DE600458C - Screening device with capacitor control for connection to AC networks - Google Patents

Description

lad- £ Χΐ ^

ISSUED ON
JULY 23, 1934

It is well known that the voltage curve of alternating current networks contains harmonics that arise as a result of high iron saturation of the network loads. Using Siebkreisen the harmonics can be directly recycled or, in particular in i6 ^{_2/3 of} the periodic train networks with the fundamental wave current to assemble such a waveform that is obtained never free light. In order to compensate for fluctuations in the harmonics and the mains voltage, regulation is required. '

~~ So far are used to regulate the filter circuit voltages and currents regulating transformers and regulating reactors are proposed been. According to the invention, capacitors with variable capacitance are used for regulation. The only low adjustment forces this type of control involves simple drives. Further advantages, especially with regard to changing the shape of the curve, emerge from the following description.

Fig. Ι the circuit shows a Mischwellensiebvorrichtung, for example, feeds a lighting circuit for flicker when connected to a 16 ^{_2/3 of} periodic network. The series-connected lamps L ₁ to L ₄ etc. are in an oscillating circuit which is formed from the capacitor C and the inductance of the supply line of the network N. Since this is used for tuning, no special tuning inductor is required. The filter circuit is tuned to a frequency that is higher than that of the fundamental wave. However, since there is strong ohmic attenuation in the resonant circuit when the lamps L ₁ to L ₄ etc. are switched on, the fundamental wave and other harmonics are also allowed to pass in addition to the harmonic that was tuned to. In the voltage of the network N , the fundamental wave is decisive, therefore the proportion of the fundamental wave in the filter circuit current is also considerable when the lamps are switched on. The capacitive resistance of the capacitor, based on the fundamental frequency, is selected to be greater than the total ohmic resistance of the series lamps L ₁ to L ₄ . Because of this and because of the geometrical composition of the resistors of the capacitor, inductor and lamps, the latter can be switched off individually without the current changing too much.

In order to completely cancel the influence of switching off individual lamps and to also compensate for changes in current due to fluctuations in the mains voltage, the capacitor C is designed to be controllable. Its capacity can be changed automatically and the control of the variable speed drive can take place due to the series connection of the lamps, for example by the current flowing in the capacitor circuit. If the current increases, the capacitive resistance is increased, and vice versa. The resonance frequency changes here, but with the strong ohmic damping this is of little importance for the curve shape and level of the lamp current.

Fig. 2 shows the circuit of a sieve circuit through which a very specific upper Avelle can be made usable. In order to keep the fundamental wave of the network .Y away from the consumer network V, for example the lamps L ₁ , L ₂ , L ₃ and L ₄ , there is a trap circuit C ₁ , D _x tuned to the fundamental frequency. To match the frequency of the ίο harmonic to be used in the consumer network V , a choke coil D and. a capacitor C ₂ . The latter can be regulated in order to compensate for the fluctuations in the harmonic voltage that is filtered out.

Such a screening device is of particular importance for connection to networks whose basic frequency is i6 ² / _s Hz. If the circuit is tuned to the third harmonic by means of the choke coil D. ₂ and the capacitor C ₂ , the current in the consumer network V has a frequency of 50 Hz.

When the resonance circuit is precisely matched to the frequency of the harmonic to be filtered out and with the smallest unregulated voltage occurring in the consumer network V , the controllable capacitor C ₂ has its smallest capacitance. If the consumer voltage increases, the capacitance of the capacitor C _{2 is} increased. In this way, the consumer voltage can be kept constant. The increase in the capacitance of C ₂ also causes the resonance circuit to be detuned in such a way that the resonance frequency approaches the fundamental frequency. However, this does not result in any disadvantages, since the fundamental wave is kept away _{by the blocking circuit C 1} , D _1. On the contrary, this detuning improves the curve shape of the strained voltage when the load is low. Because with a small load, the ohmic resistance in the consumer network V is high and therefore the resonance is fuzzy, so that in addition to the desired harmonics, other, higher harmonics can occur in the load current. However, by increasing the capacitance during regulation, the undesired higher frequency harmonic currents decrease sharply.

The capacitor is expediently regulated automatically depending on the voltage of the consumer network V. The harmonic filter device can, as shown in Fig. 2, be connected directly to the alternating current network N or with the interposition of a transformer. If the load V is connected via a transformer, then this transformer is to be dimensioned for the frequency of the filtered out harmonic.

The capacitance of the variable capacitors according to Fig. 1 and 2 can be changed by advertising So to that variable capacitors used or unchanging with a main capacitor capacitance addition to capacitors of small capacity, the capacity is constant or which are formed as variable capacitors, are connected in series or in parallel. Finally, a controllable ohmic resistor can be placed in parallel with the unchangeable main capacitor.

Claims (4)

Patent claims: i. A screening apparatus with condenser regulation for connection to alternating current networks consisting of a switched to the load in series vibration ⁷ S supply circuit for recovery of harmonics occurring in electric power systems due to high iron saturation of the network loads, characterized in that the as the oscillating circuit belonging or an upstream him capacitor Control capacitor off. forms is. 2. Sieving device according to claim 1, in which the individual consumers are connected in series and the inductance of the oscillating circuit connected in series with the consumer is that of the connecting lines is used between the power supply network and the consumer, characterized in that the capacity of the controllable capacitor changes automatically depending on the consumer current to be kept constant becomes (Fig. 1). - 3. Sieving device according to claim 1, in which the individual consumers are connected in parallel to one another, the capacitance of the oscillating circuit connected in series with the consumer is formed by a blocking circuit tuned to the fundamental wave of the power supply network, the inductance is formed by a special choke, characterized in that, that the capacitance is changed an additional variable capacitor, depending on the to be kept constant \ ^r erbraucherspannung automatically (Fig. 2). 4. Sieving device according to claims ι and 3, characterized in that the capacitance of the adjustable capacitor at the lowest value of the unregulated Load voltage and with precise adjustment of the resonance circuit to the frequency of the harmonic to be filtered out is smallest. For this purpose ι sheet of drawings