Zero cogging BLDC motors

We offer two types of cogging-free motors from our manufacturer partner ThinGap.

TG-Series: Ironless for high power density.

LSI-Series: Slotless design with back-iron for high torque density

The stator of the TG motors has no iron core ("ironless"). The motor is designed to run at high speeds to provide high power density. Thus, the ironless stator is desirable, as it reduces the back EMF. The back EMF is a voltage generated by any permanent magnet motor which is spinning. The amount of back EMF generated by a permanent magnet motor depends on a parameter called the "back EMF constant". The TG motors are designed to have a low back EMF constant.

The LSI motors have a slotless iron lamination stack which acts as a return path for the stator's magnetic field. The stator winding is bonded to the inside of the iron lamination stack. The lamination stack also provides a good heatsink for the motor at low speeds which makes it very useful for applications like gimbals or optics.

Please keep reading to find out more about each family, or, contact us to discuss your requirements with an experienced MACCON engineer.

LSI series of cogging-free slotless motors

ThinGap’s LS line targets low speed, high precision applications such as gimbals, optics, and precision robotics.
Highest torque density with high power capability. Low thermal resistance at any speed.

Key features:

  • Smooth motion with zero cogging and ultra low torque ripple when paired with a sinusoidal drive
  • High peak torque to continuous torque ratio
  • Optimized for ultimate torque density
  • Stationary lamination stack for typical bore mounting
  • 3 phase brushless, sinusoidal waveforms < 1% THD
  • Non-saturating facilitates very high peak torque (typically >4:1)
  • Exceptionally large clear apertures
  • Frame-less kit facilitates deep integration
  • Large through hole

We understand that your application has special requirement, so we offer custom motors, or modifications to our standard motors, to meet your specific design requirements to make sure you get the perfect motor for your application.  Please contact us to discuss your requirements.

TG series of ironless cogging-free motors

Our manufacturer partner ThinGap’s three-phase, permanent magnet, Brushless DC (BLDC) ring motors are made with proprietary ironless stator technology. The result are motors and generators that are lightweight and high torque which deliver high-power at exceptional rotational smoothness. The “ring” architecture allows for more highly integrated, more compact and lighter system designs.

Unlike slotless motors, only ThinGap delivers “True-Zero™” zero cogging torque.  That’s because ThinGap’s completely ironless stator has no magnetic interaction with the rotor until purposely energized by the controller. This gives them exceptionally precise rotation and unmatched rotational smoothness.

ThinGap Motors offer these advantages:

  • High torque-to-weight ratio
  • Lightweight and low inertia
  • Improved system integration due to our ring architecture
  • “True-Zero ™” Zero cogging torque for precision positioning and smooth rotational velocity
  • High power density scalable from 50W to 550kW
  • Diameters from 40mm to 900 mm

We understand that your application has special requirement, so we offer custom motors, or modifications to our standard motors, to meet your specific design requirements to make sure you get the perfect motor for your application.  Please contact us to discuss your requirements.

Application of cogging-free motors in semiconductor technology: friction rod drive

The cogging-free motors are also often used to generate a precise linear movement from a rotary motion. This is particularly important for mask inspection in the semiconductor industry. The principle is called friction rod drive and works as follows.

  • The shaft of the cogging-free motor presses on a metal rod (frictional contact between two metal surfaces)
  • Shaft and rod are hardened to minimize mechanical deformation
  • The motor shaft has two paired bearings (2x2) to eliminate radial play
  • These are specially paired bearings, which must have a very similar tolerance
  • Feedback: resolver + DC tacho
  • Drive electronics: MACCON LWM, a non-switching servo drive (a.k.a. "linear amplifier")
  • There is no heat generated in the rod, because the rod has no electric coils and is therefore completely passive.

Another application of the cogging-free motors is wafer polishing. Due to the absence of cogging torque, a high speed smoothness is achieved. This leads to a high surface evenness on the semiconductor wafer.

Contact us to talk to an experienced MACCON engineer about your application.

Servo control of cogging-free motors

When control engineers contemplate difficult tasks such as micrometre / nanometre positioning, as well as aiming for speed stability at very low speeds, they usually think about several key success factors.

Firstly, eliminating cogging force or cogging torque. This is easily achieved by using cogging-free motors such as the ones shown on this page. In addition, it is well known that a high-resolution encoder system is required. This could be an optical encoder system, such as the ones shown at this link. Finally, they consider the type of servodrive which should be used. Most servodrives use pulse-width modulation of the supply voltage to achieve the required current in the motor windings. However, this leads to current ripple, which in turn produces torque ripple. The torque ripple makes it impossible to achieve high-precision servo tasks. The solution is to use a non-switching servodrive, also known as a linear amplifier. The MACCON Family of non-switching servodrives can be found at this link.

With the following success factors in place:

  • Ironless motor
  • High-resolution optical encoder
  • Non-switching servodrive (linear amplifier)

we can now look at the remaining puzzle pieces. Of course, we should never forget the issue of cables. High-quality motor and feedback cables which are properly shielded against electromagnetic interference are a must. Last but not least, we need an experienced commissioning engineer to get the described system working. MACCON has a core team of experienced engineers who have supported machine-builders in semiconductors and optics / photonics to achieve the most difficult of nanometre positioning and low-speed motion tasks. Contact us to discuss your needs, engineer-to-engineer!