be readily softened and resoftened by repeated heating.

Thermosetting - A classification of resin which cures by chemical reaction when heated and, when cured, cannot be resoftened by heating.

Thixotropic – Describes materials that are gel-like at rest but fluid when agitated.

Tolerance – A specified allowance for error from a standard or given dimension weight, or property.

Transformer – A device employing the principle of mutual induction to convert variations of current in a primary circuit into variations of current and voltage in secondary circuit.

Tubing – Extruded non-supported plastic and elastomer materials.

Turn – One conductor making one complete loop around a magnetic circuit.

V-Ring – A special shaped insulating structure with one or more vee-shaped sections used in the construction of commutators.

Viscosity – A measure of the resistance of a fluid to flow (usually through a specific orifice).

Volt – Unity of electromotive force.  It is the difference of potential required to make a current of one ampere flow through a resistance of one ohm.

Voltage – The term most often used in place of electromotive force, potential, potential difference, or voltage drop, to designate electric pressure that exists between two points and is capable of producing a flow of current when a closed circuit is connected between the two points.

Vulcanization – A chemical reaction in which the physical properties of an elastomer are changed by reacting it with sulfur or other cross-linking agents.

Water Absorption – Ratio of the weight of water absorbed by a material to the weight of the dry material.

Wire – A conductor of round, square, or rectangular section, either bare or insulated.

Working Life – The period of time during which a liquid resin or adhesive, after mixing with catalyst, solvent, or other compounding ingredients, remain usable.

Wrapper – An insulating barrier applied to a coil in sheet from by wrapping around the coil periphery.  This is an integral part of the coil.