Patent GB-789667-A (GB)
Title: Improvements in or relating to electrical devices for producing out-put voltages or currents representing products quotients or reciprocals of in-put voltages or currents
IPC: H02H3/40
Filed: 1954-09-21
Abstract: 789,667. Electric analogue calculating systems; power and power factor measurements; semiconductor devices. SIEMENS-SCHUCKERTWERKE AKT.-GES. Sept. 21, 1954 [Sept. 21, 1953; Sept. 21, 1953; Sept. 23, 1953; Jan. 8, 1954; Jan. 29, 1954], No. 27328/54. Class 37. [Also in Groups XXXV, XXXVIII and XL (c)] Apparatus for producing from input analogue voltages or currents a corresponding analogue voltage or current of the product, quotient, or reciprocal of the input variables comprises at least one semi-conductor member responsive to a magnetic field, within which is formed a magnetic barrier layer, which has a carrier mobility of at least 6000 cm.<SP>2</SP>/volt/sec., and which is composed of a compound of constitution AIII BV ; wherein AIII is an element (boron, aluminium, gallium, or indium) of the third group of the Periodic Table and BV is an element (nitrogen, phosphorus, arsenic or antimony) of the fifth group thereof; and may particularly be indium antimonide or indium arsenide; the semi-conductor member being (a) subjected to a magnetic field dependent on a voltage or current representing a first input quantity to vary the electrical resistance thereof connected in series with a linear resistance, each resistance being traversed in opposite senses by identical currents derived from voltages or currents representing a second input quantity, So that the algebraic sum of the respective voltage drops produces an output voltage or current representing the product or quotient of the input quantities, or the reciprocal of either when the remaining quantity is held constant; or (b) subjected to a magnetic field dependent on a voltage or current representing a first input quantity, and traversed by a current dependent on a voltage or current representing a second input quantity, to generate a Hall effect voltage across such member from which is derived an output voltage or current representing the product or quotient of the input quantities, or the reciprocal of either when the remaining quantity is held constant. In Fig. 1 equal semi-conductive resistances R1, R2 as defined above and comparatively small ohmic resistances RV1, RV2 are connected in series and equal currents J2 analogous to an input quantity flow from the ends to the centre point of the resistance chain; the resistance R1 being variable in response to the magnetic field of winding W1 excited by a current J1 analogous to another input quantity. It is shown that the resultant voltage U across the ends of the semiconductive resistances R1, R2 equal to the algebraic difference between the individual voltage drops is proportional to the product of the input quantities. In Fig. 2 two identical semi-conductive resistances R1, R2 similarly connected in series with ohmic resistances RV1, RV2 and carrying equal opposed currents J2 analogous to an input quantity are subjected to magnetic fields derived from respective windings W1, W2 energized by a current J1 analogous to another input quantity, and from auxiliary windings W<SP>1</SP>1, W<SP>2</SP>1 energized by a current J3 derived from a constant voltage source, the source of currents J1 or J2, or the output. Connections are such that the resultant fields operating on resistances R1, R2 are respectively the difference and the sum of the fields of the individual windings; and as before the resultant voltage U across resistances R1, R2 is shown to be proportional to the product of the input quantities, compensated for deviations of linearity between the instantaneous values of R1, R2 and their controlling fields. In Fig. 3 (not shown) the respective voltages developed across two semi-conductive resistances energized in series by a first analogue current (one of which resistances is magnetically excited in response to a second analogue current) are supplied to separate control windings of a magnetic amplifier whose output is analogous to the product of the input quantities; while in Fig. 4 (not shown) the non-linear resistance sensitive to a magnetic field controlled analogously to the divisor is connected in series with an ohmic resistance and a source of voltage analogous to the dividend, to develop voltage across the ohmic resistor approximately proportional to the quotient. In Fig. 5 the dividend voltage U1, from a source having resistance Ri is connected in series with a semi-conductive resistance R1 controlled by the magnetic field of winding W1  energized by the divisor current J1, and with ohmic resistances R2, R3, R4 and RP. Voltage U2 appears across R2, and U3 across R3, which is also the load resistance of an A.C. energized magnetic amplifier MV incorporating an output RS rectifier bridge 8, whose control windings - are 2 connected in series across RP and whose rectified output current J3 is opposed in resistance R3 to the current J2 from voltage source U1. Disregarding RP and R4, if R3J3 = J2 (a + R2 + RS and R3 + Ri) where a is the resistance of R1 for zero field, and since #U = O = U1 + [a + R2 + RS + R3 + Ri + J1] + U3 and U3 = J2[a + R2 + RS + R3 + Ri]; then J2 = U1/c.J1 where c is a constant. In a modifica-   tion (Fig. 6, not shown) the magnetic amplifier control windings are energized directly in series with resistances R2, R3 and R4, which may be given a temperature coefficient such as to compensate for variations with temperature of the other resistances of the network. A mathematical analysis of the compensation of the system to variations of temperature and other disturbing factors is given. The magnetic amplifiers are replaceable by semi-conductor amplifiers in the circuit of Fig. 7, which is similar to that of Fig. 5 but incorporates a resistance RS corre- RS sponding to the control windings - in series 2 with R1, across which is connected the input of a transistor T, whose output in series with a unidirectional voltage source U is connected across resistance R3 in series with RS and the output resistance R2. Non-linearity of the initial region of the resistance field curve of the member R1  may be eliminated by superimposing the constant auxiliary field of a permanent or electromagnet upon that of the control winding. Fig. 8 shows structurally a control winding W1 on a two-part gapped armature 13, 14 excited by a permanent magnet M; the variable semiconductor resistance R1 being located in the central leg of the armature and insulated therefrom by layers 15, 16 of non-conductive permanent magnet material such as ferrite. Fig. 9 shows control winding W1 wound about the central leg of an armature comprising a pot 19 and a cover 20 of magnetic material; the leg comprising non-conductive permanent magnets M1, M2 of ferrite retaining a central semiconductor disc constituting the resistance R1; the external connections being made to the centre and periphery thereof. The devices of Figs. 5-9 may be applied to operate relays in combination with magnetic or transistor amplifiers, into which a time delay factor may be introduced, for the protection of electric supply systems and machines and also to determine power; and A.C. power factor by multiplying voltage U and wattful current J cos # and dividing the product by the product of the rectified values of voltage and current U and J. The devices are also applicable to determination of the running diameter of a take-up reel as the quotient of the speed of movement of the wound material and the speed of the reel, determined as voltages derived from tachometer generators; the quotient voltage being applicable to control of the winding tension. Quotients, reciprocals, and products are also determinable utilizing semi-conductors exhibiting the Hall effect, e.g. plate 62 (Fig. 10) of indium antimonide or arsenide perpendicular to the magnetic field of an armature winding 61 excited by a current J1  due to a voltage U1 (proportional e.g. to that across a motor), the plate passing a vertical current J2 due to a voltage U2 (proportional e.g. to the motor load current). A voltage appearing across horizontal electrodes 63, 64 of the plate is proportional to the product U1, U2 (or e.g. the motor power) and is amplified for indication. Resistances R1, R2 in series with constant voltages may be varied in proportion to factors to be multiplied. The wound armature 61 is replaceable by a permanent magnet whose field is either constant or mechanically variable in response to a required factor. Fig. 11 shows a device for determining a reciprocal value of a factor represented by a voltage U energizing with current J the magnetic field windings 101, 102 whose flux intersects a semiconductive resistance member 103 of indium arsenide or antimonide having Hall voltage electrodes 104, 105 developing voltage U connected to the input of an e.g. magnetic amplifier 107 through an opposing comparison voltage source 106; the amplified output producing a current through a resistance 109 in series with the semi-conductive member 103. It is shown that the amplifier output current represents the reciprocal of the input voltage U. The magnetic flux may be varied mechanically in response to the input factor. Fig. 12 shows a similar device wherein the amplifier 107 excites the magnetic field windings 101, 102 and the input voltage U in series with resistance 116 passes current J through the semi-conductive resistance 103 whose electrodes 104, 105 develop a Hall voltage which excites a bridge circuit comprising linear resistances 112, 113 in combination with compensating non-linear resistances 114, 115, whose unbalance voltage energizes the amplifier input. The output current is shown to represent the reciprocal of the input factor. Fig. 13 shows a device for determining a quotient wherein an 1 1 amplified output current - proportional to - in J U the magnetic field windings 101, 102 of the device shown in Fig. 11 represents the reciprocal of a first input factor and passes not only through semi-conductive Hall resistance 103