What is the typical application for a series motor?

A series motor is designed to provide high starting torque, making it especially suitable for applications where significant torque is needed to initiate movement. This characteristic arises from the motor's construction, where the field winding is connected in series with the armature winding. When the motor starts, the current is at its maximum, leading to a strong magnetic field and consequently a high torque output.

In practical terms, series motors are commonly used in applications such as electric trains, cranes, and other heavy machinery where a heavy load needs to be moved from a standstill. These environments often encounter high resistance at the start, thus requiring the additional torque that series motors can provide without the risk of stalling.

The other options do not align with the practical application and capabilities of series motors. For instance, series motors are not typically used in high-speed scenarios or applications that require maintaining a constant speed, as their speed tends to vary significantly with load. Similarly, they are not suitable for low torque applications due to their tendency to stall under insufficient load conditions. Therefore, the defining trait of series motors is their ability to deliver substantial start-up torque, rendering them ideal for specific heavy-load applications.