Extending the life of a fluorescent lamp. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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In [1,2], circuits are described that allow extending the life of a fluorescent lamp (LDS). They certainly deserve attention, they attract with their simplicity, accessibility and can be recommended for repetition. But when repeating these schemes, it must be borne in mind that the LDS filament, which remains "alive", operates with an overload, since the burned-out filament is shunted by a "wire jumper".

Such a forced mode of operation of the lamp, due to a decrease in the resistance of the filament circuit by half, leads to its rapid wear, and it fails. In addition, the "resuscitation" scheme given in [2] requires an additional installation of a start button, so when controlling the LDS using a wall switch, a problem arises - where to place this start button to turn on the lamp installed on the ceiling?

In the "resuscitation" scheme, which is shown in Fig. 1, there are no such shortcomings.

As can be seen from Fig. 1, the burned-out filament of the LDS is shunted not by a jumper, but by a wire resistor, the resistance of which is equal to the cold resistance of the filament. For lamps with a power of 20 and 30 W (LBK22, LBUZO), this resistance is 2 ... 3 ohms. The wire resistor R1 is made on a VS-0,25 10 kΩ resistor and consists of 2-3 turns of nichrome wire with a diameter of 0,15 ... 0,2 mm.

As a resistor R1, it is very convenient to use a variable wire resistor of the type SP5-28A with a nominal value of 33 ohms or the like, choosing the value of its resistance during setup so that the LDS filament does not overload (at start-up it should be red or pink when the lamp is ignited with confidence) . When setting up the circuit, it is also necessary to take into account the recommendations [1], which provide reliable ignition of the LDS.

In order to bring the operation of the LDS closer during its start-up to work with whole filaments, three parallel-connected incandescent bulbs of the MN 1-13,5 type (with a voltage of 0,18 V and a current of 13,5, 0,18 A). Their current-voltage characteristic (CVC) is the same as the CVC of the LDS incandescent filament. Instead of these three bulbs, you can use one 12V x 6 light car bulb.

However, during "resuscitation" there may be cases when it is not possible to achieve normal operation of the LDS using the scheme of Fig. 1. The lamp lights up heavily and blinks at a frequency of 25 Hz, despite all the tricks indicated in [1]. This flashing is not eliminated even when the starter SF1 is removed and is accompanied by increased heating of the throttle. Such operation of the lamp is explained by the fact that it has switched to a half-wave operation mode due to the loss of emission by one of the electrodes, i.e. the lamp works like a diode, passing current in only one direction, as a result, a direct component of the rectified current flows through the inductor, which causes it to heat up.

In this case, it is not possible to ensure the normal operation of the LDS directly from the AC mains. But it is possible to revive the lamp even in this case, it can still work reliably if it is switched to a current supply in one direction by connecting it to the output of a half-wave rectifier.

Figure 2 shows such a switching circuit.

The operation of the lamp according to this circuit is similar to the operation of the lamp in Fig. 1, except that a unidirectional current flows through it with a frequency of 100 Hz, while the whole filament acts as the cathode of the lamp, and the damaged one acts as the anode.

As bridge diodes VD1 ... VD4, you can use assemblies of types KTs402 ... KTs405 for 600 V and a current of 1 A for LDS with a power of 20, 30, 40 and 65 W. Very convenient assembly type KTs404, which has a fuse holder.

Literature

1. Khovaiko V. Restoration of fluorescent lamps//Radio. - 1997. - No. 7 - P. 37
2. Eserkenov K. The method of “resuscitation" of fluorescent lamps / / Radio. - 1998. - No. 2. - C.61.

Author: K.V. Kolomoytsev, Ivano-Frankivsk

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