Improvements in and relating to electrical variable impedance device

摘要

855,907. Magnetic amplifiers. ENGLISH ELECTRIC CO. Ltd. July 17, 1957 [April 18, 1956], No. 11836/56. Class 40 (9). [Also in Groups XXXV and XL (c)] A cross-field variable inductor comprises a magnetic core having a part 10a which is subjected to a saturating field due to a polarizing winding 12 which is crossed by a field due to an A.C. winding 11, the currents through the windings being proportional. In a certain range of saturation the inductance L of the A.C. winding is inversely proportional to the polarizing current so that the device may be used in a voltage stabilizer (Fig. 8). In that Figure an A.C. winding 52 is connected in series with a polarizing winding 51 fed through a full-wave rectifier 53 and filter 54. Since the current i through winding 52 is the polarizing current and the inductance of winding 52 is inversely proportional to this current, the product Li is constant and hence the voltage across winding 52 is constant at constant frequency. The Provisional Specification also discloses an automatic tuning control (Fig. 9) and a frequency doubling circuit (Fig. 10). In Fig. 9 in order that the circuit 62, 63 should resonate for any of a range of frequencies the inductance of winding 62 must be given by L = K/wSP2/SP where w is the frequency and hence I the polarizing current must be proportional to wSP2/SP, i.e. proportional to 2ww 0 -w 0 SP2/SP where w 0 is a fixed frequency in the range. Hence a first polarizing winding 61a is fed from a voltage source E with a voltage pSP2/SPE corresponding with a current proportional to w 0 SP2/SP and a winding 61b is oppositely fed with a voltage dependent on the frequency w derived from a resistor 65 through a device 67 as in Fig. 8 above, and on pE so as to correspond with 2ww 0 . The factor p is determined by sliders of three ganged potentiometers such that a different p provides a different w 0 . Fig. 10 discloses a frequency doubling circuit in which the variable inductance winding 72 is in series with a resistor 73 and is fed from a source E sin wt. Two polarizing windings are provided carrying currents I o and I 0 sin wt. Since L α K/I the current through the winding 72 comprises two components one of frequency w and the other of frequency 2w, the former being filtered out by a capacitance 74 and the output voltage being obtained across resistor 73. Various constructional forms of the impedance device are disclosed in the Provisional Specification also. Specification 841,866 is referred to.