GB2094571A

GB2094571A - Lighting control systems

Info

Publication number: GB2094571A
Application number: GB8106806A
Authority: GB
Original assignee: Lee Electric Lighting Ltd
Current assignee: Lee Electric Lighting Ltd
Priority date: 1981-03-04
Filing date: 1981-03-04
Publication date: 1982-09-15
Also published as: GB2094571B

Abstract

A lighting control system includes a ballast unit supplying a lamp head through a cable link (6, 8, 10, 12). The cable link includes three line cores and an earth core. The lamp (26) within the lamp head can be switched ON and OFF by start and stop switches (20A and 22A) at the lamp head or start and stop switches (20 and 22) at the ballast unit. The lamp is connected across two of the cores (6 and 8) of the cable link while an igniter for the lamp is connected to a third core (12) of the cable link. A pilot current is arranged to be supplied to the igniter (34) from the ballast unit through the third core (12). The flow of the pilot current is controlled by the stop and start switches and this enables the lamp to be switched ON in response to operation of either of the two start switches (20 and 20A) or switched OFF in response to operation of either of the stop switches (22 and 22A). <IMAGE>

Description

SPECIFICATION Lighting control systems The present invention relates to lighting control systems.

Mobile high intensity lighting equipment is often required for illuminating film and television sets.

Such equipment may include a ballast unit powered from a mains supply, and a lamp head incorporating a gas discharge lamp connected to the ballast unit by a relatively long cable link. The ballast unit is normally kept in one place while the lamp head is moved around according to the different lighting requirements. A control unit is provided both at the ballast unit and the lamp head to ignite and extinguish the gas discharge lamp. This allows the option of controlling the lamp either from the position of the ballast unit or the lamp head.

In a previously proposed arrangement this facility was achieved by using a cable link having seven cores, three control cores for enabling the independent operation of the two control units and four power cores representing live, neutral and earth cores as well as a starter drive core.

Seven core cable is bulky to transport, expensive to buy and difficult to manipulate. While these disadvantages can be mitigated by using a cable in which the three control cores have a lower rating than the four power cores it has been found that the lighter control cores are prone to premature break- age.

According to the invention, there is provided a lighting control system, comprising: a ballast unit having a contactor relay for controlling the energisation of two cores of a cable link, a trigger switch operative in response to operation of the contactor relay to feed a trigger signal to a third core of the cable link, a lamp head having a discharge lamp connectable to the ballast unit through the said two cores of the cable link, an igniter for igniting the lamp connectable to the trigger switch through the third core, first switching means at the lamp head and responsive to energisation of said two cores in response to operation of the contactor relay by manual switching at said ballast unit, orto manual operation, to switch the igniter into circuit with said third core whereby to be activated by said trigger signal, means at said ballast unit for supplying a pilot current to said third core which is enabled to flow only when the igniter is switched into circuit with the third core, and second switching means at said ballast unit and responsive to said flow of pilot current through said third core to operate the relay contactor, or if already operated, to maintain the relay contactor operational, whereby said discharge lamp can be switched ON both from said ballast unit and from said lamp head.

According to the invention there is further provided a lighting control system, comprising: a bal last unit connected to a lamp head through a cable link having first, second and third cores; the lamp head including a lamp connected across the first and third cores, a first relay connected in series with a manually operable normally closed stop switch, the series combination being connected across the first and third cores, an igniter for igniting the lamp, and a normally open contact set of the first relay and a normally open manually operable start switch connected in parallel, the parallel combination being connected in series with the igniter across the second and third cores; the ballast unit including a pair of input terminals, one input terminal being connected to the third core and the other input terminal being connected to the first core through a main contact set and a current regulating choke, a second relay connected in series with a normally closed manually operable stop switch between the other said input terminal and the second core to supply the second core with a pilot current, a main contactor relay controlling the operation of said main contact set, a manually operable normally open start switch connected in parallel with a normally open contact set of the second relay, the parallel combination being connected in series with the main contactor relay between the two inputterminals, and a delay switch connected between the second core and the junction between the main contact set and the choke and operable to close its contacts for a predetermined period only following closure of the main contact set whereby to provide limited energisation of the igniter sufficient to effect ignition of the lamp following operation of either one of two said start switches.

According to the invention there is still further provided a lighting system, comprising a ballast unit connected to a lamp head having a lamp and a lamp igniter, by means of a multicore cable, the ballast unit supplying an energisation voltage for the lamp through two cores of the cable, and control means at both the lamp head and the ballast unit each operable to effect or interrupt the flow of a pilot current through the third core whereby to switch the lamp ON and OFF from both the lamp head and the ballast unit.

Lighting control systems embodying the invention, will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure lisa block diagram of one of the systems; Figure 2 is a circuit diagram of the system of Fig. 1; Figure 3 is a circuit diagram of another of the systems; and Figure 4 is a circuit diagram of yet another of the systems.

The lighting control system shown in Figure 1 includes a ballast unit 2, and a lamp head 4 incorporating a 21 kW lamp. The lamp head 4 is coupled to the ballast unit 2 by a cable link 5 having four cable cores 6 to 12, namely a live core 6, a neutral core 8, an earth core 10 and a start core 12. The ballast unit has three input terminals 14to 18, one terminal 18 being connected to earth and the other two 14 and 16 being arranged to be connected to an AC or DC supply.

The ballast unit incorporates a control circuit (not shown) having a pair of start and stop push buttons 20 and 22. The lamp head 4 incorporates a control circuit (not shown) having a pair of start and stop push buttons 20A and 22A.

In the circuit diagram shown in Figure 2, terminals 14 and 16 are connected to an AC mains supply (not shown). The terminal 14 is connected through the contact set M1 of a main contactor relay M and a current regulating choke 24 to one end of the live core 6 of the cable link 5. The terminal 16 is connected to one end of the neutral core 8. At the other end of the cable link 5, a lamp 26 is connected across the cores 6 and 8.

A power factor correcting capacitor 28 is connected across the terminals 14 and 16 through a second contact set M2 of the main contactor relay M. An inductor 30 is connected across the capacitor 28 to provide a rapid discharge path for the capacitor when the contact set M2 is opened.

The energising coil of the main contactor M is connected in series with the start switch 20 across the terminals 14 and 16.

Afull wave rectifier 32 has its input terminals connected across the terminals 14 and 16 in series with a resistor 34, the stop button 22, the start core 12, the start button 20A, an igniter 34 and the neutral core 8.

The contact set B, of a relay B is connected in parallel with the start button 20A.

The output terminals of the full wave rectifier feed the energising coil of a relay A. A capacitor 36 is connected in parallel with the relay A. A first set of contacts Al of the relay A is connected in parallel with the start button 20. A second set of contacts A2 of the relay A is connected in series with an auto timer 38 and the series combination is connected between the start core 12 and the junction between the contact set M1 and the choke 24.

A current transformer 40 of which the primary winding constitutes the main supply path for the lamp 26 has a secondary winding connected in series with the relay B and the stop button 22A, the series combination being connected in parallel with the lamp 26.

The igniter 34 is coupled by means (not shown) to the lamp 26 and operates when energised to inject momentarily a very high voltage into the lamp 26 in order to initiate a gas discharge within the lamp 26.

This operation is well known by those skilled in the art and will not be elaborated on further.

In operation the lamp 26 can be turned both ON and OFF at the lamp head or at the ballast unit.

To switch the lamp 26 ON from the lamp head, the start button 20A is operated. This action closes the circuit path so that current flows from the terminal 14, through the resistor 34 and the inputwindings of the full wave rectifier 32, the stop button 22, the start core 12, the start button 20A, through the igniter 34 and back through the neutral core 8 to the terminal 16. The relay A is thereupon energised and the contact sets Al and A2 are closed. Closure of contact set Al enables the contactor relay M to be energised. As soon as contactor relay M is energised contact sets M1 and M2 are closed. Closure of contact set M2 brings the power factor correction capacitor 28 into circuit. Closure of the control set M1 feeds energising current through the choke 24 to the lamp 26.

At the same time the igniter start switch 38 will close its contact set for a predetermined duration to feed AC current through the now closed contact set A2 and the closed start button 20A to the igniter.

The igniter will now generate high voltage starting pulses to trigger the lamp 26 into conduction. Just before the lamp is rendered conductive the full mains voltage will have appeared across the relay B and will energise it. Energisation of relay B will close contact set B1.

Following ignition of the lamp 26, the voltage across the lamp 26 will drop to a level insufficient to maintain the relay B energised but the provision of the current transformer augments any existing current to maintain the relay B held.

If the lamp has ignited before the expiry of the predetermined delay period of the timer 38 and if once the lamp has ignited the start button 20A is released the flow of current through the relay A via the igniter will be maintained by the contact set B1.

If it is now desired to switch the lamp OFF from the lamp head, then push button 22A is operated. This breaks the energisation circuit for the relay B and causes contact set B1 to open. This in turn breaks the energisation circuit for relay A and causes contact set Al to open. The effect is to de-energise the contactor relay M which thereupon opens its contact sets M1 and M2. Opening of contact set M1 discontinues the supply of current to the lamp 26 which thereupon becomes extinguished. Opening of contact set M2 disconnects the supply of AC voltage to the capacitor which immediately discharges itself through the inductor 30.

To switch the lamp ON from the ballast unit the push button 20 is operated. This has the effect of energising the contactor relay M which thereupon closes its contact sets M1 and M2. Relay B is thereupon energised and the consequent closure of contact B1 completes the circuit for energising the relay A. Energisation of relay A effects the closure of contact sets Al and A2 whereupon the lamp 26 is ignited in a similar manner as already described.

To de-energise the lamp 26 from the ballast unit, push button 22 is operated. This breaks the circuit for the relay A and the lamp is extinguished in a similar manner to that thereinbefore described.

Preferably the relay A is a slow release relay (about 112 seconds relay) to avoid the need for operat- ing a start button again to re-ignite the lamp following a short interruption in the mains supply.

The contact sets A2 acts to preventthe contactor relay M and the relay A going into oscillation following the operation of a stop button.

Instead of a full wave rectifier a half wave rectifier can be used.

In the lighting control system shown in Figure 3 parts similar to those in Figure 2 are similarly referenced.

As can be seen the full wave rectifier and relay A have been replaced by an AC relay AAc.

The current transformer 40 has been omitted and the relay B is replaced by a relay having a low vol tage coil B,v.

The operation of the system of Figure 3 is generally similar to that of Figure 2.

In the lighting control system shown in Figure 4 parts similar to those in Figure 2 and Figure 3 are similarly referenced.

As can be seen the trigger circuit has been removed from the ballast unit and is incorporated into the igniter 34 which is in the lamp head. In this circuit the igniter is powered from the lamp supply core 6 via the normally closed contact set Bl. The relay B is energised solely by current through the lamp 26 via the current transformer 40 or it may be a current operated relay. The stop switch 22A is connected in series with the parallel combination of the start switch 20A and a second relay contact set B2 of the relay B. The series parallel combination is connected between cores 12 and 8 in the lamp head.

To switch the lamp 26 on from the lamp head, the start button 20A is operated. This action closes the circuit path so that current flows from terminal 14 through the relay A, the stop button 22, the core 12, the stop button 22A and the start button 20A and back through the neutral core 8 to the terminal 16.

The relay A is thereupon energised and the contact set Al closes. This action enables the relay contactor M to be energised and the contacts M1 close. The closure of the contact set Ml feeds energising current through the choke 24 to the lamp 26 and also via the relay contact set B1 to the igniter 34.

The igniter will now generate high voltage starting pulses to bring the lamp 26 into conduction. Just after the lamp is rendered conductive the lamp current will cause the current sensing relay B to be energised. Energisation of relay B will cause the contact set B1 to open to disconnect the feed to the igniter. The contact set B2 will also be closed by energisation of relay B and this will maintain the flow of pilot current through relay A after the start switch 20A is released.

If it is now desired to switch the lamp OFF from the lamp head, then stop switch 22A is operated. This breaks the energisation circuit for the relay A and causes contact set Al to open. The effect is to deenergise the relay contactor M which therefore opens its contacts M1 to extinguish the lamp.

To switch the lamp ON from the ballast unit the start switch 20 is operated. This has the effect of energising the contactor relay M which thereupon closes its contacts Ml. The lamp and igniter are thereupon energised and the lamp 26 is ignited in a similar manner as already described. The lamp current causes the relay B to be energised, closing the contacts B2 which energises the relay A, closing con Pact set 81 and so providing a holding circuitforthe contactor relay M.

To de-energise the lamp 26 from the ballast unit stop switch 22 is operated. This breaks the circuit for the relay A which releases the contactor relay M and the lamp is extinguished in a similar manner to that hereinbefore described.

Preferably the relay A is a slow release relay (about If seconds delay) to avoid the need for operating the start button again to re-ignite the lamp following any short interruption in the mains supply.

The relay B should preferably be a slow to operate relay to allow time for the lamp 26 to ignite fully before the start impulses are disconnected.

It will be appreciated that with all three of the described circuits switching at both the lamp head and the ballast unit is possible without employing any addition control cores in the cable link between the ballast unit and lamp head.

Claims

1. A lighting control system, comprising: a ballast unit having a contactor relay for controlling the energisation of two cores of a cable link, a trigger switch operative in response to operation of the contactor relay to feed a trigger signal to a third core of the cable link, a lamp head having a discharge lamp connectable to the ballast unit through the said two cores of the cable link, an igniter for igniting the lamp connectable to the trigger switch through the third core, first switching means at the lamp head and responsive to energisation of said two cores in response to operation of the contactor relay by manual switching at said ballast unit, orto manual operation, to switch the igniter into circuit with said third core whereby to be activated by said trigger signal, means at said ballast unit for supplying a pilot current to said third core which is enabled to flow only when the igniter is switched into circuit with the third core, and second switching means at said ballast unit and responsive to the said flow of pilot current through said third core to operate the relay contactor, or if already operated, to maintain the relay contactor operational, whereby said discharge lamp can be switched ON both from said ballast unit and from said lamp head.

2. A system according to claim 1, wherein said trigger switch comprises a delay switch which is responsive to operation of the contactor relay to energise said third core with an igniter triggering current for a predetermined period of time.

3. A system according to claim 1 orto claim 2, wherein the first switching means comprises a relay connected to the said two cores and having a relay contact set which connects the igniter to the third core when the relay is energised.

4. A system according to claim 3, wherein the first switching means comprises a current transformer responsive to the flow of current through the lamp when energised, to supplement the energisation current of the relay two maintain the relayener- gised.

5. A system according to any preceding claim, wherein the second switching means comprises a relay connected in series with the pilot current supplying means and the third core, the relay having a contact set for effecting energisation of the main contactor relay or, if the main contactor relay is energised by operation of said manual switching, for latching the contactor relay in an energised state.

6. A system according to claim 4, wherein the pilot current supplying means includes a full wave rectifier for supplying DC current to the second switching means.

7. A lighting control system, comprising: a bal last unit connected to a lamp head through a cable link having first, second, and third cores; the lamp head including a lamp connected across the first and third cores, a first relay connected in series with a manually operable normally closed stop switch, the series combination being connected across the first and third cores, an igniter for igniting the lamp, and a normally open contact set of the first relay and a normally open manually operable start switch connected in parallel, the parallel combination being connected in series with the igniter across the second and third cores; the ballast unit including a pair of input terminals, one input terminal being connected to the third core and the other input terminal being connected to the first core through a main contact set and a current regulating choke, a second relay connected in series with a normally closed manually operable stop switch between the other said inputterminal and the second core to supply the second core with a pilot current, a main contactor relay controlling the operation of said main contact set, a manually operable normally open start switch connected in parallel with a normally open contact set of the second relay, the parallel combination being connected in series with the main contactor relay between the two input terminals, and a delay switch connected between the second core and the junction between the main contact set and the choke and operable to close its contacts for a predetermined period only, following closure of the main contact set whereby to provide limited energisation of the igniter sufficient to effect ignition of the lamp following operation of either one of two said start switches.

8. A system according to claim 7, including a power factor correcting capacitor and a second normally open set of contacts of the main contactor relay connected in series across the two input terminals.

9. A system according to claim 7 orto claim 8, including a full wave rectifier in series with the second relay.

10. A lighting system, comprising a ballast unit connected by means of a multicore cable to a lamp head having a lamp and a lamp igniter, the ballast unit supplying an energisation voltage for the lamp through two cores of the cable, and control means at both the lamp head and the ballast unit each operable to effect or interrupt the flow of a pilot current through a third core whereby to switch the lamp ON and OFF from both the lamp head and the ballast unit.

11. A system according to claim 10, wherein the igniter is connected in parallel with the lamp and wherein the control means in the lamp head includes a relay which is operative in response to the flow of current through the lamp to interrupt the energisation of the igniter.

12. A system according to claim 10, wherein the ballast unit is arranged to supply an ignition signal forthe igniterthrough a third core of the cable and the pilot current is arranged to flow through the igniter.

13. A lighting control system substantially as hereinbefore described, with reference to Figures 1 and 2 of the accompanying drawings.

14. A lighting control system substantially as hereinbefore described, with reference to Figure 3 of the accompanying drawings.

15. A lighting control system substantially as herein before described, with reference to Figure 4 of the accompanying drawings.