Carpenter Electrification

Pathway to High Performance Stator and Rotor Stacks

Stator and rotor stack components in electric motors and generators are made of soft magnetic materials for numerous applications such as vehicles, aircrafts, pumps, and more. Some of these applications require high power and torque density that generally require optimal design, processing, and construction of the stator and rotor stacks to achieve the desired electric motor responses during the operation.

At Carpenter Electrification, our specialized materials and stack processing expertise ensure the highest-performance stator and rotor stacks. Before digging deeper into what sets our stacks apart from the competition, let’s take a step back and discuss the stator and rotor stacks in some more detail.

Stator Stack Specifics

The stator is the motor's stationary or static part and the biggest magnetic part of an electric motor. It contains a frame, winding, and static core. The frame of a stator is made from different materials, depending on the motor's output, and supports the core of the stator and protects its three-phase winding. The stator core contains thin and stacked laminations, wound with insulated wire, which helps it to generate a rotating magnetic field. 

Because of its function, it's critical for stators to have their electromagnetic capabilities — power, torque, and efficiency — maximized. In general, higher permeability in combination with higher induction and lower losses for the laminated stacks are important. Further, the mechanical responses should still be robust and sound. Carpenter Electrification can create best-in-class stators that balance a stator's magnetic and mechanical capabilities while maximizing the electromagnetic output.

Rotor Stacks Specifics

Rotors are generally situated inside the core of the stator and are the rotating section of the electric motor. They are made of rotor winding, a rotor core that may include soft magnetic laminated stacks and permanent magnets. For the rotor stacks, the desired physical properties can be different from that of stator. 

The rotation of a rotor happens due to the interaction between the windings and magnetic fields which produces a torque around the rotor’s axis. There is less flux involved with a rotor, so the magnetic property requirements such as permeability losses aren’t nearly as stringent as a stator. However, since the rotor moves, it is critical to optimize it’s mechanical properties to achieve the desired motor responses. For example, a rotor can rotate at about 20,000 rpm during an electric vehicle operation. When this happens, massive centrifugal forces are exerted on the rotor at top speeds. Because the rotor is spinning at such a high frequency, it is critical to have a robust magnetic performance to minimize the heat generated and as well, a robust mechanical performance to prevent the structure from falling apart.

Key Differences Between Stator and Rotor

There are many factors to consider when comparing stators and rotors, including movement, parts, insulation, supply, friction loss, and cooling. For instance, the stator winding is highly insulated because high voltages are induced in it. The stator winding is larger to carry the heavy current than the winding in a rotor where needed. The rotor’s friction loss is less because it weighs less than the stator.

In terms of laminated stack properties, the most critical differences to understand are the magnetic and mechanical performances. A stator must maximize magnetic properties such as induction, permeability, and losses because of its function in helping to move the rotor, while a rotor stack must maximize mechanical responses in combination with optimal magnetic properties to ensure it can withstand the speed at which it moves.

Uses of Stator and Rotor Stacks

Together, stator and rotor stacks are used in electric motors and have been around for many years.  We use them every day… in electric fans, refrigerators, air conditioners, washing machines, vacuum cleaners, garage door openers.  The list goes on and on.

These products have one thing in common: they are stationary and/or tethered and powered from outlets (or by gas engines and generators).  Recently, advances in battery and power electronics technology ushered in a new era of mobile and autonomous systems, such as electric vehicles, drones, and robots.  These applications require new levels of electric motor performance – in torque, power, and efficiency, and form compact and lightweight power and torque dense motor solutions.

Aspects and Benefits of Carpenter Electrification Stator and Rotor Stacks

There can be a number of motor design approaches to produce power and torque dense motor solutions. Example design approaches may include materials, dimension, cooling, winding, topology, stator-rotor gap optimization, to name a few. Carpenter Electrification focuses on soft magnetic stator and rotor laminated stacks with high induction, high permeability, and low loss materials in combination with expert processing methodologies to unleash the maximum benefit of high performance material solutions. 

Carpenter Electrification uses Hiperco® alloys and stack manufacturing methods for dimensional control, high-strength, and tailored magnetic properties to support the most demanding electric motor design requirements and production tolerances, creating superior motor responses. This results in the following:

  • 20-30% smaller motors
  • 15-25% higher torque
  • Up to 3% increased efficiency
  • Higher quality and repeatability

Our experienced engineers, Hiperco ® alloys, and an application-based strategy can result in optimal stator and rotor stacks for a motor that’s fast, powerful, light in weight, and generates less heat. Interested in learning more about our alloys, stacks and expert processing? Reach out. 

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