Brushless Permanent Magnet Machines (Brushless Motors)
Permanent Magnet (PM) Brushless Drive - Two types, those with sinusoidal back emfs and armature current, known as P.M. sine wave machine drives (sometimes p.m. synchronous machine drives (PMSM) and those with trapezoidal back emfs and d.c. pulses of current, known as brushless D.C. drives (BDCM). In practice the 2 drive types have much in common.
Configuration of Permanent Magnet Brushless Drive Types:
Exterior Rotor - Brushless Permament Magnet Machine Drives
The exterior rotor brushless PM drive (Such a system is known as direct drive, Gearless drive, Hub motor Drive) is a high-torque machine application at the low-speed range. Since torque increases with the square of machine diameter, the high torque requirement leads to be short and of relatively large diameter.
Recently, the development of the direct brushless PM machine drive has been greatly improved. With these improvements, motors have been able to provide high torques with relatively small sizes. This advantage allows the designer to develop the system by coupling the system’s load directly to the motor without the use of transmission elements, such as belts or gears. The elimination of the intermediate transmission provides the system with greater accuracy since there is no friction or backlash introduced to the system. The reliability of the system is also improved because a smaller number of components are used.
The design and application of high flux density of rare earth magnets to brushless PM machines has led to the advance characteristics of its magnetic circuits and the design of the machine is a very careful balance between conflicting requirements in order to arrive at an optimal combination of materials for use in motor construction.
Direct brushless PM machine drives are highly versatile, and used across all areas of industry, but cost is always a consideration, requiring very careful optimisation to realise a commercially viable cost/performance ratio.
Applications: Direct brushless permanent magnet machine drives are rapidly finding numerous applications such as Electric Vehicles, Wheelchairs, Scooters, Golf trolleys, Buggys, Forklift trucks. Lifts, Wind energy technology, generators, etc.
Design Services: SDT has many years experience of designing PM brushless machines for a variety of applications. Please see engineering services >.
Interior Rotor - Brushless Permanent Magnet Machine Drives
The interior-rotor type of brushless PM motor, (known as high speed brushless PM machine), has a high torque/inertia ratio. As one of its most distinguishing characteristics. The specific power and volumetric power density are also generally higher than in other non-PM machine types. Brushless DC motors have many advantages over brushed DC motors and induction motors. In addition, the ratio of torque delivered to the size of the motor is higher, making it useful in applications where space and weight are critical factors.
Application: Recently, Permanent magnet machines are rapidly finding numerous applications such as automotive applications, industrial products, alternators, pumps, Fans, small appliances, etc.
More recently, small and medium size PM machines are increasing being applied in many industrial applications, primarily as the result the advancements in high-energy permanent magnet materials and magnet manufacturing technologies enabling the manufacturer of high power density and high efficiency permanent magnet motors at a reasonable cost
The optimum rotor configuration, rotor electromagnetic and mechanical design, and the stator electromagnetic design must be carefully designed and matched to achieve a cost effective product while meeting optimum performance criteria.
Design Services: SDT has designed brushless PM machines for many applications requiring cost effective products, while meeting tough performance criteria. Please see engineering services >