Explanation:

A DC motor is an electrical machine that converts electrical energy into mechanical energy. It consists of a stator (stationary part) and a rotor (rotating part). The stator is the field winding and the rotor is the armature winding. The interaction between the magnetic fields of the stator and rotor produces the rotational motion.

Types of DC Motors:
There are four main types of DC motors:
1. Series DC Motor
2. Shunt DC Motor
3. Cumulative Compound DC Motor
4. Differential Compound DC Motor

Zero Speed Regulation at Full Load:
Zero speed regulation refers to the ability of a motor to maintain a steady speed even at full load without any external control. In other words, the motor automatically adjusts its speed to counteract the load changes.

Differential Compound DC Motor:
The differential compound DC motor is a type of DC motor in which the field winding consists of both series and shunt field windings. The series field winding is connected in series with the armature winding, while the shunt field winding is connected in parallel with the armature winding.

Advantages:
The differential compound DC motor has the following advantages that make it suitable for zero speed regulation at full load without any controller:
1. The series field winding provides high starting torque, which allows the motor to start and accelerate heavy loads.
2. The shunt field winding provides constant speed regulation, maintaining a stable speed even under varying loads.
3. The combination of series and shunt field windings enables the motor to automatically adjust its speed based on the load requirements, ensuring zero speed regulation at full load without the need for any external control.

Conclusion:
In conclusion, the differential compound DC motor is the type of motor that can provide zero speed regulation at full load without any controller. Its unique combination of series and shunt field windings allows it to automatically adjust its speed to counteract load changes, ensuring a steady speed even under varying conditions.