DE20007113U1 - Regulation for an electric motor, electric drive, electric pump - Google Patents

Description

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813-55.345G-AP/Kf

200 07 113.0 -4 Sep 2000

Control for an electric motor, electric drive, electric pump

The invention relates to a control system for an electric motor, an electric drive and an electric pump according to the preambles of the independent claims.

Figure 6 shows a system that is currently used, for example, to control circulation pumps in heating systems. 11 is an electric motor that drives a circulation pump. The electric motor is located directly on the heating fluid circuit. It is usually operated with mains voltage (230 V AC). Previously, the motor 11 was controlled by a pump relay that was usually located at a distance.

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68 is only switched on or off via the power supply lines 63. The switching takes place according to the instructions of a heating control 67. In recent times it has been considered desirable for many reasons to be able to operate the motor 11 in partial load operation. For this purpose, a control or regulation was provided such that the power supply of the electric motor 11 is suitably switched via a switch 65 in the immediate vicinity of the electric motor 11. They receive control signals from a control unit 66, which generates these control signals according to setpoints that it receives from outside via a line 64. The line 64 thus runs functionally parallel to the power supply 63. The signal line 64 usually carries signal levels (digital signals, e.g. 0 V or 5 V). The signals are generated by a heating control 67. A disadvantage of this technology is that signal lines have to be routed over comparatively long distances (from the heating control to the pump). This makes the system susceptible to interference. In addition, the cable 64 itself must be designed with plugs and connections and, if necessary, with optocouplers to prevent electrical loops. The design is therefore complex.

The object of the invention is to provide an electric motor control, an electric drive and an electric pump which operate with low interference and which require little electromechanical effort.

This object is achieved with the features of the independent claims. Dependent claims are directed to preferred embodiments of the invention.

A control system according to the invention for an electric motor has a power supply which supplies the power for the electric motor, a control device for the electric

tromotor and a setpoint receiving device for the control device, wherein the setpoint receiving device is connected to the power supply and determines the setpoint for the control device according to the time course of an electrical variable of the power supply and feeds it to the control device.

In addition to the power for the motor, the power supply can also supply the power for the control device or for the control. The electric motor can be a motor operated with mains voltage (230 V AC). However, the system is also suitable for three-phase motors or DC motors, for example. The setpoint is preferably determined by observing the time curve of the voltage of the power supply.

The power supply is used in practice for the coded transmission of the setpoint. The transmission is preferably not continuous. Instead, the setpoint is stored there after it has been transmitted to the control system and used for control. It can be overwritten when a new setpoint has been transmitted. This eliminates the need for signal lines 64 on the hardware side and, from a functional point of view, the low-level signal transmission in electrically harsh environments. This improves the transmission quality and eliminates the mechanical effort for additional cabling, connectors, interfaces, optocouplers and the like.

Individual embodiments of the invention are described below with reference to the drawings. They show:

Fig. 1 functional block diagrams of components of the invention,

Fig. 2 is a circuit block diagram of a control system and an electric drive,

Fig. 3 shows a characteristic curve for the transmission of a setpoint, Fig. 4 shows a course of the transmission of a setpoint, Fig. 5 shows an example of a method for the transmission of a

setpoint, and
Fig. 6 is a block diagram of the state of the art.

Fig. 1b shows a control system 2 according to the invention. It can be constructed as a module 2. The motor 11 is connected to the control system (with three conductors in the case of mains voltage, namely phase, neutral and protective conductor). The control system has a power supply 12, which again has phase, neutral and protective conductor. The power supply can be looped through the control system, but can have one or more switching elements 16 and/or measuring elements 13a. In the embodiment shown schematically, the electric motor 11 drives a pump 10. This can be a circulation pump of a heating system.

17 symbolizes a setpoint receiving device that is connected to the power supply 12 or to individual conductors from it. In the embodiment shown, it is connected between the phase and neutral conductors. It "monitors" the power supply and, based on this observation, determines the setpoint W _so n for controlling the electric motor 11. The setpoint receiving device 17 can have a memory 18 in which the setpoint W _so n is stored after it has been determined. It can then be stored there, for example, until the system is switched off or until a new setpoint W _so u is transmitted.

13a is a small measuring resistor which measures the pump current by creating a comparatively small voltage drop across it. 13b symbolizes a signal calibration which converts the voltage curve in front of the measuring resistor 13a into an actual value W ist which _is comparable to the setpoint W _so n. The control difference (W _so n-Wi _St ) is formed at the summer 14 and is entered into the controller 15. The controller 15 then controls one or more elements 16 which are located in the power supply 12 for the motor 11. The elements 16 can be, for example, switches, semiconductor switches, thyristors, GTOs, or the like. Contrary to what is shown, the actual value can also be measured using a speed sensor or similar, for example. The elements or switching elements 16 can also be in the neutral conductor.

Although Fig. Ib shows a control in the technical sense and this description and the claims also refer to a control, it is expressly pointed out that this can certainly mean a control in the technical sense, as shown in Fig. Ib and described with reference to it (setpoint, measurement of the actual value, formation of the control difference, controller, control of an actuator). In other applications, in particular when the requirements for accuracy are not so strict, it is possible (in the technical sense) to switch from a control to a control (i.e. without feedback, measurement of the actual value W _ist and formation of the control difference). In the circuit diagram in Fig. Ib, components 13a, 13b and 14 would then be omitted and component 15 would be implemented differently. In the context of this description, the term "control" should generally also include the term control. Only if and insofar as explicit reference is made to a control in the technical sense (with feedback and formation of the control difference), should a feedback control of the same kind also be used in the

The patent claims originally filed speak of a "regulation", but in the technical sense they are intended to include both a regulation (with feedback, etc.) and a control (without feedback).

The controller 15 can be a PID controller. It can be programmable. It can output control signals for one or more switching elements 16. For example, the switching elements 16 can be controlled according to a phase control (influencing, in particular switching, the power supply for AC motors within individual half-waves). A pulse packet control can also be provided (passing or blocking individual half-waves or full waves). The pulse packet control has the advantage that it can be designed so that it only switches at the zero crossings of the AC power, so that overall a lower-noise operation is achieved.

The setpoint receiving device 17 evaluates the time course of one or more electrical variables of the power supply. For example, it can be designed in such a way that it responds to short, complete interruptions of the power supply. The coding rule for transmitting the setpoint can be designed accordingly. An example of this will be explained later with reference to Figures 1 and 4.

The setpoint receiving device 17 can, for example, evaluate the voltage curve of the power supply and then determine the setpoint. For example, the effective value can be considered. As far as temporal changes are considered, the setpoint receiving device 17 can have a time measuring device 19 in order to measure time curves over time.

The control can be a speed or power control, whereby a speed setpoint or a power setpoint is then specified accordingly.

Fig. la shows a control for the control from Fig. 1b. It has connections 3 which correspond to the connections 12 of the control 2. A pump relay 4 is provided which is controlled by a heating control 6 via a suitable signal format 5. The pump relay can switch the power supply completely on or off. If necessary, e.g. with semiconductor switches, intermediate values can also be set. The setpoint W _setpoint for the control in Fig. 1b is specified by the heating control 6. The relay or switch 4 is then controlled in accordance with a coding rule. In this way, those time profiles of an electrical variable of the power supply are generated which are determined and evaluated on the control side by the setpoint receiving device 17. A separate signal line 64 from the heating control 6 to the motor control 2 is no longer necessary. In general, the control 6 can be a control for any system. Here too, component 6 does not necessarily have to be a control in the technical sense (actual value recording, feedback, control difference formation) for the purposes of the invention. It can also be a control system, which, unless explicitly stated otherwise, is to be considered to be included in the term "control". If both component 6 and component 2 are controls in the technical sense (with feedback), control 2 can be subordinate to controller 6.

Before describing an embodiment that is more closely based on a hardware structure with reference to Fig. 2,

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With reference to Figures 3 and 4, possibilities for transmitting a setpoint are described.

Fig. 3 shows one way in which a setpoint can be transmitted from control 1 (Fig. la) to control 2 (Fig. 1b). It is assumed that heating control 6 has determined the setpoint using certain algorithms and knows it. Switch 4 is controlled using signal formatting 5 based on this setpoint. The "coding rule" shown in Fig. 3 is known to both control 1 and control 2. A system is shown in which a setpoint is transmitted by temporary changes (for example, interruption) in the power supply. The example relates to speed control; the setpoint Wsoii is to be understood as a percentage and can be between 20 and 100% of the maximum speed. The characteristic curve in Fig. 3 shows how setpoints to be used in the future (on the ordinate) correspond to a change in the power supply to be set. A stepped characteristic curve is shown in which different interruption durations t, plotted on the abscissa, correspond to different target values (on the ordinate). A stepped characteristic curve will inevitably arise in digital systems due to the quantization of digital data. However, the gradation can be coarser than the digital format would allow.

In the ideal system, T _max should correspond to a setpoint of 100% (i.e. full speed of the electric motor). The ordinate of Figure 3 shows the times T _mO d/ at which the voltage supply is modified, for example interrupted. Certain fractions of the modification time period can correspond to fractions of the maximum speed. The example in Figure 3 shows a linear relationship for the

Values of 20, 40, 60, 80 and 100% of T _max and W _so ii respectively. The relationship can, but does not have to, be linear. In order to provide usable recordings in real systems, recording windows can be provided around the discrete points which preferably do not overlap and, more preferably, are adjacent to one another. This means that values which deviate from the ideal values mentioned still lead to corresponding setpoint recognition. For example, a certain modification period around T _max /5 leads to the recognition of the setpoint W _3O ii equal to 20%. Very short modification periods T _mod can be ignored in order to mask out short transient disturbances. This is symbolized by the time range 30, while 31 is the actual characteristic curve range.

In fact, modification periods that are significantly longer than Tmax (surrounded by a tolerance window) can also occur. These are indicated by time windows 32 and 33, which extend beyond T _max with a time tolerance. If modification periods (e.g. interruptions) lie in this time range, they can be ignored for the purpose of determining the setpoint, for example, or a fault can be detected and suitable measures can be taken. 31 symbolizes the modification time range that is intended for the coded transmission of the setpoint W _setpoint from the control (Fig. la) to the control (Fig. lb). If the modification takes longer (e.g. time range 32), it can be ignored (similar to the durations in time range 30); if the interruptions are even longer (time range 33), a fault can be detected. The system can then, for example, be put into a defined idle state. In time range 32, new setpoints are not determined or they are ignored; those previously used continue to be used.

T _max in Fig. 3 can be in the range of a few seconds. It can be less than 10 s, preferably less than 4 s, more preferably less than 2 s. The short-term blankings will then hardly noticeably disturb the overall operation of the system to be driven. In general, T _max can be selected according to the requirements of the system to be controlled.

Fig. 4 shows the time course of the power supply at a moment when a setpoint is being transmitted. The current effective voltage Ueff is plotted on the ordinate above the time axis as the abscissa. In the example, it is usually assumed to be 230 V and initially maintained at a stable level (line 40). At time T ₀ , the heating control 6 finds it necessary to transmit a new setpoint. It controls the signal formatting 5 accordingly. This controls the pump relay or, in general, the influencing device 4 as appropriate. In the embodiment shown (Fig. 4), the effective voltage is briefly completely blanked out (period 41). At time To + 0.6 s, the relay 4 is closed again and the power supply continues with the conventional effective voltage (line 42). The setpoint receiving device 17 in the control 2 (Fig. 1b) detects the brief interruption and evaluates it in accordance with the characteristic curve in Fig. 3. If the characteristic curve of Fig. 3 is applied to the example of Fig. 4 and T _max is assumed to be 1 s in Fig. 3, a blanking time of 0.6 s _would lead to a setpoint W set of 60 %.

Instead of completely blanking the power supply, it is also possible to simply reduce it. This is symbolized by line 43 in Fig. 4. The effective value of the voltage received by control 2 would then not fall completely to zero, but would take up a fraction (e.g. 40%). This can be done by

suitable design of the influencing device 4 to 6. The influencing can, for example, be carried out in such a way that the effective value averaged over several periods of the alternating signal takes up a fraction. This can be done by blanking out individual oscillations. The voltage value under consideration during the influencing or modification (complete blanking of the power supply or modification to line 43 in Fig. 4) can also be observed and checked with safety margins.

Fig. 2 shows a block diagram of a circuit according to the invention. In general, in this description, the same reference numbers correspond to the same components. 21 is a voltage supply which provides a suitable power supply for the control components from the power supplied (generally alternating power). For example, a 5 V direct voltage (on line 22) can be generated from 230 V alternating voltage (available at the power supply 12). A capacitor 23 can be provided for further smoothing of the direct voltage. It can also be dimensioned such that, when the power supply is blanked for setpoint transmission, it ensures the same power supply for the subsequent components for a certain period of time, but at least for T _max and the subsequent periods 32 and 33 if necessary.

The control 2 has a circuit 24 which can have analog and/or digital components. Analog components can include converters (A/D converters or D/A converters) at the input and output of the circuit. A digital logic or a microprocessor can be located between them. The circuit 24 takes on the tasks of the setpoint receiving device 17, the control difference formation device 14 if present, the controller 15 and the memory 18.

true. In the embodiment shown, the circuit 24 receives the supply voltage via line 27 and evaluates it. The voltage 27 can be converted into a digital format, for example. In addition, the feedback 13a, 13b is also provided in order to determine an actual value. This actual value can also be converted into a digital format if necessary.

A wide variety of data can be stored in a memory 26, for example in particular the characteristic curve of Fig. 3, and other parameters for the circuit 24, in particular e.g. a program, if the circuit 24 contains a microprocessor. The circuit 24 then generates control signals for the actuator 16, with which the setpoint Wsoii can be set. The control signal can initially be in digital format and converted to analogue format if necessary. In the embodiment of Fig. 2, the actuator 16 is located between the motor and the measuring element 13a. To measure modification times of the power supply, the system clock of a digital circuit, if present, can be used in the circuit 24. The use of a measuring element in the control 2 has the advantage that no sensor (e.g. speed sensor) has to be provided on the motor itself. This eliminates the expense of the sensor and corresponding signal lines. Instead, the motor can simply be connected to the control 2 via its power connections (phase, neutral and protective conductor). As already explained above, the control 2 can be provided as a module that can be connected between the motor 11 and the heating control 6. It is also possible to provide the motor 11 and the control 2 together as a module. The control 2 can then also have a modular structure, but it can also be a conventional circuit board structure.

Fig. 5 shows a more complex scheme for setpoint transmission. It is implemented when incorrect transmissions are to be excluded as reliably as possible. The currently effective setpoint W _so ii is plotted against time on the abscissa on the ordinate. Initially, 20% of the maximum speed is assumed to be the prevailing setpoint. It is further assumed that brief interruptions are made at times 51, 52 and 53 as shown in Fig. 4. Theoretically, each interruption on its own could be sufficient to set a new setpoint (60% is assumed in the example), indicated by edges 54 and 55. However, the system is designed in such a way that a new setpoint is only permitted if it has been recognized several times in the same way within a certain time scheme. An example is shown that requires three detections to actually make a new setpoint W _so n effective. After the new value has been recognized for the first time, after a waiting time ti within a time window t2, a check is made again to see whether a corresponding setpoint value is transmitted. If this is the case, then, starting from this second transmission, a check is made again after the waiting time ti to see whether the setpoint value is transmitted a third time in the time window t2 (time 53). Only when this is the case is the new setpoint value (60%) actually set to take effect.

By further influencing the power supply by means of the influencing device 4, 5, 6, programming of the control 2, in particular the circuit 24 and the memory 26, can be provided. For this purpose, for example, a start sequence can be provided that implements a specific level and time scheme that is recognized as such in the control, whereupon the control is set to a write mode. By further, suitable influencing of the power supply, data can then be transferred.

This can, for example, relate to a checking algorithm (program), or a characteristic curve or similar. A final sequence can lead to the definitive writing. The data which is transmitted to the control 2 for programming the control or for writing into the memory 26 of the control 2 has been entered into the control 1 by suitable components. There, they are prepared for transmission by maintenance personnel, for example, and then transmitted in accordance with a convention known to both the control 1 and the control 2 by the interaction of the influencing device 4 to 6 and the control 2, in particular the setpoint recording device or the circuit 24.

If the control 2 alone is provided in a modular manner, it is preferably provided in the immediate vicinity of the electric motor 11. Control 2 and motor 11 can also be provided together as a module.

Claims (16)

1. Control system for an electric motor ( 11 ), with a power supply ( 12 ) which also supplies the power for the electric motor, a control device (13-16) for the electric motor and a setpoint receiving device ( 17 ) for the control device, characterized in that the setpoint receiving device ( 17 ) is connected to the power supply ( 12 ) and determines the setpoint for the control device in accordance with the time course of an electrical variable of the power supply and feeds it to the control device. 2. Control according to claim 1, characterized in that the setpoint receiving device determines the setpoint in accordance with the voltage curve of the power supply. 3. Control according to claim 1 or 2, characterized by a memory ( 18 ) for storing a setpoint value once determined. 4. Control according to one of the preceding claims, characterized in that the setpoint receiving device ( 17 ) has a time measuring device ( 19 ) for measuring the duration of a temporary voltage change. 5. Control according to one of the preceding claims, characterized in that it is a speed or power control, wherein the setpoint receiving device determines a speed or power setpoint. 6. Control according to one of the preceding claims, characterized in that it comprises a phase control and/or a pulse packet control. 7. Control according to one of the preceding claims, characterized in that it is constructed as a module ( 2 ). 8. Electric drive with an electric motor ( 11 ) and a control according to one of the preceding claims. 9. Electric pump with a pump unit ( 10 ) and an electric drive for the pump unit according to claim 8. 10. Electric pump according to claim 9, characterized in that the pump unit ( 10 ) and the drive are constructed as a module ( 2 ). 11. Circulation pump for a heating system, characterized by an electric pump according to claim 10. 12. Circulation pump according to claim 11, characterized in that the control and the electric motor are constructed as a module. 13. Control ( 1 ) for a controllable electric drive, with a power supply ( 3 ) for the drive, characterized by an influencing device ( 4-6 ) which temporarily influences the power supply for the electric drive for the purpose of the coded transmission of the setpoint value for the drive control. 14. Control according to claim 13, characterized in that the influencing device has a switch ( 4 ) for temporarily switching off the power. 15. Control according to claim 14, characterized by a control device ( 5 , 6 ) for the switch, which controls the switch in accordance with a predetermined code. 16. Drive control system with a control according to one of claims 1 to 7 and a control ( 1 ) according to one of claims 13 to 15.