Solenoid Term Glossary

Definitions of key solenoid and solenoid valve related terms.

AC—alternating current (50 or 60 Hertz)

Air Gap—the air space between the armature and the solenoid pole

Ambient Temperature—the temperature of the environment surrounding a solenoid or valve

Ampere Turns—the level of magnetic flux determined by the magnitude of the current and the number of copper wire turns in the coil

Armature/Plunger—the moving component found in a solenoid

Axial Stroke—the amount of movement the armature travels lengthwise

B-H Curve—a graphical curve showing the ratio of flux density to magnetic field intensity

Bi-Directional Valve—a valve allowing fluid to flow both ways through the valve

Bobbins— usually made with a plastic construction in either nylon or peek and can be molded or machined

Bubble-Tight Sealing—in an air system, the installed valve’s sealing capability is virtually undetectable during a pressure decay test time period equal to 1x10-5 cc/sec

Case/Body—the outer shell and main component of the solenoid coil housing (can be made from any magnetic material from CRS (cold rolled steel) to 430FR SS (stainless steel)

Coil— the copper windings on the solenoid that provide an electrical element through which a current is passed to generate a magnetic field. During the winding process, precision wound coil follows a prescribed pattern in which each turn is laid precisely beside the previous turn. This allows the maximum amount of copper to be wound in the allotted space. A coil with no specific winding pattern is called a random wound coil.

Coil Resistance—is the property of a coil that impedes the flow of the current when a voltage is applied to the coil. Resistance values are shown in ohms.

Coil Resistance Tolerance—where precision coil windings are used, coil resistance tolerances are ±5% for heavier gage wire. Coil resistance tolerances are ±10% for finer gage wire where random winding processes are used.

Coil Voltage—the voltage at which a coil must be energized if the solenoid or valve is to perform as indicated

Continuous Duty Coil—a coil energized on a continuous basis without overheating

Current Flow—signifies the amount of current flowing through the solenoid coil when energized and is expressed as amperes

Cycle Life—the total life expectancy of a solenoid in terms of cycles (one cycle = movement from a closed position to open and back to a closed position or vice versa

Cv Factor—defined as the volume of water in US gallons per minute that flow through a valve with a pressure drop of 1 psi. Cv stands for flow coefficient.

DC—direct current (batteries produce direct current)

De-energized—the solenoid is de-energized when no current is supplied to the coil. This is the standard "fail-safe" mode.

Dielectric—is the resistance between the coil and the case. Minimum dielectric value depends on the type of solenoid and the wire gage

Differential Pressure (delta P)—the difference in pressure between the inlet and outlet of a valve

Direct-Acting Valve—the solenoid core directly opens and closes an orifice inside the direct acting valve

Drip-Proof—protection of an enclosed component against falling dirt and/or non-corrosive fluids.

Dust-Tight—protection of an enclosed component against environments that contain large amounts of dust.

Duty Cycle—the duty cycle is the percent of time that a coil is energized during normal operation (ratio of active time to total time). Standard duty cycles are 100%, 50%, 25%, 10% and 5%.

Encapsulated (Molded) Coil—when the coil is encapsulated in epoxy or other suitable resin

Energized—the solenoid is energized when current is supplied to the coil

Filter—a device used to remove contaminants from flowing media in a valve

Flow Rate—the measure of the fluid volume that is moving past a given point at a given period of time. Usually expressed as gallons-per-hour, gallons-per-minute, liters-per-hour, liters-per-minute, etc.

Flux Density—flux density is the number of Webers per square meter in a cross section normal to the direction of the flux. This number is referred to as Tesla and given the symbol B.

Flux Plate—the steel plate located at the bottom of the coil assembly that helps carry the magnetic flux

Heat Rise—the rise in temperature as a result of operating the solenoid at predetermined conditions

Holding Force—the force required to break the armature loose from the energized position when it is under power

Intermittent Duty Coil—coil which has a specified duty cycle of less than 100%. Energizing this coil continuously would likely result in overheating.

Latching Valve—a latching valve uses an electrical pulse to open and close the valve but does not need power to keep the valve in either of those positions. This low power consumption makes latching valves well suited for battery powered applications.

Magnetic Flux—magnetic flux is simply a quantity of magnetic field passing through a given area.

Magnet Wire—100% copper wire covered with a thin insulation (with temperatures capabilities of 130˚C, 180˚C, 200˚C or 220˚C) and used in the construction of solenoid, motor and transformer coils. UL regulated.

Magnetic Field Intensity—the magnetomotive force per unit length in a magnetic circuit. This quality is represented with the symbol H.

Manual Override—a mechanism used to override automated systems to manually control them.

Maximum Operating Differential Pressure (MOPD)—the maximum difference in pressure between the inlet and outlet of a valve at which a solenoid can operate a valve safely

Media—gas or liquid that flows through a valve.

Normally-Closed Valve—a valve that has a normal state of closed.

Normally-Open Valve—a valve that has a normal state of open

Orifice—the opening in a valve that media, gas or liquid flows

Peak & Hold—a technique used to reduce the power consumption of solenoids. A higher current pulse is required to energize a solenoid than is needed to keep the valve in an energized position.

Pilot-Operated Valve—utilizes line pressure to operate the valve. Pressure is allowed to the outlet port side of the piston by the solenoid plunger opening the pilot orifice.

Pinch Valve—a valve used to control flow by pinching and releasing flexible tubing

Pole/Stop—the stationary component within the solenoid that attracts the moving armature when the coil is energized

Port—the opening in a valve that allows fluid to pass through.

Pressure—the force applied to a unit area of surface usually expressed as psi (pounds per square inch)

Pressure Drop/Pressure Differential—term used to describe the change in pressure through a valve between the inlet and outlet pressures. Referred to as a “Delta P”.

PSI—common unit of measure for pressure (pounds per square inch)

PWM (Pulse Width Modulation)pulse width modulation control occurs when voltage is applied at a repeated frequency and the percentage of “on time” is varied from 20-80 percent, the current applied to the solenoid will vary and the force created by the solenoid will vary from minimum to maximum.

Rectifier—an electrical device for transforming alternating current into direct current

Residual Magnetism— the magnetism remaining in effect on magnetic material after the electromagnetic field created by the coil in the solenoid has been removed

Response Time—the time it takes for the armature/plunger to move from the start to finish position

Return Springs—typically used to return the armature to the starting position once the power is removed

SCFH— standard cubic feet per hour measures the volume of gas at a standard temperature and pressure

SCFM—standard cubic feet per minute measures the volume of gas at a standard temperature and pressure

Shading Ring—a ring of copper or silver inserted in the pole piece of an AC solenoid to minimize the oscillation or “hum” associated with AC solenoids

Sleeving—used to insulate the lead wires where they exit the solenoid case (Teflon is used on high temperature coils up to 200˚C continuous)

Solenoid—a solenoid is a device comprised of a coil of wire, the housing and a moveable plunger (armature). When an electrical current is introduced, a magnetic field forms around the coil which draws the plunger in. More simply, a solenoid converts electrical energy into mechanical work.

Vacuum—a space in which the pressure is lower than the atmospheric pressure

VDC—volts direct current

Viscosity—the measurement of the flow resistance of a substance (the harder it is for a substance to flow, the higher the viscosity)

Watt—a unit of power equal to current (in amperes) multiplied by voltage (in volts)

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