Digital motor is what’s familiar as a switched reluctance motor. Instead of powering the rotor, a switched reluctance motor has a magnetic core — so as power is switched along with the stator’s coils, the magnetic core is dragged around to line up with the magnetic field they generate.

With more coils than magnetic poles on the rotor, it’s likely to set up a switching pattern in the coils that pulls the rotor around. That implies utilizing sensors and complex switching circuitry, as controlling the motor’s magnetic fields is the key to efficient driving.

Switched reluctance motors like this can be exceptionally efficient, and Dyson claims that their motor is 84% efficient (compared to 40% for a traditional electric motor). There’s a lot to be said for a compact, high-power motor like this — not just for vacuum cleaners and hand driers. It also implied using many design tools — a lot of it using Dyson’s simulation software.

1. How Do Digital Motors Works?

While Digital motor is permanent magnets brush-less motor, I trust Dyson had to attend to a few challenges that, in my view, led to a “digital” description. It rotates at 125000 RPM speed which is 42 times more than two poles electric motor (swimming pool pump, for example) with only 3000 RPM. That creates enormous G-forces, and Dyson solution for that (among other things) is:

Ceramic shaft instead of steel – it is lighter, more robust. Therefore, the diameter can be smaller because, at 125k rpm, you try to design a motor that is the littlest diameter possible and longer. Ratio Motor Lenght/Motor Diameter is much higher than ordinary motors.

Dyson developed a unique neodymium cylindrical magnets manufacturing process that is part of the rotor. It is a long and small diameter cylinder rather than 2 (2 poles) or 4 (4 poles) independent magnets. Once again, a long cylinder can rotate at 125000 RPM (V10) while separate poles would lead to mechanical collapse and tremendous vibrations.

So when you look at the Dyson rotor, it seems like a cylinder, and you can not physically see the magnetic poles. They appear to be engraved into the cylinder structure. The shape of high-quality aluminum (low weight) air turbine is likewise crucial. Once again, small diameter.

Just so it is clear. The rotating assembly energy is E=m*omega (E is energy, m is weight, and omega is the speed in rad/s). Based on that motor turning at 125000, RPM can have 42 times less weight to achieve similar inertia energy.

Stator: Presently we should discuss stator now. The ordinary permanent brushless motor has a stator winding that, if connected to a 240VAC supply, creates a rotary magnetic field that leads to 3000RPM for 50Hz and a two-pole motor.

Dyson has, in my view, attended to something that until very recently was almost impossible. Rather than the typical stator winding, I believe they are utilizing coils, and let’s call them “digital coils.” Not sure how many, but if a rotor cylinder has four poles, I would expect (not sure) a minimum of 8 “digital coils.”

Dyson people would realize that Dyson is observing air pressure (altitude) and temperature. A few people think this is added merely as a “cool feature” like APPLE often does with their products.

This is where Dyson has done something extraordinary, “digitally cool,” to address difficulties.

2. The Value of Digital Motor Speed Control

Digital motor speed manages (‘digital controls’) are, for this discussion, microprocessor-based, user-configurable speed controls for DC permanent magnet (DCPM) motors or digital speed potentiometers for use with AC VFD’s.

They developed The digital concept in the mid-’80s to solve a customer’s requirement for accurate, repeatable speed control of a pizza oven chain conveyor. These products have set over the years into powerful, intelligent platforms for controlling and watching one or more motors’ speeds in a vast difference of applications.

Digital speed control is a motor speed control for an AC or DC motor that incorporates an integrated, programmable display of set or reference speed in engineering units, percent output, time-in-process, and percent of Master reference. The control might be an open or closed loop, where a closed loop requires incremental pulse encoder feedback.

A digital speed potentiometer is a motor speed control accessory that, when added to a traditional motor speed control (SCR, PWM, Regen, BLDC), will give that speed control the characteristics and capability of an integrated digital speed control characterized previously.

3. Digital Motor Protection Relay (Split Module): CSMPM

Range:

• Wiring: Screw type (S)/Tunnel (T)
• Panel mount: Unit or Extension
• Operation time: Select either reverse time characteristics or definite time

Features:

• Digital Relay with built-in MCU (Micro Processor Control Unit)
• Multiple protection: Overload / Phase failure/Stall /Asymmetry/ Phase reverse Earth Fault
• Current setting 0.5-6A&5-60A
• The current setting 0.5-6A can be used up to 600A with external.
• Fault diagnostic seven-segment display of fault & values

Benefits:

• Digital Ammeter function
• Time setting: Inverse time (O-60 sec), Definite time (O~60 sec) starting, and Delay time operating time
• Accuracy : Current/Timei5% of setting
• Fail-safe operation
• Alert function(60-110% of set current)
• inverse/ Definite time characteristics, site selectable
• C.T. ratio setting in CSMPM~06 frame 0nly.

4. Brushless Solution

An electronic servo structure restores the mechanical commutator contacts in brushless DC motors. An electronic sensor exposes the angle of the rotor. It controls semiconductor switches such as transistors that switch current through the windings, either reversing the current direction or, in some motors, turning it off at the correct angle.

Hence, the electromagnets create torque in one order. The elimination of the sliding contact permits brushless motors to have more negligible friction and longer life; their working life is restricted by their bearings’ lifetime.

Brushed DC motors develop the highest torque when stationary linearly reduces as velocity increases. Brushless motors can overcome some brushed motors; they include higher efficiency and lower susceptibility to mechanical wear.

These advantages come at the cost of potentially less rugged, more complex, and additional expensive control electronics. A typical brushless motor has lasting magnets around a fixed armature to remove problems associated with connecting current to the moving armature.

5. An Electronic Controller (Electric Motor)

An electronic controller restores the brush/commutator assembly of the brushed DC motor, which continually switches the phase to the windings to keep the motor turning. The controller performs similar timed power distribution using a solid-state circuit rather than the brush/commutator system.

Brushless motors offer a few advantages over brushed DC motors, including high torque to weight ratio, more torque per watt (increased efficiency), increased reliability, lessened noise, longer lifetime (no brush and commutator erosion), elimination of ionizing sparks from the commutator, and an overall trimming of electromagnetic interference (EMI).

Among no windings on the rotor, they are not subjected to centrifugal forces. Because the housing supports the windings, they can be cooled by conduction need no airflow inside the motor for cooling. This, in turn, means that the motor’s inner can be completely enclosed and protected from dirt or other foreign matter.