Introduction
Torque is a key factor in DC motor performance. While speed shows how fast a motor rotates, torque determines its ability to move or lift a load—making it critical in automotive, industrial, and marine applications.

What Is Torque?
Torque is the rotational force produced by a motor’s shaft, measured in Nm or lb-in.
It represents the motor’s “twisting strength”—higher torque means greater ability to handle heavy loads.

How Torque Is Generated
When DC voltage is applied:
• Current flows through the armature
• A magnetic field is created
• It interacts with the main magnetic field
• This produces force, causing rotation

Torque and Current Relationship

Torque increases with current. Higher load = higher current demand.

Types of Torque
• Starting Torque: High torque at startup
• Running Torque: Normal operating torque
• Stall Torque: Maximum torque at zero speed (can cause overheating if prolonged)

Torque vs Speed
• Higher torque → lower speed
• Lower torque → higher speed

Importance in Applications
Torque determines whether a motor can perform its task:
• Marine: lifting engines (tilt/trim)
• Automotive: starting engines
• Industrial: driving machinery
Insufficient torque can lead to stalling and failure.

Key Factors Affecting Torque
• Voltage and current
• Magnetic field strength
• Motor design
• Load conditions

Conclusion
Torque is the core measure of a DC motor’s working capability. Proper torque selection ensures reliable performance, efficiency, and long service life.