Glossary of Motor Terms

Ambient - Surrounding environment. Applicable to temperature, humidity, sound level, etc.

Clutch, one-way - A clutch assembly built into one of the wheels in the gear train, designed to enable the output shaft to be rotated manually in one direction without causing damage to the motor or gear train.

Duty cycle - Proportion of "on" time to "off ' time, usually stated as a percentage.

End shake - Often called "end play." The axial freedom of movement of the output shaft due to the clearances that are provided to compensate for dimensional variations.

Gear train - The complete complement of gears in proper relationships within the gearbox.

Gear train rating - Also called dynamic torque rating. A performance characteristic describing the torque that a gear train can handle at a given speed for a given life expectancy.

Gearbox - The portion of a gearmotor containing the speed reduction gears, including the housing and output shaft.

Gearmotor - A motor with reduction gearing, such as the MTS motor and gearbox assembly.

Lead egress position - The angular position at which the leads emerge from the motor.

Load - The elements coupled to the motor that resist motion.

Load torque - The measure of resistance to motion.

Output direction - The direction of rotation of the output pinion or shaft, either clockwise or counter-clockwise, when viewing the motor from the output side.

Permanent magnet - A magnet having magnetic poles without the presence of an exciting field.

Pinion, output - A gear mounted on the motor output shaft.

Radial bearing load - The forces present in a bearing that act in a radial direction. Force at right angle to the axis of the shaft. Commonly called "side load".

Shaded poles - Stator poles surrounded by a short-circuited tum of the conductor material employed to create an effective rotating magnetic field. Through proper design, losses due to shading can be minimized. In synchronous motors, the shaded poles provide self-starting and unidirectional rotation.

Static torque rating - The highest reverse torque that can be applied to a gear train one time without doing damage.

Synchronism - The condition when the rotor is exactly in step with the alternations of the power supply line. This can be observed with a stroboscopic light as a stationary pattern.

Torque - Twisting action. Force multiplied by moment arm.

Torque breakdown - The maximum torque that the motor can develop. It occurs as a point on the speed-torque curve below synchronous or full-load speed.

Torque, detent or residual - The torque developed in an unenergized motor when the permanent magnet rotor is displaced from a position of minimum stator reluctance.

Torque, dynamic (running) - The greatest torque that can be applied to the motor without stalling. The same as synchronous torque.

Torque, full load - The torque developed by a non-synchronous motor at its rated full-load speed.

Torque, holding or static - The torque required to displace the rotor from its equilibrium position with one or more stator phases energized with the rotor at standstill.

Torque, locked rotor - The torque developed with the rotor at standstill.

Torque, pull-in - The maximum torque at which a synchronous motor (stepping motor included) can accelerate its load to synchronous speed.

Torque, pull-out - The maximum torque which a synchronous motor (stepping motor included) can develop and still maintain synchronous speed.

Torque, rating - The torque value expressing the amount of torque that can be dependably produced by a motor.

Torque, stall - The greatest amount of torque that can be applied to a motor running with no load without causing the motor to stall.

Torque, starting - The greatest torque against which the motor can start and continue to run at synchronous speed.