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Servo vs. Stepper vs. Brushless DC Motors

About DC Electric Motors

DC electric motors convert direct current electricity into mechanical power by generating magnetic fields that spin rotor positioning attached to a motor’s output shaft. There are several common types of electric motors, including servo, stepper, and brushless DC motors. We’ll compare mechanical and electrical differences of each, then explain the key factors to consider when selecting the appropriate motor solution for your customer purposes.

Servo Motors

A servo motor has a similar mechanical build and flat-torque curve of a brushless DC motor with the characteristics and ability to control position, speed, and acceleration at fine-angular points. The servo’s ability to operate requires a position feedback sensor which interfaces with a servo driver module, commanded by a programmable logic controller (PLC). When installed, servo motors are “application specific” as they require manual tuning relative to the application’s inertial load, gain evaluation of the system’s command output vs. input, and homing corresponding to the motion profile’s “start” position.

Stepper Motors

A stepper motor (also commonly recognized as a step or stepping motor) has a set mechanical tooth design on both the stator and rotor components to move the front shaft’s rotational position to specific angles relative to an identified home position. Current excites the stator’s phases by a separate driver that sends revolution-specific voltage pulses using an open-loop system, demarcated by equal step divisions around the shaft. While a stepper can reliably position the rotor in equal step distance between mechanical teeth angles, closed-loop feedback remains an available option for applications that require precise angular positioning measurements. Stepper motors can also operate in continuous duty when the appropriate voltage, current, inertial load and torque are below the motor’s pullout curve. The advantages of utilizing a stepper over other motor types are high response acceleration between angular positions, continuous high torque at low speeds, the ability to add a low-cost encoder for closed-loop feedback, and the elimination of servo tuning/gain output analysis.

Brushless DC Motors

Conventional DC motors require electrical contact points, or carbon brushes, between a stationary electrical feed and the rotary shaft. The current is sent to a commutator designed to maintain the motor’s rotational energy. The disadvantage of a brushed motor is significantly lower duty cycles (less operation time between profile cycles in a single day), and brushes that wear with continued use. A brushless DC motor (BLDC) transmits direct current to the rotor electronically by intricately timed electromagnetic pulses in place of brushes. BLDC motor technology allows for continuous duty below the rated torque across a specified speed range.

Servo vs. Stepper vs. Brushless DC Motors

Deciding between a BLDC vs servo vs stepper motor is simple when you consider the simultaneous need for accurate motor positioning, design simplicity, and component longevity. The latter point is crucial when comparing a stepper to a servo motor because a functioning servo requires additional parameters than simply sending pulse signals. Servo motors cannot function independently of a complex encoder to calibrate the motor’s feedback sensor and controller. If a component fails or an inertial load is changed, the motor can risk equipment damage and costly delays.

By contrast, a stepper motor utilizes the mechanical structure of the internal components’ tooth design to execute open-loop positioning capability. With its integrated step divisions, stepper motors can position the rotary shaft with precision while also offering the ability to attach an encoder for closed-loop feedback. All that’s required is to select a stepper motor with specifications that match the intended application.

If wear is a primary consideration for variable speed applications and your motion profile requires a consistent rated torque across a speed range, a BLDC motor is an optimal choice. Eliminating the need for brushes significantly increases product lifespan, decreases the cost of maintenance, and overall is a more powerful motor capable of continuous-duty operation.

Electric Motors by Elinco International JPC

DC electric motors are present across all automation-related industries that require unmanned motion profiles. The decision to select a suitable product is as important as a motor’s quality for achieving efficiency, reliability, and effectiveness. If you have further questions about the advantages of selecting a stepper motor vs. servo motor, or how to select the right BLDC motor for you, contact us and speak with one of Elinco International’s highly knowledgeable service technicians.

Slotted vs. Slotless Brushless Motors

Slotless motors were first designed when manufacturers needed to create an improved brushless motor design built for low-power applications. Today’s slotless stators present unique advantages such as smooth performance and less cogging. Cogging, which occurs when the rotor and stator slots align and make the motor unable to start, is a common problem with motors at less than 500 rpm. It is also one of the most common reasons why people switch from slotted to slotless brushless motors.

Learn more about the different constructions of these two motor types, the advantages and common applications of each type, and the value of choosing Elinco as your supplier.

Construction of Slotted vs. Slotless Brushless Motors

Slotted and slotless brushless motors have several key differences in their construction that impact performance and longevity.

Slotted Motor

Brushless motors have a rotating, magnetic rotor with fixed windings arranged around the exterior of the rotor. In a slotted motor, the central stator core is built of laminated steel with slots and teeth. The copper wire winds between the teeth in the slots. When the teeth are longer – or closer to the central magnet – the motor has increased torque.

Slotless Motor

Slotless motors are also brushless motors with a rotating, magnetic rotor. However, the steel lamination is smooth and doesn’t have teeth (or slots) for copper wire to wind around. Instead, manufacturers wind the copper coils in a unique cylindrical shape. This configuration gives slotless motors their signature smooth performance, with low noise levels and little to no vibration, while providing high levels of power.

Performance Differences and Applications for Slotted vs. Slotless DC Motors

Because of the different winding configurations, slotted and slotless motors each provide different advantages. Slotted motors, for example, outperform slotless varieties when it comes to generating high levels of constant torque and being able to accelerate quickly. Slotless brushless motors, on the other hand, excel at smooth motion with little to no velocity ripple and having good tour constant (Kt) linearity. These motors also have the largest through holes.

These differences in performance mean they each work best for different applications and industries. 

Parameter Slotted Slotless
Smoothest Motion (Lowest Velocity Ripple)

Highest Torque Constant

Torque Constant (Kt) Linearity

Largest Through Hole

Highest Acceleration Rates

Slotted Motor

Slotted motors work best in applications where compact size isn’t an issue and the machinery needs multiple poles. They can also perform in a variety of adverse conditions and environments, because manufacturers can better protect the windings from future debris or likely damage. This means they’re commonly used in appliances, electric vehicles, and other large electrical machines.

SL Series SlotlessSlotless Motor

Slotless motors work best in small precision tools. Not only do these motors have a compact size, but their smooth torque and movement are much less likely to interfere with performance. Manufacturers often pair slotless motors with medical devices and handheld tools.

Elinco DC Motors

Elinco JPC is a leading designer and manufacturer of slotted and slotless brushless motors. Innovation and long-lasting relationships built on product quality are core tenets of our business. We serve the industrial, office, medical, and military marketing sectors with consistently reliable products that are built to be cost-effective and meet our clients’ quality standards across all fields. 

Our in-house engineering team is focused on developing new solutions and designs for both our slotted and slotless brushless DC motors. We provide assemblies capable of generating power levels from 400W to 8,000W and beyond. Our Elinco slotless SBLDC product line motors can be used in everything from high-torque surgical tools to medium-power medical pumps to fully autonomous vehicles based on our clients’ performance requirements and design considerations.

Order Your Slotted or Slotless Motor From Elinco International JPC

Slotted brushless motors are powerful, rugged assemblies for powering large machinery, while slotless brushless motors are capable of powering fine-tuned control for a wide variety of handheld tools. Our team at Elinco designs and builds DC motors of both classifications to power our clients’ systems and devices. Contact us today to learn more about our products or to place your order.