Electromagnets and Permanent Magnets

May 05, 2023

When the core is inserted inside the energized solenoid, the core is magnetized by the magnetic field of the energized solenoid. The magnetized core also becomes a magnet, so that the magnetic properties of the solenoid are greatly enhanced by the superimposition of two magnetic fields. In order to make the electromagnet more magnetic, the iron core is usually made into a hoof shape. But pay attention to the winding of the coils on the hoof-shaped iron core, which is clockwise and the other side must be counterclockwise. If the winding direction is the same, the magnetization of the iron cores of the two coils will cancel each other and the core will not be magnetic. In addition, the core of the electromagnet is made of soft iron and cannot be made of steel. Otherwise, once the steel is magnetized, it will maintain its magnetic properties for a long period of time without demagnetization. Therefore, the magnetic strength of the steel cannot be controlled by the size of the current and lose the advantages that the electromagnet should have.

An electromagnet is a device that can generate magnetic force by passing current. It is a non-permanent magnet that can be easily magnetized or eliminated. For example: Large cranes use electromagnets to lift abandoned vehicles.

When a current passes through the wire, a magnetic field is generated around the wire. With this property, when a current is passed through the solenoid, a uniform magnetic field is created within the solenoid. Assuming that a ferromagnetic substance is placed in the center of the solenoid, the ferromagnetic material will be magnetized and the magnetic field will be greatly enhanced.

In general, the magnetic field generated by an electromagnet depends on the size of the current, the number of turns of the coil, and the central ferromagnetic body. When designing an electromagnet, attention is paid to the distribution of the coils and the selection of the ferromagnetic body, and the magnitude of the current is used to control the magnetic field. Since the material of the coil has resistance, this limits the size of the magnetic field that can be generated by the electromagnet , but with the discovery and application of superconductors, there will be opportunities to surpass the existing limitations.

Compared with permanent magnets

Both permanent magnets and electromagnets can be made to produce different forms of magnetic fields. When choosing a magnetic circuit, the first thing to consider is what you need to do with the magnet. In situations where electricity is inconvenient, power cuts are frequent, or there is no need to adjust magnetic forces, permanent magnets dominate. Electromagnets are useful for applications that require a change in magnetic force or require remote control. Magnets can only be used in the original predetermined way. If the wrong type of magnet is used for a particular purpose, it can be extremely dangerous or even fatal.

Many machining operations are performed on heavy block materials that require permanent magnets. Users of many machinery factories believe that the biggest advantage of these magnets is that they do not require electrical connections.

Permanent magnets feature 330 to 10,000 lbs of lift capacity and can be turned on or off by simply turning a handle. Magnets are generally equipped with a safety lock to ensure that the magnet does not accidentally break when lifted. Magnet sets can be used for long loads that are too heavy for a single magnet to handle.

Also, parts that are ready to be machined at many times are very fine (0.25 inch or finer) and are extracted from a pile of similar parts. Permanent magnets are not suitable for only one job at a time from a pile of parts. Although permanent magnets are extremely reliable when used correctly, they cannot change the magnetic force. In this respect, the electromagnet enables the operator to control the strength of the magnetic field through the variable voltage control device and can select one of the stacked components. Self-contained electromagnets are the most cost-effective magnets in terms of lift per unit and their ability to lift up to 10,500 lbs.

Battery-powered magnets are useful, they use self-contained colloidal batteries to increase lift capacity, and can handle flat, round, and component-shaped products. The battery-powered magnet can repeatedly perform the lifting action, providing a considerable lifting capacity without an external power supply.

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Mr. Zhu Jing Hua

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