Final answer:
In a three-phase induction motor, the speed is directly proportional to the frequency of the power supply. Its principle operation is based on creating a rotating magnetic field. These motors are commonly used in various industrial applications for their high power output and reliability.
Step-by-step explanation:
In a three-phase induction motor, the speed of the motor is directly proportional to the frequency of the power supply. This is known as the synchronous speed, and it can be calculated using the formula: synchronous speed (in RPM) = 120 x frequency (in Hz) / number of poles. So, as the frequency increases, the speed of the motor also increases.
The principle operation of a three-phase motor is based on the creation of a rotating magnetic field that interacts with the rotor of the motor, causing it to turn. This is achieved by applying three-phase AC power to the motor's stator windings, which creates a rotating magnetic field.
A three-phase motor is commonly used in various industrial applications where high power output and reliability are required. These motors are used in machinery such as pumps, compressors, conveyors, and fans, as well as in manufacturing processes and electrical power generation.
General motor protection requirements outlined in the National Electrical Code® (NEC®) include protection against overload, short circuit, ground fault, and overheating. This can be achieved through the use of circuit breakers, fuses, and thermal overload relays, as well as proper grounding and insulation.