A Comparison Between Neodymium and Ferrite Magnets
In a magnet trade study, a central question comes up whether what magnet should be used in a specific purpose – ferrite or neodymium. If all the factors are considered between the magnets, a simple trade study can become more complex.
A different type of magnet can be used according to a certain goal. Therefore, designers can optimize their products based on different factors. Different factors involve lead time, aesthetics, form factor, performance, system size, system weight, efficiency, and cost.
If the deciding factor is the efficiency-per-unit volume, most designers chose neodymium magnets. This magnet can provide up to 20 times magnetic field compared to ferrite magnets. On the other hand, designers often choose ferrite magnets when the cost is the factor. These magnets have low cost production and up to 2-3 times magnetic field per dollar.
Choosing Between Ferrite and Neodymium Magnets is Not Always Simple
There are lesser-known factors that can affect a designers’ decision on which magnet to be used. Below are the different factors:
- System size
- Producibility
- Size-related magnet processing cost
What are Neodymium Magnets?
Neodymium magnets have excellent functions. These are composed of neodymium, iron, and boron elements that are brittle and hard. NdFeB magnets are coated to ensure that the surface is not easily eroded by oxidation. One of the best surface treatment for neodymium magnet is chemical passivation.
Aside from that, neodymium magnets are characterized by its high coercive force and energy product level. Its high density makes this magnet to be used for electronic technology and modern industry. These magnets are commonly used miniaturization, thin instruments, and more. Neodymium magnets are also popular because of its superior mechanical properties.
What are Ferrite Magnets?
Ferrite magnets are characterized of its high resistivity and higher dielectric functions. It also has excellent permeability at high frequency. Ferrite magnets are used for manufacturing permanent magnets starter motor, permanent magnet concentrator, loudspeakers, hearing aid, magnetic therapy sheet, magnetic thrust bearing, and more.
Ferrite magnets have low saturated flux density and magnetic energy reserve per unit volume. Thus, it is ideal for weak electric field surface, low power, and high frequency applications. Soft magnetic ferrites are also suitable for communication lines filter cores and sensors.
Strengths and Weakness of Ferrite and Neodymium Magnets
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Ferrite Magnets
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Audio systems are made with both ferrite and neodymium magnets. Neodymium magnets can produce good sound. However, audiophiles also love speaker system’s sound output that is made from ferrite magnets. The decision on whether to use ferrite or neodymium magnets on speakers are based on different factors. All the questions below may help on the decision making:
- Does the speaker will be used for home application?
- Is the speaker made from automobile installation?
- Does the magnet voice coil optimized?
- Does the magnet matched with the other speaker components?
- Are factors such as weight and size important?
- Do the speakers have any compression drivers?
Automotive speakers are designed specifically for automobile tight spaces. Therefore, its design is not ideal for home setting speakers. To better understand the difference, home system speakers have woofers that ranges from 200 up to 300mm. On the contrary, car speakers have up to 100mm woofers. Concert speaker systems tends to have larger woofer than automobile and home speakers.
A smaller neodymium magnets allows a designer to make speakers that can fit in a tighter space. Neodymium magnets have the advantages of the following:
- Miniaturization
- Coercivity
- Magnetic field strength
Different Factors that Stand Up for Neodymium Magnets
- Magnetic Field Strength
A design can be optimized by using magnet that has a very strong magnetic field. Smaller dimensions can be achieved with a strong magnetic field. The smaller motors become possible to generate more torque by using a magnet with weaker magnetic field.
- Coercive Force
One of neodymium’s advantage is its very strong coercive force in a room or mildly elevated temperatures. Therefore, you can assure that neodymium magnets can provide excellent demagnetization resistance at a temperature up to 230⁰C.
- Size-Related Processing Cost such as Miniaturization
Component sizes are minimized using a smaller motor. Small components are commonly have low cost production. Neodymium magnets have the advantage of lifecycle and efficiency costs for high duty cycle applications. The strong magnetic field of the neodymium magnet can reach the air gap while interacting greater distance magnetic component. Therefore, resulting to a stronger electric current.
- Easy to Machine
Understanding the cost for making small precision part is necessary for choosing a magnet to be used for a specific design. The cost can be determined by the machining process required rather than the material. Neodymium magnets are brittle. However, ferrite is more brittle making it difficult to machine. Therefore, neodymium magnets are cheaper than ferrite when it comes to mechanical processing.
Different Factors that Stand Up for Ferrite Magnets
- Higher Temperature Resistance Compared to Neodymium
Ferrite magnets tend to have higher curie temperature compared to neodymium. Therefore, ferrite magnets can maintain their magnetization when used at a higher temperature. Unlike neodymium, ferrite magnets allow the designers to have operating margins when used in a higher temperature. Ferrite magnets can operate up to 300⁰C temperature while providing .27%/ degree⁰C temperature coefficient. Thus, ferrite magnets tends to have stronger coercivity as the temperature rises.
- Corrosion Resistance
Neodymium magnets are designed with coatings to resist corrosion. The most used coating is the nickel-copper-nickel coating. NdFeB magnets can only be used in corrosive environments if coatings are applied. However, ferrite magnets are naturally resistant to corrosion even without the use of different coatings. That is why designers consider using ferrite magnets for few designs.
- Lower Cost
When we talk about magnet’s cost-per-volume, ferrite magnets are cheaper compared to neodymium. Ferrite magnets are perfect for lots of applications that does not require higher magnetic flux.
More Analysis Requirements for Magnet Design Factors
One of the magnet designs factors that needs a complicated analysis is its application. Motors for continuous use have different considerations compared to occasionally used motors. For example, motors for vacuum machine and washing machine are used occasionally with less than 1% duty cycle. However, during a hot climate, an air conditioner motor can run 40 up to 70% most of the time.
One of the motors that run for many hours are the refrigerator compressor motors. It is important for the continuous-use motors to have efficiency. Stronger magnets provides for efficiency for the motor. Neodymium magnets are most likely to be used for continuous-use motors than ferrite magnets.
Different Factors to Consider for a Specific Applications
- Size and Space Limitations
Applications that are space constraints sensitive commonly used neodymium magnets. These applications include:
- Automotive traction motors
- Mobile phones
- Continuous-use motors
- Earbuds
- Smart speakers
- Road musician speakers
- Electric motors, and more
On the other hand, ferrite magnets are ideal for higher temperature applications such as:
- Holding magnets
- Refrigerator magnets
- Low cost speakers
- Large stationary woofer speakers, and more
How to Choose the Right Magnet for Your Application?
The basic factors to consider on choosing the right magnets for your application is the following:
System Effect
The magnet size to be used has an effect to the entire system. Permanent magnet direct current motors are specifically designed to be used for continuous use. Lots of PMDC motors uses ferrite magnet successfully. However, there are also motors that can achieve extra performance and efficiency provided by a neodymium magnet.
Suitable Magnet for Air Conditioner Motors – Which is Better, Neodymium or Ferrite?
A more efficient motor that is used for heavy-duty cycles typically uses neodymium magnet. These magnets are usually found in different motors that are used continuously. If the motor have higher efficiency, it can help in minimizing the lifecycle cost and used energy. That is why most residential air conditioner motors are integrated with neodymium magnets to ensure high efficiency.
Conclusion
Both ferrite and neodymium magnets have differences. There are lots to consider before choosing either neodymium or ferrite magnet for your applications. Each type of magnet has different characteristics and properties to suit different designs. Thus, it is important to make a thorough analysis to make sure that you made the right decision. Here at Dailymag, we can help you perform magnet analysis for different applications.