7 3/8 x 9 1/4 T echnical / Build Your Own Electric Vehicle / Leitman / 373-2 / Chapter 6
CHAPTER
6
Electric Motors “The superior AC system will replace the entrenched but inferior DC one.” —George Westinghouse (from Tesla: Man Out of Time)
T
he heart of every electric vehicle is its electric motor. Electric motors come in all sizes, shapes, and types and are the most efficient mechanical devices on the planet. Unlike an internal combustion engine, an electric motor emits zero pollutants. Technically, there are three moving parts in an electric motor. Even with three parts, electric motors outlive internal combustion engines every day of the week. The parts are the rotor and two end bearings. This is just one of the main reasons why widespread adoption of EVs or electric drive vehicles are a planet-saving proposition. Recently, I had a discussion with an engineer at my office. At the end of the conversation about fuel cell cars, I reminded him that even a fuel cell car generates electricity and that is why electric cars are the way of the automotive future. What this means to you is that ownership of a fun-to-drive, high-performance EV will deliver years of low-maintenance driving at minimum cost, mostly because of the inherent characteristics of its electric motor—power and economy. The objective of this chapter is to guide you towards the best candidate motor for your EV conversion today, and suggest the best electric motor type for your future EV conversion. To accomplish these goals, this chapter will review electric motor basics and provide you with useful equations; introduce you to the different types of electric motors and their advantages and disadvantages for EVs; introduce the best electric motor for your EV conversion today and its characteristics; and introduce you to the electric motor type that you should closely follow and investigate for future EV conversions.
Why an Electric Motor? In Chapter 1 you learned that the electric motor is ubiquitous because of its simplicity. All electric motors by definition have a fixed stator or stationary part, and a rotor or moveable part. This simplicity is the secret of their dependability, and why in direct contrast to the internal combustion engine with its hundreds of moving parts, electric motors are a far superior source of propulsion: • Electric motors are inherently powerful. By selecting a design that delivers peak torque at or near stall, you can move a mountain. Nearly all traction motors deliver near peak torque at zero rpm. That’s why electric traction motors have powered our trolley cars, subways, and diesel-electric railroad locomotives for
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