Short Answer:

DC motors are classified based on how the field winding is connected with the armature winding. The main types of DC motors include separately excited and self-excited motors. Self-excited motors are further divided into series, shunt, and compound types.

Each type of DC motor has different characteristics suitable for specific applications. For example, series motors are used where high starting torque is needed, while shunt motors offer constant speed. Compound motors combine features of both and are used in lifts, rolling mills, and heavy-duty tasks.

Detailed Explanation:

Classification of DC motors

DC motors are widely used in various machines and devices due to their easy speed control and good torque characteristics. To understand their performance and choose the right type for an application, it is important to classify them. The classification of DC motors is mainly done on the basis of how the field winding is connected with the armature winding.

There are two major categories:

1. Separately Excited DC Motor
   In this type, the field winding is supplied from a separate external power source, not from the armature circuit. This allows independent control of field flux and armature current, which is useful for applications where wide speed control is required.

• Features:
  • Independent field control
  • Good speed control over a wide range
  • Used in laboratories, testing setups, and electric traction

2. Self-Excited DC Motor
   In self-excited motors, the field winding gets its power from the same source as the armature. Based on how they are connected, self-excited motors are divided into three sub-types:
3. DC Series Motor
   In this motor, the field winding is connected in series with the armature.

• Characteristics:
  • High starting torque
  • Speed varies with load
  • Cannot run without load (dangerous)
• Applications:
  • Electric trains, cranes, hoists, elevators

1. DC Shunt Motor
   Here, the field winding is connected in parallel (shunt) with the armature winding.

• Characteristics:
  • Nearly constant speed regardless of load
  • Moderate starting torque
• Applications:
  • Fans, blowers, lathes, conveyors

1. DC Compound Motor
   This type combines both series and shunt windings to gain the advantages of both. There are two types:

• Cumulative Compound Motor: Series and shunt field assist each other
• Differential Compound Motor: Series field opposes the shunt field
• Characteristics:
  • Good starting torque
  • Better load handling than shunt motors
• Applications:
  • Rolling mills, printing machines, elevators

Conclusion:

DC motors are classified based on how their field winding is excited. The main types are separately excited and self-excited, which includes series, shunt, and compound motors. Each type has unique performance features suited for different industrial and domestic uses. Proper understanding of this classification helps in selecting the right motor for a specific task, ensuring better efficiency and longer motor life.