Permanent Magnet Motor is a synchronous electric motor with permanent magnets, internationally referred to as a Permanent Magnet Synchronous Motor (PMSM) or a Brushless Direct Current Motor (BLDC).
Permanent magnet motors have been known and used for several decades. Their production and application have been developing particularly intensively due to recent advances in power electronics, microprocessor-based control systems, software technologies, and the manufacturing of high-energy permanent magnets.
Design
Rotor
Permanent magnets are installed inside the motor rotor, generating the magnetic field. Depending on the number of magnets arranged in the rotor cross-section, the motor will have a corresponding number of poles.
The rotor of the submersible electric motor manufactured by our Company is assembled from several sections. A rotor section is a universal assembly unit used for all motor types with the same number of poles. The power output provided by a motor assembled with one section is approximately 8 kW. Therefore, to achieve a motor with the required power rating (multiples of 8 kW), the necessary number of rotor sections is installed on the shaft: for example, a 32 kW submersible motor requires four rotor sections.
Currently, submersible permanent magnet motors are predominantly manufactured in 8-pole, 6-pole, and 4-pole configurations.
Stator
The stator has a conventional design and is similar to the stator of an induction motor. It consists of a housing, an electrical steel core, and copper windings placed into slots along the perimeter of the core. The number of windings determines the number of motor phases. Two phases — sine and cosine — are sufficient for self-starting and rotation. Permanent magnet motors are typically three-phase.
System Integration
The permanent magnet motor has connection dimensions that allow the use of standard motor protectors and cable lines with standard couplings as part of electric submersible pump systems.
Control
Unlike a variable-speed drive with an induction motor, a permanent magnet motor is not self-sufficient. It cannot operate without a variable frequency drive and a control system. Permanent magnet motors are electromechanical energy conversion devices that combine the properties of both an electric machine and an integrated variable-speed drive system.