LEESON Electric Corporation  

Glossary of Terms

 
Temperature Rise:
The amount by which a motor, operating under rated conditions, is hotter than its surrounding ambient temperature.
 
Temperature Tests:
These determine the temperature of certain parts of a motor, above the ambient temperature, while operating under specific environmental conditions.
 
Thermal Protector:
A device, sensitive to current and heat, which protects the motor against overheating due to overload or failure to start. Basic types include automatic rest, manual reset and resistance temperature detectors.
 
Thermal Rating:
The power or torque a gear reducer can transmit continuously. This rating is based upon the reducer’s ability to dissipate the heat caused by friction.
 
Thermistors:
Are conductive ceramic materials, whose resistance remains relatively constant over a broad temperature range, then changes abruptly at a design threshold point, creating essentially a solid-state thermal switch. Attached control modules register this abrupt resistance change and produce an amplified output signal, usually a contact closure or fault trip annunciation. Thermistors are more accurate and faster responding than thermostats.
 
Thermostat:
A protector, which is temperature-sensing only, that is mounted on the stator winding. Two leads from the device must be connected to a control circuit, which initiates corrective action. The customer must specify if the thermostats are to be normally closed or normally open.
 
Thermocouple:
A pair of dissimilar conductors joined to produce a thermoelectric effect and used to accurately determine temperature. Thermocouples are used in laboratory testing of motors to determine the
internal temperature of the motor winding.
 
Thrust Load:
Force imposed on a shaft parallel to a shaft’s axis. Thrust loads are often induced by the driven machine. Be sure the thrust load rating of a gear reducer is sufficient so that its shafts and bearings can absorb the load without premature failure.
 
Torque:
The turning effort or force applied to a shaft, usually expressed in inch-pounds or inch-ounces for fractional and sub-fractional HP motors.
  • Starting Torque: Force produced by a motor as it begins to turn from standstill and accelerate (sometimes called locked rotor torque).
  • Full-Load Torque: The force produced by a motor running at rated fullload speed at rated horsepower.
  • Breakdown Torque: The maximum torque a motor will develop under increasing load conditions without an abrupt drop in speed and power. Sometimes called pull-out torque.
  • Pull-Up Torque: The minimum torque delivered by a motor between zero and the rated RPM, equal to the maximum load a motor can accelerate to rated RPM.
 
Transformer:
Used to isolate line voltage from a circuit or to change voltage and current to lower or higher values. Constructed of primary and secondary windings around a common magnetic core.
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