Browse Prior Art Database

Variable Inductance

IP.com Disclosure Number: IPCOM000097522D
Original Publication Date: 1961-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Bradford, RC: AUTHOR [+2]

Abstract

In the construction of a variable inductance, control core 1 is wound with a fine wire 2. It is then placed in a plastic insert 3 and the windings 2 are soldered to relatively stiff wires 4 which are imbedded in 3. In a similar manner an inductance core 5 is combined with a plastic insert 6. The inductance and control core assemblies are placed in a metal case 7 (shown dotted) and are rotated until the cores are at right angles to each other. After this adjustment, the ends of the case are sealed with an epoxy resin to hold the cores in this position and also to lend strength to the wires connected to each of the windings. As a final step the case 7 is covered with a mu metal shield (not shown) to reduce the magnetic field around the device and also reduce the effect of ambient magnetic fields.

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Variable Inductance

In the construction of a variable inductance, control core 1 is wound with a fine wire 2. It is then placed in a plastic insert 3 and the windings 2 are soldered to relatively stiff wires 4 which are imbedded in 3. In a similar manner an inductance core 5 is combined with a plastic insert 6. The inductance and control core assemblies are placed in a metal case 7 (shown dotted) and are rotated until the cores are at right angles to each other. After this adjustment, the ends of the case are sealed with an epoxy resin to hold the cores in this position and also to lend strength to the wires connected to each of the windings. As a final step the case 7 is covered with a mu metal shield (not shown) to reduce the magnetic field around the device and also reduce the effect of ambient magnetic fields.

This device may be utilized in a Colpitts type oscillator shown at the right. L1 is the control core winding and L2 is the inductance core winding. The inductance of L2 is varied by impressing a voltage across the windings of control core L1. Varying the inductance L2 varies the frequency of oscillation. Of particular note is the fact that there is a very low inductance coupling between the control winding L1 and the inductance winding L2. This is due to the fact that the stray magnetic fields are in quadrature, an important factor in oscillator control.

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