Design of High-Speed Permanent Magnet Motor Considering Rotor Radial Force and Motor Losses

Abstract

Different from the design of conventional permanent magnet (PM) motors, high-speed motors are primarily limited by rotor unbalanced radial forces, rotor power losses, and rotor mechanical strength. This paper aimed to propose a suitable PM motor with consideration of these design issues. First, the rotor radial force is minimized based on the selection of stator tooth numbers and windings. By designing a stator with even slots, the rotor radial force can be canceled, leading to better rotor strength at high speed. Second, rotor power losses proportional to rotor frequency are increased as motor speed increases. A two-dimensional sensitivity analysis is used to improve these losses. In addition, the rotor sleeve loss can be minimized to less than 8.3% of the total losses using slotless windings. Third, the trapezoidal drive can cause more than a 33% magnet loss due to additional armature flux harmonics. This drive reflected loss is also mitigated with slotless windings. In this paper, six PM motors with different tooth numbers, stator cores, and winding layouts are compared. All the design methods are verified based on nonlinear finite element analysis (FEA).

Radial force cancellation of bearingless brushless direct current motor using integrated winding configuration

“…The currents of the six-suspension pair of poles which required to cancel the radial force 4. Noted that the maximum values for cancellation current are (31) Ampere in coil (1,7) and (46) Ampere in coils (2,8), (3,9), (4,10), and (85) Ampere in coils (5,11), (6,12).…”

“…Bearingless machines solve the limitations of axial length, large-volume motors, complex system structure, and the high cost of pure magnetic bearings. The main challenge of these machines is the rotor radial force which creates magnetic pull-out force and vibration, especially at high-speed rotation, resulting in extra mechanical losses and bearing reliability degradation; therefore, the resultant radial force of the rotor must be minimized or canceled to zero at the equilibrium position for rotational motion [5]- [7]. The interaction between the rotor magnets and the stator armature core are the main sources of the radial force.…”

“…The interaction between the rotor magnets and the stator armature core are the main sources of the radial force. The radial force disappears when the symmetric stator is designed with an even number of stator slots [5]. In an integrated winding configuration, the cancellation current and the motor current are passing through the same winding in the stator slots.…”

“…The most common divisor (MCD) is the main indication for the required slot/pole combination. A higher even MCD number gives a higher number of symmetrical sectors for the machine, and as a result, a balance radial force with a lower magnitude will obtain [5], [11], [12]. In this paper, integrated winding configuration has been implemented with a 12/8 slot/pole combination.…”

Reducing Rotor Temperature Rise in Concentrated Winding Motor by Using Magnetic Powder Mixed Resin Ring

“…Electrification is progressing in automobiles and aircraft, and it is expected that the demand for increased motor efficiency will further increase [5][6][7]. Permanent magnet servomotors capable of accurate positioning and speed control are widely used in the industrial sector [8,9], and the demand for increased motor speed is increasing [10][11][12][13]. Therefore, the servomotor is required to reduce the losses associated with the high-speed rotation range and the high-torque range.…”