Switchable amplifier

Abstract

In order to provide a light and robust voltage amplifier and current amplifier for a test device (10) for testing electrical components, the amplifier (8) is designed to output a test signal to a signal output between a positive output terminal (P) and a negative output terminal (N), wherein the amplifier comprises a first half-bridge (HB1) and a second half-bridge (HB2), wherein a switching unit (7) is provided, which is designed to connect the first half-bridge (HB1) and the second half-bridge (HB2) in parallel to the signal output in a first operating mode (Mi) and to connect the first half-bridge (HB1) and the second half-bridge (HB2) in series to the signal output in a second operating mode (Mu).

Description

Technical Field

[0001] The invention relates to an amplifier for a test device suitable for testing electrical components, wherein the amplifier is designed to output a test signal to a signal output between a positive output terminal and a negative output terminal, wherein the amplifier comprises a first half-bridge and a second half-bridge. Background Art

[0002] Test devices are often required for testing the control devices of electromechanical or electronic switching devices. In particular, in the field of electrical protection technology and electrical energy supply, testing the functionality of switching devices and their control devices is important and often even mandatory. For example, switching devices installed on utility poles in medium-voltage power networks are usually equipped with electromagnetic actuators and are connected to the control device via control connections. A test device is usually used, which is intended to simulate the switching device. To this end, the control connections of the switching device and the control device are disconnected, and instead the test device is connected to the control device via an adapter cable in order to test its functionality. The test device then generates corresponding electrical test signals, which are intended to stimulate the control device to perform a specific reaction. This reaction is detected and evaluated by the test device.

[0003] The test signal consists of a test current and a test voltage. The test signal can have a high test voltage, for example, in the range of 300V, and a low test current, for example, in the range of 1A. For this purpose, a voltage amplifier is provided in the test device, which is designed to generate a test signal with a high test voltage and a low test current. Alternatively, the test signal can also be provided with a high test current, for example, in the range of 30A, and a low test voltage, for example, in the range of 25V. For this purpose, a current amplifier is provided, which is designed to generate a test signal with a high test current and a low test voltage. Due to the output of a high test voltage and a low test current or a high test current and a low test voltage, a relatively low power output is obtained.

[0004] If a current amplifier and a voltage amplifier are provided in the test device, they have different, separate topologies. The voltage amplifier is provided with a dedicated voltage output (comprising a positive voltage output terminal and a negative voltage output terminal), and the current amplifier is provided with a dedicated current output (comprising a positive current output terminal and a negative current output terminal) separate from the voltage output. Because neither the current nor the voltage output outputs a test signal having both a high test voltage and a high test current, relatively low power is output at both the voltage and current outputs. Nevertheless, both the current amplifier and the voltage amplifier must be dimensioned to be sufficiently robust to be able to output a high test current or a high test voltage. If the test device includes both a voltage amplifier and a current amplifier, it is not only correspondingly large but also heavy, which of course negatively impacts portability. This is disadvantageous because testing of control devices for switching devices is typically performed on-site, where high mobility is desirable. Summary of the Invention

[0005] The object of the present invention is to provide a light and robust voltage and current amplifier for a test device.

[0006] According to the invention, this object is achieved in that a switching unit is provided in the amplifier, which is designed to connect the first half-bridge and the second half-bridge in parallel to the signal output in a first operating mode and to connect the first half-bridge and the second half-bridge in series to the signal output in a second operating mode.

[0007] The first operating mode is optimized for outputting a test signal with a high test current, so the amplifier can be considered a current amplifier in the first operating mode. In the first operating mode, the amplifier can therefore output a test signal with a high test current, for example, in the range of 25 to 50 A, and a low or negligible test voltage, for example, in the range of 0 to 25 V, at the signal output via the parallel connection of the first and second half-bridges.

[0008] The second operating mode is optimized for outputting a test signal with a high test voltage, so the amplifier can be considered a voltage amplifier in the second operating mode. Thus, in the first operating mode, the amplifier can output a test signal at the signal output via the series connection of the first and second half-bridges, having a high test voltage, for example, in the range of 50 V to 10 kV, and a low and / or negligible test current, for example, in the range of 0 to 1 A.

[0009] Thus, the amplifier according to the present invention, which can be switched from a first operating mode to a second operating mode and vice versa, implements both a current amplifier and a voltage amplifier, depending on the operating mode. Depending on the operating mode, a test signal having either a high test voltage and a low test current, or a high test current and a low test voltage, can be output at the signal output, that is, between the positive and negative output terminals. Thus, the amplifier according to the present invention allows the use of the same signal output in both the first and second operating modes. In contrast, test devices according to the prior art (i.e., having separate voltage and current amplifiers) have separate voltage and current outputs. Of course, separate signal outputs for the first and second operating modes can also be provided in the amplifier according to the present invention, but this would incur additional wiring costs. Because a common wiring topology is provided for both operating modes according to the present invention, fewer components are required than in a design with separate voltage and current amplifiers. Consequently, the switchable amplifier is smaller in size and weight, which translates to greater portability.

[0010] Preferably, the first half-bridge includes a first switching element and a second switching element connected in series with the first switching element, and the second half-bridge includes a third switching element and a fourth switching element connected in series with the third switching element. Of course, other switching elements may also be provided in the first and / or second half-bridges, for example, to increase the power that can be output at the output end.

[0011] Preferably, the amplifier includes a first DC voltage source and a second DC voltage source connected in series through a connection point, wherein the first and second half bridges are respectively connected in parallel to the first and second DC voltage sources connected in series, and the connection point of the first switching element and the second switching element constitutes a first intermediate point, and the connection point of the third switching element and the fourth switching element constitutes a second intermediate point, wherein the first intermediate point is connected to the positive output terminal.

[0012] In the first operating mode, the second intermediate point can be connected to the positive output terminal and disconnected from the negative output terminal, and the connection point can be connected to the negative output terminal to connect the first half-bridge and the second half-bridge in parallel to the signal output terminal. Thus, a test signal with a high test current can be output at the signal output terminal.

[0013] Furthermore, a filter inductor, preferably with a switchable inductance, may be provided at the signal output. The filter inductor can be connected in series with either the positive or negative output terminal. Preferably, the inductance of the filter inductor is switched to a lower inductance, for example, 10 μH, in the first operating mode and to a higher inductance, for example, 200 μH, in the second operating mode. This can be achieved by center tapping the filter inductor. As a result, the ripple of the test signal can be kept low in the second operating mode due to the higher inductance. Provision can also be made for the filter inductor to be connected to the signal output only in the first operating mode and disconnected, for example, bridged, from the signal output in the second operating mode. In the second operating mode, the test voltage of the test signal is essentially adjusted, thereby enabling the connection of particularly high-resistance loads to the signal output. If the filter inductor is connected to the signal output in the second operating mode, the test current of the test signal can be adjusted more easily in the second operating mode because the filter inductor smoothes the test current. Consequently, both low-resistance loads and high-resistance loads can be operated due to the high output voltage. The filter inductor is optional, but has a positive influence on the control behavior and the signal quality of the output signal.

[0014] Preferably, in the second operating mode, the negative output terminal is disconnected from the connection point and connected to the second intermediate point. Thus, the first half bridge and the second half bridge are connected in series and output a test signal having a high voltage at the signal output terminal.

[0015] In the second operating mode, the second intermediate point can be connected to the negative output terminal via the first converter controlled by the conversion unit.

[0016] The amplifier according to the present invention can be used in a test device for testing electrical components, preferably control devices of switching devices of electrical switching devices. To this end, a test signal can be applied to the electrical component to enable testing. Furthermore, the test device can receive input signals to test the electrical component. However, the functionality of the electrical component can also be tested independently of the test device.

[0017] Thus, for example, a test energy counter can be provided. The energy counter measures the current and voltage within a predetermined time period in order to accurately determine the energy consumed. The energy counter usually has a roller counter. Or provide counting pulses, for example, an LED with 1000 pulses / kWh. The accuracy of the energy counter can be evaluated using a test device. This can be done by having the test device's amplifier output a test signal to simulate a current and / or voltage within a predetermined time, such as a simulated secondary variable of a current and / or voltage converter. These currents and / or voltages, i.e., test signals, are fed to the energy counter, but are also directly recorded and used to calculate the actual energy output. In addition to or as an alternative to recording the current and / or voltage, the energy output by the test device can also be recorded directly. The energy counter also determines the energy from the current and / or voltage and then compares the actual output, i.e., the recorded or calculated energy, with the energy determined by the energy counter. This allows the accuracy of the energy counter to be determined. This determination itself can be performed by a comparison unit that compares the output energy with the determined energy. This comparison unit can be provided on the test device itself or as a separate component or device. Of course, the comparison can also be performed by the user.

[0018] Furthermore, the secondary signals of operating components (converters, protective relays) of electrical equipment can also be tested using a test device including an amplifier according to the present invention. To this end, a test signal is output by the amplifier of the test device, which is used as the primary signal. The primary signal is applied to the primary side of the operating component and further determines the secondary signal on the secondary side of the operating component. The secondary signal can be checked for correct polarity, correct level, etc., thereby, for example, testing the wiring of the secondary side. The secondary signal can be analyzed by an analysis unit, which is provided on the test device itself or as a separate component or device. Of course, the analysis can also be performed by the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 1 to 3. Figure 5c The invention will be explained in detail. The drawings show advantageous embodiments of the invention by way of example, schematically and non-limitingly.

[0020] Figure 1a An electrical switching device with a control unit is shown,

[0021] Figure 1b Shows the test device connected to the control unit,

[0022] Figure 2 A design scheme of the amplifier is shown.

[0023] Figure 3a The amplifier is shown in a first operating mode,

[0024] Figure 3bThe amplifier is shown in a second operating mode,

[0025] Figure 3c The amplifier in the second operating mode is shown with a filter inductor Lx at the output.

[0026] Figure 4a shows the test signal in the first operating mode at a duty cycle of 50%,

[0027] Figure 4b shows the test signal in the first operating mode at a duty cycle of 40%,

[0028] Figure 5a shows the test signal in the second operating mode with a duty cycle of 50%,

[0029] Figure 5b shows the test signal in the second operating mode at a duty cycle of 40%,

[0030] Figure 5c The test signal is shown in the second operating mode at a duty cycle of 60%. DETAILED DESCRIPTION

[0031] FIG1 shows a portion of a power supply network 1, here a three-phase overhead line, whose conductors 3 are conventionally stretched between utility poles 2. A switchgear 4 is provided on the utility pole as a safety device. The switchgear comprises a switching device 5 and an associated control device 6. The switching device 5 is, for example, a recloser or a circuit breaker in the form of an electromagnetic actuator including a coil, in a known manner. The switching device 5 can disconnect or connect at least one of the lines 3 by a switching operation triggered by the control device 6.

[0032] For this purpose, the switching device 5 is connected to the control device 6 via a control connection 12. For this purpose, the control connection 12 usually comprises a plurality of control lines for transmitting control input variables and control output variables. The switching operation is typically triggered by the control output variable.

[0033] To test the switching device 4, the control connection 12 between the switching device 5 and the control device 6 is disconnected, as in Figure 1bAs shown in . It is also possible that the switching device 5 is not connected to the control device 6 at all before testing, for example during initial startup, thereby eliminating the need for disconnecting the control connection 12. This is often the case, as the control device 6 is often parameterized before installation and its functionality is subsequently tested using a test device 10 before it is placed "on site" and installed. For testing, the control device 6 is connected to the test device 10 using an adapter cable 11. The test device 10 simulates the switching device 5 so that the proper functionality and parameterization of the control device 6 of the switchgear 4 can be tested. The adapter cable 11 is connected on one side to the signal input of the control device 6 and on the other side to the signal output 9 of the test device 10. The test device 10 is thus used to simulate or emulate the switching device 5. In order to verify the correct operating principle of the control device 6, simulated secondary variables (e.g., three-phase) of the current converter and / or voltage converter can be simulated by the test device 10 and fed into the control unit 6. After a predetermined time, the control device 6 transmits a signal for disconnecting at least one of the lines 3 to the test device 10, for example, via binary contacts, depending on the fault type and fault manifestation. The test device 10 simulates the switching device 5. The generation of the secondary variable fed into the control device 6 can be performed by the test device 10, which includes an amplifier according to the present invention. Thus, the test signal serves as the secondary variable.

[0034] The test device 10 including the amplifier 8 according to the invention is of course not limited to use in power supply networks 1 in the form of overhead lines, but can be used in any device for transmitting or distributing electrical energy, which has a safety device in the form of a switching device 4 with a switching device 5 and an associated control device 6. The amplifier 8 according to the invention can also be used in a test device 10 for testing electrical components of electrical switching devices, wherein a test signal is applied to the electrical components.

[0035] An amplifier 8 of a testing device 10 for testing an electrical component, preferably a control device 6 of a switching device 5 of an electrical switching device 4, is designed to output a test signal at a signal output between a positive output terminal P and a negative output terminal N. According to the invention, a switching unit 7 is provided in the amplifier 8, which is designed to selectively switch the amplifier 8 into a first operating mode Mi and a second operating mode Mu.

[0036] The test signal consists of a test current ia and a test voltage ua. In the first operating mode Mi, the test current ia of the test signal is preferably adjusted, and in the second operating mode Mu, the test voltage ua of the test signal is preferably adjusted. FIG3 shows a preferred design of an amplifier 8. Here, a first half-bridge HB1 is provided, preferably including a first switching element S1 and a second switching element S2 connected in series with the first switching element S1; and a second half-bridge HB2 is provided, preferably including a third switching element S3 and a fourth switching element S4 connected in series with the third switching element S3.

[0037] The signal output is connected to a load Z, preferably a low-resistance load Z in the first operating mode Mi and a high-resistance load Z in the second operating mode Mu. Another electrical component, such as the control device 6 corresponding to the switching device 5 of the electrical switching device 4 in FIG1 , can be considered a load L. In the first operating mode Mi, the first half-bridge HB1 and the second half-bridge HB2 are connected in parallel to the signal output. In the second operating mode Mu, the first half-bridge HB1 and the second half-bridge HB2 are connected in series to the signal output. In the illustrated embodiment, the amplifier 8 includes a first DC voltage source UQ1 having a first DC voltage Uq1 and a second DC voltage source UQ2 having a second DC voltage Uq2, connected in series via a connection point V. Furthermore, the first half-bridge HB1 and the second half-bridge HB2 are connected in parallel to the series-connected first and second DC voltage sources UQ1 and UQ2, respectively. The connection point between the first switching element S1 and the second switching element S2 forms a first center point M1, and the connection point between the third switching element S3 and the fourth switching element S4 forms a second center point M2. Furthermore, the first intermediate point M1 is connected to the positive output terminal P, which can be done directly or via other components. In particular, a line filter inductor L' can be provided as a further component. Figure 2 (as well as Figure 3a 、 3b , 3c) is the case because an optional line filter inductance L' is provided between the first intermediate point M1 and the positive output terminal P. Figure 2 (and Figure 3a 、 3b In 3c), an optional line filter inductor L' is provided between the second center point M2 and the negative output terminal N. Furthermore, the line filter inductor L' is each connected to ground via an optional line filter capacitor C. If the line filter inductor L' is omitted and the line filter capacitor C is nevertheless provided, the first and second center points M1, M2 are each connected to ground via the line filter capacitor C.

[0038] Furthermore, a filter inductor L is provided at the signal output, the inductance of which can be switched or bridged by a second converter R2. Preferably, the filter inductor is bridged by the second converter R2 in the first operating mode Mi. However, an optional third converter R3 is also provided, which is used to switch the filter inductor L back on in the second operating mode Mu. Of course, the filter inductor L can also be switched on in the second operating mode Mu by another converter (not shown) implemented separately from the second converter R2.

[0039] If the filter inductor L is switched on in the second operating mode Mu, a low-ohmic load Z can also be connected to the signal output in the second operating mode Mu. If it is assumed that the amplifier 8 can output a test signal with a test current ia of 1 A in the second operating mode Mu, a load Z with a resistance of 300 ohms can be provided at the signal output, for example, because the voltage sources UQ1 and UQ2 provide sufficiently high DC voltages Uq1, Uq2 to operate this load.

[0040] In addition, Figure 2 The optional filter capacitor Cx is arranged between the positive output terminal P and the negative output terminal N. In the embodiment shown, the second converter R2 is also used to switch the filter capacitor Cx between the positive output terminal P and the negative output terminal N in the second operating mode Mu and to bridge the filter capacitor Cx in the first operating mode Mi.

[0041] The first converter R1 and / or the second converter R2 and / or the third converter R3 and / or further converters can be controlled by the switching unit 7. Therefore, the filter inductor Lx is located between the first intermediate point M1 and the positive output terminal P (as shown in the figure).

[0042] It is also conceivable that the filter inductor Lx is arranged between the second center point M2 and the negative output terminal N. Alternatively, a filter inductor Lx may be provided between the first center point M1 and the positive output terminal P and between the second center point M2 and the negative output terminal N. In the first operating mode Mi, the second center point M2 is disconnected from the negative output terminal N, and the connection point V is connected to the negative output terminal N, so that the first half-bridge HB1 and the second half-bridge HB2 are connected in parallel to the signal output and a test signal having a high test current ia is output at the signal output.

[0043] Alternatively, in the first operating mode Mi, the first intermediate point M1 is also disconnected from the positive output terminal P, with the connection point V connected to the positive output terminal P. This allows the first half-bridge HB1 and the second half-bridge HB2 to be connected in parallel to the signal output and to output a test signal with a high test current ia at the signal output. In this case, a filter inductor Lx is advantageously provided between the second intermediate point M2 and the negative output terminal N.

[0044] The switching of the connection of the second intermediate point M2 from the negative output terminal N to the connection point V and vice versa (or optionally the switching of the connection of the first intermediate point M1 from the negative output terminal N to the connection point V and vice versa) is preferably carried out by a first converter R1, for example, which is controlled by the switching unit 7, wherein, in the embodiment shown, the connection point V is connected to ground and the first converter R1 disconnects the negative output terminal N from the second intermediate point and switches it to ground.

[0045] In the second operating mode Mu, the second intermediate point M2 is connected to the negative output terminal N and disconnected from the connection point V (this is also done here by the first converter R1) in order to connect the first half-bridge HB1 and the second half-bridge HB2 in series and output a test signal with a high test voltage ua at the signal output.

[0046] Of course, embodiments in which the first converter R1 performs two functions (disconnecting the negative output terminal N from the second center point M2 and switching the second center point M2 to ground) and embodiments in which the second converter R2 performs multiple functions (connecting / bridge-over the filter inductor Lx and connecting the first and second center points M1 and M2) are preferred. Alternatively, for example, a converter may be provided for each function, such as a converter for connecting (or switching) the filter inductor Lx, a converter for connecting the first and second center points M1 and M2, a converter for connecting the filter capacitor Cx, a converter for disconnecting the second center point M2 from the negative output terminal, a converter for switching the second center point M2 to ground, or any combination thereof.

[0047] exist Figure 3a Shown in Figure 2 The first converter R1 (not shown) connects the negative output terminal N to the connection point V (ie, both the negative output terminal N and the connection point V are grounded here) and disconnects the output terminal N from the second intermediate point M2.

[0048] In the first operating mode Mi, the second converter R2 (not shown) connects the half-bridges HB1 and HB2 in parallel, also bypassing the filter capacitor Cx and connecting the first center point M1 to the second center point M2 (in each case via a coil L'). The second converter R2 is in a position where the filter inductor Lx switches between the first center point M1 and the positive output terminal P. The third converter R3 is disconnected so that the filter inductor Lx is not bypassed. The parallel connection of the half-bridges HB1 and HB2 doubles the test current ia of the test signal at the signal output in the first operating mode Mi. For example, if the switching elements S1, S2, S3, and S4 (e.g., implemented as transistors) used in the half-bridges HB1 and HB2 can each withstand 15 A, the parallel connection of the two half-bridges HB1 and HB2 can output a test signal with a high test current ia, for example, in the range of 30 A. If an additional half-bridge is connected in parallel with the two half-bridges HB1 and HB2, a test signal with an even higher test current ia can be generated.

[0049] The first switching element S1 and the second switching element S2 of the first half-bridge HB1 are switched alternately, and similarly, the third switching element S3 and the fourth switching element S4 of the second half-bridge HB2 are switched alternately. If the first switching element S1 is active, the second switching element S2 is inactive, and vice versa. Similarly, if the fourth switching element S4 is inactive, the third switching element S3 is active, and vice versa. The duty cycle, as is well known, describes the ratio of the control signals of the switching elements S1, S2, S3, and S4 of the half-bridges HB1 and HB2. Specifically, in this case, it is the ratio of the control signal of the first switching element S1 of the first half-bridge HB1 to the second switching element S2, and the ratio of the control signal of the third switching element S3 of the second half-bridge HB2 to the fourth switching element S4. Preferably, the first and second half-bridges HB1 and HB2 are operated with the same duty cycle. The control signals are generated by a pulse generating unit. Preferably, the conversion unit 7 is an integrated component of the pulse generating unit.

[0050] In the first operating mode Mi, the first half-bridge HB1 and the second half-bridge HB2 are preferably controlled with a 180° offset, whereby a (triangular) ripple current is obtained for the half-bridge output currents i1 and i2 provided by the half-bridges HB1 and HB2, respectively, which are offset by 180°. The test current ia of the test signal is obtained from the sum of the half-bridge output currents i1 and i2. In this case, at a duty cycle of 50%, the ripple currents of the two half-bridge output currents i1 and i2 cancel each other out. When the duty cycle is not equal to 50%, the ripple currents of the half-bridge output currents i1 and i2 do not completely, but partially cancel each other out. Figure 3a In the first operating mode Mi, the test current ia of the test signal is adjusted.

[0051] Figure 4a For the first operating mode Mi, the control signals for the first switching element S1 and the third switching element S3 with a duty cycle of 50% and offset by 180° are shown by way of example in the above figure. The slight offset of the control signals shown serves only to be able to visually distinguish overlapping control signals from one another in the figure. A switching period T is set for the control signals. Accordingly, the voltage signal u1 generated thereby at the first center point M1 and the voltage signal u2 generated at the second center point M3 are shown in the middle figure. From the voltage signals u1, u2, the first half-bridge output current i1 in the line filter inductance L' connected to the first intermediate point M1 is derived, and the second half-bridge output current i2 in the line filter inductance L' connected to the second intermediate point M2 is derived. As a result, the test current ia of the test signal is obtained as a sum current consisting of the half-bridge output currents i1, i2, wherein Figure 5a In the case shown in FIG, no ripple current appears in the test signal.

[0052] exist Figure 4b shows the control signals for the first switching element S1 and the second switching element S3 with a duty cycle of 40% (again shifted by 180° relative to each other). The ripple current of the test current ia is no longer zero here, but has twice the frequency of the control signal, wherein the amplitude of the ripple current is also reduced.

[0053] exist Figure 3b Shown in Figure 2 The wiring of the amplifier 8 in the second operating mode Mu. The first converter R1 (not shown) connects the negative output terminal N to the second intermediate point M2 and disconnects the negative output terminal N from the connection point V (i.e., grounded here). In addition, in the second operating mode Mu, the filter capacitor Cx between the positive output terminal P and the negative output terminal N is switched, because the second converter R2 does not connect the filter capacitor Cx. However, the second converter R2 connects the filter inductor Lx here. Figure 3b In the second operating mode Mu, the test voltage ua of the test signal is adjusted.

[0054] Figure 3c A second operating mode Mu is also shown, which, however, is different from the Figure 4b The difference of the second operating mode Mu is that the third converter R3 is disconnected and ensures that the filter inductor Lx is not connected across. Figure 3c In the second operating mode Mu, the test current ia of the test signal is adjusted. As a result, a test current having high signal quality and stable control characteristics for low-resistance and high-resistance loads Z can be output in the second operating mode Mu.

[0055] Of course, it is also possible, but not shown in the figures, to adjust the test voltage in the first operating mode Mi. The following table briefly describes which figures show which operating modes Mi, Mu and which adjustment methods (adjustment of the test current ia, adjustment of the test voltage ua):

[0056] The first operating mode Mi The second operating mode Mu Adjustment of test current ia Figure 3a Figure 3c Adjustment of test voltage ua (not shown) Figure 3b

[0057] exist Figure 5a , the control signals for the first switching element S1 and the second switching element S2 in the second operating mode Mu are shown. The slight offset of the control signals shown is used to be able to visually distinguish the control signals from one another. Figure 5a A 50% duty cycle is shown, meaning the control signals are in phase with each other. The half-bridge output voltages u1 and u2 at the first and second intermediate points M1 and M2 have the same shape as the control signals, thereby compensating for current ripple in the coil current flowing through the line filter inductor L'. The voltage signal ua is derived from the difference between the half-bridge voltages u1 and u2. In the illustrated case, no voltage ripple occurs, resulting in a zero test voltage ua.

[0058] exist Figure 5b shows a 40% duty cycle, while in Figure 5c A duty cycle of 60% is shown in FIG. This results in a test voltage ua (again derived from the difference between the half-bridge voltages u1, u2) that has twice the frequency of the control signal. Consequently, the current ripple of the coil current flowing through the line filter inductance L' is halved. Consequently, the voltage ripple of the test voltage ua is halved at the filter capacitor Cx by twice the frequency of the control signal.

Claims

1. An amplifier (8) for a test device (10) suitable for testing electrical components, wherein: The amplifier (8) is designed to output a test signal to a signal output end between a positive output terminal (P) and a negative output terminal (N), wherein the amplifier (8) comprises a first half-bridge (HB1) and a second half-bridge (HB2), wherein the first half-bridge has a first switching element (S1) and a second switching element (S2) connected in series with the first switching element (S1) via a first intermediate point (M1), and the second half-bridge has a third switching element (S3) and a fourth switching element (S4) connected in series with the third switching element (S3) via a second intermediate point (M2), and is characterized in that a conversion unit (7) is provided in the amplifier (8), which is designed to connect the first intermediate point (M1) of the first half-bridge (HB1) and the second intermediate point of the second half-bridge (HB2) in a first operating mode (Mi). (M2) is connected and connected to one of the positive output terminal and the negative output terminal (P, N) of the signal output end, and in the second operating mode (Mu), the first middle point (M1) of the first half bridge (HB1) and the second middle point (M2) of the second half bridge (HB2) are connected to the corresponding one of the positive output terminal and the negative output terminal (P, N) of the signal output end, and the amplifier (8) is also designed to control the first half bridge (HB1) with a control signal in the first operating mode (Mi), and the control signal is phase-shifted by 180 degrees relative to the control signal for controlling the second half bridge (HB2), and to control the first half bridge (HB1) and the second half bridge (HB2) with the same phase control signal in the second operating mode (Mu).

2. The amplifier (8) according to claim 1, characterized in that The amplifier (8) comprises a first DC voltage source (UQ1) and a second DC voltage source (UQ2) connected in series via a connection point (V), wherein the first half-bridge and the second half-bridge (HB1, HB2) are respectively connected in parallel to the first and second DC voltage sources (UQ1, UQ2) connected in series.

3. The amplifier (8) according to claim 2, characterized in that In a first operating mode (Mi), the first intermediate point (M1) is connected to the positive output terminal (P), the second intermediate point (M2) is connected to the positive output terminal (P) and disconnected from the negative output terminal (N), and the connection point (V) is connected to the negative output terminal (N).

4. The amplifier (8) according to claim 2, characterized in that In the second operating mode (Mu), the first intermediate point (M1) is connected to the positive output terminal (P), and the second intermediate point (M2) is disconnected from the connection point (V) and connected to the negative output terminal (N).

5. The amplifier (8) according to claim 4, characterized in that In a second operating mode (Mu), the second intermediate point (M2) is connected to the negative output terminal (N) via a first converter (R1) controlled by the conversion unit (7).

6. The amplifier (8) according to any one of claims 1 to 5, characterized in that A filter capacitor (Cx) is provided, which can switch between the positive output terminal (P) and the negative output terminal (N).

7. The amplifier (8) according to any one of claims 1 to 5, characterized in that A filter inductor (Lx) having a switchable and / or bridging inductance is provided at the signal output.

8. The amplifier (8) according to claim 6, characterized in that The filter capacitor (Cx) is switchable between the positive output terminal (P) and the negative output terminal (N) in a second operating mode (Mu).

9. The amplifier (8) according to claim 7, characterized in that The inductivity can be converted and / or bridged by the conversion unit (7).

10. A testing device (10) for testing an electrical component, comprising an amplifier (8) according to any one of claims 1 to 9, the amplifier outputting a test signal for testing the electrical component.

11. The testing device (10) according to claim 10, characterized in that The electrical component is an associated control device (6) of a switching device (5) of an electrical switching device (4).

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