In general, it is important to know that individual electric motors are more energy-efficient than multiple transmissions. In these cases, a large reduction of the efficiency of a three-phase asynchronous four-pole motor can also occur, due to the load presented in normal operation. In the case of electrical losses, also known as thermal losses, they can be changed, depending on the square of the conjugate of the existing load. In case an electric motor is considered to be well dimensioned, the rugged torque must be less than the rated torque. If it is similar or subtly higher, the resulting heating should be considered.
An underloaded electric motor can present a considerable reduction in efficiency, and the ideal load needs to match the load of the work to be done, a factor that is not always simple to generate. If the expected work of the driven machine shows any temporary overloads, the power of the motor should be slightly higher than the required power.
We must limit the increase of the losses, making the correct maintenance of the machines and mechanical components of drive, for example, of the regulation of the clearances, proper lubrication and verification of the alignments.