GB2338844A

GB2338844A - Interface for by-passing a failed uninterruptible power supply

Info

Publication number: GB2338844A
Application number: GB9807166A
Authority: GB
Inventors: Peter Jesse
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-04-03
Filing date: 1998-04-03
Publication date: 1999-12-29
Also published as: GB9807166D0

Abstract

In an on-line type interruptible power supply system in which the UPS receives power from a mains supply at L1, N1 and normally provides an output at L4, N4 for a load, and the UPS continues to provide power for the load on interruption of the mains supply L1, N1, an interface circuit is provided which connects the mains supply L1, N1 directly to the load L4, N4, by-passing the UPS, in response to sensing failure of the supply of current from the UPS. The interface circuit may have a relay with a coil R connected across the output L3, N3 from the UPS, so that when the UPS is operating normally the coil R is energised to open normally-closed contacts of a switch R1 and to place a changeover switch R2 in a state connecting the load line terminal L4 to the output terminal L3 of the UPS. If the UPS fails, relay R drops out, so that switch R2 connects load terminal L4 directly to mains line terminal L1, by-passing the UPS, and switch R1 closes to connect a warning alarm buzzer AL across the mains L1, N1. The circuit may be locked into the by-pass state by operation of a switch SW to allow replacement of the failed UPS. When the replacement UPS has been connected, the switch may illuminate to indicate that the UPS is operating correctly. An equivalent solid state circuit may be used instead of the relay-controlled circuit.

Description

2338844 INTERFACE FOR UNINTERRUPTIBLE POWER SUPPLY This invention relates

to an interface, which may be constituted in the form of a panel, intended to be electrically placed between a supply of mains electricity, an uninterruptible power supply (UPS) and a load.

In the normal operation of systems of this nature, a mains supply is connected to supply the unlinterruptible power supply and the latter supplies the load. If there is a failure of the mains supply, the uninterruptible power supply provides electrical power to the load.

is The problem with which the present invention is concerned is the occasion of failure of the uninterruptible power supply or its blowing of an output fuse, such that the load may be have to be turned off until a new UPS is fitted or an electrician is able to wire the faulty UPS out of circuit. Those options may require the load to be without power for a considerable time.

The present invention concerns an improved system wherein on the fflure of the UPS supply the systems acts to by-pass the UPS and to supply power from the mains supply directly to the load. The invention is particularly intended to enable the by-pass to occur in a short time, preferably only a few milliseconds, so that such devices as electronic tills, petrol pump controllers and card readers are not affected by the by-pass operation.

The accompanying drawing illustrates one embodiment of a system according to the invention.

As is shown in the drawing, the single phase mains supply has terminals L 1 and NI which are connected by way of a two pole circuit breaker 5 to the input terminals L2 and N2 of an urunterruptible power supply (UPS), which is not explicitly shown in the drawing. The return or output terminals of the uriinterruptible power supply are shown as L3 and N3 respectively. The load has terminals L4 and N4.

The input line between the mains line tem-iinal NI and the line input terminal L2 of the uninterruptible power supply is connected by way of a fuse FI and an alarm buzzer AL through a first pole of a switch SW and a relay control led switch RI to the input neutral 1 terminal N2 and to the output neutral N3) of the uninterr-uptible power supply. The coil of a relay R is connected between the neutral input terminal N2 of the uninterruptible power supply, through a second pole of the switch SW and by way of a fuse F2 to a line extending from the output line terminal N3 of the uninterruptible power supply. The line terminal NI is connectible by way of a switch R2 (controlled by relay R) to the output line terminal R4.

The arrangement shown is a relay-controlled circuit. An equivalent may be realised in a solid state form.

In normal operation, terminal LI is connected to terminal L2, terminal NI to terminal L2, terminal L3 is connected to terminal L4 (by way of switch R2) and terminal N3 is connected to tern-iinal N4. On the occurrence of mains failure or the operation of the circuit breaker, the uninterruptible power supply continues to supply the load from its output tern-dnals L3 and N3.

The purpose of the relay R is to sense the cessation of current output from the uninterruptible power supply and to operate the respective switch to cause by-pass of the uninterruptible power supply and the connection of the mains supply directly to the load. For this purpose the relay R will operate the switch R1 to operate the warning alarm AL and to operate switch R2 so that the load line terminal L4 is connected to the mains line terminal L1 rather than the UPS output line terminal L1 When the UPS fails, the warning buzzer will sound. It can be muted by operation of the switch SW. The circuit may be thereby "locked" into by- pass state, whereby the UPS can be removed and replaced while not interrupting the supply of power to the load from the mains. When the replacement UPS is connected, the switch may illuminate, indicating that the UPS is operating correctly. Reverting the switch back to its normal position will bring the UPS back into the circuit (by changeover of switch R2) whereby the new UPS can provide backup during a mains failure.

3

Claims

CLAIM

1. An interface for an electrical mains supply, an uninterruptible power supply which is adapted to receive power from the mains supply and to provide an output for a load, the interface being arranged so that on the interruption of the mains supply the uninterruptible power supply continues to provide electrical power to the load, the interface including means for sensing fAure of the supply of current from the uninterruptible power supply and operative to connect the mains supply directly to the load, by-passing the uninterruptible power supply.

is 4 Amendments to the claims have been rded as follow CLAIMS 1. An interface for use between an electrical mains supply, an unlinterruptible power supply and a load output, and comprising a first pair of terminals (L 1,N1) for connection to the electrical mains supply; a second pair of terminals (L2,N2) for supplying power to the uninterruptible power supply, the second pair of terminals being coupled to the mains supply terminals; 0 a third pair of terminals (L33,N3)) for receiving power from the uninterruptible power supply; a fourth pair of terminals (L4,N4) connected to receive power from the third pair of terminals., and a switching relay (R) connected so as to be normally energised by a voltage appearing across the third pair of terminals and arranged on the cessation of that energisation to disconnect a line terminal (L4) in the fourth pair of terminals from the line terminal (L.3) in the third pair and to connect that line terminal (L4) to the line terminal in the first pair (L I).

2. An interface according to claim 1 wherein said relay (R) is also operative to close a switch (R1) to complete an alarm circuit (FIAL) between the line mains terminal and the neutral terminal in the fourth pair.

A circuit according to claim 2 wherein ganged switches (SW) are provided both in said alarm circuit and in series with said relay.