Patent GB-1395961-A (GB)
Title: Electromagnetic arrangements
IPC: H01F29/12
Filed: 1972-05-08
Abstract: 1395961 Inductors and transformers MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 8 May 1972 [10 May 1971 16 June 1971 18 June 1971 (3)] 21316/72 Heading H1T Electromagnetic induction apparatus for use as a voltage regulator or variable inductor comprises coaxial inner and outer cores and two groups of windings, each having conductor portions lying substantially in the axial direction in the space between the inner and outer cores, the groups being rotatable relative to each other such that the degree of inductive coupling between the groups may be varied. In general the windings are wound on the cores, one of which is rotatable with respect to the other. However, embodiments are disclosed (Fig. 21) where both cores are stationary and only a winding moves. In one embodiment (Fig. 3), a pair of primary windings 3 on the stator 1 and a pair of secondary windings 7 on the rotor 2 are wound in the same direction in each 180 degrees section such that fluxes (# 1 , # 2  produced by an A.C. input voltage applied across the primary windings induce a maximum output voltage in the secondary windings in phase with the input. Rotation of the rotor through 180 degrees results in the primary and secondary windings in each 180 degrees sector having opposite directions such that a maximum voltage 180 degrees out of phase with the input is induced in the secondary windings. Rotation through 90 degrees results in zero net induced voltage since half the windings have the same direction and half have opposite directions in each 180 degrees section, a linear change in induced voltage with respect to angle of rotation being produced. Connection of the primary and secondary as in Fig. 6c results in an output range of -100 to +100 volts for a 100 volt input; connection of one terminal of the secondary to one terminal of the primary or to the centre tap of the primary resulting in different output voltage ranges (Figs. 6A, 6B, not shown). Omission of the secondary windings on one side of the rotor may be employed to produce a different output voltage. Similarly, in the arrangement of Fig. 10, the secondary windings 12a-12c are connected in series with the primary windings 10a-10j, the input being applied across the primary windings 11a-11j such that the output taken across primary windings 10a-10j or 10a-10j in series with 12a-12c is larger than or smaller than the input depending upon the angle of rotation. In a further variation (Figs. 14A, 14G) the secondary windings S1 and S2 in quadrature relation to S3 and S4 result in an output variation across S3 and S4 of 0-100 volts to be produced from a 100 volt input over a 90 degree angle of rotation. The output range may be increased by adding a further coil S5 as shown, the addition of S6 compensating for any voltage drop due to the resistance of the windings. The arrangement of Fig. 15A may be used to produce variation in the output over a 180 degree angle of rotation, the input being applied across all the windings connected in series and the output being taken across P2 and S2. Alternatively four primary windings may be used to produce the same variation over a 90 degrees angle of rotation. The slots in the inner and outer cores (Fig. 3) may be circular, square or rectangular in crosssection and may be inclined with respect to the axis of the cores to attain uniform coupling between the primary and secondary windings. Uniform coupling may also be attained by providing more slots in one core than in the other. Leakage flux paths produced by the windings may be caused to link all the windings by machining the inner and/or outer core to increase the magnetic resistances of the leakage paths or by using a rectangular outer core, Figs. 18-21 (not shown). Other embodiments are disclosed in which the arrangement of the windings differs. In the above the windings pass through the centre hole in the inner core but in others they are wound across the inner core through diametrically opposite slots or placed in slots symmetrical with respect to a fixed diameter. In an alternative embodiment a group of windings is wound around the inner and outer peripheries of the outer core and another group around the outer peripheries of the inner and outer core, the outer core being rotatable. In all of the embodiments either the outer or inner core may be rotatable and either group of windings may be regarded as the primary. Also, the outermost windings are concentrated together (Fig. 16) to form passages through which the supporting members of the rotor may move. The apparatus may also be used as an angle detector.