What Distinguishes Servo Motors from DC Motors?

by Alex Hales
Servo Motors

There are several types of DC motors, each best suited for multiple purposes across multiple industries. DC motors can be brushed or brushless, depending on the internal mechanisms. Brush DC motors incorporate rotating brushes and commutators, while brushless motors have few moving parts.


Fleming’s left-hand rule suggests that a direct current (DC) motor converts electrical energy into mechanical energy. Simply put, a conductor in a magnetic field carrying current generates torque that moves the motor.


On the other hand, the Servo Motor does not run continuously for an extended period, but a feedback system controls it. In addition, the three phase motor system’s arrangement allows the motor to rotate at a particular angle for greater precision and accuracy.


So, what distinguishes a servo motor from a DC motor?


DC Motors

A brushed DC motor comprises an armature, windings, commutator rings, carbon brushes, and a stator and runs on a DC power supply. The stator creates constant magnetic field lines that pass through the tutor assembly that encompasses the output shaft and armature. The armature yields the armature coil around the output shaft and then connects to the commutator rings. When kickstarting the brushed motor, the rotor assembly gets energised by squeezing the brushes onto the commutator rings. Current flows through the brushes and winding to generate an electromagnet with a magnetic field. This new field then opposes the stator field and causes the motor to turn.


A brushless motor varies from the brushed motor in current delivery to the rotor. In this case, the coils are not on the rotor. Rather, the rotor is a permanent magnet that rotates by changing the direction of the magnetic fields generated by the stationary coils.


DC motors are a key moving component of many electric appliances in the market, including toys, kitchenware like a blender, and the automotive industry.


Servo Motors

Servo motors are available in AC, like the 1 phase induction motor, DC, brushed, and brushless designs. They are also called rotary actuators and comprise many specialised units besides the motor. They are distinguishable by the closed-loop design and need position feedback for the rotor to control its speed and position. In addition, the design optimises precision and accuracy, giving the best output angle resolution.


Comparison of DC and Servo Motors:



Both the DC and servo motor are easy to control. The DC motor is less complex than the servo and reverses the leads to change direction while changing the voltage to change the speed. The servo motor is highly controllable using the feedback loop system that indicates the optimal output angles to set.



DC motor types have varying speed ranges. On the other hand, servo motors combine the torque range with the ability to regulate the ranges at will. In addition, the feedback system allows users to set the desired speed and power, allowing the servo motor to cover more range per unit.



The reliability of the DC and servo motor depends on maintenance. For example, brushed motors are prone to wear and tear because of the many moving parts. However, with regular service and responsible use, the motor lasts longer without suffering failure. Moreover, replacing a DC motor is easy as they are low-cost and easily replaceable. On the other hand, the servo motor is not as easily disposable but is more reliable than the average DC motor. Moreover, its maintenance is more challenging as the system needs to adjust for accuracy whenever a new component is added to maintain error correction.


Sustainable Output

DC motors are largely unaffected by running for extended periods and maintain a steady torque. Alternately, servo motors work best in intermittent applications where the motor does not spin too long. In addition, they only provide peak torque for a short period of their operating time, or they will suffer damage. Therefore, their best application is as positioning motors, not continued use.


The choice of DC or servo motor boils down to the user’s requirements. Review the specifications and match them against the budget. DC motors are more affordable and do not need extra controllers or sensors. Conversely, servo motors and accessories are a more expensive and greater financial concern. However, they compensate for the expense by offering great speed, torque, and position control. Evaluate the suppliers and eliminate them based on experience, proven history, and client reviews until the right fit presents itself.

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