GB698899A - Improvements in thermionic valve amplifiers capable of amplifying direct electric currents or voltages - Google Patents

Abstract

698,899. Magnetic amplifiers. ELLIOTT BROS. (LONDON), Ltd. Jan 29, 1952 [Jan. 30, 1951], No. 2349/51. Class 40 (iv). [Also in Group XL (c)] In a magnetic inverter, a D.C. potential is fed over a filter 29, 35, 28 to an input-output winding 16 arranged as a common winding over two primary windings 15, 15a on the central limbs of E-shaped cores energized from an A.C. supply 23 over resistors 17, 17a and 18. With no polarizing current flowing, the e.m.f's induced in winding 16 by balanced windings 15, 15a is zero, but with a polarizing current even harmonics appear in the winding 16 with one or other of the halfcycles showing a greater peak. The winding 16 is shunted by a low impedance network 30, 31 which may feed an A.C. amplifier 33, 34 (see Group XL (c)). In order to reduce odd harmonics, the windings 15, 15a are balanced by adjusting the resistors 17, 17a, a final zero adjustment being made by potentiometer 27 connected to balancing winding 24. In a modification, Fig. 4 (not shown), the output is taken from winding 17 or alternatively Fig. 5 (not shown) through a transformer from both windings 17, 17a. The adjustment may be made by sliding one of the laminations 14, Fig. 2 (not shown), or by the use of a variable resistor across one winding, Fig. 3 (not shown).