Patent GB-316573-A (GB)
Title: Improvements in or relating to means for controlling the terminal pressure of an electric device
IPC: G05F1/32
Filed: 1929-06-27
Abstract: 316,573. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. July 31, 1928, [Convention date]. Regulation, automatic.-The terminal pressure of, or voltage supplied to, an electric device receiving energy either directly or indirectly from a single or polyphase source is automatically controlled by means of an iron-cored inductance in the supply circuit the induction in which is varied by an auxiliary coil on the core carrying a direct current which is dependent on overload current or the voltage supplied or both, the auxiliary coil being in the anode. circuit of a triode, the anode or grid voltage or both of which is or are dependent on the load current or the terminal voltage or both. The invention is, according to the Specification as accepted, restricted to rectifiers and is applicable to those supplying the anode circuits of transmitters for wireless telegraphy, to prevent the fall of voltage which occurs each time the load is imposed by the transmitting key. Fig. 1 shows a smoothed rectifier supply to a device 4 including an inductance 9 the effective value of which is lessened by a coil 8 carrying the load current as this current increases. The coil 8 may be connected across a resistance, which may be a regulating resistance, in the load circuit. The operation may be reversed if a second auxiliary coil is provided carrying a direct current from an independent source which opposes the effect of the coil 8. To prevent the generation of an alternating current in the rectified circuit two inductances 9, Fig. 3, may be used in series their auxiliary coils 8 being also in series and oppositely connected. The direct current in the auxiliary coil may be furnished by an independent source under the control of the load current, for example by relay 12, Fig. 3. A three phase arrangement employing rectifiers in a six phase circuit is shown in Fig. 4, the auxiliary coils 8 being in series in the output circuit and adjustable in their action by means of a variable shunt resistance 25 to control the load characteristic of the rectifier. The auxiliary coils 8 may replace the usual smoothing inductance. Fig. 5 shows one of the circuits of a 'similar rectifying arrangement in which the auxiliary coil 8 is controlled bv a triode 12 and a resistance 18 in series with the load. At normal load the battery 19 balances the potential drop in the resistance or a resulting voltage is imparted to the grid such that current flows in the coil 8 whereas at no load the grid is so negative as to pass no or very little current. The resistance 18 may form part of the smoothing coil 7. The above described arrangements disclose merely the principles involved in the invention. According to the invention in one arrangement the output potential may be employed to control the current in the coil 8, for example, as shown in Fig. 6, wherein a resistance 20 is tapped to give a grid potential on a triode 12 to prevent current flow until the cathode and grid are connected by a switch 21. This switch may be directly or indirectly connected with a switching device by which the load is imposed on the rectifier so that the voltage supplied is raised as soon as the load current starts. Auxiliary contacts on a key in the grid circuit of a transmitting installation may constitute the switch 21 or it may be worked by a relay under load current control. If the terminal pressure falls the voltage on the grid of the triode 12 will vary and the arrangement may be such that at a voltage below normal a discharge current commences and flows with diminishing voltage, an unduly great fall of voltage being prevented. The anode current of the triode 12 may be obtained from the rectifier. A further arrangement is shown in Fig. 7, in which the grid and cathode nf the triode 12 are connected by a resistance 22. The anode current is dependent on supply voltage and falls with fall of voltage so that the load current is kept within admissible limits. As in Fig. 6 a switch 23 may be coupled to the load switching device so that it is opened and the triode becomes conducting- as soon as the load is imposed but a relay 24 controlled bv the load current may operate the switch. The voltage of the battery 10 is preferably such as to stop the current in the triode when the switch 23 is closed.