Figure of Merits for Electric Motors — Lesson 4

This lesson explains how to determine the dimensions of a machine based on given power or torque ratings. The lesson also discusses the concept of power density and torque density, which are used to compare different machines. It introduces the concept of magnetic shear stress and how it affects the output power and torque of a machine. The lesson further explains how to decouple the product of the inner diameter of the stator and the length of the core using the parameter aspect ratio. It also discusses the effect of the aspect ratio on the volume, weight, and cost of the rotor. The lesson concludes by highlighting the limitations of the power equations discussed and the factors not considered in these equations.

Video Highlights

00:00 - Introduction
01:44 - Discussion on power density and torque density
04:23 - Explanation of magnetic shear stress
13:31 - Decoupling the product of the inner diameter of the stator and the length of the core
32:12 - Effect of aspect ratio on the volume, weight, and cost of the rotor
35:00 - Limitations of the power equations

Key Takeaways

- Power density and torque density are important parameters for comparing different machines.
- Magnetic shear stress significantly affects the output power and torque of a machine.
- The parameter aspect ratio can be used to decouple the product of the inner diameter of the stator and the length of the core.
- The aspect ratio has a direct impact on the volume, weight, and cost of the rotor.
- The power equations discussed have certain limitations and do not consider factors such as the magnetic fields with respect to the air gap, slot dimensions, and geometry of the stator and rotor.