DE955708C - Arrangement for improving the power factor in inverters for feeding consumers who require an at least approximately sinusoidal current - Google Patents

Description

ISSUED JANUARY 10, 1957

L 12349 VIIIb / 21 d ^

has been named as the inventor

need sinusoidal current

Addition to the additional patent 911

The subject of patent 911 033 is an arrangement to improve the power factor in inverters whose connected consumers approximate a require sinusoidal voltage or current. By means of a sieve circle, in particular for the third harmonic, there the nearly rectangular alternating voltage is converted into a sinusoidal one. Each consumer circuit is equipped with a filter circuit. The burden is there made of fluorescent lamps, each of which is protected from overload by a current limiting reactor is. The arrangement has the disadvantage that the many individual sieve throttles of the sieve circles are proportionate cause large losses and also become particularly expensive. According to a further development of the invention should therefore a common filter throttle larger for a larger number of electricity consumers Type power can be used.

An example of the invention is illustrated in Figure 1 of the drawings. An inverter TW with a mercury beam connects the battery B alternately by means of the two electrodes A ₁ and A ₂

the left, ι, or right half 2 of the primary winding of the transformer T. A small Kon capacitor C ₁ is used to compensate for the leakage voltage of the transformer T. The entire secondary current generated flows through the throttle D ₁ Before the throttle D ₁ , the voltage curve is approximately rectangular , behind the throttle D ₁ sinusoidal. A number of fluorescent lamps, which can be switched off individually, are connected to the distribution line. Each lamp L with an igniter Z is limited by the choke D ₂ in the current to the normal value. Before each choke D _{2 there} is a capacitor C _{2 which} , with the choke D _{1, forms} the filter circuit. The capacitors C ₂ compensate the power factor of each lamp circuit to cos ψ = ι. Each consumer circuit therefore consists of a fluorescent lamp with its igniter, a series-connected choke and a capacitor bridging this series connection. With a switch S each Lanipenkreis can be switched on or off individually.

The harmonic filter circuit works in the following way: The approximately rectangular alternating voltage on the secondary side of the transformer, i.e. also on the capacitor C ₁ , contains mainly a triple harmonic in addition to the sinusoidal fundamental wave. If one denotes the alternating voltage at D ₁ with JJ ₁ , at C ₂ with U ₂ , then

U ₁

W ² LC

Is z. B. the ratio of C ₂ to U ₁ for the fundamental wave 2, is so that for the third harmonic _^2/9 = 0.22, ie, the third harmonic is approximately one tenth of the fundamental wave. The amplitude of the third harmonic on the transformer is only about one third as large as the fundamental wave, so that it is only about one-thirtieth of the fundamental wave _{on the capacitor C 2.} The effect of the following fifth harmonic and the others are reduced even more, which is why an almost sinusoidal voltage arises across _{the capacitor C 2.}

Fig. 2 shows the vector diagram of the circuit of Fig. 1 for the fundamental wave, wherein

Ut secondary voltage at the transformer, Ud AC voltage at the choke D ₁ , AC voltage at the capacitor C ₂ , transformer current,
Secondary current of all connected fluorescent lamps,

Capacitor current of all capacitors C ₉ means.

Jt Jl

Yo

The diagram was recorded with a vector knife with the third harmonic eliminated. In order to obtain the sums of the capacitor and lamp currents, which are of interest in terms of power, all that was needed was to measure in a Lanipenkreis. Since the currents flow in phase in the various lamp circuits, the length of the vectors J ₀ and J _{1 is obtained} simply by multiplying the relevant measured values by the number of connected lamps. The lamp current J _L approaches the load voltage U ₀ by approximately 6o °, the capacitor current J ₀ 90 ⁰ before. Both result in the transformer current J _T , which is almost in phase with the transformer voltage Ut. The apparent current of the lamps can thus be compensated to cos φ = ι by means of the capacitors. The reactive voltage drop across the choke D ₁ , Up is about half as large as the voltage U ₀ .

The third harmonic is only _{practically effective at the throttle D 1} and causes additional iron losses here, which, however, are of little importance if the design is correct.

As a result of the higher inductive resistance, the third harmonic in the choke D _{2 is} significantly reduced. The current in the lamp circuit is therefore approximately sinusoidal, although the lamp voltage is trapezoidal due to the lamp current voltage characteristic.

The circuit of patent 911 033 also has the disadvantage that when a fluorescent lamp burns out, the circuit of chokes and capacitor is almost in series resonance and the current therefore rises _{to impermissibly high values in choke D 1.} In contrast to this, in the event of malfunctions in the circuit according to FIG. 1, there are no inadmissible loads due to the capacitor C ₂ then connected without any lamp load.

The circuit according to FIG. 1 can also be supplemented by further additional filter circuits, e.g. B. by adding a second choke D ₁ and a corresponding total capacitor at the junction of the two chokes.

Furthermore, for better utilization of the current limiting _{choke D 2,} two lamps can be connected in series with only one choke.

Claims (5)

PATENT CLAIMS: 1. Arrangement to improve the power factor in inverters for feeding Consumers who require an at least approximately sinusoidal current, according to the patent 911 033, characterized in that the rectangular or approximately rectangular voltage curve of the inverter behind this one such dimensioned harmonic filter throttle, especially for the third harmonic, with the consumer is connected in series that is connected to the terminals of the consumer circuit with parallel connected Capacitor or capacitors have a sinusoidal or approximately sinusoidal voltage results. 2. Arrangement according to claim 1, characterized in that that with many individual electricity consumers the entire necessary capacity in a corresponding number of individual capacitors iao which are switched on and off in parallel with each individual consumer and proportionally the reactive power of the individual circuits are measured. 3. Arrangement according to claim 1 and 2, characterized in 1 * 5 marked that the individual load circuits consist of individual fluorescent lamps, each with a current limiting choke connected upstream. 4. Arrangement according to claim 1 to 3, characterized in that each has a load circuit consists of two series-connected fluorescent lamps with a current limiting choke (tandem circuit). 5. Arrangement according to claim 1 to 4, characterized in that a second or more Harmonic filter chokes and a corresponding number of harmonic smoothing capacitors are used will. Considered publications: German patent specification No. 730 955. 1 sheet of drawings © 6OJ 547/228 6.56 (609 742 1.57)