Using the Frameless Brushless Torque Motor for Angular Acceleration Applications

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An unhoused arc segmented frameless brushless torque motor (TWR-070-410-1150-3PH) with low inertia moving coil assembly has been developed by H2W for high angular acceleration applications.

The rotary 3-phase brushless motor, also known as a rotary servo motor, is a direct drive motor that is suitable for unlimited or limited, closed loop servo, rotary motion applications. It can produce a continuous/peak torque of 480 in-lbs [53 Nm]/1440 in-lbs [159 Nm].

It has been engineered to have a 70° rotation and function on a 20” (500 mm) radius; however, extra modular magnet tracks (33° each) can be incorporated to boost angular displacement. When coupled with a rotary encoder for position feedback, the frameless brushless torque motor can provide highly precise position, acceleration control, and velocity.

The vacuum encapsulated moving motor coil assembly moves through a gap in the long U-shaped magnet assembly. There is a requirement for a customer supplied bearing system to direct the moving coil assembly and to maintain a 0.050" [1.25 mm] clearance between the coil assembly and the magnet.

Attractive force is not present between the magnet and the motor coil assembly. The 3-phase motor coil assembly can be commutated trapezoidally using integral hall effects or commutated sinusoidally using software commutation in conjunction with the appropriate motion controller, amplifier, and encoder feedback.

A brushless servo amplifier provides power to the motor that is conveyed through a high-flex motor power cable. Motors can be designed to match the specific application needs of customers.


The main features of the Frameless Brushless Torque Motor are as follows:

  • Low inertia
  • Zero cogging
  • High speed and accelerations of light loads
  • Uses standard three-phase brushless amplifier
  • Multiple motors coils within one magnet assembly

This information has been sourced, reviewed and adapted from materials provided by H2W Technologies

For more information on this source, please visit H2W Technologies

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