A thermocouple is a pair of dissimilar metal conductors so joined at one point that an electromotive force (EMF) is developed by the thermoelectric effects. Any given set of thermocouple wires have a known "EMF vs. Temperature" characteristic.

Thermocouples can only generate a low-voltage, low-power signal, that is in the milli-volt range. Therefore the customer must supply the electronic control equipment to translate the thermocouple voltage signal into a temperature reading, or to operate the control’s alarm or shutdown devices.

There are many types of thermocouples. Standard types used in U.S. MOTORS® products are copper-constantan, chromel-constantan and iron-constantan.

The standard installation procedure is to install the thermocouples in the slot portion of the winding. If required by the customer, they can also be installed in end turns of the winding.

Selection
The customer’s choice of monitoring equipment dictates the type of thermocouples to be installed in the motor, so orders need to specify the exact type of thermocouples required.

The standard quantity of thermocouples is six (6), installed two per phase.