DE2831734A1 - SIGNAL GENERATOR FOR GENERATING SINUS-SHAPED OUTPUT SIGNALS WITH A PRE-DETERMINED PHASE POSITION - Google Patents

Description

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LGZ LANDIS & GYR ZUG AG CH-6301 ZUG, Switzerland

Signal generator for generating sinusoidal output signals with predetermined phase position

PA 2Ο3Ο

909881/0535

Signal generator for generating sinusoidal output signals with predetermined phase position

STATE OF THE ART

It is a signal generator of the type mentioned in the preamble of claim 1 Art known (IEEE Transactions on Audio and Electroacoustics, March I97I, pp. 48-57), the two 90 ° out of phase with each other Output signals generated. A computer with a ROM memory and a number generator serve as the function generator Accumulator. For each phase step marked by the number generator, the associated sine value is simultaneously displayed in the computer and cosine value are calculated and output to a digital / analog converter each. This solution requires a complex function generator.

TASK

The invention specified in claim 1 is based on the object to create a signal generator which is characterized by a simpler circuit structure.

ADVANTAGES

With the signal generator according to the invention, a simpler construction of the function generator is achieved. The technical effort is in particular relatively small when a large number of output signals are to be generated.

DISCLOSURE OF THE INVENTION

Two exemplary embodiments of the invention are illustrated below the drawing explained in more detail.

1 shows a basic circuit diagram of a signal generator,

Fig. 2 is a diagram and

3 shows a basic circuit diagram of a further signal generator.

PA 2O3O

909 881/0535

The signal generator shown in FIG. 1 generates three respectively to 12O ° mutually phase-shifted AC voltages U _0, U U_ and _T as well as three to 12O ⁰ respectively mutually phase-shifted alternating currents I, I and I. The current triangle I _D , I_, I is _{shifted relative to the voltage triangle U R} , U ₁ -, U _T by the phase angle φ, which can be preselected at an angle input element 1O and is output by this in binary coded form. In the example shown, a second angle input member 11 outputs an angle value of 121 ° in binary-coded form as well. Depending on the position of a switch 12, which is shown symbolically in the drawing and can consist of several gates corresponding to the number of bits of the binary coded angle values, either the angle input member 10 or the angle input member 11 is connected to a first input 13 of an adder 14, the second of which Input 15 is connected to the output of an accumulator 16 and the output of which is connected on the one hand to the input of the accumulator 16 and on the other hand to the input of a function generator 17. The function generator 17 is followed by a digital / analog converter 18, which is connected on the output side to the memory inputs of six sample and hold circuits 19 to 24. A low-pass filter 25 to 30 is connected to each of the sample-and-hold circuits 19 to 24, and an amplifier 31 to 36 is connected downstream of each of these. The amplifiers 31, 33 and 35 are voltage amplifiers and emit the output voltage U ₀ or U _c or U _x . Working as current amplifiers

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stronger 32, 34 and 36 supply the output current I _n or I- or

A clock generator 37 generates clock pulses with the frequency f. These get to a clock distributor 38, which on the one hand with clock pulse

f
sen the frequency f = - the accumulator 16 clocks and the switch

ter 12 controls and on the other hand clock signals f ^ to fg with the frequency - to the clock inputs of the sample and hold circuits 19 to

6th
24 outputs, whereby these are clocked cyclically.

PA 2O3O

909881/0535

The accumulator 16 and the adder 14 together with the angle input members 10 and 11 and the switch 12 form a number generator, the binary-coded phase step signals Ph emits to the function generator 17, which is coded in binary by the function generator 17 Instantaneous value signals and are converted by the digital / analog converter 18 into an analog signal. The number generator generates how further is explained in more detail below, for each of the output signals U,

I, U_, I _c , U _x and I _x in cyclic order phase step signals Ph, which are converted into binary-coded instantaneous value _{signals by the function generator 17 and into a corresponding analog signal proportional to a reference voltage U f} and converted into the associated Sample and hold circuits 19 to 24 are stored in analog form until the next cycle. The function generator 17 therefore outputs only an instantaneous value within each phase step and can accordingly be of simple construction. A ROM memory is preferably suitable as function generator 17, in which the associated instantaneous value of the sine function is stored for each occurring phase step signal. Since only the sine function of the 1st quadrant has to be written into the ROM memory and the sine values of the three other quadrants can be obtained by mirroring the 1st quadrant, a relatively small storage capacity is sufficient.

In the following, the method of operation will be explained with reference to the diagram of FIG the described signal generator explained in detail. In FIG. 2, the numbers 0 to 7 denote individual phase steps. The different clock signals are in turn with f, f and

os

f "to f". From the line labeled S is the 1 ο

The position of the switch 12 can be seen in the individual phase steps. In the line Ph is the respective value of the phase step signal Ph at the output of the adder 14 and in the line A is the each value stored in the accumulator 15 is entered.

To make it easier to understand, it is initially assumed that the switch 12 is permanently in the 121 ° position. Through a Clock pulse of the clock signal f at phase step 1, the phase step signal Ph assumes the value 0 °, this value is stored in the accumulator PA 20 3O

909881/05 3 5

mulator 16, the function generator 17 forms the associated sine value in binary coded form and the digital / analog converter 18 in analog form, at the clock input of the sample-and-hold memory 19 appears a clock pulse of the clock signal f and the analog value assigned to the output voltage U stored in the sample and hold circuit 19. At the next clock pulse of the clock signal f, ie at phase step 3, the value 121 ° of the angle input element 11 is added to the old value 0 ° of the accumulator 16 in the adder 15, the new value 121 ° is transferred to the accumulator 16 and the corresponding output voltage The sine value assigned to U_ is stored in the sample-and-hold circuit 21. In phase step 5, the _{sine value of 242 ° assigned to the output voltage U "T is transferred} to the sample-and-hold circuit 23,

in phase step 7, the Sirs assigned to the output voltage LL ·

The value of 363 ° = 3 ° is stored in the sample-and-hold circuit 19 etc.

If one looks at the formation of the output voltage U, for example

By itself, it seems that the number generator would do nothing else than increase the value of the phase step signal Ph by 3 ° with every sixth phase step. For each output voltage U _a , U _c and U, the number generator works as a separate triangle number generator. At the output of the sample-and-hold circuits 19, 21 and 23, step-shaped output voltages appear which approximate a sinusoidal curve and are each phase shifted by exactly 120 ° with respect to one another. The stepped output voltages are smoothed with the low-pass filters 25, 27 and and amplified to the required value with the voltage amplifiers 31, 33 and 35. ■

The sine values assigned to the output currents I ₁₃ , I_ and I _T are formed in the next phase step after the calculation of the sine value of the output voltage U, U_ or U- the corresponding phase, i.e. with the phase steps O, 2, 4, 6 ... . In the example shown, the switch 12 changes to the position φ at phase step 2, the adder 12 performs the addition ° + cp, the phase step signal Ph therefore takes the value φ

PA 2Ο3Ο

..- "■" 909881/0535

on, the function generator 17 outputs the associated sine value, a clock pulse of the clock signal f _o appears at the clock input of the sample-and-hold circuit 20 and the analog signal assigned to the output current I _D

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logvalue is stored in the sample and hold circuit 20. At the At the clock input of the accumulator 16, no clock pulse of the clock signal f appears in phase step 2, so that the value φ does not enter the Accumulator 16 is stored. In phase step 4, how it can be seen from the drawing, which is assigned to the output current I_ Sine value of 121 ° + φ into the sample-and-hold circuit 22, in phase step 6, the sine value of 242 ° + cp assigned to the output current I is stored in the sample-and-hold circuit 24 etc. The resulting stepped output voltages of the Sample and hold circuits 20, 22 and 24 are used with the low pass filters 26, 28 and 3O smoothed and with the current amplifiers 32, 34 and 36 transformed into corresponding currents of the required strength .

The signal generator described thus forms a voltage _{triangle U 1,} U ₅ , U and a current triangle I _R , I ₅₁ I _Jt which rotate counterclockwise and are rotated against each other by the angle φ. Although the number generator executes steps of 121 ° and not 120 °, the triangles are exactly equilateral because the corresponding sine value is sampled correspondingly later. As a result of the delayed sampling of the sine values of the output currents I,

ΓΛ

I and I _{T in} relation to the sine values of the assigned output voltages U, U _c and U, the current triangle is not rotated by the angle φ in relation to the voltage triangle, but in the example described by the angle φ-0.5 °. This fact must be taken into account when preselecting the angle φ in the angle input element 1O.

Said angle value of 121 ° of the angle input member 11 is to be understood only as an example and depends on the desired Fineness of the staircase curve of the analog signals at the output of the sample and hold circuits 19 to 24. Of course, can the angle value of the angle input member 11 is also smaller than 120 °

PA 2030

909881 / Q535

so that the voltage and current triangles rotate clockwise. In an 8-bit binary system, this angle value becomes preferred represented by the binary number O1O1O1O1, which

Corresponds to an angle of «119.5 °.

In the example shown, the digital / analog Waridler 18 has a reference voltage input 39 which is connected _{to a reference voltage source U f.} The analog signal at the output of the digital / analog converter 18 is proportional to the reference voltage, so that the amplitude values of all output voltages and output currents can be influenced jointly by changing the reference voltage. If the reference voltage input 39 can be connected to several adjustable reference voltage sources via a multiple switch controlled by the clock distributor 38, the amplitude values of the output voltages U ₀ , U_ and U -, and those of the output currents I, I_ and I can be set independently of one another by changing the reference voltages. Automatic readjustment of the output signals based on their effective values is possible if the voltage amplifiers 31, 33 and 35 and the current amplifiers 32, 34 and 36 are connected to an effective value measuring device whose output signal controls the reference voltage sources. Automatic readjustment of the phase angle is also possible by connecting a voltage amplifier 31, 33, 35 and a current amplifier 32, 34 of the same phase to a phase angle measuring device whose output signal controls the angle input element 1O.

In FIG. 3, the same reference numerals as in FIG. 1 indicate the same parts. Instead of the sample and hold circuits 19 to 24 (FIG. 1), the signal generator according to FIG. 3 has digital Read-write memory (RAM) 39 to 44, their memory inputs to the function generator 17 and their clock inputs to the clock distributor 38 are connected. Each of the read / write memories 39 to 44 is followed by a digital / analog converter 45 to 50, the output of which leads to one of the low-pass filters 25 to 3O.

^PA2O3 ° 909881/15535

The signal generator according to FIG. 3 is in comparison to that somewhat more complex according to FIG. 1, but has the advantage that the operating speed of the digital / analog converter 45 to 50 must be less than that of the digital / analog converter 18th

The digital / analog converters 45 to 50 advantageously have reference voltage inputs for connecting a reference voltage with which the amplitude values of the output voltages and output currents can be set or regulated. Furthermore, it is advantageous to connect an adder upstream of the function generator 17 which allows an angle signal to be added to the phase step signal Ph, in order to additionally influence or readjust the phase angle of the output voltages and output currents.

The described signal generators are advantageously used as three-phase voltage and three-phase power generator used to calibrate electricity meters.

PA 2Ο3Ο

909881 / ÖS35

Claims (10)

PATENT CLAIMS ( 1.J Signal generator for generating sinusoidal output signals with a predetermined mutual phase position, with a number generator controlled by a clock, a function generator and at least one digital / analog converter, the number generator sending binary-coded phase step signals to the function generator, which are coded in binary by the function generator Instantaneous value signals and are converted into an analog signal by the digital / analog converter, characterized in that the number generator (10 to 16) for the cyclical generation of each of the output signals (U _o ; I _n ; U ₅ ; I _s ; U _T ; I _T ) assigned phase step signals (Ph) is set up that each output signal (U _D ; I ₀ ; U ₁ -; I_; U-, I _T ) is connected to the digital / analog converter (18) or to the function generator (17) Memory (19 to 24; 39 to 44) is assigned and that a clock distributor (38) connected to the clock generator (37) is arranged for the cyclical clocking of the memories (19 to 24; 39 to 44) is. 2. Signal generator according to claim 1, characterized in that the memories (19 to 24) are sample-and-hold circuits and that the digital / analog converter (18) all output signals (U_; I _R ; Ug; I _s ; U _T ; I_) is assigned jointly. 3. Signal generator according to claim 1, characterized in that the memories (39 to 44) are digital read-write memories and that each memory (39 to 44) is followed by a digital / analog converter (45 to 5O). 4. Signal generator according to one of claims 1 to 3, characterized in that that the number generator (1O to 16) from at least one angle input member (10; 11), an adder (14) and one Accumulator (16) consists, the angle input member (1O "; 11) to a first (13) and the output of the accumulator (16) is connected to a second input (15) of the adder (14) and the output of the adder (14) to the input of the Accumulator (16) is connected. PA 2Ο3Ο 9 0 9 8 8 1/0535 5. Signal generator according to claim 4, characterized in that two angle input members (10; 11) via one of the clock generator (37) controlled switch (12) are connected to the first input (13) of the adder (14). 6. Signal generator according to claim 2, characterized in that a reference voltage input (39) of the digital / analog converter (18) via a multiple switch controlled by the clock distributor (38) Can be connected to at least two adjustable reference voltage sources is. 7. Signal generator according to one of claims 1 to 6, characterized through three via one low-pass filter each (25; 27; 29) to one the memory (19; 21; 23) or one of the digital / analog converters (45; 47; 49) connected voltage amplifiers (31; 33; 35) for Generation of a voltage triangle and by three each via a low-pass filter (26; 28; 3O) to one of the memories (2O; 22; 24) or a current amplifier connected to the digital / analog converter (46; 48; 50) (32; 34; 36) for generating a current triangle. 8. Signal generator according to claims 6 and 7, characterized in that that the voltage amplifier (31; 33; 35) and the current amplifier (32; 34; 36) are connected to an effective value measuring device whose output signal controls the reference voltage sources. 9. Signal generator according to claim 7, characterized in that in each case a voltage amplifier (31; 33; 35) and a current amplifier (32; 34; 36) are connected to a phase angle measuring device, the output signal of which controls the angle input element (10). 10. Use of the signal generator according to one of claims 1 to 7 as a three-phase voltage and three-phase current generator for Calibration of electricity meters. PA 2030 909881/0535