Arc magnets, also known as tile magnets, are a common type of magnet that is widely used in a variety of permanent magnet DC motors. Arc magnets could be designed as single or double arcs depending on the clients’ requirements, and then are installed in the motor to provide a magnetic field.
Basically, arc magnets are customized products, no magnet factory will produce arc magnets in advance and then wait for clients to purchase them. This article today helps you understand the considerations for customized arc magnets.
Image Source: Researchgate & Strong-magnetics & Stanfordmagnets
Sufficient Time for Production
Unlike some standard magnets, customized arc magnets require a longer time.
Produce samples | Clients will ask for samples to test the magnet properties before they formally place an order. Normally, it takes 14 days to 18 days for the factory to produce the samples. If the client needs high-grade arc magnets, the factories need to check whether the raw materials are available in the market, which will take longer.
Send Samples | After the sample is finished, it takes a few days for the logistics to deliver the sample to the client.
Test Samples | It takes 1-2 days for the client to check whether the sample meets the requirements.
Production Time | Mass production usually takes 16-22 days.
Please note that these are estimated times, i.e. the samples are fully compliant with the customer’s requirements. If the samples do not pass the test, then the final delivery time will be extended. So clients need to allow enough time.
Detailed Information on Specification
Detailed and completed information about the arc magnets is needed if clients want to speed up the production schedule and save the time of repeated discussions with the magnet producer. The following information must be shown on the drawing: arc, arc length, height, width, thickness ID, OD, plating, grade, and tolerance.
This drawing shows the information needed to customize an arc magnet:
Image Source: Web & Linkedin
Arc | 55 deg.
Length | 27mm (magnets are usually measured in MM, millimeters, not centimeters)
Height | 6mm
Width | 3±0.05
Thickness | 2.2±0.05
Inner Diameter | 26.2mm
Outer Diameter | 29.2mm
Plating | Nickel
Grade | N50M (Indicates that the magnet will work properly at temperatures below 100 degrees Celsius. If you are not sure what grade you need, please tell the factory the operating temperature range).
Tolerance | The width is 3±0.05mm and the thickness is 2.2±0.05mm.
“±” is the sign of tolerance. So if the width is 3.05mm or 2.95mm, it is acceptable. If your product is a high-tech product, your tolerance must be smaller. Different industries and different shapes have different tolerances. As with round magnets, the standard tolerance for curved magnets is ±0.05mm, and for square magnets, the length and width are ±0.1mm, and the thickness is ±0.05mm.
If there are stricter requirements on the dimensions, the tolerances can be narrowed down even further, e.g., for round shapes the tolerance can be 0.02mm, and for square shapes, the length and width can be ±0.05mm, and the thickness ±0.03mm.
Nowadays, many magnet producers can make the tolerance to ± 0.01mm. However, it should be noted that the smaller the tolerance, the higher the production cost, the more expensive the purchase price. In fact, standard tolerances can satisfy most applications.
Temperature
The arc magnets used here are N50M, which means that the magnets work fine if the operating temperature is less than 100 degrees C.
M means that the magnets work fine if the temperature is 100 degrees Celsius or less. For more information about the relationship between temperature and grade, you can check the table below.
| Grade | N | N*M | N*H | N*SH | N*UH | N*EH | N*AH |
| Temperature | 80 | 100 | 120 | 150 | 180 | 200 | 230 |
*Indicates a number, such as N*M, which can be N35M, N38M, N40M, N42M, N45M, N48M, N50M, N52M.
Number of S and N Pole
Most arc magnets for the motors are paired magnetization, that is, 2 magnets, one magnet is N-pole in the outer arc and S-pole in the inner arc. The other magnet is S pole in the outer arc and N pole in the inner arc, which means that the number of magnets is an even number, such as 12, 24, and 26. For example, the need for 2,600 sets of paired-magnetization arc magnets means 2,600 magnets with N pole in the outer arc and 2,600 magnets with S pole in the outer arc.
Image Source: Magnosphere
Magnetization Direction of Arc Magnets
Magnetization direction is a very important factor. Arc magnets have various magnetization directions: diameter direction, radiation direction, and thickness direction. Different magnetization directions make the magnet have different magnet performance. If you get it wrong, the magnet produced is also worthless, so customers should pay attention to this point.
Other Technical Information on Arc Magnets
Arc magnet grades for electric vehicle drive motors are mostly high magnetic energy product and high coercivity, such as 45UH, 48UH, 50UH, 42EH, 45EH, etc.
Arc magnets for electric motors require good high-temperature magnetic stability, flux uniformity, and adhesion. For magnets used in wind turbines, arc magnets also need to undergo rigorous salt spray testing.
Laminated Arc Magnets
The magnets generate eddy currents when the motor is running, and the eddy currents cause the magnets to heat up, and thermal demagnetization occurs when the temperature gets too high. To solve this problem, the engineers used laminated arc magnets and added epoxy coating to the magnet surface to enhance its insulation. These methods can effectively improve the insulation and resistance between the layers of the arc magnet, thus reducing the size of the eddy currents. Now laminated magnets have been widely used in the field of high-temperature motors.
Arc Magnets Manufacturer
At Tengye, we’re thrilled to be early participants in your new product development. Our passion for cooperation extends from magnetic material selection and design optimization to injection molding service. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects. For further information on bespoke arc magnets, please contact us
