Brushless DC Motor Design

Brushless DC (BLDC) motors deliver high efficiency, torque and speed, and are available in dimensions to suit a wide variety of applications. Portescap continues to engineer performance improvements in its slotted and slotted brushless DC motors. When finding the right motor for your application you may have many questions. How does a brushless motor work, and what is the difference between brushless and brushed motors? What advantages can be achieved via BLDC motor design, what are the advantages of brushless motors in general, and Portescap brushless motors in particular? Learn more about how your business can benefit from Portescap BLDC motors.

How does a brushless DC motor work?

Conventional DC motors use a stationary magnet with a rotating armature combining the commutation segments and brushes to provide automatic commutation. In comparison, the brushless DC motor is a reversed design: the permanent magnet is rotating whereas the windings are part of the stator and can be energized without requiring a commutator-and-brush system. The commutation of the brushless DC motor is made electronically and can be done either by looking at the back-EMF of the motor or by using a position sensor.

Brushless DC Motor Diagram

What is the difference between a brushless and brushed motors?

Brushless motors have no mechanical commutation. Brushed motors, the more conventional design, use a mechanical commutation where a rotating armatures with brushes are used to make the electrical connections. The reduced moving parts give brushless motors a long life, limited only by wear on ball bearings.

BLDC Motor Design


During the brushless DC motor design phase, Portescap engineers aim to optimize the brushless motor torque. Motor torque is the amount of rotational force that a motor generates during operation. The key components involved in producing torque are the magnet, the winding and the flux path. The higher the number of pole pairs in the magnet, the higher the amount of brushless motor torque for the same dissipated power. Copper content of the winding contributes to the power provided by the motor while flux path guides all of the magnetic field in the usable channel, minimizing losses. Striking the right balance is important while creating a motor with maximum brushless motor torque that does not draw a tremendous amount of power. Understanding the complete motor design allows Portescap engineers to pack the most power possible into the smallest motor package.

Portescap’s Ultra EC™ platform offers 3 families of brushless slotless motors to help you address a wide range of requirements for brushless motor torque and speed. The patented U coil provides outstanding performance, including minimal iron losses, increased efficiency and cooler operation. The key to the outstanding performance of these mini brushless motors is this new coil, designed by Portescap in Switzerland. This unique coil design allows two-pole motors, for example, to deliver 30 % more brushless motor torque compared to the same size motor using a conventional coil design, while substantially lowering iron losses.

Brushless DC Motor Technology: Slotted & Slotless

Portescap offers mainly two types of brushless DC motor technologies: slotted and slotless. Both of these brushless DC motors have permanent magnet rotors with 2 or 4 pole pairs. Slotted brushless DC motors have coils inserted in the slots of the stator. Due to these slots, the rotor has preferred equilibrium positions when the motor is unenergized. This resistant torque is called cogging or detent torque. Slotless brushless DC motors have a self-supporting cylindrical coil, creating no detent torque thus the rotor does not have preferred equilibrium positions. Both of these brushless DC motor technologies feature high efficiency, high speed, and hall sensors/sensorless options.

One technology uses a stator that consists of stacked steel lamination with winding placed in the slots that are axially cut along the inner periphery. This is called the BLDC motor, slotted iron structure. The other technology uses a self-supporting cylindrical ironless coil made in the same winding technique as for our ironless rotor DC motors. This is called the BLDC motor, slotless iron structure.

Advantages of Brushless DC Motors

Even while operating at extremely high speeds, brushless DC motors achieve a long, trouble-free life, as there is no mechanical commutation. They have mainly linear motor characteristics, with excellent speed and position control. In brushless motors, static windings are attached to the motor housing, resulting in improved heat dissipation and overload capability. Brushless motors are high efficiency.

Portescap Brushless DC Motors

Portescap Brushless DC motors are extremely reliable and built to deliver the best performances. Their high power density allows a reduction in the overall size of most of the applications. They feature silent running even at high speed. The autoclavable option is ideal for medical applications.

They have a maximum continuous stall torque of up to 39 oz-in (276 mNm). Their peak torque is up to 332.7 oz-in (2’278 mNm). They can achieve speeds of up to 100’000 rpm. Standard diameters range from 0.5 to 2.3 in (12.7 to 58 mm).

Portescap can provide custom motors for your project’s needs. Various stack lengths are available in each frame size. Autoclavable options are available for devices which require sterilization.

Portescap offers custom winding, shaft modification including hollow shaft, and special materials, coating and plating. Lead length, type, color and connector, gearheads, and encoders can be customized.

Most of our BLDC products can be customized or modified with special features that include:

  • Special shafts (longer or shorter, larger or smaller diameters, cross holes, axial holes, cannulated, special materials and coatings)
  • Special construction for non-medical applications (aluminum housing/end bellws, steel gearhead components, steel bearings)
  • Special windings (higher voltage, different speeds)
  • Special lead terminations (no connections, special connectors, integral connectors, special colors)
  • Special mounting features
  • Alternate lam materials
  • Alternate magnet materials
  • Sterilizable option
  • Encoder options

Brushless DC Motor Applications

Brushless DC motors are integral to many applications, especially those in the Medical Device, Industrial Automation, Aerospace and Defense, Security and Access, and other industries.

MEDICAL
BLDC motors are ideal for high speed surgical and dental hand tools, including small bone and large bone tools and dental tools such as drills. They are also very effective for respirators and ventilators, infusion and insulin pumps, dental imaging, and analyzers.

  • High speed surgical hand tools
  • Small bone surgical hand tools
  • Large bone surgical hand tools
  • Dental hand tools
  • Respirators & ventilators
  • Infusion & insulin pumps
  • Dental imaging
  • Analyzers
  • Surgical robotics
  • Bionics and Exoskeleton systems

INDUSTRIAL AUTOMATION
Brushless DC motors are used in industrial nut runners and screwdrivers, air pumps, conveyors, and electronic assembly devices.

  • Industrial nut runners
  • Industrial screwdrivers
  • Air pumps
  • Conveyors
  • Electronic assembly
  • Electric grippers

AEROSPACE & DEFENSE
The longevity and reliability of BLDC motors make them a good choice for aircraft on-board instrumentation, gyroscopes, and satellites. They are also commonly used in valves, fuel metering systems and electric actuators.

  • Aircraft on board instrumentation
  • Gyroscope
  • Satellites
  • Valves
  • Fuel metering system
  • Electric actuator
  • Detection and service robots

SECURITY & ACCESS
The compact size and low running temperatures of Brushless DC motors make them excellent for use in barcode readers, cameras, locks, and ticket printers and dispensers.

  • Barcode readers
  • Camera
  • Locks
  • Ticket printer & dispenser

OTHER
Other applications for brushless DC motors are robotics, precision instrumentation, and engraving.

  • Robotics
  • Precision instrumentation
  • Engraving

Composition and Variations of Brushless DC (BLDC) motors

DetailsCharacteristicsAdvantages
Permanent magnet brushless DC motor designEssentially linear torque/speed curve (neglecting iron losses), with torque proportional to current and speed proportional to voltageEase of speed and position control
Brushless DesignLife is not limited by brush wear but only by wear in ball bearingsVery long life, high reliability, insensitive to environment. No arcing, dust free. Reduced audible and electrical noise
Autoclavable versionSuitable sealing and optimized designWithstand autoclaving and sterilization cycles. Sealing prevents contamination
Static winding attached to motor housingImproved heat dissipationOverload capability

Slotted vs. Slotless BLDC Motor Technologies

DetailsSlottedSlotless
Ability to withstand harsh environment / Autoclavability+++
Torque / Power ratio+++
High speed capability+++
Battery life+++
Detent torque-+

Feedback options

DetailsCharacteristicsAdvantages
Versions without hall sensorTypically used in spindle applicationsCost effective. Less sensitive to environment. Only three connecting wires
Versions with hall sensorsTypically used in applications where speed or load variation are neededVery simple commutation circuitry
Versions with encoder or resolverTypically used in incremental motionVery precise speed and position control
Version with integrated electronicHall sensors and commande circuitry are integrated to the motorPlug and play configuration
Can be driven like a brush DC motor

BLDC Slotted Motors - Additional Information


Brushless DC slotted - Rear end bell and PCB

Brushless DC slotted - Laminations stack

Brushless DC slotted - PCB

Brushless DC slotted - Rotor

Brushless DC slotted - Molded stator