Almost all permanent magnet motors in the industry today require a different type of control for variable speed drive (VSD) and matching transformers.
The variable speed control allows for a smooth adjustment to changing well conditions and softer startups for unconsolidated formations and other critical operating needs, allowing a better well optimization with an improved run life.
Permanent magnet motors rely on neodymium. “Rare earth production is as bad as you can get in terms of environmental damage,” according to a trader in rare earth metals. China, the top producer of neodymium, restricted shipments to Japan in 2010 during a controversy over disputed ownership of islands.
China imposed strict export quotas on several rare earth metals, saying it wanted to control pollution and preserve resources. The quotas were lifted in 2015. Although neodymium is relatively abundant, global demand for neodymium outstripped production by about 10% in 2017.
The main application for permanent-magnet motors is in variable-speed drives where the stator is supplied from a variable-frequency, variable-voltage, electronically controlled source. Such drives are capable of precise speed and position control. Because of the absence of power losses in the rotor, as compared with induction motor drives, they are also highly efficient.
