GB2140988A

GB2140988A - Power supply control unit

Info

Publication number: GB2140988A
Application number: GB08314415A
Authority: GB
Inventors: Kenneth William Banks; Donald Philip Rolt
Original assignee: BEDFORDSHIRE COUNTY COUNCIL
Current assignee: BEDFORDSHIRE COUNTY COUNCIL
Priority date: 1983-05-25
Filing date: 1983-05-25
Publication date: 1984-12-05
Also published as: GB8314415D0

Abstract

The control unit comprises a first switch 4 which can be operated by any personnel to energise a primary power supply circuit 7, and second switching means 8, 11 which is effective only when the first switch 4 has been operated and is operable only by authorised personnel, for example by use of a removable key, to energise a secondary power supply circuit 14. Timing means 9 de-energises the secondary circuit at a predetermined time following operation of the second switching means. The second switching means includes a relay 10 having main contacts 12 for energising the secondary circuit 14 and hold-on contacts 13 for latching the relay, the switch 8 being biased open and being temporarily closed by the authorised person. Continuous operation of the circuit 14 may be obtained on closure of a by-pass switch 16 also operable only by the authorised personnel. The circuits 7, 14 may be connected to lighting or heating loads, and if heavy loads are to be supplied, the circuits 7, 14 may control contactors in the load supply lines. <IMAGE>

Description

SPECIFICATION Power supply control unit This invention relates to an electric power supply control unit, and particularly, but not exclusively, to a unit for controlling the artificial illumination of an area by electricity.

In areas where numerous electric lighting units are provided, there is a tendency for personnel to switch all of the lighting units on, irrespective of whether full illumination of the area is required at that time.

Once the lights are switched on, the tendency is for the personnel to forget about them, so that the whole area is brightly illuminated throughout the day, even though for part, or even the whole, of the day a much lower level of lighting would be adequate, and possibly no lighting at all would be needed in some parts of the area.

Clearly, this results in a considerable wastage of energy, which is especially serious in the case of large illuminated areas such as occur in public buildings.

It is an object of the present invention to provide a power supply control unit for controlling two or more separately-switchable electric power supply circuits, whereby unnecessary consumption of electric power may be reduced.

According to the invention, a power supply control unit for controlling at least one primary power supply circuit and at least one secondary power supply circuit comprises first switching means which is operable to energise the or each primary power supply circuit; second switching means which is effective only when the first switching means has been operated and is operable only by authorised personnel to energise the or each secondary power supply circuit; and timing means to de-energise the or each secondary power supply circuit at a predetermined time after operation of the second switching means.

The second switching means may be controlled directly by a key available only to authorised personnel or by a push-button requiring a positive re-set action by the user.

When used for lighting control, the unit therefore enables any person to turn on those lights which serve a minimum lighting requirement, but restricts the switching-on of further lights to authorised persons, and those further lights are then automatically switched-off after a predetermined time and must be deliberately switched on again by an authorised person if they are still required.

Means may be provided for use by authorised persons for disabling the timing means so that once the secondary lighting circuit is energised it remains energised until either the first or the second switching means is turned off.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying circuit diagram of a circuit for controlling the lighting in a building.

An A.C. supply 1 has line and neutral terminals 2 and 3, respectively. A 2-gang on-off switch 4, having paralleled contacts connected to the line terminal 2, can be closed to energise lines 5 and 6 simultaneously. The line 5 is connected to an output 7 to which can be connected any desired number of lighting units constituting a primary lighting circuit.

The primary lighting circuit can, therefore, be energised by merely closing the switch 4, which is available for use by anybody in the building.

The line 5 is also connected via a switch 8 and a timer 9 to the operating coil 10 of a relay 11. The switch 8 is biased into a normally-open contact position and may be temporarily closed by turning a key which is made available only to authorised personnel or by a push-button requiring a positive re-set action.

The relay 11 has two pairs of normally-open contacts 12 and 13. The contacts 12 are connected between the line 6 and an output 14to which can be connected any desired number of lighting units constituting a secondary lighting circuit. The contacts 13 bridge the switch 8 to act as a relay hold-on circuit.

When the switch 8 is closed, the relay coil 10 is energised, pulling-up the contact pairs 12 and 13.

The output 14 is thereby energised, and the secondary lighting circuit is activated. The contacts 13 bridge the switch 8, so that when the switch 8 is released the relay coil 10 remains energised. After a predetermined period, contacts of the timer 9 open, thereby de-energising the relay coil 10. The contact pairs 12 and 13 therefore open, and the secondary lighting circuit is de-activated.

Alternatively, if the switch 4 is opened, the line 5 will be de-energised and the relay 11 will drop out. In either case, the timer 9 immediately resets to zero, ready for re-energisation of the relay coil 10 when the switches 4 and 8 are again closed.

The switching and timing components are preferably all contained within a single housing 15 which is protected against unauthorised interference. If the lighting loads are large, it may be necessary to connect the outputs 7 and 14 to the operating coils of contactors instead of connecting the outputs directly to the lighting units. The contactors will be selected to have contacts which can handle the lighting currents, and the switch 4 and contacts 12 can be of quite low current ratings. The contactors may be too large for mounting in the housing 15, and may then be mounted remotely from the housing.

In use of the above-described unit, the secondary lighting circuit will be disconnected automatically after a period determined by the timer 9 and will have to be switched on again if those lights are still required. However, on certain occasions this may be inconvenient or even hazardous for users of the area. A bypass switch 16 may therefore be provided, either within the housing 16 or at a remote location, for use only by authorised persons. This switch bypasses the contacts 12, so that both the primary lighting circuit and the secondary lighting circuit will be energised whenever the switch 4 is in the closed condition.

A fuse 17 protects the timer and relay coil circuit, and allows the safe use of cable of low current rating for supplying that circuit.

Although it is described above in respect of lighting circuits, the unit could alternatively be used to control other electrical loads, such as heating loads.

Claims

1. A power supply control unit for controlling at least one primary power supply circuit and at least one secondary power supply circuit, comprising first switching means which is operable to energise the or each primary power supply circuit; second switching means which is effective only when the first switching means has been operated and is operable only by authorised personnel to energise the or each secondary power supply circuit; and timing means to de-energise the or each secondary power supply circuit at a predetermined time after operation of the second switching means.

2. A unit as claimed in claim 1, wherein the second switching means is controlled by a removable key.

3. A unit as claimed in claim 1, wherein the second switching means is controlled by a push button which must be pressed if the or each secondary power supply circuit is to be- re-energised following de-energisation by the timing means.

4. A unit as claimed in any preceding claim, further comprising means operable to override the timing means to allow continuous operation ofthe or each secondary power supply circuit.

5. A unit as claimed in claim 4, wherein the overriding means comprises bypass switching means for bypassing the second switching means and the timing means.

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6. A unit as claimed in any preceding claim, wherein the second switching means includes a relay having a relay coil energisable by closure of a switch, first relay contacts for energising the or each secondary power supply circuit on energisation of the relay coil, and second relay contacts for holdingon the relay when the switch is opened.

7. A unit as claimed in claim 6, wherein the timing means comprises a timer having contacts connected in series with the relay coil for deenergising the relay coil at said predetermined time after energisation of the relay coil.

8. A unit as claimed in any preceding claim, wherein each power supply circuit supplies power to respective contactor means for energising a respective load.

9. A unit as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

10. A lighting installation including a unit as claimed in any preceding claim.