GB466881A - Improvements in or relating to electric distant control systems - Google Patents

Abstract

466,881. Electric control systems. JAPOLSKY, N. Oct. 5, 1935, No. 27592. [Class 40 (i)] Hunting of a receiver is prevented by controlling it in accordance with the extent of its want of coincidence in position with the transmitter and with the relative speeds. A mathematical discussion of the problem is included. First system, Fig. 1. The generator 10 is not self-exciting but when the transmitter 1 moves the slider along the potentiometer 5, exciting current flows in the winding 9 and the current generated drives the motor 15 until the position of slider on resistance 19 corresponds with the position of the slider at the transmitter. Oscillation of the receiver is minimized with the aid of a winding 20 on the generator 10 fed from a generator 23 driven by the transmitter. The effect of this, in conjunction with the back E.M.F. generated by the receiver motor and producing a current in winding 12, is to produce a control on armature 15 proportional to the difference in the speeds of the transmitter and receiver. In a modification, Fig. 2 (not shown), winding 12 is omitted and winding 20 is in series with the armature 10. Second system, Fig. 5. Normally the transmitter, which comprises brushes 75 fed with current proportional to the speed of the transmitter handle as well as brushes fed with constant current to compensate for lag between the receiver and transmitter as described in Specification 449,901, supplies 3-phase current to the exciter windings 77 of a generator 49 which supplies 3-phase current to the receiver 54 which acts as a synchronous motor. If the receiver falls out of step, current flows in the circuit of relay 61 via the potentiometers and the relay causes the connections of the machines 49, 54 to be altered so that the former, which has so far been acting as a power amplifier as described in Specification 221,041, [Class 40 (i)], becomes a D.C. generator, and the latter becomes a D.C. motor. The current supplied by the generator depends,. owing to the effect of winding 78, on the extent of want of agreement, and also owing to the joint effect of winding 76 which is fed bv the correction booster 74 and windings 77 which are influenced by the back E.M.F. of the receiver, on the difference in the speeds. Control of several receivers, Fig. 6. Current for the D.C. operation of each receiver when it is out of step is derived from an individual D.C. generator such as 91 which is non-self-exciting normally and is brought into action by current in winding 93 when there is relative displacement between the sliders of the transmitting and receiving potential dividers. Winding 95 receives current proportional to the angular velocity of the transmitter and together with winding 97, which provides a field proportional to the back E.M.F. of the receiver, furnishes the necessary control proportional to the difference in speeds between the transmitter and receiver to prevent hunting. The circuit of the receiver is adapted for operation by D.C. by relay 105 which disconnects the A.C. windings. Non-hunting control acting through transmitter brushes, Fig. 7. The receiver 114 is a self-synchronizing synchronous motor and the rotating brush transmitter 107 is supplied as described in Specification 449,901 from a constant current booster 130 and from a booster 131, the output of which is proportional to the speed of rotation of the transmitter. The transmitter handle, however, is geared to the brushes through a differential gear 117, the intermediate member of which is geared to a motor 121 which is normally held stationary by current flowing to it through slip rings 122, These conditions persist while the transmitter and receiver are in phase. When the receiver falls out of step, however, current flows in circuit 127 connecting the two potential dividers and as a result relay 126 is energized to unlock motor 121 and current is supplied to it from generator 138 which is not self-exciting but now has its field coil 128 energized from circuit 127. Owing to the effect of coil 139 which is affected by the back E.M.F. from motor 121, the latter is controlled in accordance with the extent of disagreement between the potential dividers and also in accordance with its own speed. Since this speed is proportional to the difference in speed between the transmitter handle and the transmitter brushes and since, owing to the design of the receiver, the speed of the transmitter brushes can be regarded as always the same as that of the receiver, the conditions previously set out for the elimination of hunting are present. Specification 466,952 also is referred to.