Air Gap
The air space between the armature hub and the base or the air space between the stationary and the moveable pole piece.

Ampere Turns
The absolute value of magnetic flux determined by the number of copper wire turns in the coil and the magnitude of the current. Permissible temperature rise of the coil limits the magnitude of the power input. Heat makes the coil less efficient because it reduces the ampere turns and hence the flux density and the torque or force output

Anchor Plate
The thin formed sheet metal plate fitted over the mounting studs on the base of rotary solenoids to provide containment for the return spring. It has tabs formed up around the circumference which are used to attach the end of the spring and allow adjustment.

Armature Assembly
The assembly consisting of the armature plate, the hub, and the shaft which is the complete moving element in a rotary solenoid.

Armature Plate
The large diameter plate which forms the main rotating element of the solenoid and contains the ball races which convert linear to rotary motion. Made from SAE #1008 or 1010 CRS and case hardened for wearability in the ball races.

Axial Stroke
The amount of longitudinal movement the armature assembly travels as it rotates through its stroke. Value range from 0.022 to 0.100 inches depending on solenoid size and length of stroke.

B-H Curve
The graph of the ratio of flux density to magnetic field intensity. The magnetic field intensity is usually plotted logarithmically.

Bearing Balls
Precision stainless steel balls used in rotary solenoid ball races to provide essentially friction free rotary movement between the armature plate and the case.

Bobbins
Most bobbins are made of nylon 6/6 and meet UL file #E-41938 or E-39806B.

Bobbin Wound Coil
A coil, usually random wound on a spool which maintains the form and shape of the coil and also provides the coil insulation.

Case
The outer shell and main component of the solenoid coil housing. Made of CRS #1008, #1010, 12L14 or 1215 case hardened to 513 on the Vickers scale (RC50) for sizes 0 to 6 (sizes 7 and 8 are not case hardened). The case has the three coined ball races, and is formed from flat stock drawn into a cup (size 7 is machined from bar stock and size 8 is made from tubing stock because of their size and thickness).

Coil
Copper windings providing the electrical element of the solenoid through which current is passed to generate a magnetic field. Coils may be precision wound which allows the maximum amount of copper in the space provided or random wound or bobbin wound.

Coil Arc Suppression
The application of electronic protection devices across switch contacts and coils to reduce the arc caused by interrupting the current flow through an inductive device such as a solenoid. Appropriate coil suppression greatly reduces this arcing.

Coil Resistance
Coil resistance is the property of the coil which impedes the flow of current through it when a voltage is applied. Resistance values are shown in ohms for each solenoid wire awg for a temperature of 20°C. A resistance conversion factor may be used to determine what the resistance would be at other temperatures. This is particularly helpful in determining the effects of temperature on output torque or force. Use the resistance factor chart on page I8 or refer to the Temperature and Force/ Torque Resistance section on page I3 for further calculation of resistance at temperatures other than 20°C.

Coining
The process of striking the armature plate or case to form the three ball races on rotary solenoids. This process provides an extremely smooth, mirrorlike surface in the ball races.

Dielectric
Dielectric is the resistance between the coil and the case. Minimum dielectric value is 500 VRMS and range up to 1,500 VRMS depending on the solenoid size type and wire gage. Dielectric values are shown for each solenoid in the specifications chart.

Dust Cover
A protective sheet metal cover pressed over the armature plate end of the rotary solenoid to protect the armature and bearing balls from dirt and other contaminants.

Duty Cycle
ON Time/ON+OFF Time = Duty Cycle. Standard duty cycles used in this catalog are 100%, 50%, 25%, 10% and 5%. Other values can be determined by interpolation between any two columns.

Elongated Coils
These coils are 16% longer than standard precision wound rotary solenoid coils, and provide 30% more copper. These units will provide approximately the same torque with less wattage. If the same wattage as the standard precision coils is used, they will provide slightly more torque.

Ending Torque
Torque that a rotary solenoid develops in the last degree or two of stroke.

End Play
The amount of free axial movement built into a rotary solenoid in the completely de-energized position. This axial movement, normally only a few thousandths of an inch, assures that the solenoid is capable of returning to the completely de-energized position and does not stop before the balls reach the end of their races.

Flux Density
The number of Webers per square meter in a cross section normal to the direction of the flux. This quantity is known as Tesla and given the symbol B. The typical knee in the BH curve where iron becomes difficult to further magnetize is around 1.6 Tesla.

Flux, Magnetic
The physical manifestation of a condition existing in a medium or material subjected to a magnetizing influence. The quantity is characterized by the fact that an electromotive force is induced in a conductor surrounding the flux during any time there is a change in flux magnitude. A unit of flux is a Weber which is defined as that which being linearly attenuated to zero in 1 second, induces in a surrounding turn, an EMF of 1 volt.

Gross Torque
The starting torque available from a rotary solenoid before subtracting the nominal return spring torque.

Heat Rise
The rise in temperature which results from operating the solenoid at the predetermined conditions established in the coil data charts, with the specified heat sink. Standard solenoids will have a temperature rise of 80°C over ambient.

Heat Sink
The maximum allowable watts for each solenoid are based on an unrestricted flow of air at 20°C with the solenoid mounted on the equivalent heat sink specified for each size. Inadequate heat sink or restricted air flow may result in overheating of the solenoid.

Holding Torque
The torque required to break the armature loose from the energized position while under power. Normally checked under continuous duty operation and after reaching the stabilized operating temperature.

Hub
Part of the armature plate assembly which forms the moving pole face. Made of 12L14 or 1215 CRS. The shaft is pressed into the hub which is staked to the armature plate.

Lead Wires
Standard temperature rated coils use PVC insulated stranded lead wire, UL style 1007 rated for 80°C at 300 volts. It also meets CSA type TR- 64, 90°C at 600 volts; and MIL-W-16878/2, 105°C at 1000 volts. High temperature coils use Teflon Type E, TFE, and meets MIL-W-16878/4A rated at 200°C at 600 volts.

Lubricant
Standard rotary solenoids are lubricated in the ball races and in the sleeve bearing with Nye Rheolube #719L, a lithium soap-based synthetic hydrocarbon grease with wide temperature capabilities from -54°C to over 93°C. The base oil is compatible with most ester-vulnerable plastics and elastomers. It contains a rust inhibitor and an ultraviolet sensitive dye. Endurance engineered solenoids are lubricated with Shell Alvania #2 which is also a lithium soap-based grease with a temperature range of - 29°C to 121°C.

Magnet Wire
100% copper wire, ULrecognized, single film insulation rated at 200°C (Class H), meets UL file E-37683 or E-34609. Also meets Federal specification J-W-1177/13 or J-W-1177/14. Tubular and Open Frame solenoids use single-build insulation rated at 130°C. It is UL File E-34609 or E-37683 and meets Federal specification J-W-1177/9.

Magnetic Field Intensity
The closed loop integral of this quantity is equal to the total current enclosed, as defined by Maxwell’s equation. Or, the magnetomotive force per unit length in a magnetic circuit. This quantity is given the symbol H.

Magnetomotive Force
See ampere turns.

Needle Bearing
A bearing used in long life rotary solenoids which is a circle of long needles forming the bearing surface for the shaft.

Net Torque
The starting torque available from the solenoid after subtracting the nominal return spring torque.

PWM
(Pulse Width Modulation)
If a solenoid is controlled by a transistor which is signaled from a microprocessor, the PWM can be considered as an alternate means for reducing sizes or saving energy. PWM reduces the effective voltage by pulsing the voltage input. For example, if a solenoid has 12 volts supplied, but at 500 Hz at a 50% duty, the solenoid acts exactly as if it is connected to a 6- volt supply. If the duty cycle is changed to 25%, then the solenoid performs like one hooked to a 3-volt supply. The frequency must be higher than the solenoid can respond to otherwise chatter or humming will occur. Due to the inductive nature of the solenoid coil, the current is smoothed resulting in a constant force. Initially, the microprocessor must leave the transistor on long enough to allow the solenoid to energize. After that point, the microprocessor must alternately issue ON and OFF pulses to the transistor to achieve the appropriate duty cycle.

Permeability
The ratio of flux density in a given medium to the magnetic field intensity. The symbol used is m and has the value of 4pE-7 in a vacuum.

Permeance
The ratio of the flux through any given cross section of a given medium (bounded by equipotential surfaces) to the difference in magnetomotive force between the two surfaces.

Plunger
The magnetic moving component of a linear solenoid, typically made from cold, rolled steel.

Precision Wound Coil
A coil whose individual turns have a prescribed pattern which they must follow during the winding process whereby each turn is laid precisely next to the previous turn. This process allows for the maximum amount of copper in the allotted space. Normally carries a ±5% tolerance on coil resistance.

Random Wound Coil
A coil whose turns are allowed to wind randomly in no specific pattern. One turn may overlap another or may lay side by side or even spiral completely across the surface of the coil. Normally carries a ±10% tolerance on resistance

Relative Permeability
The ratio of the flux density in a given medium to that which would be produced in a vacuum with the same magnetizing force. Nonmagnetic materials, including air, have a relative permeability of 1, while magnetic materials such as iron, have initial relative permeabilities of around 2,000.

Residual Magnetism
The magnetism which remains in effect on a piece of magnetic material or between two pieces of magnetic material after the electromagnetic field created by the coil has been removed. An air gap is usually maintained between two magnetic poles to minimize the effects of residual magnetism.

Resistance Tolerance
Coil resistance tolerances are generally ±5% for heavier gage wires where precision coil windings are used and ±10% for finer gage wire where random winding processes are used. Tolerances are shown for each solenoid in the individual specification charts.

Return Springs
All standard stock rotary solenoids have scroll type return springs. Values range from 1 oz-in to 1 lbin depending on the solenoid size. Tolerance on springs are ±20% of the nominal value shown. Return springs are an available feature on any solenoid.

Safety Factor
The ambient temperature range, voltage fluctuation, return springs and temperature rise all affect the net available output torque or force of a solenoid. A 1.5 safety factor should be applied to preliminary calculations of torque or force.

Shaft—Other Solenoids
The main axle of the solenoid which runs from the armature through the base and out the bottom and provides the main bearing. The shaft is also used for external attachment to the solenoid. Normally made of non-magnetic #303 stainless steel. On long-life rotary solenoid models the shaft is made of CRS #12L14 or 1215 which has been case hardened in the bearing area for wear resistance.

Shaft-Tubular Solenoid
The small diameter portion of the plunger assembly of a push-type tubular solenoid which protrudes through the base or stationary pole face and provides push capability; usually made from #303 stainless steel.

Sleeve Bearing
The cylindrical bearing in the base of the solenoid which provides a guide for the shaft. Usually made from phosphor bronze, it can be made of other materials for different applications requiring longer life.

Sleeving
Sleeving used on standard solenoids to insulate the lead wires where they exit the solenoid case is black Vinylite per Mil-I-631B, Type F, subform Ua, Grade C, Class 1, Category 1, and meets UL file #E13565 and E-18459. Sleeving on high temperature coils is Teflon for temperatures up to 200°C continuous and will meet the requirements of AMS 3655 and UL file #E- 20344 and E-39513.

Starting Torque
The torque which is produced by a rotary solenoid in the first degree or two of stroke from the de-energized position.

Stator Assembly
That portion of any solenoid which contains the coil, case and base. This portion remains stationary during operation.

Tape
Coil wrapping tape is clear Mylar brand polyester film 0.002" thick which has been slit to the desired width and is used to wrap the coil in an overlapping manner. The film is per Mil-I--631 Type G, Form Tf, Class I, rated for 130°C continuous and meets UL file #E-39505. Coil banding tape is Mylar polyester film, adhesive backed per Mil-I-15126 Type MFT. This tape is used to wrap around the O.D. of the coil one thickness of 0.0025".

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