"T" Frame: Current NEMA designation identifying AC induction motor frames. (NEMA has dimension tables which offer standard frame measurements) Replaced the previous standard "U" frame in 1965.

 
Tachometer: A small generator normally used as a rotational speed sensing device. Tachometers are typically attached to the output shaft of DC or AC inverter motors requiring close speed regulation. The tachometer feeds its signal to a control which adjusts its output to the DC motor or AC inverter motors accordingly (called "closed loop feedback" control).

"T": (Temperature Codes) See N.E.C. Temperature Codes

 
Temperature Rise: Some of the electrical energy losses inherent in motors are converted to heat causing some of the motor parts to heat up when the motor is running. The heated parts are at a higher temperature than the air surrounding them thereby causing a rise above room (ambient) temperature.
It is important to match the proper motor and insulation system (NEMA temp. codes) to the appropriate ambient temperature. If a motor has been built with greater than 1.0 service factor then it can run at a temperature some what higher than the motor's rated operating temperature. In all cases, the actual insulation thermal capability usually is higher than the motor's operating temperature to allow for any excessive heat areas. This is called hot spot allowance. (See Insulation Systems for NEMA standard temperature codes.) Each temperature code has an associated temperature rise which when added to the ambient and hot spot should not exceed the temperature handing of the insulation system.

Thermal Protector: (inherent) An inherent overheating protective device which is responsive to motor temperature and which, when properly applied to a motor, protects the motor against dangerous overheating due to overload or failure to start. This protection is available with either manual or automatic reset.

 
Thermistor-Thermally Sensitive Resistor: A semiconductor used to measure temperature; can be attached to an alarm or meter to detect motor overheating.

 
Thermocouple-Thermal Detection Device: A temperature detecting device made of two dissimilar metals which generate a voltage as a function of temperature. Thermocouples can be attached to a meter or alarm to detect overheating of motor windings or bearings.

 
Thermostat: Units applied directly to the motor's windings which senses winding temperature and may automatically break the circuit in an overheating situation.

 
Torque: Turning force delivered by a motor or gearmotor shaft, usually expressed in lbs. ft derived by completing H.P. x 5250/RPM = full load torque.

 
Totally -Enclosed Enclosure: A motor enclosure which prevents free exchange of air between the inside and the outside of the enclosure but is not airtight. Different methods of cooling can be used with this enclosure.

 
Totally -Enclosed Air-To-Air-Cooled Machine: A totally enclosed machine cooled by circulating internal air through a heat exchanger which, in turn, is cooled by circulating external air. Provided with an air-to-air heat exchanger for cooling ventilating air and fan or fans integral with rotor shaft or separate, for circulating external air.

 
Totally -Enclosed Fan-Cooled Enclosure: Provides for exterior cooling by means of a fan(s) integral with the machine, but external to the enclosed parts.

 
Totally -Enclosed Non-Ventilated Enclosure: Has no provisions for external cooling to the enclosing parts. The motor is cooled by heat radiation from the exterior surfaces to the surrounding atmosphere.