The magnetisers deliver the energy (via the fixture coil) to the permanent magnet material to magnetise it. The magnetiser consists of a low-voltage capacitor charging circuit, a modular expandable bank of capacitors rated at a maximum voltage (1000V or 3000V), and an energy discharge circuit connected to the fixture. The amount of energy stored in the capacitor bank is in joules, and the larger the stored energy, the larger the volume of magnetic material that can be magnetised. The energy determines the number of shots needed to magnetise or saturate a magnet or magnet assembly. Generally, it is desirable to deliver this energy in as few shots as possible to increase production throughput and reduce the likelihood of demagnetisation. The speed at which these capacitors charge up and the number of magnetiser shots determine the throughput of the magnetiser in production. Proton magnetisers come with industry-standard interfaces such as RS232, RS422 and optical fiber interfaces.
Magnetisers are used to magnetise parts and charge magnets. There are several different types of magnetising products. Choices include coil magnetisers, electronic capacitance switching (ECS), and yoke magnetisers. Coil magnetisers pass the parts through a magnet or lay them on top. ECS magnetisers allow users to electronically select the voltage and capacitance required for proper magnetisation. This flexibility enables a single piece of equipment to serve as a small or large magnetiser, depending on the application requirements. Yoke magnetisers are also commonly available. These electromagnets are shaped like horseshoes and are often used during magnetic-particle testing. Yoke magnetisers work by creating an intense magnetic field between the yoke legs. Magnetic poles are then made at flaws, cracks, or other discontinuities. Magnetisers differ in terms of product specifications. For example, ECS magnetisers have parameters for maximum energy, current, voltage range, capacitance range, and input line power. Weight, dimensions, and the required output cable type are also important considerations. In terms of features, some ECS magnetisers are designed to sit atop a desk or within a cabinet. Benchtop devices may include capacitor banks discharged internally through a safety circuit. Often, the front panel consists of an overtemperature interlock circuit to prevent the magnetiser from operating during overheating. An external output allows the user to monitor the magnetic current pulse with an oscilloscope. Product features such as automatic recharging, variable voltage, and solid-state silicon-controlled rectifier (SCR) switching are also available. Magnetisers are used with parts made from a variety of magnetic materials. In terms of their magnetic behaviour, these materials can be divided into five classes: diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic, or anti-ferromagnetic. Diamagnetic materials consist of atoms that do not have net magnetic moments. In other words, all of their orbital shells are filled. By contrast, paramagnetic materials include some atoms or ions with partially-filled orbitals and, therefore, some net magnetic moment. Magnetisers for ferromagnetic materials are made of iron, nickel, and magnetite. In these substances, the atomic moments display potent interactions. However, crystal structures for ionic compounds such as oxides result in more complex forms of magnetic ordering.
