The three-phase induction motor is the work-horse of industry. It combines an economical and rugged construction with operating characteristics that fit the requirements of most driven devices. The operating characteristics of the motor can be adjusted at the design stage to emphasize certain features at the expense of others, so that the motor can match the operating situation with a better balance of attributes.
The basic attributes of interest are: 1) the change of torque with speed, especially during motor start and acceleration to operating speed; 2) the "in-rush" or energizing current during starting; and 3) the efficiency during continuous operation. These attributes also affect the associated equipment required for the motor installation. Thought must also be given to the motor controller ("starter"), circuit conductors, protective devices, and the method of shutting the motor off and interrupting power to the circuit.
In addition, voltage dips due to high in-rush currents during starting could affect other devices if the system is not properly designed. The use of reduced-voltage starters and/or other precautionary measures can reduce most of the difficulties caused by the starting characteristics of motors. However, a different motor design might be required in some extreme situations.
