What are Synchronous Reluctance Motors and its working?

What are Synchronous Reluctance Motors and its working epoch automation

This article contains everything you need to know about Synchronous Reluctance Motor working.

Introduction to Synchronous Reluctance Motors

These motors operate on the reluctance torque, as their name suggests. Simply said, resistance to current is similar to opposition to magnetic flux. 

In more technical terms, magnetic fields always prefer to travel along the path with the least resistance. 

Stator and rotor are the two main components of Synchronous Reluctance Motors. Simple iron is used to create the rotor.

Air provides more resistance to magnetic forces than iron does here. Synchronous Reluctance Motors provide rotation by utilizing this phenomenon. 

We carved slots in the rotor to provide this rotational motion. The rotor turns when the magnetic field is out of alignment with these grooves or cuts. 

This is due to the magnetic field’s need for minimal resistance. Without a doubt, the induced transient magnetic poles in the rotor are what cause this rotation.

Due to its simple & robust construction, this type of motor is currently becoming increasingly popular as a choice for hybrid and electric vehicles. 

The primary advantage of this motor is the absence of rotor cage losses, which allows for a permanent torque that is larger than that of an IM (Induction Motor) of the same size.

Advantages of Synchronous Reluctance motors over Induction Motors

Due to Synchronous Reluctance Motors’ exceptional performance, induction motors have begun to be replaced in most industries. 

The need for Synchronous Reluctance Motors is considerable in the electrical industry. I’ll now list some advantages of Synchronous Reluctance Motors compared to induction motors.

Synchronous Reluctance Motors

  • There are no I squared R losses.
  • Synchronous Reluctance Motors always operate at RMF’s synchronous speed.
  • The rotor used by Synchronous Reluctance Motors features a straightforward design, no magnet, and a short-circuited winding.
  • Synchronous Reluctance Motors has affordable production costs.
  • Increased effectiveness at the same power rates.

Induction Motors

  • I squared R losses.
  • Continuously operating at a lower speed than its synchronous speed induction motor.
  • The rotor winding in an induction motor is of the squirrel-cage variety.
  • Induction motors are expensive to produce.
  • At the same power ratings, less efficiency

Synchronous Reluctance Motors working principle

The outer stationary stator and the inner rotor, which are separated by a small air gap, are the two main parts of a reluctance motor. 

The design of these two components varies depending on the type of reluctance motor, but their fundamental workings are the same.

The protruding, “salient,” pole pairs that make up the stator are produced by passing electricity through a wire that is twisted around these protrusions. 

The rotor is made of ferromagnetic metal and has its own poles that (either with protrusions or air gaps/notches) follow the contours of the stator’s magnetic field.

It is referred to as being “completely un-aligned” when a stator pole aligns with a rotor’s notches, barriers, or slots, or when the rotor is at its position of maximum reluctance. 

The rotor produces a “reluctance” torque when it is entirely out of alignment because, due to the conservation of energy, it always moves to the point of least resistance. 

The rotor will be drawn to the closest salient stator pole by this torque, which will then cause rotation. 

This phenomenon has the potential to produce continuous rotational output if timed properly using control systems equipment or a particular rotor geometry.

Phasor Diagram

The constant speed of synchronous reluctance motors is one of their key features. Damper winding enters the picture if the rotor initially fails to line up with the magnetic field of the stator. 

Additionally, synchronous motors employ them. Due to the relative speed difference between the magnetic fields of the rotor and stator, damper windings positioned in pole shoes provide damping torque.

When the rotor and stator are out of alignment, this occurs. According to Lenz Law, the damping torque attempts to counteract the speed disparity between the magnetic fields of the rotor and stator, which is what causes it to be produced.

As a result, the damping torque pulls the rotor winding to the point where it magnetically locks with the magnetic field of the stator. The rotor then continues to spin at synchronous speed for the remaining period of time.

Phasor diagram of a synchronous reluctance motor epoch automation
Source: researchgate.net | Phasor diagram of a synchronous reluctance motor

Above is a diagram of a synchronous reluctance motor’s phasors. The two-axis theory of synchronous machines is the foundation upon which the q-axis and d-axis are defined. 

The voltage across the d and q axes, respectively, is defined as Vd and Vq. Gamma is the angle between the stator current Is and the d-axis. 

This can also be specified, and once the synchronous torque is produced, the rotor angle plays a part.

Construction of Synchronous Reluctance Motors

The key constructional characteristics are the stator and rotor windings. Three phases make up the stator winding. Thus, they are joined together in a star or a delta. 

This is due to the fact that they must generate a rotating magnetic field when activated by a three-phase supply. Silicon steel stampings are used to make the stator winding.

Construction of Synchronous Reluctance Motors epoch automation
Source: researchgate.net | Construction of Synchronous Reluctance Motors

Ferromagnetic material makes up the rotor windings. Due to the reluctance principle’s requirement that the rotor aligns with the magnetic material of the stator, the rotor windings’ reluctance must be as low as possible. 

The field winding is mounted on the rotor, and the armature windings are mounted on the stator, as indicated in the figure. 

The DC generator is exactly the opposite of this. Since the armature windings transport the armature currents, it is preferable to maintain them static. The main cause is related to insulation issues.

As depicted in the picture, a three-phase supply is used to excite the stator winding. Rotor windings in low-rating machines are made of permanent magnets. They don’t require any further excitement.

Application of Synchronous Reluctance Motors

  • The applications of reluctance motors vary depending on the kind; nonetheless, these motors have discovered several common uses that set them apart from other electric motors, and are now overtaking their more established motor cousins.
  • They don’t use slip rings, rotor field windings, permanent magnets, commutators, or brushes, which is their first key benefit. Their efficiency, dependability, production costs, maintenance costs, and overall elegance are all increased by their simplicity.
  • Reluctance motors can actually deliver 2-4 times the starting torque of conventional induction machines of the same size, allowing them to be 1-2 frames smaller for the same power output. They offer extremely high power density in a tiny size.
  • Only their input current and bearings prevent them from being employed in scenarios needing 0 RPM to hundreds of thousands of RPMs.
  • Due to its straightforward construction and intricate electrical circuitry and control mechanisms, these advantages come at a cost. Reluctance motors must be purchased and installed along with their electronic circuits because they are inextricably linked to them, which might raise the cost of the system. Epoch Automation provides best in quality Synchronous Reluctance motors and much more. Click here to get details.
  • Their current-to-torque connection is quite nonlinear, and this needs to be taken into account while designing their control system. In switched reluctance motors, the accurate switching of the salient poles is essential to the motor’s operation.
  • To minimize torque ripple, the phase current needs to be closely watched. Additionally, they cause electrical and acoustic disturbance to enter any system of which they are a part.
  • They also add electrical and acoustic disturbance to any system they are a part of, which is undesirable for some applications.
  • These motors currently find widespread application in washing machines, analog electric meters, control-rod drives for nuclear reactors, hard drive disc motors, electric cars, windscreen wiper drivers, recording equipment, and many other things.
  • They are particularly effective at high speeds. Due to their advantageous qualities, they are still being improved today and may eventually displace the induction motor as the industry standard.

To read more about pumps and motors, Follow this link.

Leave a Comment

Your email address will not be published. Required fields are marked *