What determines the minimum number of sets of contacts a motor starter has?

The minimum number of sets of contacts a motor starter has is primarily determined by the number of power leads required. In motor control applications, each motor needs at least one set of contacts for each power lead that is involved in supplying electricity to the motor. This typically means that if a motor is three-phase, there will be a necessity for three sets of contacts to effectively control the power supply to each of the phases.

Other factors, such as the type of motor, manufacturer specifications, and the size of the motor, may influence the overall design or the options available, but the fundamental requirement for the number of contact sets is directly tied to how many power leads the motor starter is designed to accommodate. This ensures that the motor is provided with the proper electrical connections it needs for operation and control.