1.7 Relay Terms and Definitions-Glossary

The following definitions do not include terms peculiar to mathematical formula, statistical analysis, relay reliability studies, and the like. Such terms are defined in the appropriate chapter. When cross-references are made, the preferred terminology is the one under which the definition appears.

Actuating card. See card, armature.
Actuating system. See actuator.
Actuation time. See time, actuation.
Actuator. The parts of a relay that convert electrical energy into mechanical work.
Add-and-subtract relay. See relay, bidirectional.
Adjustment. The modification of any or all of the elements of tension, shape, or position of relay parts (to affect one or more of the operating characteristics or to meet mechanical requirements);e.g., adjustments of armature gap, restoring spring force, contact force or contact pressure.(See Figure 1.13.)


Air gap. See gap, armature; gap, contact; gap, heel.
Airline See gap, heel.
Ampere-turns. The product of the number of turns in an electromagnetic coil winding and the current in amperes passing through the winding. On ac, the rms current value is generally used in the product of current and turns and is referred to as rms ampereturns.
Antifreeze pin. See residual screw, pin, plate, stud, or shim.
Arm, armature. (1) on some types of armature, the protrusion or lever employed to actuate the associated contact spring pileup. (2) The moving part or pans of a reed switch.
Arm, contact. A current-carrying protrusion, resilient or nonresilient, onto which contacts may be fastened. Also see spring, contact.
Armature. The moving magnetic member of an electromagnetic relay structure.
Armature, balanced. A relay armature that rotates about its center of mass and is therefore approximately in balance with both gravitational (static) and accelerative (dynamic) forces.
Armature contact. See contact, movable.
Armature, end-on. A relay armature whose principal motion is parallel to the longitudinal axis of a core having a pole face at one end.
Armature, long-lever. An armature with its contact-actuating arm greater in length than the distance from the armature hinge, bearing, or fulcrum to the portion of the armature opposite the pole face. (See Figure 1.14.)
Armature, plunger or solenoid. A relay armature that moves within a tubular core in a direction parallel to its longitudinal axis.
Armature residual gap. See gap, residual.
Armature, short-lever. An armature with its contact-actuating arm length equal to or lesser in length than the distance from the armature hinge, bearing, or fulcrum to the portion of the armature opposite the pole face.(See Figure 1.14.)


Armature, side or armature, flat. A relay armature whose motion is perpendicular to the longitudinal axis of a core having a pole face at one side.
Armature stroke. See buffer, armature.
Armature stud. See contact, normally closed.
Back contact. See contact, normally closed.
Backstop, armature. That part of the relay which limits the movement of the armature away from the pole face or core. In some relays a normally closed contact may serve as the backstop.
Bank. One or more contact levels of a stepping switch.
Bar. See card, armature; relay bar.
Bearing, armature. The point at which the armature bears against the heelpiece (fulcrum) or the member securing the armature to the relay (See hinge, armature).
Bias, electrical. An electrically produced force tending to move the armature towards a given position.
Bias, mechanical A mechanical force tending to move the towards a given position.
Blade. (1) See spring, contact. (2) Sometimes used to define the centilever portion of the reed switch contained with the glass envelope.
Blocking. The minimum number of continuous hours that a relay will block rated rms off-stage voltage at maximum case temperature.
Bobbin. A spool of structure upon which a coil is wound.
Bounce, armature. See rebound, armature.
Bounce, contact. Internally caused intermittent and undesired opening of closed contacts, or closing of open contacts, of a relay, caused by one or more of the following: (1) Impingement of mating contacts; (2) Impact of the armature against the coil core on pickup or against the backstop on dropout; (3) Momentary hesitation or reversal of the armature motion during the pickup or dropout stroke (See Figures 1.1 and 1.2).
Bounce time. See time, contact bounce.
Break. The opening of closed contacts to interrupt an electric circuit.
Bridging
(1)Normal bridging: The normal make-before-break action of a make-break or D contact combination. In a stepping switch, the coming together momentarily of two adjacent contacts by a wiper shaped for that purpose in the process of moving from one contact to another.
(2)Abnormal bridging: The undesired closing of open contacts caused by a metallic bridge or protrusion developed by arcing.
Buffer, armature or bushing, armature of lifter, armature or pusher, or stud armature. A normally insulating member that transmits the motion of the armature from one movable contact spring to another in the same pileup.
Buffer, spring or buffer, contact spring, or bushing, spring or stud, spring. A normally insulating member that transmits the motion of the armature from one movable contact spring to another in the same pileup.
Bunching, contact. The undesired, simultaneous closure of make-and-break contacts during vibration, shock, or acceleration. Also, the simultaneous closure of the contacts of a continuity transfer or bridging contact combination.
Bushing, armature. See buffer, armature.
Capacitance CISO The maximum allowable capacitive coupling between two specified test points.
Card, armature. An insulating member used to link movable contact springs to the armature on some relay types (also called lifter). (See relay, bar.)
Change-over contact; Two-way contact (deprecated). A combination of two contact circuits including three contact members, one of them being common to the two contact circuits. When one of these contact circuits open, the other is closed and vice versa. (IEC) (See double throw contact.)
Characteristic quantity (of a measuring relay). An electrical quantity, or one of its parameters the name of which characterized the relay and the values of which are the subject of accuracy requirements. (IEC)
Characteristic, static. See load curve and pull curve.
Chatter, armature. The undesired vibration of the armature due to inadequate ac performance or external shock and vibration.
Chatter, contact. Externally caused, undesired vibration of mating contacts during which there may or may not be actual physical contact opening. If there is no actual opening but only a change in resistance, it is referred to as dynamic resistance. (See Figures 1.1 and 1.2)
Clapper. Sometimes used for an armature that is hinged or pivoted; see armature, end-on.
Close, to close. A latching relay closes when it changes from the unoperated to the operated condition. Usually refers to the completing of continuity of the main contact.
Close pulse. A short, high level pulse applied to the coil of a latching relay.
Closed value, measured As the current or voltage on an unoperated latching relay is step applied the lowest value at which all contact function.
Closed value, specified As the current or voltage on an unoperated latching relay is step applied the value at or below which all contact must function.
Coil An assembly consisting of one or more windings, usually wound over over an unsulated iron core on a bobbin or spool. May be self-supporting, with terminals and any other required parts such as a sleeve or slugs.
(1)Concentrically Wound-A coil with two or more insulated windings wound one over the other.
(2)Double Wound-A coil consisting of two windings wound on the same core.
(3)Parallel Wound-A coil having multiple windings wound simultaneously, with the turns of each winding being contiguous.(see winding, bifilar.)
(4)Sandwich Wound-A coil consisting of three concentric windings in which the first and third windings are connected series aiding to match the impedance of the second winding. The combination is used to maintain transmission balance.
(5)Tandem Wound-A coil having tow or more windings, one behind the other, along the longitudinal axis. Also referred to as a two, three, or four-section coil, etc.
Coil, blowoutSee magnet, blowout.
Coil, close.The coil of latching relay which, when power is applied, closes the relay.
Coil, trip. The coil of a latching relay which, when power is applied, trips the relay.
Comb. An insulating member used to position a group of contact springs as on wire-spring relays
Combination, contact or contact form. A single-pole or basic contact assembly.(See Figure 1.6.)
Contact.
(1)The portion of current-carrying members at which electrical circuits are opened or closed.
(2)The current carrying pans of a relay that engages or disengages to open or close electrical circuits.
(3)Used to denote a combination or set. (Contacts also used)
Contact armature.
(1) A contact mounted directly on the same armature.
(2) Sometimes used for a movable contact.
Contact assembly. An assembly of contact members, with their insulation, which close or open their contact circuit by their relative movement. (IEC)
Contact follow.The further specified movement of the contact tips (points) when making and after they have just touched and while they are traveling in the same direction as that of the moving contact member. (IEC)
Contact force. The force which two contact tips (points) exert against each other in the closed position under specified conditions. (IEC)
Contact gap.The gap between the contact tips (points) under specified conditions, when the contact circuit is open. (IEC)
Contact member. A conductive part of a contact assembly which is electrically isolated (points) after they have just touched.(IEC)
Contact roll. When a contact is making, the relative rolling movement of the contact tips (points) after they have just touched.(IEC)
Contact tip. That part of contact member at which the contact circuit closes or opens. (IEC)
Contact wipe. When a contact is making, the relative rubbing movement of the contact tips (points) after they have just touched. (IEC)
Contact, auxiliary. A contact combination used to operate a visual or audible signal to indicate the position of the main contacts, establish interlocking circuits, or hold a relay operated when the original operating circuit is opened.
Contact, back. See contact, normally closed.
Contact, bifurcated. A forked, or branched, contacting member so formed or arranged as to provide some degree of independent dual contacting.
Contact bounce. See bounce, contact.
Contact, break. See contact, normally closed.
Contact, break-before-make. A contact combination in which one contact opens its connection to another contact and then closes its connection to a third contact. (See "C" contact combination in Figure 1.6.)
Contact, break-make. See contact, break-before-make..
Contact, bridging. A contact combination designed to close one contact before opening another. (Usually applied to stepping switches: for relays, see contact, continuity transfer.)
Contact, chatter. See chatter, contact.
Contact, continuity transfer. A contact combination in which contact closes connection to another contact and then opens its prior connection to a third contact. (See "D" contact combination in Figure 1.6.)
Contact, double break. A contact combination in which contact on a single conductive support simultaneously open electrical circuits connected to two independent contacts. This provides two contact air gaps in series when the contact is open (see V or Y contact combination in Figure 1.6 ). Note: In B combination is terminal is brought out form the movable contact. In the Y combination , it is not.
Contact, double make. A contact combination in which contacts on a single conductive support simultaneously close electrical circuits connected to the contact of two independent contacts, and provides two contact air gaps in series when the contact is open. (Sometimes called normally open, double-make contact.) (See U or X contact combination in Figure 1.6) Note: In U combination a terminal is brought out from the movable arm. In the X combination it is not.
Contact, double throw. A contact combination having two positions as in break-make, make-break, and the like. (See Figure 1.6.)
Contact, dry circuit. A contact that carries current but neither opens nor closes while its load circuit is energized. Incorrectly used if referring to low level contacts.
Contact, dynamic resistance. See dynamic contact resistance.
Contact, early. A contact combination that is adjusted to functions before other contact combinations when the relay operates.
Contact final actuation time. Total time from beginning of coil energization or de-energization to the end of bounce; i.e., contacts mechanically in final resting position. (See Figures 1.1 and 1.2.)
Contact, fixed. See contact, stationary.
Contact, front. See contact, normally open.
Contact, initial actuation time. Time from beginning of coil energization or de-energization to first opening of closed contact; i.e., at beginning of bounce. (See Figures 1.1 and 1.2)
Contact interrupter. On a stepping relay or switch, a contact combination operated directly by the armature that opens and closes the winding circuit, permitting the device to step itself.
Contact late. A contact combination that is adjusted to function after other contact combinations when the relay operates.
Contact, low level. Contact that control only the flow of relatively small currents in relatively low-voltage circuits; e.g., alternating currents and voltages encountered in voice or tone circuits, direct currents in the order of microamperes, and voltages below the softening voltages of record for various contact materials (that is, 0.080 volt for gold, 0.25 volt for platinum, etc.) Also defined as contacts switching loads where there is no electrical arc transfer of detectable thermal effect and where only mechanical forces can change the conditions of the contact interface.
Contact, main. The primary set of contacts of a relay, usually defined as those having the highest current rating.
Contact, make. See contact, normally open.
Contact, make-before-break.See contact, continuity transfer.
Contact, make-break See contact, continuity transfer.
Contact, movable. The member of a contact combination that is moved directly by the actuating system. This member is also referred to as the armature contact or swinger contact.
Contact, nonbridging. A contact combination in which the opening contact opens before the closing contact closes. (Usually applied to stepping switches; for relay's, see contact, break-before-break)
Contact, normally closed. A contact combination which is closed when the armature is in its unoperated position. (See "B" contact combination in Figure 1.6.)
Contact, normally open. A contact combination that is open when the armature is in its unoperated position. (Generally applies to monostable relays.) (See "A" contact combination in Figure 1.6.)
Contact, off. normal-A form C contact combination on a stepping switch that is in one condition when the relay or stepping switch is in its normal position and in the opposite condition for any other position of the relay or stepping switch; i.e., when not in its reset or home position.
Contact, operate time. Time from initial energization to the first opening of closed contact or first closing of open contact, prior to bounce. (See Figure 1.1 and 1.2)
Contact, passing. The combination of a contact assembly designed for opening or closing in a passing fashion the corresponding contact circuit when the relay changes over. The passing may occur either when the relay picks up or when the relay drops out or both during picking-up and dropping out.
Contact, permissive make. A term applied to a contact combination in which the movable contact spring is pretensioned so that it will close of its own force when unrestrained. Also, defined as a contact that is mechanically driven open and permitted to make. (See Figure 1.15.)
Contact, preliminary. See contact, early.
Contact, reed.
(1)A glass-enclosed, magnetically operated contact using thin, flexible, magnetic conducting strips as the contacting members.
(2)Contact assembly, the contact members of which are blades either fully or partly of magnetic material and which are moved directly by a magnetic force. (IEC)
Contact release time. Time form initial de-energization of the relay coil to the first opening of a closed contact prior to bounce. (See Figures 1.1 and 1.2.)
Contact, sealed. A contact assembly sealed in a compartment separate from the rest of the relay.
Contact, snap action.A contact assembly having two or more equilibrium positions. In one, the contact maintain a substantially constant contact force during the initial motion of the actuating member until stored energy snaps the contacts to a new position of equilibrium.
Contact, stationary A member of a contact combination that is not moved directly by the actuating system.
Contact, transfer. Either a contact, break-make or contact, continuity transfer.
Contact transfer time. Time during which the moving contact first opens from a closed position and first makes with the opposite throw of the contact. It is floating in a non-contacting position prior to bounce and after energizing or de-energizing the coil. (See Figure 1.1 and 1.2.)
Contact weld. A contact failure due to fusing of contacting surfaces to the extent that the contacts fail to separate when intended.
Contactor. See relay, power.
Continuous on. The minimum number of hours a relay will continuously conduct rated rms current.
Core, coil. The portion of the magnetic structure of a relay about which the coil is positioned.
Crosstalk. The electrical coupling between a closed contact circuit and other open or closed contact on the same relay or switch, expressed in decibels down form the signal level.
Current, intermediate. The range of current (milliamperes) at which formation of carbonaceous material may significantly affect contact resistance.
Current, leakage. (Maximum off-state current)TD (rms)-The parameter is an effective current and is specified at maximum-load voltage. In solid-state relays, it is the current that flows through the load when the relay is in the off-state. Does not apply to electromechanical relays where contacts are open and current cannot flow.
Current, minimum load.ITMIN(rms)-The minimum current required to maintain the relay in the on-state (nominal load voltage applies). Applies mainly to solid-state relays.
Current, non-repetitive surge-ITSM. The maximum allowable, non-repetitive, peak, sinusoidal current that may be applied to the output for one full cycle at nominal line frequency. Relay control may be lost during and following the surge until the junction temperature falls below the maximum rated temperature.
Current rated contact. The current which the contacts are designed to handle for their rated life. See rating, contact.
Current, maximum rate of rise on state (di/dt). The maximum non-repetitive rate of current rise the output can withstand without being damaged.
(1) With the relay output(s) turned on by the application or removal of the control voltage and/or current.
(2) With the relay output(s) driven into break-over with the input at non-operate level. Current, repetitive overload-ITO (rms)-The maximum allowable repetitive rms overload current that may be applied to the output for a specific duration and duty cycle while still maintaining output control. Applies mainly to solid state relays.
Cycle. A monostable relay cycles when it picks up and then drops out, or vice versa.(IEC)
Cycling. The minimum number of hours during which a relay may be switched between the off state and the on state at a fixed, specific cycle rate, load current, and case temperature without failure.