ECG-SPOT 2/2004 - Osram

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Three-phase system and ECG Power supply in European systems A line voltage of 230 V and a frequency of 50 Hz are customary in Europe. Regardless of the primary energy carrier selected, power stations generate three-phase current. The three-phase system comprises the phase conductors L1, L2 and L3, the neutral conductor N and an earth connection. The voltage of each phase conductor to the neutral conductor is 230 V and is used for the majority of consumers. Neutral conductor and protective earth conductor both have earth potential. In this Y-connection (Fig. 1), the neutral conductor supplies the consumers, together with L1, L2 and L3. The protective earth conductor ensures the personal safety, e.g. by earthing metal housings. The sinusoidal voltages of L1, L2 and L3 are each 120° out of phase. OSRAM ECG-SPOT 2/2004 8 Generator I1 U1N I3 I2 U3N U2N Line voltage and the effect of voltage fluctuations L1 I1 L2 I2 L3 I3 N IN Fig. 1. Three-phase network with consumer The voltage between two phase conductors is usually 400 V, or 230 V in exceptional cases, and is not suitable for operating most commercially available consumers. This delta connection is customarily used only in industry and in drive systems. Given absolutely uniform loading of the three circuits, the current in the neutral conductor is equal to zero. Spotlight on uniform loading Although network operators aim for uniform loading of the three circuits, this requirement is only approximately met in practice. If the loading of the three circuits is non-uniform, what is known as a compensating current flows in the neutral conductor. When operated on a threephase system, an input voltage of 230 V is present at the electronic control gear - provided Y-connection I1 U1N I3 I2 U3N U2N that a neutral conductor is incorporated in the cable and connected. Effect of asymmetry If the load in the three-phase system is asymmetrical, and the neutral conductor is not corrected or connected incorrectly, neutral point displacement can occur (Fig. 2). Since no neutral conductor is connected, the total of the conductor currents at the neutral point is always zero. To ensure that this condition is met, phase voltages U1N, U2N and U3N change their magnitude, among other things. This leads to what is known as neutral point displacement and an associated overvoltage or undervoltage in the three-phase system. The result is the voltage profile of the three phase voltages, as shown in Fig. 3. The phenomenon in practice A lighting installation can be taken as an example for a practical explanation of the phenomenon of neutral point displacement. If the neutral conductor is not connected in a "three-phase installation", the result is both overvoltage and undervoltage at the consumers, i.e. the electronic control gear units. This means that the input voltage at the ECG can theoretically be between 0 V and 400 V. U1N L1 L2 L3 210 Ω U2N N L1 U31 U1N U12 N U2N U3N 170 Ω U3N 300 Ω L3 U23 L2 Fig. 2. Neutral point displacement Effects on the electronics The power supply in Europe is so stable that voltage fluctuations in excess of 10% in either direction are generally not exceeded. Electronic control gear from OSRAM is engineered in such a way that the probable fluctuations in the line input voltage are already taken into account in the design. PROFESSIONAL pays off Operators of lighting installations equipped with electronic OSRAM control gear from the Professional segment cannot detect any difference in brightness in this fluctuation range of ± 10%. This ECG is designed in such a way that, on the lamp side, hardly any fluctuations in the line input voltage in the range from 207 V to 254 V are transmitted. The lamp output remains virtually constant in this voltage range.
U [V] 230V· 2 U1N U2N U3N 250 0 -250 Line voltages in excess of 264 V either occur briefly in the form of "voltage peaks", or they are permanently present as a result of faulty installation in the three-phase system. With ECG from the Professional segment, the input voltage can even assume values of up to 350 V for a defined period of time. This has no effect on the operation of the ECG. In most cases, faulty installation involves the neutral conductor not being connected. This can, for example, happen following official acceptance of a largescale installation by a test institute, since the neutral conductor has to be disconnected for some tests. Depending on where the neutral point is displaced to (Fig. 2), the applied input voltage can also drop to below 200 V. QUICKTRONIC ECG from the Professional segment is likewise designed to cope with this phenomenon. However, regardless of the ECG used, a fluorescent lamp can only be ignited at above 198 V. In other words, reliable "switching on" of the lighting cannot be guaranteed below this voltage value. Experience acquired by OSRAM in recent years has shown that these product characteristics of QUICK- TRONIC control gear from the Professional segment are perfectly adequate (Table 1) for preventing the ECG from being damaged by overvoltage or undervoltage. U [V] 230V· 2 250 Without neutral With neutral point displacement point displacement 10 20 t [ms] Fig. 3. Oscillogram of the phase voltages without and with neutral point displacement U1N U2N U3N 0 -250 OSRAM ECG from the Professional segment is equipped for all phenomena in the network and requires no additional audible or visual signals, which put an additional burden on the electronics as a result of rapidly alternating high voltages and 0 V on the components. Cornelia Fürst and Markus Heckmann, OSRAM Munich Characteristics of QUICKTRONIC ECG from the Professional segment: • Input voltage 220 V to 240 V • AC voltage from 198 V to 264 V for reliable lamp ignition • No damage in case of a permanent input voltage of up to 320 V • Short-term input voltages of 350 V (up to 2 hours) do not damage this ECG 10 20 t [ms] T5 FQ T5 FH T8 Compact fluorescent lamps fluorescent lamps fluorescent lamps fluorescent lamps QTi DALI 1x/2x… DIM* QTi DALI 1x/2x… DIM* QTi DALI 1x/2x… DIM* QT DALI-FQ 1x/2x... QT DALI-FH 1x/2x/3x/4x… QT DALI-L 1x/2x/3x/4x... QT DALI-T/E 1x/2x… QTi 1x/2x… DIM* QTi 1x/2x… DIM* QTi 1x/2x… DIM* QT-FQ 1x/2x… DIM QT-FH 1x/2x/3x/4x… DIM HF 1x/2x/3x/4x… DIM QT-T/E 1x/2x… DIM QTi 1x/2x…* QTi 1x/2x…* QTi 1x/2x…* QT-FQ 1x/2x… QT-FH MULTIWATT 1x/2x... QTP 1x/2x/3x/4x… QTM 1x/2x... QT-FQ 1x/2x… F/CW QT-FH MULTIWATT 1x/2x... F/CW QT-FH 3x/4x14 * Additional product characteristics can be found at www.osram.com/products/electronical/quicktronic/qti Table 1. QUICKTRONIC control gear from the Professional segment OSRAM ECG-SPOT 2/2004 9
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ECG-SPOT 2/2004 - Osram

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