Conductor - Solenoid
Spec tab
The dimensions of the solenoid are specified by three quantities on the Spec tab of its edit window:
| innerRadius,RI | inner radius of winding cylinder (xy plane) |
| outerRadius,RO | outer radius of winding cylinder(xy plane) |
| length,L | length of cylinder (z direction) |
To make a pancake solenoid, simply set the length equal to zero. To make a thin solenoid, make the inner radius equal to the outer radius. A thin pancake solenoid is equivalent to a current loop.
The figure below shows these quantities in the object coordinate frame.
Posn tab
The position and orientation (Euler angles) of the solenoid are specified on the Position tab of the edit dialog. Euler angles are specified in degrees, and default values are zero. The solenoid is rotated about the origin of its own coordinate system, before being displaced by the position quantities.
On the Posn tab, the orientation of the solenoid is set by three Euler angles, and the position of the center of the solenoid is set by three position coordinates positionX, positionY, and positionZ.
A solenoid is axially symmetric, so the third Euler angle eulerPsi has no effect on the magnetic field. This angle can, however, be used to rotate conductors with visual cutaways.
The solenoid is a spool of uniform current density that represents a dense spool of wire. The current density is determined by the number of turns, given by the winding parameter (winding). The winding parameter can be specified or calculated from the wire diameter. The magnetic field is found by decomposing the solenoid into loops and summing the loop fields. The finesse of this decomposition is set by the resolution box.
Supply tab
The name of the current supply and a scale factor is set on the Sup tab:
The name of the current supply can be any string not containing blanks. The current flowing in a current supply is set by bringing up an edit window for the Current object (using the Modify menu).
The current flowing through the solenoid is the value specified by the current supply multiplied by the scale factor. A typical use of the scale factor would be to set it to -1 to reverse the connection to power supply.
Do not use the current scale factor to specify number of turns. Instead using the winding parameter.
Winding tab
The number of windings is specified on this tab. For bulky conductor types (Solenoid and Racetrack) you have a choice of specifying the wire diameter, the winding, or both. You use the Specify: selector to indicate which quantity you are specifying. If only the wire diameter is specified, the winding will be calculated from the wire diameter. If only the winding is specified, the wire diameter will be calculated from the winding. If you are specifying both, you must enter numbers in both the wire diameter and winding fields.
The wire diameter is specified with units. If no units are given, the default units (meters) will be used.
The wire packing option is used to relate wireDiameter and winding when only one is specified. It is selected from the following options:
Square. To calculate the winding from the wireDiameter the cross sectional area is divided by the square of wireDiameter, rounding to the nearest integer. The reverse calculation is done without rounding, since wireDiameter need not be integral.
Hexagonal. The way wires pack naturally, a bit tighter than square packing.
Note that the choice of packing does not change the packing of conductor elements used in field calculation, only the relation between wireDiameter and winding. The conductor elements using in field calculation are always square packed.
Paraxial calculations
A solenoid can use paraxial calculations to improve the speed and accuracy of the calculated magnetic field near the axis.