Which DC motor type offers good torque and speed across a range of loads?

Which DC motor type offers good torque and speed across a range of loads?

• A. PM Motor
• B. Series Motor
• C. Compound Motor
• D. Shunt Motor

Answer: (C)

A DC machine that has both a series and a shunt winding combines the best of two worlds: it gets high starting torque from the series path and steady speed from the shunt path. The series winding reacts to the load current, giving a strong torque when starting or under heavy load. The shunt winding, with its field current largely independent of armature current, keeps the speed from wandering too much as the load changes. Together, this means the motor can deliver good torque when needed and maintain a reasonable, controlled speed across a range of loads. In contrast, a series motor offers very high starting torque but its speed can drop dramatically as load increases, and it can run away if unloaded. A shunt motor regulates speed well but tends to have lower starting torque. Permanent magnet motors can be efficient and have decent speed regulation, but they don’t inherently balance torque across a wide load range as well as a compound setup.

A DC machine that has both a series and a shunt winding combines the best of two worlds: it gets high starting torque from the series path and steady speed from the shunt path. The series winding reacts to the load current, giving a strong torque when starting or under heavy load. The shunt winding, with its field current largely independent of armature current, keeps the speed from wandering too much as the load changes. Together, this means the motor can deliver good torque when needed and maintain a reasonable, controlled speed across a range of loads.

In contrast, a series motor offers very high starting torque but its speed can drop dramatically as load increases, and it can run away if unloaded. A shunt motor regulates speed well but tends to have lower starting torque. Permanent magnet motors can be efficient and have decent speed regulation, but they don’t inherently balance torque across a wide load range as well as a compound setup.