Motor Driver｜Basic

Comparison of the Features, Performance, and Characteristics of Small Motors

2023.09.27

Points of this article

・Comparisons of the features, performance, and characteristics of small motors are used as reference when choosing a motor.

・Even motors in the same category may have widely different specifications, so these guidelines should serve only as rough rules of thumb.

・Ultimately, it will be necessary to study the details of the data sheets for individual motors.

table of contents

When selecting a small motor, it is important to compare their features, performance, and characteristics.

Features of Small Motors

The features of the stepping motors, brushed motors, and brushless motors that we have described in this series of articles are summarized in the table below.

  Stepping motors Brushed motors Brushless motors
Rotation method A driving circuit excites each of the phases (2, 3, or 5 phases) of armature windings in a predetermined order Armature currents are switched through a sliding-contact commutation mechanism using brushes and a commutator Brushes are eliminated by substituting magnetic pole position sensors and semiconductor switches for the brush and commutator action
Driving circuit Necessary Unnecessary Necessary
Torque Comparatively large torque
(Particularly at low speeds)		 Large startup torque; torque proportional to armature current
(Comparatively large torques at moderate to high speeds)
Rotation speed Proportional to the input pulse rate.
Erratic behavior at low speeds		 Proportional to the voltage applied to the armature. If the load torque increases, the speed falls
High-speed rotation High-speed rotation difficult (speed must be increased gradually) Up to several thousand rpm, due to limits of commutation mechanism using brushes and commutator Several thousand to tens of thousands of rpm
Rotation lifetime Determined by the bearing lifetime; tens of thousands of hours Limited by wear on the brushes and commutator;
hundreds to thousands of hours		 Determined by the bearing lifetime;
tens to hundreds of thousands of hours
Forward, reverse rotation methods The order of phase excitation by the driving circuit must be switched Rotation is reversed if the polarity of the terminal voltage is reversed The order of phase excitation by the driving circuit must be switched
Control properties Open-loop control, in which rotation speed and position (rotation amount) are determined by command pulses, is possible (however step-out is a problem) Speed control (feedback control using a speed sensor) is necessary for constant-speed rotation
Torque is proportional to the current, making torque control easy
Availability Easy: comparatively many models Easy: both manufacturers and models are numerous, making for many options Difficult: Mostly specialized motors for specific uses
Price High, when driving circuitry is included
Cheap compared with brushless motors		 Relatively cheap; coreless models are an upgrade from magnet models and somewhat more expensive Relatively high, when driving circuitry is included

Comparison of the Performance of Small Motors

The performance of the different types of small motors is compared in the following radar chart.

Rotation Rate of Small Motors – Torque Characteristics

The rotation rate-torque characteristics for different small motor types are summarized. Brushless motors and brushed motors should be regarded as having basically the same characteristics.

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