Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1983-09-30
1986-05-27
Wong, Peter S.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363134, H02M 3335
Patent
active
045919640
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a method for interruption of the supply of electric power from a low-frequency or D.C. voltage source to a load, and also to an apparatus for carrying out the method.
BACKGROUND
In railway signalling technology, the interruption of electric power to a load is of the greatest importance, the load being e.g. a signal lamp which, when illuminated, announces "permission to pass" for a train. Relays have so far been used in the art to achieve this interruption. However, relays are burdened with the disadvantages that they are of large size as well as heavy, expensive to manufacture, and environmentally sensitive and in that they have limited working life with respect to the number of interruptions which can be expected.
SUMMARY OF INVENTION
An object of the present invention is to eliminate the disadvantages associated with relays in connection with their use in the above-indicated manner.
In achieving the above and other objects of the invention, there is provided a method of reliably controlling the energizing of a load comprising providing a source voltage having a low frequency or direct current voltage, controllably providing a chopping voltage having a frequency substantially greater than said low frequency, the chopping voltage being controllably switchable between on and off states, chopping said source voltage in response to said chopping voltage such that, when said chopping voltage is present, a high frequency voltage is generated, and coupling the high frequency voltage to the load solely through a high frequency path.
In further accordance with the invention, there is provided an apparatus for reliably effecting interruption of the supply of electric power from a low frequency or direct current voltage source to a load, said apparatus comprising high frequency voltage generating means for generating a high frequency control voltage, said high frequency voltage generating means being controllably switchable between off and on states, high frequency control voltage responsive chopper means for chopping the output voltage of said voltage source to a high frequency output voltage only when said high frequency control voltage is present, and galvanically isolating high frequency coupling means for coupling said high frequency output voltage to said load.
The above and other objects, features and advantages of the invention will be found in the detailed description which follows hereinafter as illustrated in the accompanying drawing.
BRIEF DESCRIPTION OF DRAWINGS
The invention will next be described in detail, with reference to the accompanying drawing wherein:
FIG. 1 is a circuit diagram of an embodiment of the invention, and
FIGS. 2a-2k illustrate the voltages at different points in the diagram of FIG. 1.
DETAILED DESCRIPTION
FIG. 1 is a circuit diagram of an apparatus for reliably interrupting the supply of electric power from a low-frequency source 1 to a load 2. In the illustrated embodiment this load is assumed to be a railway signalling lamp which when it is lit announces passage permission to a train. A direct-current voltage source may of course be used instead of the low-frequency source 1.
In accordance with the invention, the output voltage a of the low-frequency source 1 is applied to a chopper device 4, adapted for chopping the low-frequency voltage a, the wave form of which will be seen in FIG. 2a, to a high-frequency alternating-current voltage in response to a high-frequency signal b, the wave form of which will be seen in FIG. 2b, and which is supplied to the chopper device 4 from a signal source 3. The high-frequency input signal b to the chopper device 4 may be interrupted, as indicated in FIG. 1 by a break-contact 39. The high-frequency alternating-current voltage generated by the chopper device 4, illustrated in FIGS. 2e and 2f, is applied to an interface with the property of only being able to transfer high-frequency energy. In the embodiment illustrated, this interface includes two transformers 5 and 6, having primar
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patent: 3657631 (1972-04-01), Martens et al.
patent: 3869658 (1975-03-01), Hanke et al.
patent: 3970916 (1976-07-01), Kienscherf
patent: 4236187 (1980-11-01), Mochizuki et al.
patent: 4327406 (1982-04-01), Ashley
Telefonaktiebolaget LM Ericsson
Wong Peter S.
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