Technology / Motors Glossary

AC Motors: A Motor (see motor definition) operating on AC current that flows in either direction (AC current). There are two general types: Induction, and Synchronous.

Active Iron: The amount of steel (iron) in the stator and rotor of a motor. Usually the amount of active iron is increased or decreased by lengthening or shortening the rotor and stator (they are general . . . View Full Definition

Air Gap: The space between the rotating (rotor) and stationary (stator) member in an electric motor.

Air Pressure Switch: Used on motors with blowers to measure the difference in pressure across the filter so as to detect a clogged filter.

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-t . . . View Full Definition

Alternating Current (AC): The commonly available electric power supplied, an AC generator and is distributed in single or three-phase forms. AC current changes its direction of flow (cycles).

Altitude: The atmospheric altitude (height above sea level) at which the motor will be operating: NEMA standards call for an altitude not exceeding 3,300 ft. (1,000 meters). As the altitude increases . . . View Full Definition

Ambient Temperature: The temperature of the surrounding cooling medium, such as gas or liquid, which comes into contact with the heated parts of the motor. The cooling medium is usually the air surrounding the m . . . View Full Definition

Anti-Friction Bearing: An anti-friction bearing is a bearing utilizing rolling elements between the stationary and rotating assemblies.

Armature: The portion of the magnetic structure of a DC or universal motor which rotates

Armature Current (Amps): Rated full load armature circuit current.

Armature Inductance (Mh): Armature inductance in milli-henries (saturated).

Armature Reaction: The current that flows in the armature winding of a DC motor tends to produce magnetic flux in addition to that produced by the field current. This effect, which reduces the torque capacity, . . . View Full Definition

Armature Resistance (Ohms): Armature resistance is measured in ohms at 25f C. (cold)

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)

Back End Of A Motor: The back end of a normal motor is the end which carries the coupling or driving pulley. (NEMA) This is sometimes called the drive end (D.E., pulley end P.E.) etc.

Base Speed (RPM): The speed which a DC motor develops at rated armature and field voltage with rated load applied.

Bearing Life: Rating life, L10 (Bl0), is the life in hours or revolutions in which 90% of the bearings selected will obtain or exceed. Median life (average life), L50(B50)

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