FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (SEE SECTION 10, RULE 13)
TITLE
An energy saving device for high pressure gas discharge lamps
APPLICANTS
Tata Motors Limited, Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai- 400001, Maharashtra, India, an Indian company
INVENTOR Under Section 28(2)
Joshi Vivek Vishwanath, Manufacturing/Auto Maintenance Division, Tata Motors Limited, Pimpri, Pune - 411018, Maharashtra, India, an Indian National
The following specification particularly describes the nature of this invention and
the manner in which it is to be performed :
Granted

18-1-2005

/An energy saving device for high pressure gas discharge lamps
This invention relates to an energy saving device for high pressure gas discharge lamps.
A gas discharge lamp such as a high pressure sodium or mercury vapour lamp consists of a hard glass inner tube containing sodium or mercury and rare gases such as argon or xenon under pressure. This inner tube is provided with an outer glass tube provided with a metal cap at one end. A pair of electrodes are
located within the inner tube at opposite ends. An auxiliary electrode is provided

within the inner tube adjacent to one main electrode and is connected to the other
electrode through a resister of high resistance. This electrode is connected to AC
mains through a ballast choke. A condenser or a capacitor is connected across the
AC mains.
When the lamp is switched on, electrical discharge takes place in the rare gas and an arc is struck between one of the electrodes and the auxiliary electrode. The rare gas medium becomes conducting and an electrical discharge takes place between the two main electrodes. Due to the high resistance in the auxiliary electrode, the discharge is pale blue. Heat produced during the discharge warms up the inner tube, evaporating
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Sodium/mercury contained therein, thereby building up pressure within the inner tube. This discharge produces an intense glow between the electrodes and the lamp is in full glow. It is found that the lamp operates at the same applied voltage viz 230V through out. Energy consumption of the lamp is, therefore, very high.
The object of this invention is to develop an energy saving device, which will reduce energy consumption considerably after the lamp achieves full glow. Advantages of using the energy saving device of this invention are that full voltage is required only at the start till full glow is achieved. Once stabilized the voltage may be required by 8 to 10% and the loss of illurnination is found to be minimal. Upto 22% electrical'energy may be saved by using this device.
The energy saving device for high pressure gas discharge lamps comprises a three way selector switch having three poles, 1, 2 and 3 each pole having two terminals la, lb, 2a, 2b, 3a, 3b, the first and second poles 1 and 2 being normally in the closed position, and the third pole being in the open position, the terminal 3(b) of pole 3 is connected to terminal 2(b) of pole 2, said selector switch being connected to a voltage step down transformer in substractive mode, one end of the primary windings of said transformer is connected to a terminal of said diree way switch through a normally open
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contact, the other end being connected to the neutral terminal of AC mains, a timer circuit connected to the neutral terminal of AC mains, through make and break contacts and a gas discharge lamp connected to terminal 2 of said three way switch and the neutral terminal of AC mains.
This invention will now be described with reference to Figs I, II and III which show circuit diagram'of the energy saving device.
Fig I shows the circuit when energy saving device is in By Pass Mode.
Fig II shows the circuit energy saving device in initial glow.
Fig III shows the circuit when the energy saving mode is activated.
Glow mode operation in Fig II shows poles 1 and 2 in the closed position and pole 3 in the open position. Contacts 4, 4a remain closed and the contactor C1 (5) gets activated. Normally closed contact of C1 (5) i.e. NC 7a and 7b with the help of throw 7 c become closed. The secondary windings of the transformer becomes short circuited and the current flows through the circuit as shown by the arrows. The primary wiring of the transformer remains open and disconnected from the circuit. Timer contact 8a and 8b remain open till the preset period is over.

The energy saving mode is shown in Fig III. When the bulb has glown for 8 to 10 minutes; on delay timer having normally closed contacts 4 a or 4b becomes open. Contactor coil becomes off and the normally closed contact 7(a) and 7(b) comes open and the normally open contacts 8(a) and 8(b) become closed. The primary transformer gets 230V AC. Voltage induced in the secondary windings will be in the opposite direction with respect to the primary voltage. Induced voltage in the secondary will be 230V - 15V = 215V. Direction of current is shown by die arrows. Please note that the poles and terminals of the selector switch connections are altered due to the opening and closing of contacts. In Fig 1,1(a) and 1(b) and 2(a) and 2(b) are open, 3(a) and 3(b) are closed, 3(b) is connected to 2(b). This is the by pass mode. In Figs II and III, 2(a), 2(b) are connected. 1(a) and 1(b) are connected while 3(a) and 3(b) are not connected. Here again 3(b) is connected to 2(b).
Timer circuit is shown by reference number 9 and reference number 10 shows the high pressure sodium vapour lamp. Terminal 2(a) of the pole 2 is connected to one end of the secondary winding 6(a) of the step down transformer. The other end of the secondary winding of die transformer is connected across terminal 1(b) of the three pole switch. A second, normally closed contact 7 is connected across the secondary wiring. The terminals of contact 7 are marked as 7(a) and 7(b). Their throw
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is shown as 7(c). One end of the primary winding 6(b) is connected to 1(b) of terminal 1 through a normally open contact indicated by numeral 8. The other end of the primary wiring is connected to the negative terminal of AC mains. Terminals of contact 8 are marked as 8(a) and 8(b) and their throw is indicated by 8 (c). Terminal 3(a) of pole 3 is connected to the positive of AC mains.
In the energy saving mode shown in Fig III, the timer goes off at the set time. By the opening of contact 4 and closing of contact 8, the control circuit gets disconnected and contact 7 opens. As a result, the entire input voltage appearing across the primary winding induces a voltage in the secondary winding of the transformer. Current induced flows in the opposite direction and the voltage appearing across the gas discharge lamps is less than the input of 230V
This energy saving device can be used in any gas vapour pressure lamp such as tube lights, high pressure sodium and mercury lamps.
Though this invention has been described herein above with a specific embodiment, alterations and modifications known to persons skilled in the art are within the scope of this invention and the appended claims.
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We Claim :

1) An energy saving device for high pressure gas discharge lamps comprising a three way selector switch having three poles (1), (2) and (3) each pole having two terminals (la, lb; 2a, 2b; 3a and 3b), the first and second poles (1) and (2) being normally in the closed position, the third pole being in the open position, the terminal 3(b) of pole (3) being connected to terminal 2(b) of pole (2), said selector switch being connected to a voltage step down transformer in substractive mode, one end of the primary winding of said transformer being connected to a terminal of said three way switch through a normally open contact, the other end being connected to the neutral terminal of AC main, a timer circuit connected to the phase terminal of said AC main, through make and break contacts and a gas discharge lamp connected to terminal 2 of said three ways switch and the neutral terminal of said AC mains; and contacts 4, 4a remain closed and the contactor C1 (5) gets activated, normally closed contact of C1 (5) i.e. NC 7a and 7b with the help of throw 7c become closed, the secondary windings of the transformer becomes short circuited and the current flows through the circuit, the primary wiring of the transformer remains open and disconnected from the circuit; on delay timer having normally closed, contacts 4a or 4b becomes open, contactor coil becomes off and the normally closed contact 7(a) and 7(b) becomes open and the normally open contacts 8(a) and 8(b) become closed, and the primary transformer gets activated.
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