The nominal voltage is the working voltage that the electric motor has under normal conditions, and it should not be exceeded for very long periods of time, running the risk of damaging the motor.
Every motor shall be capable of operating perfectly when it is supplied with either a voltage 10% below or 10% above the rated voltage, provided the frequency is rated. However, the new standard NBR 7094 establishes a new guideline for the operation of the motor under frequency and voltage with deviations.
There are two zones (A and B) for the combination of frequency and voltage variations. The motor should be able to operate continuously in zone A, with some deviations and the temperature may also be higher.
In zone B, the engine must be able to operate for a limited time, with deviations higher than those in zone A and with a higher temperature rise. In both operating zones the motor must be capable of having its rated torque.
Generally the electric motors are manufactured to operate at a maximum temperature of 40 degrees and a maximum altitude of 1000 m above sea level.