Understanding Magnet Performance Table Parameters When enterprises buy magnets, they usually get a magnet performance table from the magnet manufacturers. This table typically lists details like the magnet's brand, remanence, coercivity, and more. But what do these parameters mean? Let's take a closer look!
1. Remanence (Br)
The units for remanence are Tesla (T) and Gauss (Gs), where 1Gs = 0.0001T.
Think of remanence like this: manufacturers take a magnet and expose it to an external magnetic field in a closed-circuit setup. They keep doing this until the magnet reaches a state of saturation. Then, they remove the external magnetic field. The magnetic induction intensity that the magnet still has at this point is called remanence. It shows the maximum magnetic flux that a magnet can generate.
If you look at the demagnetization curve, remanence corresponds to the situation where the air gap is zero. In a real-world magnetic circuit, the magnetic induction intensity of the magnet will be less than the remanent magnetic field. For example, if you have a really strong magnet with a high remanence value, when you use it in a circuit with some air gaps or other components, the actual magnetic effect you observe will be a bit less than what the remanence value might suggest.
2. Magnetic Coercivity (Hcb)
The units for magnetic coercivity are Ampere/meter (A/m) and Oersted (Oe), with 1 Oe≈79.6A/m.
When a magnet has been magnetized to technical saturation and then we try to reverse-magnetize it, the value of the reverse magnetic field intensity needed to make the magnetic induction intensity drop to zero is called magnetic coercivity (Hcb). But here's an interesting thing: when the magnetic induction intensity becomes zero, the magnetization of the magnet isn't zero. It's just that the added reverse magnetic field and the magnet's magnetization are cancelling each other out (so the external magnetic induction intensity reads zero). If we remove this external magnetic field, the magnet still has its magnetic properties.
Imagine you have a magnet that's stubborn. Magnetic coercivity tells you how strong a reverse push (magnetic field) you need to give it to make it seem like it has no magnetic effect for a moment. But as soon as you stop pushing, it bounces back to being magnetic again.
3. Intrinsic Coercivity (Hcj)
The units for intrinsic coercivity are also Ampere/meter (A/m) and Oersted (Oe), with 1 Oe≈79.6A/m.
Intrinsic coercivity is the strength of the reverse magnetic field needed to completely zero out the magnetization of a magnet. It's a measure of how resistant a magnet is to demagnetization.
If you apply a magnetic field equal to a magnet's intrinsic coercivity, you can eliminate its magnetism. Now, here's something important about neodymium-iron-boron (NdFeB) magnets. Their Hcj value goes down as the temperature rises. So, if you plan to use a magnet in a high-temperature environment, like inside an engine where it gets hot, you should pick a NdFeb magnet brand with a high Hcj. Otherwise, the heat might make the magnet lose its magnetic strength too easily.
4. Magnetic Energy Product (BH)
The units for magnetic energy products are joule/meter³ (J/m³) or Mega - Gauss - Oersted (MGOe), where 1 MGOe≈7.96 kJ/m³.
On the demagnetization curve, if you take any point and multiply the magnetic field strength (H) and the magnetic flux density (B) at that point, you get the magnetic energy product BH. The highest value of B×H is called the maximum magnetic energy product (BH)max.
The magnetic energy product is a key parameter that shows how much energy a permanent magnet can store. The larger the (BH)max value is, the more magnetic energy the magnet holds. When designing magnetic circuits, engineers try their best to make the magnets work at or near the point of maximum magnetic energy product (where B and H combine to give the highest value). This way, the magnet can be used most efficiently.
That's the basic knowledge about the four main parameters on a magnet performance table, shared by Qianci Magnet Manufacturers. Next time, we'll keep exploring more basic parameter knowledge!
