Isolated mains socket and mains circuit arrangement

Abstract

 An electrically isolated mains circuit arrangement comprises a 1:1 transformer having a primary winding connected across the incoming mains conductors and an ungrounded secondary winding (103) which is isolated from the primary winding and connected to one or more domestic mains sockets (105-1 .... ), (105-n). Since the secondary circuit is unearthed there is no danger of an electric shock and since the core (101) or alternatively, the casing of the transformer is earthed the circuit arrangement is also protected against lightning.

Description

[0001] The present invention relates to an electrically isolated mains socket and to a mains circuit arrangement having mains sockets connected to an electrically isolated secondary winding of a transformer.

[0002] In a conventional transmission and distribution system one of the conductors is normally grounded in order to provide protection against lightning. As a result, however, any user who touches a live mains conductor is liable to receive an electric shock.

[0003] Such a danger is particularly liable to arise in a bathroom.

[0004] The present invention provides an electrically isolated mains socket comprising a transformer having a primary winding arranged to be connected across the mains supply and an ungrounded secondary winding which is isolated from the primary winding and connected to the socket contacts, said socket contacts being located and dimensioned to receive a mains plug. Preferably the transformer has a grounded core and/or a grounded casing.

[0005] The invention also provides a mains circuit arrangement comprising a transformer having a primary winding connected across the incoming mains conductors and an ungrounded secondary winding which is isolated from the primary winding and connected to one or more domestic mains sockets. Preferably the transformer has a grounded core and/or a grounded casing.

[0006] A preferred embodiment of the invention is described below by way of example only with reference to Figure 1, which is a schematic diagram of a mains circuit arrangement in accordance with the invention.

[0007] The arrangement comprises a 1:1 transformer having an earthed core (101) and a primary winding (102) connected to the incoming mains supply via a safety cutout device (104) which may be a residual current circuit breaker for example. One of the conductors connected to primary winding (102) may be earthed (not shown). The secondary winding (103) is connected to a plurality of mains sockets (105-1, 105-2....., 105-n).

[0008] In an alternative embodiment, the transformer may be integral with a mains socket. The safety cutout device (104) may also be either separate from or integral with the or each mains socket.

[0009] The or each transformer may have a metal casing (not shown) which may be earthed in addition to or as an alternative to earthing the core.

Claims

1. An electrically isolated mains socket comprising a transformer having a primary winding (102) arranged to be connected across the mains supply and an ungrounded secondary winding (103) which is isolated from the primary winding and connected to the socket contacts, said socket contacts being located and dimensioned to receive a mains plug, characterised in that the transformer has a grounded core and/or a grounded casing.

2. An electrically isolated mains socket according to claim 1, further comprising a safety cut-out device connected to said primary winding (102).

3. A mains circuit arrangement comprising a transformer having a primary winding (102) connected across the incoming mains conductors and an ungrounded secondary winding (103) which is isolated from the primary winding and connected to one or more domestic mains sockets (105-1, 105-2...., 105-n), characterised in that the transformer has a grounded core (101) and/or a grounded casing.

4. A mains circuit arrangement according to claim 3, further comprising a safety cut-out device connected to said primary winding (101).

Drawing