Magnetless Motors and the Environment

Various manufacturers might claim that a differently built electric motor is more environmentally friendly because it doesn’t use certain materials. But the problem is that all materials require mining and, although not all of them are created equal, each motor has its own environmental footprint to face. In the end, all underlying technology has trade-offs.  

To understand this better, let’s quickly look at the two main magnetless (called this because they don’t use permanent magnets) electric motor options, which tend to be seen as greener due to the, lack of rare earth minerals in their composition. And then let’s see why the less green options are used so commonly.  

Induction motors 

In various circles, the cheaper induction motors can be perceived as “greener” because they don’t use magnets. However, because of this, they need power to create the magnetic field in the first place, which uses energy and needs additional devices. Also, steel and copper are required in induction motors and their mining is not exactly environmentally-friendly.  

Induction motors are much larger than permanent magnet motors and they are also less efficient. They need more materials to build and can get very complex to ensure they function properly. Additional issues also abound, such as vibrating cogging, poor starting torque, and speed control difficulties. 

Reluctance motors 

Reluctance motors have an advantage of delivering high power density at lower costs. In switched reluctance motors the power is delivered to windings in the stator (meaning that it’s not being delivered to a moving part), simplifying mechanical design. Another benefit is that switched reluctance motor is more resistant to heat and can be run hotter than a permanent magnet motor.  

However, reluctance motors are affected by high torque ripple—fluctuations in torque as the rotor rotates—which also caused them to earn a reputation of being noisy. Switched reluctance motors also struggle with weaknesses in performance. 

They can use copper or aluminium, with the latter being problematic because it’s not a great conductor. It is also more difficult to wind. However, it’s much cheaper than copper and much easier to recycle.  

Greener motors are efficient motors 

Permanent magnet motors do have their environmental challenges. Among others, rare-earth magnets are difficult to source, they are also expensive, subject to market fluctuations, and can produce toxic byproducts. So why are they still used?  

Firstly, permanent magnet motors create a magnetic field without needing additional energy or bulky design often seen in magnetless motors.  

Secondly, greener materials for magnetless motors are usually required in larger quantities because more of them are used in the end product, resulting in motors that are bigger and heavier, needing more energy to run them, and including more parts that can break or wear out. Simply put, permanent magnets make motors smaller and more powerful. 

The main point is this: a much smaller quantity of permanent magnets could end up being greener in the long run. Especially if it’s used in a much more efficient motor that runs longer without needing replacement parts, uses less energy, and extends the vehicle’s battery life. 

In the end, saying that any raw material is green is simply pretending that it doesn’t have to be mined, processed, and transported, which is never ecologically friendly.  

This is why manufacturers and designers need to focus on economics and efficiency, considering what their end product is going to be used for and where. It all matters: manufacture, usage, the cleanliness of the grid used to power the motor, etc. So when we’re comparing motors, greener should also mean more efficient.