Permanent Magnet Motor vs. Induction Motor Compared

Electric vehicles have exploded in popularity in recent years, and with this newfound success comes competition to find out which electric motor is best. The two most popular electric car engines are permanent magnet motors and induction motors. 

Continue reading this piece for an in-depth look into the difference between the permanent magnet and induction motors. I will also explore the benefits and drawbacks of each type of motor. 

Difference Between a Permanent Magnet Motor and an Induction Motor?

Permanent magnet motors and induction motors are popular electric vehicles used in various vehicles. However, most people don’t know what sets these two apart. So what are the differences between a permanent magnet motor and an induction motor? 

Permanent magnet motors contain a physical magnet inside the motor. A current is then applied to the motor, which generates a torque due to electromagnetism. Whereas, an induction motor creates a magnetic field using electrical current to generate torque without containing a magnet. 

In general, permanent magnet motors and indication motors operate using similar principles, just in a different way. Apart from this, the only other differences involve the materials used, cost, and performance, and each comes with pros and cons, as we can generally see from the table below:

Motor Type	Cost	Efficiency	Convenience	Drawbacks
Permanent Magnet	Expensive to source materials for production	Highly efficient, especially at low speeds	Small in size, great for tiny spaces	Limited speed range; less efficient at high speeds
Induction	Low-cost production	Efficient at high speeds, but not as efficient overall	Works reliably in hot conditions	Poor speed control; less efficient at low speeds

Overall, permanent magnet motors are considered more efficient; but let’s take a closer look at the benefits and drawbacks of each to see why this is the case.

Pros and Cons of a Permanent Magnet Motor?

The main pros of a permanent magnet motors are their small size and high efficiency, especially at low speeds. Noteworthy cons are that they are expensive to produce, have a limited speed range, and become less efficient at high speeds.

Here’s a breakdown of the main pros of permanent magnet motors:

• High Efficiency. Permanent magnet motors are highly efficient electric motors. Permanent magnet motors easily outperform induction motors when it comes to efficient performance. The highly efficient nature of these motors is favorable amongst car manufacturers as it allows the vehicle to travel further off with less power. 
• Small in Size. Another key advantage to permanent magnet motors is the size. A permanent magnet motor is much smaller in scale than an induction motor relative to power output. As a result, vehicles can have more storage space if they use the smaller permanent magnet motor, or the vehicle could have more power from a motor the same size as an indication motor. 
• Efficient at Low Speeds. Permanent magnet motors remain efficient at low speeds. This is a significant advantage in choosing permanent magnet motors over induction motors, especially for drivers living in congested cities or low-speed limits. Increased efficiency at lower speeds enhances the overall efficiency of the vehicle. 

And here’s a closer consideration of the cons of a permanent magnet motor:

• Expensive to Produce. Perhaps the biggest drawback to permanent magnet motors is the materials required to make them. Permanent magnet motors usually contain rare earth metals like cobalt. These materials are expensive to source, and mining processes can have a negative impact on the environment. 
• Less Efficient at High Speeds. Permanent magnet motors are highly efficient overall. However, at high rpm, permanent magnet motors will become less efficient when using electricity. This is a drawback for high-speed vehicles or any vehicles that require high rpm usage. Induction motors are more efficient at high speeds. 
• Limited Speed Range. Another drawback to permanent magnet motors is the limited speed range. Due to the components of a permanent magnet motor, it has a limited speed range. At the same time, an induction motor has a much broader speed range and can maintain high rpm efficiently for an extended period. 

Pros and Cons of an Induction Motor?

Now that you know the benefits and potential issues with permanent magnet motors, it’s time to explore the main alternative. What are the positives and negatives of induction motors? 

The pros of an induction motor include low cost and high reliability. They work well in hot conditions and are efficient at high speeds. Cons include poor speed control and poor efficiency at low speeds. In general, they’re less efficient than permanent magnet mowers. 

Let’s take a look at the pros of induction motors: 

• Low cost. Induction motors are pretty cheap to produce. The motors contain no rare metals and are composed of relatively inexpensive materials. This is a significant advantage for induction motors as the production cost drops dramatically compared to permanent magnet motors. 
• Reliable. Another fantastic advantage to induction motors is their reliability. Induction motors are influenced very little by the conditions outside. As a result, they are reliable for vehicles in unfavorable conditions. However, permanent magnets are also more resilient than alternate electric motors. 
• Works in hot conditions. Induction motors are highly effective at high temperatures. Induction motors can operate efficiently at temperatures exceeding 40°C (104 °F). This makes induction motors helpful for various industrial applications and suitable for specialized vehicles. Permanent magnet motors do not perform well at high temperatures. 
• Efficient at high speeds. Induction motors do not lose their efficiency as they increase in speed. As a result, induction motors can even be more efficient than permanent magnet motors at high speeds. This is crucial in any vehicle or process requiring a motor capable of remaining at high rpm for an extended period. 

And here are the cons of an induction motor:

• Less efficient than a permanent magnet motor. It’s important to note that more energy is needed to generate the same force from an induction motor as a permanent magnet motor. However, induction motors are still highly efficient and better than alternate electric motors, like dc motors. 
• Poor efficiency at low speeds. Induction motors do not perform very well at lower speeds. When these motors move slowly, they will likely be far less efficient than at higher speeds. As a result, indication motors are not well suited to slow-moving vehicles. Permanent magnet motors perform more efficiently at low speeds. 
• Poor speed control. An often overlooked issue with induction motors is speed control. Induction motors were designed to spin at a constant rate so that altering speeds can be unresponsive and difficult. While manufacturers design effective ways of controlling the speed, over time, these additions can deteriorate. 

Which Electric Motor Has the Highest Efficiency?

Electric vehicles are becoming more and more common on the roads. This is in no small part due to people’s growing concern with climate change and attempting to reduce their energy usage. So which electric motor offers the most efficient use of electricity? 

ABB Synchronous Motor is the electric motor with the highest efficiency. This motor measured 99.05%, which is the highest efficiency ever reached by an electric motor. This result scored higher than ABB initially predicted when tested in a lab.

Electric motors make up a large proportion of the earth’s energy usage. As a result, switching to motors with higher efficiency can significantly impact energy usage as electric vehicles grow in popularity. As electric motors become more efficient, our reliance on fossil fuels will decline. 

Frequently Asked Question

Permanent magnet motors operate using a magnet and current to generate torque. However, traditional motors use a conductor like copper and direct current to generate torque. So does a permanent magnet motor also use direct current or does it use alternate current to function?

This differs from traditional electric motors that function using DC. 

For a detailed presentation explaining how permanent magnet AC motors work and how to control them, check out this video:

https://www.youtube.com/watch?v=H97HpwZNqZI

Notably, induction motors also operate using alternating currents. Alternating current performs best with these varieties of motors, and it helps to maximize efficiency.

DC motors are less effective, less powerful, and less efficient when compared to alternating current motors like permanent magnets and induction motors. 

EV Speedy’s Take 

Permanent magnetic motors are more expensive to produce as they often contain rare earth metals. Mining for these metals is often harmful to ecosystems and very costly. 

Permanent magnet motors are more efficient than induction motors, especially at lower speeds. Permanent magnet motors also perform better and allow for a smoother ride. However, induction motors are efficient at high speeds and effective.

---