A three-phase induction electric motor is fundamentally a constant speed motor when it is connected to a source of constant voltage and fixed frequency. The steady speed is very adjacent to the synchronous speed, however, when the required torque increases, the speed reduces. We can observe that for the load requesting a high torque at the point of operation, the motor has a lower speed. Therefore, the motor speed is given by the encounter between the torque curve for the motor find here baldor vem3709t and the load curve.
In many industrial uses, variable or continuously adjustable speeds are indispensable. Traditionally, DC motors have always been used in applications where speed variation was required. However, DC motors are expensive, requiring brush and switch maintenance and are prohibitive in harsh environments. In compensation, induction motors are inexpensive, maintenance-free, capable of operating in harsh environments and are usable for high speeds. With the advent of static converter technology, frequency inverters have allowed the dispersion of three-phase induction motors in applications where speed control is required.