The field of the disclosure relates generally to electric motors, and more particularly, to radially embedded permanent magnet rotors and alternative materials for use in electric motors.
Various types of electric machines include permanent magnets. For example, a brushless direct current (BLDC) motor may include a plurality of permanent magnets coupled to an exterior surface of a rotor core. Typically, the permanent magnets are coupled to the exterior surface of the rotor core using an adhesive and/or an outer retaining covering. This coupling between the permanent magnets and the rotor core must resist forces exerted on the permanent magnets during high speed rotation tending to separate the permanent magnets from the motor.
Permanent magnets may also be positioned within a rotor core, commonly referred to as an interior permanent magnet rotor. Slots are formed within the rotor, and magnets are inserted into the slots. The magnet slots must be larger than the magnets to allow the magnets to be inserted. However, the magnets must be secured within the slots to prevent movement of the magnets during operation of the machine. The performance of the machine depends on maintaining the magnets in a known position within the rotor. An adhesive may be used to secure the magnets in a fixed position relative to the rotor. However, adhesives have a limited life due to factors such as temperature, temperature cycling, and environmental conditions.
Many known electric machines produce work by generating torque, which is the product of flux, stator current and other constants. In electric motors, flux is typically produced by permanent magnets positioned on a rotor within the motor. Some known rare earth permanent magnets, such as neodymium iron boron magnets, generate greater amounts of flux than typical ferrite permanent magnets. However, the cost of rare earth magnets has drastically risen in recent years, prompting the need for low-cost permanent magnet systems that generate similar amounts of flux and provide efficiencies similar to systems using rare earth magnets.