What primarily determines the starting current of a motor?

The starting current of a motor is primarily influenced by motor size and type. Larger motors generally require more current to overcome inertia and start turning, which is tied to their physical characteristics such as winding resistance and reactance. Different types of motors, such as induction motors or synchronous motors, also have unique starting characteristics that affect how much current they draw at startup.

For instance, an induction motor can have a significantly higher inrush current compared to a smaller motor of the same type due to its rotor design and the nature of its operation. In contrast, a synchronous motor may have different starting requirements based on how it is constructed and the method used to bring it up to speed. Therefore, understanding the specific motor type and its size provides critical insight into its starting current behavior.

While voltage rating, load type, and frequency may have an influence on performance, they play a secondary role in determining the starting current compared to the inherent design and size of the motor itself.