A Permanent Magnet Motor Consists Of An Annular Brush Ring Assembly, A Permanent Magnet Stator Ring, And A Laminated Wound Rotor

 

Permanent Magnet Motor

A Permanent Magnet Motor is a type of electric motor that uses permanent magnets on its field in addition to windings. For certain high-efficiency applications, such as electric vehicles, permanent magnet motors outperform induction motors or motors with field windings. In most cases, a variable frequency drive (VFD) is used to control the speed of ac motors. While many scenarios involve using VFDs with induction motors with stator windings to generate a rotating magnetic field, they can also achieve precise speed control by referring to speed or position feedback sensors. In some cases, it is possible to achieve comparable precision speed control without the use of feedback sensors. This is made possible using a Permanent Magnet (PM) Motor and a process called the “high-frequency signal injection method.”

SPM motors (Surface Permanent Magnets Motors) and IPM motors are the two main types of Permanent Magnet Motor (Internal Permanent magnets motors). The main distinction is that SPM motors have magnets on the outside of the rotor, whereas IPM motors have magnets on the inside of the motor. There are several advantages to placing the magnetics internally, including structural integrity and reduced back EMF. Because holes must be cut into the rotor for the placement of the magnets, areas of high reluctance are created, allowing carmakers to use some of the benefits of both reluctance and permanent magnet motors.

Hard ferrites, alnico, samarium cobalt, and neodymium iron boron are some of the permanent magnet materials used in permanent magnet motors. Hard ferrites are the most common permanent magnet material found in Permanent Magnet Motor (by weight). This is because they are inexpensive. If other factors such as size, temperature capability, calibration, coercivity, and so on are important, motor design engineers will typically use one of the other permanent magnet materials. Rare earth production results in waste with elevated radioactivity compared to the natural radioactivity of the ores (waste that is referred to by the US EPA as TENORM, or Technologically Enhanced Naturally Occurring Radioactive Materials).

China, the world's largest producer of neodymium, restricted shipments to Japan in 2010 due to a dispute over island ownership. China imposed strict export quotas on several rare earth metals, claiming that it was doing so to reduce pollution and conserve resources. In 2015, the quotas were removed. Despite the fact that neodymium is relatively abundant, global demand outstripped supply by about 10% in 2017.