摘要:

Alternating-current circuits that can be classed as noninductive may be broken by a switch in which the separation between the sparking contacts is extremely small. In these micro-gap switches the separation of the contacts on a 250-volt circuit is of the order of 5 thousandths of an inch, and, by the use of a back stop, is not allowed to be more than that distance. The current is interrupted, not by stretching the arc at break, but by the mutual repulsion of .electrons that enter the gap from the contacts. Oscillograms are given which show that, when the contacts in these switches begin to open at any point in a half-wave, the current breaks at the next zero point and does not restrike. If broken at zero it persists for the next halfwave. This type of switch is most suitable for the thermostatic control of electric heating systems.

DOI:10.1049/jiee-1.1937.0066

出版商:IEE    

年代:1937

数据来源: IET

摘要:

Restriking voltage and its principal significance are described, and the problem of relating these to circuitbreaker operation in power systems is stated. An instrument for showing inherent restriking-voltage characteristics is described in some detail, reasons being given for the leading features adopted; and the method of operation is outlined. The scope of possibilities in system investigations and in circuit-breaker development is indicated. A short appendix deals with design of the instrument.

DOI:10.1049/jiee-1.1937.0067

出版商:IEE    

年代:1937

数据来源: IET

DOI:10.1049/jiee-1.1937.0073

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The speaking clock, introduced recently by the General Post Office, provides an accurate time service which is continuously available to telephone subscribers in the London area. A subscriber connected to an automatic exchange on dialling the code T-I-M, or a subscriber connected to a manual exchange on asking for “Time,” is routed to the clock and hears the time announced every 10 seconds. Each announcement is followed by three audio-frequency “pips,” the last of which indicates within ± 0.l sec. the exact time spoken.The announcements are made by photo-electrically reproducing words or phrases, which are selected in the correct sequence from recordings made photographically on four glass discs. The mechanism for rotating the discs, for building up the announcement, and for changing from one announcementto another, is driven by a low-speed synchronous motor. The frequency of the a.c. supply to this motor is directly controlled by a seconds-beating free pendulum. Every hour the clock is checked automatically against a signal transmitted from Greenwich Observatory, and any small error is corrected. Should the error exceed the prescribed limits the service is transferred to a duplicate .standby clock.Facilities are provided to connect up to 100 simultaneous calls to the installation.

DOI:10.1049/jiee-1.1937.0074

出版商:IEE    

年代:1937

数据来源: IET

DOI:10.1049/jiee-1.1937.0076

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper discusses the behaviour of a rectifier system consisting of a thermionic tube, output load, and smoothing condenser. An equation is derived relating the d.c. output current and output voltage, and this equation is verified experimentally. The dependence of the mean output voltage and ripple on the size of the reservoir condenser is discussed and examined experimentally. The efficiency of the rectifier is expressed as a function of the voltage-drop on load, and tables are given which show the power factor of the system and also the effective heating current in both windings of the supply transformer. The effect on the output voltage of the leakage inductance of the transformer is examined experimentally and discussed in general terms. It is shown that the resistance of the transformer is competent to increase appreciably the voltage-drop on load. Finally it is shown that the analysis is valid in the main for bi-phase half-wave rectification, including the cascade system used by J. D. Cockcroft.

DOI:10.1049/jiee-1.1937.0081

出版商:IEE    

年代:1937

数据来源: IET

DOI:10.1049/jiee-1.1937.0083

出版商:IEE    

年代:1937

数据来源: IET