Ac solenoids are a type of electromagnetic actuator, consisting of a magnetizing coil and a plunger. Applying current to the coil produces a magnetic field that draws in the plunger, reducing the air gap as well as the reluctance of the flux path. As the gap closes, the magnetic field grows stronger, increasing solenoid force. Removing the current lets the plunger return to its original (open) position, usually with the help of a spring.Solenoid force is a function of the field strength, which varies with plunger position and coil current. When the plunger is open, it produces the least amount of force; when its closed, the maximum amount. Rated force should match the load, or the solenoid may hammer itself to pieces (in the case of a small load) or burn up (in the case of a large load).Questions & AnswersQ: How does heat affect performance?A:Heat is the number one enemy of solenoids. Not only does it reduce pulling force, it can melt coil insulation and cause a short. Anything that reduces current, both in amplitude and frequency, will reduce heat. Steel laminations, like those used in transformer cores, also help.Q: What are shading coils?A:Ac solenoids are prone to chatter as load forces battle with fluctuating plunger forces. To stem the noise and increase holding power, some solenoids have additional windings (shading coils) atop the C stack that magnetically latch onto the plunger.Q: Why is there a limit on how fast a solenoid can be cycled?A:Solenoids produce most heat when turning on, and thus require a given amount of time between on cycles to cool. When cycled too quickly, heat (from inrush current) builds up faster than the solenoid can dissipate it. Eventually the solenoid will become too weak to close and will burn out.

Solenoid Valve CoilsWhat is a solenoid valve coil?The purpose of a solenoid valve coil is to convert electrical energy into linear motion. The coil consists of copper wire (or aluminum) wound around a hollow form. When electric current flows through the coil, a magnetic field is created. This is accomplished by placing a ferromagnetic core inside the coil. In a solenoid valve, the ferromagnetic core is called thevalve plunger. When the current flows through the coil, the lines of magnetic flux turn the plunger into an electromagnet. The magnetic field causes the plunger to slide further up into the coil, opening the valve body orifice or pilot orifice.Solenoid Valve Coils (DC) and Electrical PolarityA common question about solenoid valve coils is whether the electrical current polarity matters in a DC coil. Most coils with lead wires use the same color wire for both terminals and have no polarity markings. The answer is that polarity does not matter. You can connect the positive terminal to either of the two wires without affecting the operation of the valve.Solenoid Valve Coil VoltagesSolenoid valve coils are available for both DC and AC electricity. Although a coil can be made to work with almost any imaginable voltage, the most common voltages available are: 6-Volt DC 12-Volt DC 24-Volt DC 24-Volt AC 120-Volt AC 220/240-Volt AC

The advantage of the low voltage coils is obviously electrical safety. Hobbyists and do-it-yourselfers often power the low voltage solenoid valves with wall transformers. Most smaller valves 12 VDC valves can be powered by a 12-Volt / 500 mA power supply. However, always make sure your power supply does meet or exceed the power requirement of the solenoid. The 24 VAC solenoid valves appeal to hobbyists as well since they can be easily controlled by irrigation timers. Most industrial applications and heavy machinery use solenoids with 24 VDC coils.

Tape Wrapped Coil

Tape Wrapped Coil(Tape Removed)

Encapsulated(Molded) Coil

Types of Coil ConstructionSolenoid valve coil construction usually falls in one of the following two categories: Tape Wrapped Coils Encapsulated (or Molded) CoilsA tape wrapped coil is manufactured by looping conductor wire (also called magnet wire) around a spool or bobbin. The magnet wire has a thin insulation layer around it. The completed winding is then protected by a insulation tape. Thus, the name tape wrapped coil.Encapsulated coils basically follow the same basic principle as the tape wrapped coil. However, instead of being protected by tape, the winding is encapsulated or molded over in suitable resin.Tape wrapped coils are used in applications with relatively mild environments. Tape wrapped coils allow for much smaller production runs. However, tape wrapped coils have a much lower resistance against moisture than encapsulated coils. In addition, encapsulated coils have much stronger lead wires (to protect against pull-out).Coils with DIN ConnectorsValve manufacturers often offer a DIN connector option on their coils. Instead of lead wires, the coil will have prongs or pins to accept a standard DIN connector. The coil is considered to have a male connection and the plug connecting to the coil is a female connector. Using a DIN connector provides many advantages: quick valve or coil exchange, excellent insulation properties, possible water tightness etc.The connector standard used for solenoid valves is DIN 43650 . The DIN 43650 series consists of five connectors, which have the following pin spacing: DIN 43650 Form A - 18 mm Industrial Form B - 11 mm DIN 43650 Form B - 10 mm DIN 43650 Form C - 8 mm Micro-Mini - 9.4 mmDIN connectors can be purchased as shells to be wired by the installer or they may be factory molded with a cable assembly. They have usually contain three or four terminals or pins. Some DIN connectors are available with LED indicators which indicate the power state of the coil for diagnostics purposes.Can the same valve be used with different coils?This depends on the specific brand of the valve. It is often possible to swap coils in order to use a different voltage with the solenoid valve.Latching SolenoidsA latching solenoid valve does not require current to stay in its energized position. Electrical energy is only consumed to open and close the valve, not to keep it in either of those positions. Latching valves are often used in battery powered applications (e.g. automatic faucets) as they only need a pulse power to change open/closed state of the valve. The polarity of the pulses are reversed between the opening pulse and the closing pulse.Hit and Drop"Hit and drop" is technique used for reducing the power consumption of solenoids valve coils. A larger voltage (current flow) is required to energize a valve than is needed to keep the valve in the energized position, making it possible to lower the power consumption of the coil."Hit and Drop" is also known as'Pulse and Hold', 'Spike and Hold', 'Hit and Hold', and 'Pick and Hold'.