Absolute Measuring System: The measuring value is determined by reading information from a scale, without counting. The value is immediately available after switch-on.
AC (Alternating Current): The commonly available electric power supplied by an AC generator and is distributed in single- or three-phase forms. AC current changes its direction of flow (cycles).
Acceleration: A change in velocity as a function of time. Acceleration usually refers to increasing velocity, and deceleration to decreasing velocity.
Accuracy: A measure of the difference between expected position and actual position of a motor or mechanical system. Motor accuracy is usually specified as an angle representing the maximum deviation from expected position.
Accuracy Grade: Grade of quality, determined by the maximum permissible measuring deviations within a predetermined measuring range (e.g. 1m).
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 generally the same length).
Air Gap: The space between the rotating (rotor) and stationary (stator) members in an electric motor.
Air Pressure Switch: Used on motors with blowers to measure the difference in pressure across the filter to detect a clogged filter.
Air Temperature Switch: A device used with an air hood motor 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.
Altitude: The atmospheric altitude (height above sea level) at which the motor will be operating; NA standards call for an altitude not exceeding 1,000 meters (3,300 feet). As the altitude increases above 1,000 meters (3,300 feet) and the air density decreases, the air's ability to cool the motor decreases. For higher altitudes, higher grades of insulation or motor derating are required. DC motors require special brushes for operation at high altitudes.
Amplitude Evaluation: Method of evaluating signals generated by dynamic scanning (with carrier frequency): the amplitude variation of two alternating voltages of the same frequency are used to determine the measuring value.
Angular Accuracy: The measure of shaft positioning accuracy on a servo or stepping motor.
Anti-Friction Bearing: An anti-friction bearing is a bearing utilizing rolling elements between the stationary and rotating assemblies.
Armature Current, AM: 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, is called armature reaction and can effect the commutation and the magnitude of the motor's generated voltage.
Armature Resistance, OHMS: Armature resistance is measured in ohms at 25 degrees C (cold).
Axial Load: Axial load is the force applied to a shaft end surface directed along the axis of rotation.
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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