This article takes an in depth look at solenoid coils:
What is a solenoid coil?
A solenoid coil is a common electrical component that uses a wire tightly wound around a core usually made of metal to create an electromagnetic field. When current passes through the coil, the resulting electromagnetic field moves the iron armature, allowing or blocking fluid from passing through the solenoid. Solenoids are commonly used in a variety of applications, such as controlling fluid flow in hydraulic and pneumatic systems.
Solenoid Coil Structure
- Coil: Copper wire tightly wound around a fixed core.
- Spring: A stainless steel spring that returns the armature to its normal position when the coil is de-energized.
- Static iron core: A ferromagnetic cylinder
- Movable iron core: The part of the fixed core that moves when the coil is energized, also known as the solenoid plunger.
- Can: Thermoplastic housing for general environments.
How does a solenoid coil work?
When current flows through the coil, a magnetic field is generated. The strength of the magnetic field is proportional to the current, the number of windings, and the magnetic permeability of the ferromagnetic material of the fixed core. The core acts as a magnetic circuit for the magnetic field. In other words, the core acts as a closed path that confines the magnetic field.
The magnetic field creates a force on the armature that pulls the armature upward, but extending the side of the armature close to the fixed core with a push rod causes the magnetic field to push the armature downward. The armature remains in that position as long as the magnetic field is present. When the magnetic field dissipates, the spring returns the armature to its original position.
Finally, the shading ring provides a low impedance path for the high voltage spike that is generated when the magnetic field dissipates. This reduces the magnitude and duration of the voltage spike, thereby protecting the circuit.
DC / AC Solenoid Coils:
There are advantages and disadvantages to using either DC or AC solenoids. When the magnetic force overcomes the spring force and the armature is fully raised, the current flowing through the coil can be reduced to save energy.
- DC Solenoid Coil: The DC current flowing through the solenoid creates enough magnetic force to overcome the spring force and lift the armature into the coil. When the coil is de-energized, the spring pushes the armature back into place. DC is slower to respond because DC provides a steady, unchanging current that takes longer to build up and reduce the magnetic field.
- AC Solenoid Coil: AC coils are more complicated because AC switches polarity. Twice per cycle, the current is zero, making the magnetic force zero. As the spring force constantly pushes the armature down, the armature vibrates and creates a buzzing sound and puts stress on the components. To combat this, a copper shading ring around the armature stores some of the magnetic energy, reducing vibration. AC changes direction quickly, allowing it to adjust the magnetic field more quickly and efficiently, making AC coils more energy efficient.
Solenoid Coil Applications
There are many types of solenoid coils.
Solenoid coils perform a variety of tasks in the field of fluid control and regulation in hydraulic systems. One of the main applications of solenoid coil is in solenoid valves. These valves precisely control the flow of hydraulic fluids by activating or deactivating the solenoid coil.
Examples of typical types of applications for solenoids include:
- Locking applications: A magnetic field attracts a plunger inside a solenoid, causing it to move and lock the mechanism in place. When the current is turned off, a spring pushes the plunger back, releasing the lock. Solenoids can be used in a variety of locking applications, including automatic door locking systems, vending machines, access barriers, and many other security devices.
- Automotive applications: Solenoids are used in a variety of vehicle applications, including shifting gears, starting engines, operating fuel injection systems, locking doors, and actuating valves.
- Medical applications: Used in medical applications to control fluid flow, regulate valves in medical gas systems, operate pumps and dispensers, and control the movement of medical equipment.
- Industrial applications: Used in industrial applications to control valves, operate pneumatic and hydraulic systems, control equipment movement, and in automation, robotics, and manufacturing processes.
- Home Applications: Used in home hydraulic systems including showers, sprinklers, dishwashers, washing machines and other high pressure washers.
For many years, solenoid coils have been an integral part of the feedback system in modern hydraulic systems and Dust Collector Pulse Valve Systems.