The Landscape of Brushed DC Motors Used in the Standing Desks of Today
Before explaining the advantages of going brushless, let’s just cover the basics of what 99+% of standing desks have been built with since the inception of the industry: the conventional “brushed” DC motor.
It is relatively easy to build linear actuators using brushed DC motors; both their design and construction are simple. Because they don’t require extra circuitry for control, they’re easier and cheaper to manufacture. To nerd out for a moment, they feature a “constant stator field,” which means that these motors respond very quickly to voltage changes. They have good torque (twisting force on the shaft) at low speeds, but that torque diminishes at higher motor speeds. We see this when we load up lower-quality Chinese-made standing desks in the test lab even well within their published maximum lift capacity specifications.
From a reliability and durability standpoint, carbon commutator brushes are the most significant disadvantage of brushed motors. Because of continuous friction against the armature, those brushes wear down with use. Once they wear down to the point that they fail to conduct electricity to the motor, the entire lifting column needs to be replaced. Brushed motors have more parts, like the electromagnetic armature and the brushes, making them larger than brushless motors.
Premium quality linear actuators like those made by Linak have exceptionally low field failure rates as compared to commodity-grade standing desks (that’s what you’re paying the premium price for), but wear and tear can result in diminishing performance on all brushed motor mechanisms.
Brushed motors also have a tendency to lose their magnetic properties over time, reducing their power efficiency, though this will take many years to manifest in something like a standing desk application. More relevantly, brushes can generate a lot more “electrical noise” as they wear down, degrading the functionality of anti-collision detection circuitry and making the legs noisier when they move up and down. This is something we do, again, commonly see happen relatively quickly with commodity-grade, Chinese-made standing desks.
To the average consumer, however, probably the most noticeable difference between brushed and brushless DC motors is their noise signature. This is particularly the case with commodity-grade standing desks. Brushed motors are generally louder because there is arcing across the brushes that creates electrical and magnetic interference, in addition to the physical contact between the brushes and the armature. (Again, we have to point out that this is not the case with premium lifting columns like those made by Linak, which are known for their low noise signatures and super-high reliability.)
Brushless motors hold a constant drive speed regardless of the load on the desk, as compared to lower-quality brushed motor lifting columns that get noisier as the load increases (something we’ve seen consistently over the years with Jiecang bases, for example). As load increases on these cheaper bases, the groaning from the motors also illustrates their fundamental difficulty in maintaining a smooth, constant drive speed.
So, when it comes to how the ear perceives the difference between brushed and brushless motor drives, there is a noticeable difference. Brushless standing desks are quieter than commodity-grade units containing brushed motors, and neither their noise level or the transit speed of their lifting columns change as load increases on the desk. They are, however, still louder than premium-grade brushed-motor units made by Linak (e.g. in the iMovR Lander and Lander Lite desks), which also maintain perfect torque regardless of load. The attention Linak pays to the brush composition, the springs holding the brush to the commutator, the materials technology used in the “glides”, the tolerances of the commutator contacts and the overall tight manufacturing tolerances ensure high quality–but this quality does add to the cost.
The Advantages of Going Brushless
As the name implies, brushless motors have no brushes to conduct the electricity that creates the dynamic magnetic field that turns the motor shaft. To get nerdy again for a moment, that field is instead formed by placing permanent magnets on the armature and moving the electromagnets to the stator.
The result is a higher power density for the size of the motors, meaning they can be smaller and more discreetly hidden “inline” (at the top of the spindle inside the lifting columns, as compared to brushed motors that require a motor housing typically mounted at a 90-degree angle to the spindle). This results in a much sleeker-looking leg and fewer mechanical parts to wear out and potentially fail.
Brushless motors have an easier time maintaining or increasing the torque at various speeds, and generally have greater mechanical power with less electrical power energizing the motor. Since there are no brushes, there are fewer parts to wear out, and maintenance issues drop to near zero. While circuit boards can still fail, brushless-motor lifting columns will surely outlast any commodity-grade brushed motor mechanism you’ll find on a cheap import, for a relatively small price increment as compared to desks build with super-premium componentry like Linak’s.
Specifically analyzing the LogicData actuators that iMovR has started using in their new Jaxson standing desk line, there are some other notable advantages. The inline motors are remarkably small for the amount of power they deliver, making the legs a little thinner while maintaining the same excellent stability as iMovR’s more premium-priced Lander line based on Linak componentry. The “glides” between the telescoping segments of the lifting columns are completely hidden; this makes for a very clean look that home office users in particular will appreciate. The anti-collision circuitry is impressively consistent, due to the elimination of any electrical noise caused by arcing across the brushes.
