The DC Motor, which can provide zero speed regulation at full load without any controller is

Concept:

A DC Motor having both shunt and series field windings is called a Compound Motor. The connection diagram of the compound motor is shown below.

The compound motor is further subdivided as cumulative compound motor and differential compound motor.

Cumulative compound motor:

• In a cumulative compound motor, the flux produced by both the windings is in the same direction.
• It provides high starting torque
• Good speed regulation at high speeds
• Adjustable varying speed

Differential compound motor:

• In differential compound motor, the flux produced by the series field windings is opposite to the flux produced by the shunt field winding
• It provides low starting torque

Explanation:

Differentially compound motor can provide zero speed regulation at full load without any controller.

Note:

In the Differential compound motor, the series flux opposes the shunt field flux. As load increases, flux will decrease for differential compound motor. Therefore speed will increase and the speed regulation will be negative.