www.hpmag.co.uk HYDRAULICS & PNEUMATICS January/February 2024 17 include brushed DC coreless designs, as well as brushless cylindrical and flat motors. The brushed DC coreless motor includes a coil arrangement rotor, free of iron laminations, and a stator with fixed magnets. Meanwhile, brushless DC (BLDC) cylindrical motors utilise a stationary coil with a rotating permanent magnet and coil windings as part of the stator, and these designs remove the need for brush commutation. In addition to the cylindrical designs, a BLDC slotted flat motor includes coils in lamination slots, but unlike their cylindrical counterparts, they incorporate an outer rotor in a flat architecture. Selecting the right motion solution As each design offers varying advantages, the motor selection depends on the prioritisation of parameters, particularly within the required size and weight envelope. Of these parameters, torque density is a typical priority. High-energy magnets that generate high flux density coupled with a coreless coil configuration is an optimal design, and both BLDC slotless and slotted motor technologies can provide high continuous torque without magnetic saturation. In comparison to cylindrical motors, BLDC flat designs typically offer the highest torque density to form factor. Maximum motor speed is also a common requirement, and electrically commutated BLDC motors can achieve higher speeds, with cylindrical designs achieving over 40,000 rpm. At these high speeds, motors require specially designed bearing systems, and the package is balanced to minimise vibration. For dynamic speed operation, the BLDC slotted motor is the preferred choice for low rotor inertia due to the relatively small rotor diameter. Friction counteracts heat and energy efficiency, so LEFT: Portescap motion solutions have numerous applications in smart munition development
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