How is the capacity of a magnetic starter determined?

The capacity of a magnetic starter is primarily determined by the size of its contacts and the wire cross-sectional area. These factors are crucial for ensuring that the starter can handle the electrical load it is designed for. The contacts within the starter must be able to carry the intended current without overheating or degrading, which is influenced by their size. Larger contacts can handle more current and provide better durability.

Additionally, the wire cross-sectional area is significant because it affects the amount of current that can safely flow without excessive heat buildup. If the wire is too small, it can lead to overheating and potential failure of the starter, ultimately jeopardizing the entire electrical system.

While voltage rating and current rating (as mentioned in another option) are important for assessing the overall suitability of a starter in a given application, they do not directly determine the starter's capacity in the sense of its physical design and construction. Similarly, the manufacturer and model number, as well as the motor speed and torque rating, are more related to specifications and operational parameters rather than the capacity directly tied to the starter’s components.