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L&S Glossary of Terms


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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


  • ABSOLUTE LOSSES: Production deferred or lost due to the specified element or system. Expressed as a percentage of the total potential production.

  • AC MOTORS: A motor that operates on AC current that flows in either direction (AC current). There are two general types: induction and synchronous.

  • ACCELERATION: Acceleration is the rate of change of velocity of a point in a system. Normally, accelerometers are used to detect accelerations. When measuring small vibration levels, an accelerometer is more effective compared to displacement, or velocity transducers.

  • ACCELEROMETER: A transducer or pickup that measures acceleration.

  • ACCREDITATION: Certification by a recognized body of the facilities, capability, objectivity, competence and integrity of an agency, service or operational group or individual to provide the specific service or operation needed.

  • ACCREDITATION BODY: An organization with authority to accredit other organizations to perform services such as quality system certification.

  • ACCURACY: The characteristic of a measure.

  • ACOUSTIC EMISSION ANALYSIS: Like vibration analysis, patterns of acoustic emission spectra are monitored and diagnosed. Acoustic emission analysis technology is applied in order to study bearing faults, detect flaws and cracks in welding and pipe-work, and study de-lamination, de-bonding, and fracture in aerospace materials.

  • ACTIVE IRON: The amount of steel (iron) in the stator and rotor of a motor. The amount of active iron is usually increased or decreased by lengthening or shortening the rotor and stator (they are generally the same length).

  • AGING: An irreversible change in the properties of any material (such as lamination steel or insulation) that occurs over time and is accelerated by increases in temperature, applied voltage, or other stresses.

  • AIR GAP: The space between the rotating (rotor) and stationary (stator) member in an electric motor.

  • AIR-GAP AREA: The total area around the bore of an induction machine, computed by multiplying the axial length of the bore by its circumference. For a D.C. machine, it refers to the area of the bore that is covered by the main poles.

  • AIR-OVER: Motors intended for fan or blower service that are cooled by the air stream from the fan or blower.

  • AIR PRESSURE SWITCH: Used to detect clogged filters by measuring pressure differences across the filters of motors with blowers.

  • AIR TEMPERATURE SWITCH: A device used in air-hooded motors to detect the temperature of the exhausted air. When used in this manner, an air temperature switch will detect blockage in the cooling air system or long-term motor overload.

  • ALIGNMENT (Precision): Bringing or placing machine(s) shaft(s) in line. Misaligned shafts often cause problems with machine components (i.e., bearings). Specialized tools and personnel are employed for precision alignment. A number of tools are based on laser technologies.

  • ALIGNMENT: In the context of quality, alignment is defined as actions to ensure that a process or activity supports the organization's strategy, goals and objectives.

  • ALTERNATING CURRENT (AC): A commonly available electric power that supplies an AC generator and is distributed in single or three-phase forms. AC current changes its direction of flow (cycles).

  • ALTERNATOR: An electric generator designed to produce an alternating current. It usually consists of rotating parts that create the changing magnetic field required to produce the alternating current.

  • ALTITUDE: The atmospheric altitude (height above sea level) at which the motor will operate. NEMA standards call for an altitude not exceeding 3,300 ft. (1,000 meters). As the altitude increases above 3,300 ft. and the air density decreases, the air stability required to cool the motor decreases. For higher altitudes, higher grades of insulation or a motor de-rating are required. D.C. motors require special brushes for high altitudes.

  • ALUMINUM BRONZE: Copper-based alloys with aluminum as the principal alloying element (normally in the range of 3 to 11%), sometimes with the addition of other elements.

  • AMBIENT: The temperature of the space around the motor. Most motors are designed to operate in an ambient of less than 40 ºC.

  • AMBIENT TEMPERATURE: The temperature of the surrounding cooling medium. Commonly known as room temperature when air is the cooling medium in contact with the equipment.

  • AMERICAN NATIONAL STANDARDS INSTITUTE AMERICAN SOCIETY FOR QUALITY (ANSI-ASQ): Organization that accredits certification bodies for ISO 9001 quality management systems, ISO 14001 environmental management systems and other industry specific requirements.

  • AMERICAN SOCIETY FOR QUALITY(ASQ): A professional, not-for-profit association that develops, promotes and applies quality related information and technology for the private sector, government and academia. ASQ serves more than 108,000 individuals and 1,100 corporate members in the United States and 108 other countries.

  • AMERICAN SOCIETY FOR TESTING AND MATERIALS(ASTM): Not-for-profit organization that provides a forum for the development and publication of voluntary consensus standards for materials, products, systems and services.

  • AMERICAN WIRE GAUGE (AWG): A standard measure that represents the size of wire: the larger the number, the smaller the wire.

  • AMORTISSEUR WINDING: Pole-face bar windings that are embedded in the cores of the field poles of synchronous machines. They can be used to dampen rotor oscillations and as squirrel cage windings for starting synchronous motors. Also referred to as damper winding.

  • AMPACITY: The maximum continuous current that a conductor can carry without exceeding its temperature rating.

  • AMPERE: Electric current produced by applying one volt across a resistance of one ohm. It is also equal to the flow of one coulomb per second.

  • AMPERE-HOUR:The flow of electricity that is equal to one ampere per hour. Commonly used to rate the capacity of batteries.

  • AMPLITUDE: The extreme range of a signal, either fluctuating (AC) or static (D.C.).

  • ANALOG: A measuring or display methodology that uses continuously varying physical parameters. In contrast, digital represents information in a discrete binary form, using only zeros and ones.

  • ANALYSIS:

    • (1) A step-by-step process of determining the solution to a problem.

    (2) The collection, viewing, and examination of data and information.

    (3) The process of determining the composition of a substance or material using chemical or physical methods.


  • ANDON BOARD: A production area visual control device, such as a lighted overhead display. It communicates the status of the production system and alerts team members to emerging problems (from a Japanese word meaning "light").

  • ANODE: The positive pole of an electrode.

  • ANTI-FRICTION BEARING: A bearing that utilizes rolling elements between the stationary and rotating assemblies.

  • APPARENT POWER: The mathematical product of voltage and current on AC systems. Voltage and current may be out of phase on AC systems; as such, the apparent power thus calculated may not equal the real power, but may, in fact, exceed it.

    Reactive loads (inductance and/or capacitance) on AC systems will cause the apparent power to be larger than the real power.

  • ARMATURE CURRENT, AMPS: Rated full-load armature circuit current.

  • ARMATURE INDUCTANCE, MH: Armature inductance in milli-henries (saturated).

  • ARMATURE INDUCTANCE: The apparent inductance of the armature, as seen by the brushes.

  • ARMATURE REATION: In a D.C. machine, the current that flows though the armature produces a magnetic flux in addition to that produced by the field current. This, in turn, reduces the output capacity and affects commutation.

  • ARMATURE RESISTANCE: The resistance of the armature winding, commutator connections, and the commutator (measured in commutator bars), normally spanned by a pair of opposite polarity brushes. It does not include the brush film. The resistance is usually taken at room temperature (25 ºC).

  • ARMATURE: The portion of a rotating machine that carries the AC winding. The rotor of a D.C. motor or generator and the stator of an induction motor, synchronous motor, or alternator. The movable magnetic structure of a relay or solenoid.

  • ARMATURE: The rotating portion of the magnetic structure that is found in machines with commutators.

  • ASSESSMENT: A systematic evaluation process of collecting and analyzing data to determine the current, historical or projected compliance of an organization to a standard.

  • AUTONOMOUS MAINTENANCE: Operators in independent groups carry out routine and preventive maintenance. These groups – which may include maintenance workers – solve problems without management intervention. The maintenance department is only relied upon for problems that require more resources, technology, or downtime.

  • AVAILABILITY (Achieved): In achieved availability, the mean time between maintenance (MTBM) is used as a measurement of uptime. This mean time includes both unplanned and planned maintenance. The mean (expected) system downtime includes unplanned and planned (preventive/predictive) maintenance, but does not include delays in supply or maintenance resources.

  • AVAILABILITY (Inherent): The inherent availability is solely based on distribution failure and repair-time distribution; it does not assume delays in supply and maintenance or planned (preventive/corrective) maintenance. It is considered an equipment design parameter. Inherent availability fulfills the need to distinguish expected performance between planned shutdowns.

  • AVAILABILITY (Operational): Similar to achieved availability, but delays in supply and maintenance resources are included in the mean system downtime. Operational availability is required to isolate the total effectiveness and efficiency of maintenance operations.

  • AVAILABILITY: The probability that a system or component is performing its required function at a given point in time – or over a stated period of time – when it is operated and maintained in the prescribed manner.

  • AVAILABLE HOURS: The total number of hours that a piece of equipment is capable of performing its specified functions. It is equal to the total number of hours in any given period, minus the downtime hours.

  • AVERAGE LIFE: How long, on average, a component lasts before it suffers a failure. Average life is commonly measured by Mean Time Between Failures (MTBF), and is usually expressed in hours.

  • AUDIT: The on-site verification activity, such as inspection or examination, of a process or quality system, to ensure compliance to requirements. An audit can apply to an entire organization or might be specific to a function, process or production step.

  • AXIAL CRACKS: An inner ring cracked in the axial direction. Slightly rounded fractured edges indicate that the fracture originated during operation and was cycled (cracked edges may break off after prolonged operation). Sharp-edged cracks indicate that the fracture originated during dismounting.

  • AXIAL END PLAY: Shaft displacement along the motor axis, due to a reversal of the axial force. It is measured in inches or mm.


    • Free End Play: The displacement measured when the moving force is removed after the shaft is positioned axially from one extreme position to the other.


    Cushioned End Play: The displacement measured when a force of known value causes the shaft to move axially from one position to another. When specifying cushioned endplay, the force and direction of movement must also be specified.


  • AXIAL THRUST: The force or loads that are applied to the motor shaft in a direction parallel to the axis of the shaft (such as from a fan or pump).


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