WO2009030369A1

WO2009030369A1 - Device and system for processing a voltage by means of signals

Info

Publication number: WO2009030369A1
Application number: PCT/EP2008/006837
Authority: WO
Inventors: Ingo Baetz; Waldemar Lau
Original assignee: Abb Ag
Priority date: 2007-08-30
Filing date: 2008-08-20
Publication date: 2009-03-12
Also published as: EP2181490A1; DE102007041247A1; CN101790826B; CN101790826A; DE102007041247B4

Abstract

The invention relates to a device (1) for processing an electrical input voltage (30, 50) by means of signals, exactly one value of an electrical output voltage (34, 54) being assigned to each value of the input voltage using a partially linear assignment function. Said assignment function has at least two neighbouring assignment ranges (60_1 60_n), which can be set by respective limiting voltages (31_1 31_n, 51_1 51_n). The assignment function in the assignment range (60_1 ) with the lowest value for a limiting voltage (31_1, 51_1 ) is a gradation function, defined by a gradient and an offset and the assignment function of each additional assignment range is achieved by linking the assignment function of the neighbouring assignment range having the next smallest value for the limiting voltage to another gradation function. The invention is characterised in that: it comprises at least one threshold value module (10_1,... 10_n, 13_1,... 13_n), which provides a respective output voltage (32_1,... 32_n, 52_1,... 52_n) for the threshold value module from the input voltage (30, 50) and a pre-definable limiting voltage (31_1,... 31_n, 51_1 51_n), said output voltage being fed both to a master module (11, 14) and an output module (12, 15); the master module (11, 14) adds a voltage that results from the respective output voltage (32_1,... 32_n, 52_1,... 52_n) for the threshold value to the input voltage (30, 50) as an offset and said totalled voltage is fed to the output module (12, 15) as an auxiliary voltage (33, 53). The output module multiplies this auxiliary voltage with a factor resulting from the respective output voltages (32_1,... 32_n, 52_1,... 52_n) for the threshold value module, said factor corresponding to the respective gradient of each gradation, to produce an output voltage (34, 54).

Description

Device and system for signal processing of a voltage

description

The invention relates to a device for signal processing of an electrical input voltage, wherein each value of the input voltage is associated with a piecewise linear assignment function exactly one value of an electrical output voltage, wherein the assignment function has at least two respectively adjacent assignment regions, which are adjustable by a respective limit voltage in which the assignment function in the assignment field with the lowest value of a limit voltage is a degree function defined by a slope and an offset, wherein the assignment function of each further assignment area is the combination of the assignment function of the respectively adjacent assignment range, which is the next smaller value of Boundary voltage results, with another degree function.

It is well known that for overload protection of electrical loads, in particular of asynchronous motors, calculation models are used to emulate the heating. Input variables of such calculation models are usually measured values which describe the time profile of the three phase currents of the A synchronous motor. Asynchronous motors can have rated values of a few kW up to several MW

The heat development in an asynchronous motor is dependent, among other things, on the time, the power which is obtained as a thermal input at its internal ohmic resistances, as well as other thermal influencing variables, such as heat capacity. capacity, thermal conductivity, heat radiation and / or ambient temperature. These influencing factors must be taken into account when implementing a calculation model corresponding to the desired accuracy of the calculation model.

In particular, for calculating the thermal input of power, it is advantageous to perform this according to the known formula p (t) = i ² (t) * R, where p (t) the instantaneous power, i (t) the instantaneous current and R the equivalent effective resistance within the asynchronous motor is where the thermal power dissipation occurs. These quantities are usually available by measurement.

Consequently, for safe and simple implementation of thermal overload protection in an overload protection device, for example in an overload relay, squaring of the measured current signal of at least one of the three phase conductors is necessary. Usually, such a squaring is done by means of a well-known diode circuit. A disadvantage of this approach, however, is that the ambient temperature significantly affects the diode circuit, the accuracy of the thus determined sizes significantly decreases.

Based on this prior art, it is an object of the invention to provide a device and a system for signal processing, in particular the squaring, an electrical variable whose transfer function is not or only to a very limited extent dependent on the ambient temperature.

This object is achieved by a device for signal processing of an electrical voltage with the features specified in claim 1.

Accordingly, the device for signal processing of an electrical voltage of the type mentioned above characterized by the fact that at least one limit value module is present, which provides a respective Grenzwertmodulausgangsspan- voltage from the input voltage and a respective predetermined limit voltage, which is fed to both a basic module and an output module in that the basic module outputs to the input voltage in each case a voltage resulting from the respective limit module output voltage as an offset added and this sum voltage is supplied as an auxiliary voltage to the output module, which multiplies this voltage with one of the respective Grenzwertmodulausgangs- resulting, the respective slope of the gradients corresponding factor and provides as an output voltage.

The transfer function is therefore divided by the device according to the invention into a plurality of allocation areas, within which the assignment of an output value to an input value of the voltage corresponding to a degree function, characterized by an offset and a slope, respectively. The respective upper voltage limit value of an allocation range is determined by a predefinable voltage value, the lower voltage limit value corresponds to the upper limit value of the adjoining assignment range below. The lowest allocation area is unlimited downwards, the highest allocation area is unlimited upwards.

The number of assignment ranges results from the number of limit value modules increased by the number one, wherein according to the invention at least one limit value module is present, resulting in a minimum of two assignment ranges. By means of a correspondingly high number of limit value modules, an arbitrarily high accuracy of the assignment function to be displayed can be realized in an advantageous manner.

Each grade is characterized by an offset and a slope. The respective offsets are determined by the basic module, the gradients of the respective grades by the output module.

In particular, the realization of the device according to the invention by standard electrical components, such as a resistor, a capacitor or an operational amplifier, allows a robust construction and high independence of the mapping function of the ambient temperature, with any temperature dependencies of the standard components compensate each other. In this way, an arbitrarily accurate assignment function can be realized, in particular a second-order origin parabola, which is suitable for achieving the squaring of a voltage signal.

Advantageously, the input voltage supplied to the device according to the invention is proportional to the measured load current of at least one phase of an asynchronous motor.

In this way, it is particularly easy to determine the thermal power input into an asynchronous motor.

In a further embodiment of the device according to the invention, the signal of the input voltage is previously rectified, provided that the assignment function to be represented supplies the same values of the output voltage for equal input voltages in terms of magnitude. This is the case, for example, with a second-order origin parabola function.

In this way, the effort to replicate the assignment function is particularly low. Only the respective positive or negative range of the function is to be approximated by degrees.

In a further development of the embodiment, a plurality of devices according to the invention for signal processing of an input voltage are arranged in parallel.

It is thus possible to determine the thermal input caused by all three phases of an asynchronous motor, in particular in the unbalanced load state.

It is particularly advantageous if the device according to the invention for further processing an electrical voltage is followed by an evaluation device.

By this evaluation, for example, based on the characteristics of the A synchronous motor and based on the current through the leads of the asynchronous motor proportional and squared signals a determination of the registered thermal power possible. Based on a thermal model, the temperature of the asynchronous motor can be determined as a function of time in a further step based on integration over a certain period of time. In this way, a thermal overload protection of the asynchronous motor can be realized, which initiates a shutdown of the asynchronous motor in case of overload.

In a further advantageous embodiment, the determined temperature of the asynchronous motor is provided from the evaluation device as an output variable.

In this way, the device and / or individual modules have at least one standard electronic component, for example a resistor, a capacitor, a diode and / or a differential amplifier. By using such standard components, the construction and / or linking of the individual modules can be realized in a particularly simple and robust manner.

In a further development of the subject invention, one and / or a plurality of modules together with components which continue to be useful for the use of the device, for example one or more fuses, switching devices and / or display devices, are arranged in a common housing.

In this way, the number of required for the protection and / or monitoring of one or more electrical loads, in particular asynchronous motors, total components is reduced and the assembly or maintenance of the device is simplified.

The modular construction of the device in a plurality of housings is particularly favorable if further functionalities are to be implemented for the further protection and / or monitoring of one or more electrical loads, in particular asynchronous motors. These functionalities share a common part of the voltage signals available in the device. Such a modular construction advantageously reduces the number of individual modules and / or components required. In an advantageous embodiment, additional functionalities are integrated into the same housing as the device according to the invention. This is particularly favorable if several functionalities are to be used predominantly in common, for example protection against thermal heating in the case of an asynchronous motor and unbalanced load protection.

Thus, the number of housings used is further reduced in a favorable manner.

In a further embodiment, the housings, in which individual and / or a plurality of modules and / or components are arranged, have as flexible connection possibilities as possible, for example at least one screwable and / or clampable connection possibility. A common, pluggable connection bus system for information, current and / or voltage transmission is also conceivable.

Thus, the modular design significantly reduces the handling of one or more housings.

The object is further achieved by a system for calculating the power of a thermal one-day in an asynchronous motor, wherein a measurement signal of the current is provided by at least one of the three supply lines of the asynchronous motor in the form of a proportional thereto voltage signal, characterized in that the voltage signal on the input side of a device for signaling Processing of an electrical voltage according to claims 1 to 14 made available and squared by the device and that the squared voltage signal can be linked by means of an evaluation device with other parameters.

Thus, an effective electrical power is determined in an advantageous manner from the multiplication of the voltage signal with, in particular, the equivalent ohmic resistance of the asynchronous motor, which corresponds to the thermal input.

Further advantageous embodiment possibilities can be found in the further dependent claims. Reference to the embodiments illustrated in the drawings, the invention, further embodiments and other advantages will be described in detail.

Show it:

1 is a schematic diagram of the device for signal processing of an electrical input voltage,

Fig. 2 shows an example of a mapping function and

3 shows a circuit example of a device with three allocation regions.

FIG. 1 shows a block diagram of an exemplary embodiment of the device 1 according to the invention with which a piecewise linear function having a plurality of allocation regions is realized. An input voltage 30 is supplied to a plurality of limit value modules 10_1,..., 10_n as the first limit module input quantity, although in principle any number of these limit value modules 10_1, 10_2... 10_n can be installed / connected in parallel and in this way an arbitrarily accurate approximation allow the assignment function. Each limit value module 10_1,... 10_n is supplied with the individually predefinable limit voltage 31_1,... 31_n as the second limit value module input variable. If the value of the input voltage 30 is greater than the respective predefinable limit voltage 31_1,... 31_n, then the relevant limit value module 10_1,..., 10_n outputs a first voltage value as limit value module output quantities 32_1,..., 32_n, otherwise a second voltage value in each case, which is preferably OV. As an alternative to the real voltages, voltage information is also conceivable, for example digitized numerical values.

The minimum number of limit value modules is logically one, so that this results in a minimum of two assignment ranges, namely a first one for all values of the input voltage which is less than or equal to the predefinable limit voltage and a second for those input voltage values which are greater than the threshold voltage.

The input voltage 30 is further supplied to a basic module 11. Further input variables for the basic module 11 are the limit module output variables 32_1,... 32_n. In the basic module 11, 30 predefinable offsets are added to the input voltage, namely exactly one offset per limit module output variable 32_1,... 32_n. The height of the respective offset for the respective limit module output variable 32_1,... 32_n and a base offset can be defined in the basic module or stored as values. Thus, by linking the different offsets in the different allocation areas for each allocation area a separate offset can be realized. The output of the basic module 11 is an auxiliary voltage 33 which is supplied to an output module 12.

Further input variables for the output module 12 are the limit value module output variables 32_1,... 32_n of each limit value module 10_1,... 10_n. The output of the output module 12 is an output voltage 34, which results from the combination of the auxiliary voltage 33 with a predeterminable in the output module basic multiplication factor. Another multiplication factor, by which the ratio of the output voltage 34 to the auxiliary voltage 33 can be influenced, results from the output module 12 supplied Grenzmodmodulausgangsgrößen 32_1, ... 32_n. Each of the aforementioned input variables is assigned a separate multiplication factor that can be specified in the output module 12. Thus, by combining the different multiplication factors in the different assignment regions, a separate multiplication factor can be realized for each assignment region, which corresponds to the slope of the straight line of the assignment function.

In this way, a predeterminable assignment function between the input voltage 30 and the output voltage 34 is realized. The voltage values for such a device according to the invention are usually between 0V and 10V.

2 schematically shows a diagram of an assignment function of an exemplary output voltage 44 to an exemplary input voltage 40 with three exemplary limit voltage 41_1, 41_2, 41_3 and the resulting output voltage. Four assignment regions 60_1, 60_2, 60_3, 60_4. The respective allocation regions and the respective assignment functions are selected such that an approximation of a second-order pararelax is used, as used for squaring a signal. The negative branch of the parabola is not shown in this example, because the imaginary input signal is assumed to be rectified in this case and thus only values of the exemplary input voltage 40 greater than or equal to zero can occur.

3 shows a concrete circuit example of a device according to the invention for signal processing of a further input voltage 50, wherein two further limit value modules 13_1, 13_2 are shown.

The further limit value modules 13_1, 13_2 are implemented in this example by a commercial operational amplifier in each case, in the illustrated example a first N3 for the further first limit value module 13_1 and a second N4 for the further second limit value module 13_2. The power supply of the operational amplifier is effected by a marked connection VCC. The specification of a further first limit voltage 51_1 and a further second limit voltage 51_2 is effected by a separate voltage source, which is not shown in more detail.

Another basic module 14 also has an operational amplifier, in this case N1. The gain of the operational amplifier fixed by the resistors R7 and R8 is compensated by the resistor divider R1 and R2, so that the gain of the further basic module 14 is one. By a suitable choice of the resistors R1, R2, R7 and R8, however, this factor can be changed as desired. The offsets are taken into account via the resistors R3 to R6, wherein R5 and R6 take into account the base offset of the further basic module 14, and R3 or R4 the offset determined by the further modules 13_1 and 13_2, respectively. The further basic module 14 provides another output module 15 with a further auxiliary voltage 53. The further output module 15 also has an operational amplifier, namely N2, in this example. The basic amplification factor of the further output module 15 is determined by the resistors R11 and R12. This factor can still be changed by a parallel connection of the resistors R9 and / or R10 to R11. Connected in series with R9 and R10 are in each case the transistors V1 and V2 whose conduction values can depend on the further limit module output voltages 52_1, 52_2 supplied to the further output module 15 and can either assume the state of conducting or nonconducting.

LIST OF REFERENCE NUMBERS

I Device for processing an input voltage 10_1 first limit module

10_2 second limit module

10_n nth limit module

I I basic module

12 output module

13_1 another first limit module

13_2 further second limit module

14 additional basic module

15 additional output module

30 input voltage 31_1 first limit voltage

31 _2 second limit voltage 1 _n nth limit voltage 2_1 output voltage of the first limit module 2_2 output voltage of the second limit module 2_n output voltage of the nth limit module 3 auxiliary voltage 4 output voltage 0 exemplary input voltage 1 _1 exemplary first limit voltage 1 2 exemplary second limit voltage 1 _3 exemplary third limit voltage 4 exemplary output voltage 0 further input voltage 1_1 further first limit voltage 1 2 further second limit voltage 2_1 further output voltage of the first limit value module 2_2 further output voltage of the second limit value module 3 additional auxiliary voltage 4 further output voltage _1 first allocation area_2 second allocation area_3 second allocation area_4 fourth allocation area_n nth allocation area

Claims

claims

1. Device (1) for signal processing of an electrical input voltage (30, 50), wherein each value of the input voltage based on a piecewise linear assignment function exactly one value of an electrical output voltage (34, 54) is assigned, wherein the assignment function at least two each adjacent allocation areas (60_1 60_n), which are adjustable by a respective limit voltage (31_1, ..., 31_n, 51_1 51_n), wherein the assignment function in the assignment region (60_1) with the lowest value of a limit voltage (31_1, 51_1) is a degree function, which is defined by a slope and an offset, wherein the assignment function of each further assignment area results from the combination of the assignment function of the respectively adjacent assignment area, which has the next lower value of the limit voltage, with a further degree function, characterized in that at least one limit value module (10_1, ... 10_n, 13_1, ... 13_n) is present, which from the input voltage (30, 50) and a respective predeterminable limit voltage (31_1, ... 31_n, 51_1, ..., 51_n) a respective Grenzwertmodulausgangsspannung (32_1, ... 32_n, 52_1, ... 52_n) which is supplied to both a basic module (11, 14) and an output module (12, 15) that the basic module (11, 14) to the input voltage (30, 50) in each case one of the respective limit module output voltage (32_1, ... 32_n, 52_1, ... 52_n) resulting voltage added as an offset and this sum voltage as an auxiliary voltage (33, 53) is fed to the output module (12, 15) which multiplies this by a factor corresponding to the respective gradient of the grades from the respective limit module output voltages (32_1,... 32_n, 52_1,... 52_n) and makes them available as output voltage (34, 54).

2. Device (1) according to claim 1, characterized in that the input voltage (30, 50) is proportional to a measured current.

3. Device (1) according to claim 1 or 2, characterized in that the input voltage (30, 50) is rectilinear.

4. Device (1) according to one of the preceding claims, characterized in that a plurality of assignment functions can be represented by a plurality of individual devices arranged in parallel.

5. Device (1) according to any one of the preceding claims, characterized in that at least one output voltage (34, 54) is supplied to an evaluation module.

6. Device (1) according to claim 5, characterized in that a value proportional to an electrical power can be determined by the evaluation module.

7. Device (1) according to claim 6, characterized in that the determinable by the evaluation module of the electrical power proportional size over a certain period of time is integrally processed further.

8. Device (1) according to claim 7, characterized in that at least one output variable of the evaluation module represents the thermal heating of an electrical load.

9. Device (1) according to one of the preceding claims, characterized in that at least one module has at least one electronic component.

10. Device (1) according to one of the preceding claims, characterized in that a plurality of modules are arranged in a single common module.

11. Device (1) according to one of the preceding claims, characterized in that the modules and / or components used are arranged in a common housing.

12. Device (1) according to claim 8 to 11, characterized in that the modules used and / or further components are arranged in at least two different housings.

13. Device (1) according to one of the preceding claims, characterized in that further modules and / or components for further functionalities are integrated in at least one housing and / or integrated.

14. Device (1) according to claim 11 to 13, characterized in that a housing has at least one klemmbare plug connection option and / or a screw connection option for connecting lines.

15. System for calculating the power of a thermal one-day in an asynchronous motor, wherein a measurement signal of the current is provided by at least one of the three supply lines of the asynchronous motor in the form of a voltage signal proportional thereto, characterized in that the voltage signal on the input side of a device for signal processing of an electrical voltage to Claims 1 to 14 is provided and squared by the device and that the squared voltage signal can be linked by means of an evaluation device with other parameters.