Basket winding
Encyclopedia
Basket winding is a pattern of winding electrical wire in a coil, used in making certain types of electronic component
s, such as inductor
s and transformer
s. The purpose of this type of winding is to minimize having adjacent turns of wire running parallel. In a basket winding the wires in successive layers of the coil cross each other at large angles, as close to 90 degrees as possible. At high frequencies, such a winding has lower values of parasitic capacitance
, and less electrical resistance
due to proximity effect
, as compared with an ordinary winding with the same number of turns. However, the physical dimensions are greater which leads to higher leakage inductance
.
Basket winding is employed in coils used at high frequencies
, particularly radio frequencies
. As the frequency
of the electric current through a coil of wire increases, the coil has higher resistance and capacitive reactance, resulting in energy losses. In tuned circuits the increased resistance can reduce the Q factor
of the circuit, increasing the bandwidth
. The parasitic capacitance can cause the coil to become self-resonant. Basket wound coils have lower values of these undesirable characteristics, and so are used in radio
equipment, such as radio receivers.
Basket windings are often wound with a Litz wire
, or a wire insulated with cotton or silk. This type of insulation is also important from a mechanical point of view during the winding process, because a common enamelled magnet wire
would not provide sufficient surface friction to hold the subsequent turns at the large angle.
Electronic component
An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...
s, such as inductor
Inductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...
s and transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
s. The purpose of this type of winding is to minimize having adjacent turns of wire running parallel. In a basket winding the wires in successive layers of the coil cross each other at large angles, as close to 90 degrees as possible. At high frequencies, such a winding has lower values of parasitic capacitance
Parasitic capacitance
In electrical circuits, parasitic capacitance, stray capacitance or, when relevant, self-capacitance , is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other...
, and less electrical resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
due to proximity effect
Proximity effect (electromagnetism)
In a conductor carrying alternating current, if currents are flowing through one or more other nearby conductors, such as within a closely wound coil of wire, the distribution of current within the first conductor will be constrained to smaller regions. The resulting current crowding is termed the...
, as compared with an ordinary winding with the same number of turns. However, the physical dimensions are greater which leads to higher leakage inductance
Leakage inductance
Leakage inductance is the property of an electrical transformer that causes a winding to appear to have some inductance in series with the mutually-coupled transformer windings...
.
Basket winding is employed in coils used at high frequencies
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
, particularly radio frequencies
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
. As the frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of the electric current through a coil of wire increases, the coil has higher resistance and capacitive reactance, resulting in energy losses. In tuned circuits the increased resistance can reduce the Q factor
Q factor
In physics and engineering the quality factor or Q factor is a dimensionless parameter that describes how under-damped an oscillator or resonator is, or equivalently, characterizes a resonator's bandwidth relative to its center frequency....
of the circuit, increasing the bandwidth
Bandwidth
Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies. It is typically measured in hertz, and may sometimes refer to passband bandwidth, sometimes to baseband bandwidth, depending on context...
. The parasitic capacitance can cause the coil to become self-resonant. Basket wound coils have lower values of these undesirable characteristics, and so are used in radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
equipment, such as radio receivers.
Basket windings are often wound with a Litz wire
Litz wire
Litz wire is a type of cable used in electronics to carry alternating current. The wire is designed to reduce the skin effect and proximity effect losses in conductors used at frequencies up to about 1 MHz...
, or a wire insulated with cotton or silk. This type of insulation is also important from a mechanical point of view during the winding process, because a common enamelled magnet wire
Magnet wire
Magnet wire or enameled copper wire is a copper or aluminum wire covered with thin insulation. It is used in the construction of transformers, inductors, motors, headphones, loudspeakers, hard drive head positioners, potentiometers, and electromagnets, among other applications...
would not provide sufficient surface friction to hold the subsequent turns at the large angle.