Conjugate and Rated Speed

In case the required work of the driven machine will suffer temporary overloads, the motor power will need to be higher than the required power. It is extremely important to limit the significant increase of the losses, with proper maintenance of the machines and their mechanical components, such as adjustment of clearances, proper lubrication and verification of alignments, among others. An electric motor is designed so that it can provide a nominal torque Cn, at a nominal speed Nn.

This means that for a nominal power Pn, one must consider the expression Pn = CnxNn. It is noteworthy that the electrical losses, also known as thermal losses, change according to the square of the resistant conjugate, which is the load. On a well sized motor, this rugged torque must be less than the rated torque. If it is equal to or slightly higher, the resulting heating will be considerable. However, a motor considered under-loaded will have a noticeable reduction in efficiency. The ideal load should correspond to the workload that will be carried out, a factor not very simple to determine in most cases.