SynRM-Synchronous Reluctance Motor:

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The SynRM-Synchronous reluctance motor is a high-efficiency alternative to the induction motor in recent years. 

SynRM is a more recent motor solution with interesting advantages such as low rotor inertia, a high power-to-weight ratio, good acceleration performance, flux weakening operation, low material costs, and ease of manufacturing.

SynRM-Synchronous Reluctance Motor
SynRM Motor

SynRM MotorWorking Principle:

SynRM motor utilizes Iron’s reluctance property to rotate the motor. Magnetic reluctance (S) is defined as the opposition offered by the magnetic circuit to the magnetic flux (Φ).

Whenever a piece of ferromagnetic material is located in a magnetic field, a force is exerted on the material, tending to align the material with an auxiliary winding to produce a synchronously revolving magnetic field.

The reluctance motor includes both a stator and rotor with multiple projections; the stator’s poles are wrapped with windings that are energized, while the rotor’s magnetically permeable electric steel plates store magnetic energy by reluctance leveraging the tendency of magnetic flux to follow the path of least magnetic reluctance in order to repeatedly align the rotor and stator poles.

SynRM-Synchronous Reluctance Motor Construction:

SynRM motor stator structure is identical to the one used in conventional 3-phase Induction or Synchronous Machines.SynRM Motor stator has three-phase stator winding used to produce RMF, and the rotor is formed by using electric steel plates stacked together.

The SynRM operation relies on the reluctance torque, which depends on the saliency, defined as the ratio between the inductance in the direct and quadrature axes. Synchronous reluctance motors are designed to run at exact, “synchronous” speeds. 

SynRM motors have cut slots in the rotor as shown in the below figure.

SynRM Synchronous reluctance motor Rotor
SynRM Rotor

In the above figure, it is noticed that air gaps are used as internal magnetic flux barriers that offer high reluctance; whereas steel magnetic paths are used to provide low reluctance.  

The motors are fed by a variable speed drive executing suitable control algorithms to maximize torque and motor efficiency.

Line-start synchronous reluctance motors are also a suitable alternative to induction motors in fixed-speed direct-on-line (DOL) applications such as pumps and fans.

IPM-SynRM Motor:

To increase the efficiency of the Synrm motor further, we can put permanent magnets in these slots. This makes the motor IPM-SynRM Motor utilizes both permanent magnet torque and reluctance.

IPM-SynRM  Motor Rotor
IPM-SynRM Rotor

IPM-SynRM motor (Internal Permanent Magnet – Synchronous Reluctance Motor), known also as PMA-SynRM Permanent Magnet Assisted Synchronous Reluctance Motor.

In general, it’s a type that combines the Interior Permanent Magnet Motor type with the Synchronous Reluctance Motor rotor type to achieve a more desired characteristic in Electric Vehicle applications which is high efficiency at low and high speeds.

IPM-SynRM Motor Rotor Construction
IPM-SynRM Rotor Construction

Advantages of SynRm Motor:

  • Indeed the SynRM rotor is made of iron lamination, no brushes/slip-rings, and expensive rare earth Permanent Magnets are needed.
  • These motors don’t have back EMF issues making them suitable for high-speed operations.
  • Unlike in an induction motor, a SynRM rotor has no induced current and thus no losses. Only Iron losses are present in the rotor no more copper losses.
  • Lower bearing and winding temperatures for enhanced reliability and long life.
  • A bearing lifetime is longer.
  • Better partial load efficiency and offers more precise process control. This makes them an ideal upgrade option for standard induction motors in pumps, fans, and compressors as well as in more demanding applications like extruders, concha mixers, winches, and conveyors.
  • By upgrading to the latest motors like IE5 SynRM motor, you can reduce energy losses by 40%. Changing just one motor can make a significant difference.
  • These motors offer industrial users a great opportunity to reduce their electricity usage and hence CO2 emissions while also benefiting from increased productivity and lower life-cycle costs.

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