The solenoid is a device that can generate a magnetic force through a current. It is a non-permanent magnet that can be easily activated or eliminated magnetically. As we all know, the solenoid is made up of solenoid coil and iron core.

When current is passed through the wire, a magnetic field is created around the wire. When a current is passed through the solenoid coil, a uniform magnetic field is created within the coil. When the iron core is inserted inside the energizing solenoid, the iron core is magnetized by the magnetic field of the energizing solenoid. The magnetized iron core also becomes a magnet, so that the magnetic properties of the solenoid are greatly enhanced because the two magnetic fields are superimposed on each other.

In general, the magnetic field generated by a solenoid is related to the magnitude of the current, the number of turns of the solenoid coil, and the ferromagnet at the center. When designing an solenoid, attention is paid to the distribution of the coil and the choice of the iron core, and the current is used to control the magnetic field. Since the material of the coil has electrical resistance, which limits the amount of magnetic field produced by the solenoid, but with the discovery and application of superconductors, there will be opportunities to go beyond existing limits.

Solenoid classification

The solenoid can be divided into two types: DC solenoid and AC solenoid. According to the uses, the solenoids are mainly divided into the following five types: (1) Traction solenoids – mainly used to pull mechanical devices, open or close various valves to perform automatic control tasks. Such as on-off solenoid, proportional solenoid, etc. (2) Lifting solenoids – used as lifting devices to lift ferromagnetic materials such as steel ingots, steel, and iron sand. (3) Brake solenoid – mainly used to brake the motor to achieve accurate parking. (4) Electromagnetic systems of automatic appliances – such as electromagnetic systems of electromagnetic relays and contactors, electromagnetic trips of automatic switches, and operating solenoids. (5) solenoids for other purposes – such as electromagnetic chucks for electromagnetic machines and electromagnetic vibrators.

different hydraulic proportional solenoids

Solenoid advantages

  • The solenoid has many advantages:
  • The magnetic properties of solenoids can be controlled by on and off currents;
  • The magnitude of magnetism can be controlled by the strength of the current or the number of turns of the coil;
  • It is also possible to control the magnetic size by changing the magnitude of the resistance control current.
  • Its magnetic pole can be controlled by changing the direction of the current, and so on. That is, the magnetic strength can be changed, the presence or absence of magnetism can be controlled, the direction of the magnetic pole can be changed, and the magnetic properties can disappear due to the disappearance of the current.

Solenoid application

The solenoid is an application of current magnetic effects (electromagnetic), which is also close to our life, such as electromagnetic relays, electromagnetic cranes, maglev trains, electronic door locks, intelligent passages, electromagnetic flowmeters, etc.

different applications of solenoid

  1. Crane: It is a powerful solenoid for industrial use, which can be used to lift steel plates, containers, scrap iron, etc.
  2. Telephone: The next section introduces.
  3. Ammeter, voltmeter, galvanometer
  4. Bells and so on.
  5. Automation control equipment
  6. Industrial automation control, office automation.
  7. Packaging machinery, medical equipment, food machinery, textile machinery, etc.
  8. Electromagnetic relay
  9. Maglev train


Solenoid: A device that uses magnetic properties of current to make soft iron magnetic.

  • Inserting a soft iron rod into a solenoid coil, when the coil is energized, the magnetic field inside the coil magnetizes the soft iron rod into a temporary magnet, but, when the current is cut off, the magnetic properties of the coil and the soft iron rod disappear.
  • The magnetic field generated by the magnetization of the soft iron rod plus the magnetic field in the original coil makes the total magnetic field strength greatly enhanced, so the magnetic force of the solenoid is greater than that of the natural magnet.
  • The larger the current of the coil, the more the number of coil turns, and the stronger the magnetic field of the solenoid.

Solenoid vs. permanent magnet

Both permanent magnets and solenoids can be fabricated to produce different forms of magnetic fields. When choosing a magnetic circuit, the first thing to consider is the work you need to do with the magnet. Permanent magnets predominate in situations where power are inconvenient, frequent power outages occurring, or when it is not necessary to adjust the magnetic force. Solenoids are beneficial for applications that require a change in magnetic force or remote control. Magnets can only be used in the original intended way, and if applying a wrong type of magnet to a particular application can be extremely dangerous or even fatal.

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

Permanent magnets feature 330 to 10,000 pounds of lift capacity and can be turned on or off with a single handle. The magnets are typically fitted with a safety lock to ensure that the magnet does not accidentally break when lifted. The magnet set can be used for heavy loads that are heavy and cannot be handled by a single magnet.