AT414298B - DEVICE FOR MAGNIFYING THE EFFECTIVE CAPACITY OF A CONDENSER IN AN ALTERNATING CIRCUIT - Google Patents

Description

2

AT 414 298 B

The invention relates to a device according to the preamble of claim 1, for increasing the effective capacitance of a capacitor in an AC circuit by periodically bridging and enabling the capacitor, wherein the series-connected with the switched capacitor ohmic-inductive impedance of a series 5 Resistance and a partitioned in two parts inductance. Further, the source voltage terminal facing the part of the inductance, according to the characterizing part of claim 1, a controlled source in series with another ohmic-inductive impedance in parallel. By periodic low-resistance bridging and subsequent release of a capacitor in an AC circuit, the effective capacitance of the capacitor can be changed with respect to the fundamental frequency of the source voltage of the circuit. This approach may be important if the switched capacitor is operated in series with an ohmic inductive load on the AC voltage source. Such a case is e.g. when the auxiliary line of a single-phase asynchronous motor connected to the source in relation to the main-branch winding is connected to the source via a capacitor connected in the manner described.

To the prior art, the following 4 publications are called ([1] ____ [4]). 20

In [1], (US Pat. No. 4,532,465, Renard, 30-JUL-1985), an asynchronous motor is described in which capacitors are connected in series with the respective phase windings of the asynchronous motor, so that the motor is connected to the voltage source via these capacitors. At least one of the windings is connected in shunt with variable 25 impedance in parallel. By this means, a variable engine torque can be achieved.

In the single-phase asynchronous machine treated in [1], Sp.8, Z.5, the winding (2) is connected in series with a constant operating capacitor, parallel to this LC circuit 30 is a winding (3) and the short-circuiting device is arranged. This circuit is capacitively connected to the single-phase source. This circuit needs compared to the invention, which also allows a controllable torque and thus the speed control on the timing of the auxiliary string capacitor, two capacitors. 35 For the sake of clarification, a differentiation from the one widely used today is given, where a single-phase asynchronous machine with start-up capacitor, centrifugal force switch and an operating capacitor is realized. This case has the following disadvantages compared to the invention: the operating capacitor is permanently connected in series with the auxiliary line, parallel to the operating capacitor, the starting capacitor is connected via a centrifugal-40 switch. This configuration allows a 2-point optimization of the running behavior (for example for start-up and for nominal operation). For multi-point optimization, accordingly, a plurality of capacitors to be connected in parallel should be provided (expense). With the aid of the device according to the invention, precisely this specific impedance optimization (continuous!) Can be carried out. 45

In [2], (US Pat. No. 4,424,558, N'Guyen Uyen, 3-JAN-1984), a free-commutating DC-DC converter is described. In this context, a series resonant circuit is treated, consisting of capacitor and inductance. According to [2], the capacitor of the series resonant circuit can be discharged by a discharge circuit (in the simple case by an ohmic resistor such as partial or thyristor.) In [2], Sp4 Z40 the discharge circuit ((10) -discharge circuit) for In the absence of this discharge circuit, due to leakage currents of the semiconductors and their protective circuitry, the capacitor would remain charged during continuous operation of the DC adjuster

AT 414 298 B • n [3], (patent EP 0 540 968 A1; Siemens, 12-MAI-1993), the wiring of a 3-phase generator is treated, in each of which a capacitor is connected in series to one phase winding. In [3] a switched bridging of the capacitors in series with the inductors is described. 5

In the embodiment described in [3], Sp.3 Z.4, capacitors switched in series with a three-phase generator are short-circuited when a maximum frequency is exceeded by a frequency-dependent controlled switch. This measure is used in contrast to the invention of limiting the generator current to an almost frequenzunabhängi-io gene continuous short-circuit current.

In [4], (US Pat. No. 4,677,364; Williams, 30-JUN-1987), the wiring of a generator with capacitors is also described. These capacitors are between the individual phases of the generator and the zero phase, they are separated in response to phase 15 and current zero-phase voltage by means of thyristor. In [4], Sp.2, Z.58 -Sp.3, Z.17 a general variant of the switched bridging of capacitors is discussed, in Sp.8, Z.15 - 40 general physical relationships for the derivation of the control signal are discussed Phase current and voltage for bridging the parallel-connected capacitors given, in Sp.14, Z.11 - 20, the dependence of the changing Wech-20 selstromwiderstandes is given due to the switched bridging of the capacitors.

In [4] switched capacitors are used for reactive power compensation in connection with a three-phase generator, in contrast to the invention, the switched capacitors are not bridged but connected between the output terminals of the fixed instal lated capacitors generator connected via a control circuit to the neutral point of the generator and can be solved by this again.

In contrast to [1] .... [4] In the context of the present invention, the case in which the inductance of the ohmic-inductive impedance operated with the switched capacitor in 30 series is partitioned into two parts should be addressed, wherein the partial inductance facing the source voltage terminal is connected in parallel to a controlled source and to this source in series, another ohmic-inductive impedance is present.

The ohmic-inductive impedance in series with the switched capacitor with 35 partitioned inductors whose partial inductance, one controlled source is connected in series with another ohmic-inductive impedance, also appears as that impedance in the specific case of a single-phase asynchronous machine. According to an embodiment, as specified in claim 2, this impedance can be mapped to the auxiliary terminal clamps of a single-phase asynchronous machine, when the main winding of this single-phase asynchronous machine is connected directly to the voltage source of the AC circuit.

In the case of the above-described connection of the auxiliary line in series with the switched capacitor can, according to claim 3, the device also replace the starting capacitor and centrifugal force switch of a single-phase asynchronous machine.

On the basis of embodiments shown in the drawings, the invention will be explained in more detail below. 1 shows a device with a controlled switch mounted in parallel with a capacitor and the components of an AC circuit combined in a subsystem at an AC voltage source, the state of the switch being determined by an actuator and the state of the switch the quantities of source voltage and voltage across the capacitor detected by the actuator are proportional.

Claims (3)

4 AT 414 298 B FIG. 2 shows the internal circuit of the remaining components of an AC circuit combined in a subsystem, which are connected in series with the switched capacitor at the AC voltage source, wherein the internal circuit consists of a part-inductance ohmic-inductive impedance whose partial inductance is one controlled source in series with another ohmic-inductive impedance is connected in parallel. FIG. 3 shows an adjusting device which determines the state of the controlled switch and which detects and evaluates the quantities of source voltage and voltage across the capacitor. As shown in the device in FIG. 1, a capacitor (2), to which a controlled switch (3) is arranged in parallel, is connected on the one hand via terminal (1a) of the AC voltage source (1), and on the other hand via terminal (4a) an impedance summarized in subsystem (4). On the other hand, this impedance is connected via terminal (4b) to terminal (1b) of the alternating voltage source 1. The impedance summarized in subsystem (4) and shown in FIG. 2 consists of an ohmic-inductive impedance (6), (7), (8) connected to the terminals (4a) and (4b) whose inductance is divided into two partial inductances ( 7) and (8) is partitioned, wherein the partial inductance (8) a 20 controlled voltage source (11) in series with another ohmic-inductive impedance (9), (10) is connected in parallel. The controller of FIG. 3 includes an O-pass detector 12 for the source voltage, the voltage at the source (1) being supplied to the controller via terminals (5a) and 25 (5b). The O-crossing voltage detector (13) across the capacitor (2) (voltage between the terminals (1a) and (4a)) is connected across the terminals (5c) and (5d). In the control element (14), a switch control signal is generated, which determines the state of the switch (3) via the buffer stage 30 (15). The generation of the switch control signal can be done via different ways. In the following, a scenario will be described in which the switch control signal generation is first carried out in a voltage-analog way and finally the desired state of the switch (3) via a flip-flop: 35 If in (14) in the sense described to be generated switch control signal eg is to be generated by means of RS flip-flop, the resulting from (13) O-pass signal, the switch state "switch closed" by setting the flip-flop cause. From the O-passing signal resulting from (12), a signal delayed by t (with 0 <t <T / 2, T-2tt / tuQueiispanming and t: constant or variable) is generated as follows: the required delay by the time t can eg with the aid of a ramp, which is started in each case with the O-pass signal resulting from (12), and which thus has a ramp duration of T / 2. In this case, the desired delay time t can be given a t-proportional voltage by 45 and the achievement of this voltage can be signaled by the ramp voltage via a voltage comparator. The latter process can be used to reset the flip-flop, resulting in the "switch open" state. 50 Claims: 1. A device for increasing the effective capacitance of a capacitor, which is arranged in series with an ohmic-inductive impedance in an AC circuit, wherein the capacitor 55 is bridged with a switch, which via an adjusting device in 5 AT 414 298 B dependency the phase position of the voltage applied to this series circuit source voltage is opened, and is closed depending on the O-passage of the voltage across the capacitor, wherein the actuating device required for closing the switch control signal via an O-passage detector, which the voltage across the capacitor C 5 capacitor monitors, achieves, and the control signal needed to open the switch via an O-pass detector which monitors the source voltage and which is followed by a delay, by which the source voltage O-pass signal is timed (with 0 <t <T / 2 , T = 2TT / u) QueiiSpannung) constant or variable vers is achievable, characterized in that the ohmic inductive impedance in series with the switched capacitor consists of a series resistor and an inductor partitioned in two parts, and the source voltage terminal facing portion of the inductance is a controlled source in Series is connected in parallel with another ohmic-inductive impedance. 15 2. Device according to claim 1, characterized in that the ohmic-inductive impedance shown in Figure 2 occurs with source at the auxiliary line terminals of a single-phase asynchronous machine in appearance. 3. Device according to claim 1 and 2, characterized in that the switched Kon capacitor replaced the starting capacitor and centrifugal switch of a single-phase asynchronous machine. 25 For this purpose 1 sheet of drawings 30 35 40 45 50 55