DE102007017285A1 - Method for monitoring three-phase machine, involves supplying input parameters of converter unit, where one of these input parameters is commutating angle of three-phase machine to be operated - Google Patents

Abstract

The method involves supplying input parameters of a converter unit (2), where one of these input parameters is a commutating angle of a three-phase machine (4) to be operated. The input parameters are transformed into output parameters in the converter unit and the output variables of a three-phase machine are fed to operate them. The angular speed of the commutating angle is monitored and another transformation of the input parameters are implemented in the output parameters for verifying the transformation in the converter unit. An independent claim is also included for a device for monitoring the number of revolutions of three-phase machine.

Description

The This invention relates to a method of monitoring the speed of three-phase machines, it being the three-phase machines especially multi-phase synchronous, permanent magnet synchronous, Asynchronous or reluctance motors can act. In particular, refers the invention relates to production machines. Such production machines must, especially during maintenance, in a safe Condition can be offset. Furthermore, it is particular To avoid personal injury also required that the individual drives a predetermined maximum speed do not exceed. For this purpose are in the state of Technology various devices and methods for monitoring the known electrical drives.

In the DE 100 35 783 A1 a device for monitoring a measuring system of an electric drive is described. In this case, a measuring system for detecting a measured variable of the electric drive and a signal processing for error detection of this measuring system are provided. More precisely, a second channel for monitoring system variables in the current controller is set up there. As long as the field orientation of a voltage control variable remains within certain limits, it is assumed that the measured encoder position must be correct. For this type of monitoring, however, it is necessary that the control parameters are precisely matched to the engine to be controlled. This limits the reliability of the monitoring, since in many cases it is possible for monitoring to respond without cause, ie without the actual presence of a fault.

From the DE 43 30 823 C2 is a drive device with a safety device for special operation known. The course of a three-phase motor current is evaluated in order to determine the speed of the motor independently of the encoder. However, this can only be done reliably in the stationary operating state, with this stationary state being rather the exception in the case of highly dynamic servo drives. Thus, the reliability is not always given even with this method.

Of the The present invention is therefore based on the object, a method and a device for monitoring three-phase machines provide which reliable under working different operating conditions. In addition to a inexpensive and simple method or a corresponding inexpensive and simple device available be put.

This According to the invention by a method according to Claim 1 and an apparatus according to claim 12 achieved. advantageous Embodiments and developments are the subject of Dependent claims. In the inventive Method for monitoring three-phase machines and in particular such three-phase machines in which the three-phase machine over an inverter is operated in field-oriented control, become input variables of a first converter unit fed, one of these input variables is a commutation angle of the three-phase machine to be operated and wherein the input quantities in the first conversion unit be transformed into output quantities and these Output variables of the three-phase machine for operation be supplied to the same. In this case, the invention Angular velocity of the commutation monitored and a further transformation of the input variables into the output variables in a second converter unit for verifying the transformation in the first transducer unit carried out. Here are the output variables the three-phase machine advantageous not immediately available but previously further processed, such as by pulse width modulation and reinforcement.

More accurate that is, the rotating field rotation speed generated by the inverter using the coordinate transformation used Monitored commutation angle. It is proposed according to the invention that the coordinate transformation from the rotor related to the stator-related voltage, in particular in a second independent Calculator is preferably cyclically controlled to ensure that the monitored commutation angle the rotation of the Rotary field determined.

Prefers the further transformation is in one of the first converter unit independent second converter unit performed.

In modern three-phase servomotors with field-oriented control, the speed is usually calculated from the angular position, which is measured by means of position encoders. Since not all position transmitter for secure, two-channel evaluation own and a second encoder would mean an additional expense, is achieved by the inventive method that the second channel can be realized without a second encoder. Thus, the inventive method is in principle also safe Monitoring encoderless, speed-controlled drives suitable.

As a general rule require servo drives with integrated safety technology to achieve the standard level of safety in the industry a two-channel monitoring of a relevant movement size. This movement size may be the Speed, the position or the torque or the like act. Becomes The security achieved by two - channel, the allowed both channels should not be identical. in the Trap of encoderless speed control, the actual speed is through an engine model appreciated.

Of the Invention is thus based on the fact that there is a three-phase motor active can not turn faster than the speed of the applied Three-phase system, d. H. the field speed corresponds. More precisely Synchronous motors run exactly at this speed and asynchronous motors turn around the slip speed slower. So if the field speed (the rotating voltage vector) is safely monitored lies also the speed of the shaft in the safe area. It is important to take into account the field speed must be divided by the number of poles of the motor. This can be ensured especially for safety-related drives Be sure that the three-phase machine in question is not turns faster than allowed, and that way Danger of injury for example for the Operating staff are reduced. The invention Procedure is also related to externally imposed overspeed feasible. Here it should be noted that a three-phase motor, whose electric field is turning slower than the rotor itself, basically generates a braking torque. The engine is at Elimination of external forces, ie of get out, return to a safe work area.

As common in the art, so also in the inventive Method a three-phase current as the output of a Inverter generated. Basis for this generation is the transformation of the rotor-related voltage on the stator side using the commutation angle. This commutation angle is a multiple of the rotor position angle in systems with encoders, Increased by the fixed commutation offset in synchronous or the Slip on asynchronous motors. This is illustrated in detail below.

requirement for that the angular velocity of the commutation angle is equal to the speed of the feeding three-phase system, is that the most commonly implemented in software vector transformation error-free is working. It is precisely this vector transformation that is redundant in accordance with the invention monitored on different systems or converter units. It is preferred to carry out the transformations in the first transducer unit and to perform the transformation in the second converter unit different data processing programs used. In particular, different calculation methods come into use.

On This way can be particularly advantageous an independent Transformation in the two converter units and thus a very secure verification of the transformation. The voltage values resulting from the transformation still converted into so-called PWM (pulse width modulation) switching signals. However, this implementation can not change even if the function is incorrect or even increase the field speed cause, as in the PWM modulator no means for rotating the field are present. More specifically, in the context of pulse width modulation, no rotation operation carried out. Although are different types of disorders by the implementation do not rule out this lead but not to a speed increase, which in particular for the relevant aspect of operational safety is crucial.

Preferably The first converter unit and the second converter unit differ in at least one characteristic of each other. Particularly preferred different processors used for the converter units.

in principle it would also be possible, for example in the case of three-phase motors, the three voltage control variables behind the transformation to detect the rotating field and its Turning speed to use. However, this is less so advantageous because the voltage vector to be transformed is not constant is, but for example due to control operations changes in length and angle within certain limits. These angle changes are also transformed to the output and cause uneven rotation there of the voltage vector. Thus, the output voltage is not in each Case suitable for safe determination of the engine speed, because control technology justified, fast angle changes faulty interpreted as exceeding the set speed limit could become. This problem could be caused be corrected, taking into account the field angle the motor currents, for example by means of a motor model is corrected. This solution would be comparatively consuming.

Preferably become the output quantities transformed in the first converter unit and the outputs transformed in the second converter unit compared to each other. This comparison is particularly preferred crosswise. This will be the same in the second safety channel Transformation as executed in the active controller and the three output voltages are compared. When equality is the transformation is correct and the commutation angle is beyond doubt the speed determining size of the inverter generated rotating field and is thus for safe monitoring suitable.

alternative to or beside the comparison of the three output voltage values can also the voltage angles formed by each are compared, which means a reduction of the data to be exchanged.

at Another preferred method is the comparison of the output variables and from the voltage angle, each of the three voltage values is made. This is done here is no direct Comparison made.

For monitoring the encoder or in general the rotational speed of the controlled three-phase motor, which may be a PM synchronous motor, an asynchronous motor, a reluctance motor or the like, so that the internal control commutation angle is monitored. This commutation angle is, as stated above, in conjunction with the so-called coordinate transformation, the determining variable that causes the rotation of the voltage vector at the output of the controller. This voltage vector is usually represented by the phase voltages U _u , U _v , and U _w . Before the coordinate transformation, the voltage is present in the rotor-related components Ud (longitudinal voltage) and Uq (transverse voltage), which are constant variables regardless of the rotational speed.

Prefers the first converter unit and the second converter unit communicate in particular for the purposes of mutual surveillance. The converter units can communicate with one another via a bus system be connected. In another preferred method, the Commutation angle determined using a sensor. In this Trap is done so that monitoring in the drive. At this Variant preferably the first channel monitors the encoder and the second channel commutation. This monitoring is safe, if the encoder monitoring and commutation monitoring independent systems with different processors be performed. In practice, this can be achieved be that one of the two functions is not in the drive processor but realized in an FPGA. The required synchronization However, this is more difficult because in both channels independent Zeitbasen must be realized.

It However, it is also possible, both the encoder monitoring as well as to perform the commutation in the drive processor. In this case, a second processor is preferably used, which performs the redundant commutation monitoring. In this case, three monitors can be activated, from but only two run on different systems. there For example, the security processor can use dual-port RAM coupled to the drive processor.

There In this variant, the encoder is monitored and he through the Kommutierungsüberwachung additionally constantly controlled, a safe position can always be guaranteed become. However, it is also possible with a motor encoder supported system commutation monitoring to make externally. There is the above-mentioned monitoring processor, d. H. the processor of the second transducer unit, outside of the drive controller and is via a safe fieldbus (eg Sercos Safety, Profisafe). Here is the same Possibility of additional control of the encoder, so that a secure monitoring of the situation can take place.

Farther is also a monitoring in systems without motor encoder possible in the drive. In this case, the commutation monitoring is duplicate, d. H. next to the drive processor, the commutation performs and monitors (first channel) is a second processor to provide in the second converter unit, the for example, via dual-port RAM is coupled. there It is also possible that the monitoring processor located outside the drive controller and over a secure fieldbus, as mentioned above, is connected.

Thus, the second processor which performs the redundant monitoring of the commutation angle, the check of the coordinate transformation is either integrated in the drive or is located outside the drive and communicates with the drive via a safe fieldbus. It is also possible that the function of an external second processor, ie the second converter unit in a zen tral computer, which is assigned to several drives. In this embodiment, in this embodiment, the second converter unit monitors a plurality of three-phase machines, wherein the associated transformation is preferably carried out in each case for a plurality of three-phase machines. In sensorless systems, the commutation angle is preferably determined by means of a motor model.

Preferably is the function of the external second processor or the second Converter unit a subfunction of a higher-level controller. Furthermore, the input variables are preferred cyclically transmitted in their entirety to the second transducer unit.

For checking the coordinate conversion requires the security processor or the second converter unit cyclically the input values and the associated output values of the coordinate converter. Conveniently, the limited values are used as they are for a downstream one PPM modulator to be passed. It is possible that this check at fixed time intervals, for example every 1-4 seconds and preferably every 2 seconds is carried out. To determine the speed only the commutation angle needed, in which case each and every nth Value is used.

to Differentiation of the commutation angle, d. H. through education of Velocity of the commutation angle, the field velocity is calculated which is compared to the set limit. This will be in the Comparison to prior art methods except the number of poles no engine data needed and it must be no Engine model can be expected.

in principle can, as stated above, the second transducer unit or the security processor also monitor several drives. In this case it is possible that the drive cyclically the commutation angle and in predetermined circumstances, a data packet consisting of Input and output values of the coordination transformation, sends.

It However, it would also be possible, the input variables to pass sequentially to the second transducer unit. More specifically, the six data would be passed sequentially so that's a check after six each Cycles takes place. The monitoring processor can in case of error ensure network separation or the start-up lock of the relevant Actuate drive. The drive itself needed no additional hardware. This is the invention Method also ideal for compact servo motors.

The present invention is further directed to an apparatus for monitoring three-phase machines. This device has a first converter unit, which transforms input variables supplied to this first converter unit into output variables, wherein one of these input variables is a commutation angle of a three-phase machine to be operated and the output variables are used to operate this three-phase machine. According to the invention, the device has a second converter unit that can be operated independently by this first converter unit 12 on, wherein the second transducer unit 12 also the input variables supplied to this second converter unit are transformed into output variables, wherein one of these input variables is the commutation angle of the three-phase machine to be operated and that a comparison device is provided which determines the output variables output by the first converter unit or the variables output therefrom with the output variables output by the second converter unit or from these derived quantities.

Preferably this is the derived characteristic by the angle of the voltage vector, which is the output variables or the (three) voltage components is formed.

Preferably the device has a shutdown device, which is the three-phase machine in response to a specific outcome of the comparison between the output from the first converter unit outputs and the output from the second converter unit outputs in a safe state spends, for example, in terms the speed is reduced or switched off.

In contrast to the monitoring of a position sensor, the rotating field frequency does not provide any information as to whether the motor has been accelerated by external forces to higher speeds. However, this limitation is irrelevant in terms of the backup function. As mentioned in the introduction, it is precisely the dangerous movements emanating from the drive itself that are to be prevented, and thus, to ensure safety, it must merely be ensured that the rotational speed was below the limit value at the time the safety function was activated. In the case of maintenance, this is not a restriction since the machine is typically shut down before maintenance in safe mode. If the safe speed limit should be constantly active in normal operation, the above problem also does not occur because Higher speeds than the limit speeds must not occur operationally.

Further Advantages and embodiments will be apparent from the attached Drawings.

In this demonstrate:

1 a simplified block diagram of a device according to the invention; and

2 a monitoring structure for a drive.

1 shows a block diagram for a device according to the invention. In this case, the reference numeral refers 4 to a three-phase machine, which is supplied with the three output variables U _u , U _v and U _w . This is a three-phase energized motor. In a first converter unit 2 a coordinate transformation is performed. More precisely, the voltage vector calculated in the rotor-fixed coordinate system with the two components Ud (longitudinal voltage) and Uq (transverse voltage) is transformed into the stator or stator-fixed three-phase voltage system U _u , U _v , U _w by means of the following transformation equations.

In this case, γ _{el is} the electrical rotation angle or commutation angle of the voltage vector, which differs from the mechanical rotation angle γ _mech by the number of pole pairs PPZ of the motor in synchronous motors. More precisely, the electrical angle of rotation results from the product of the number of pole pairs and the mechanical angle of rotation: γ el = PPZ · γ mech

The motor 4 is about a wave with a giver 6 connected. An encoder angle detection unit is denoted by the reference numeral 9 characterized. The encoder angle is in a differentiating element 15 differentiated according to the time and continues to a voltage actual value Vist to a voltage regulator 14 issued. Furthermore, the actual voltage value Vist also becomes a field controller 18 output. The outputs of the voltage regulator 14 and the field controller 18 supply cross current setpoints (Iqsoll) and longitudinal current setpoints (Idsoll) to a current controller 16 , At the same time caused by the transformation voltage values U _u, U _v U and _W are in a detection unit 10 recorded and fed to a transformation. The actual current values Idist and Iqist resulting from this transformation, together with the above-mentioned reference values, become the current regulator 16 fed. At the output of this current regulator 16 the respective longitudinal and transverse voltages U _d and U _{q are} output and in turn the first converter unit 2 fed. Furthermore, (in 1 not shown) a second transducer unit 12 provided, which the same transformation as the first converter unit 2 performs.

The respective voltage values U _u , U _v and U _w and U _v , U ' _v , U' _w resulting from the two transformations are compared with each other, and in case of deviation the power supply to the motor becomes 4 interrupted.

The refer to internal control circuits for the torque control on a rotor-fixed coordinate system. All streams and stresses in this system are equal quantities, regardless of how fast the engine is turning. Especially the manipulated variable "output voltage" is a vector, which changes due to the regulation, the but not rotated. The task of coordinate transformation consists of applying this voltage vector to the stator Convert coordinate system. The commutation angle used for this and its angular velocity are the determining factors for the speed of the motor feeding the inverter provided, three-phase system.

From the above-mentioned fact that a three-phase motor does not accelerate by itself can rotate as the rotational frequency of the feeding three-phase system, the monitoring of this rotational frequency to a predetermined limit is sufficient for limiting the speed. If this monitoring is carried out with two channels, the prerequisites for the required safe speed monitoring mentioned above are met.

U_u = U_u – Offset
U_v = U_v – Offset
U_w = U_w, – Offset 2 shows a representation of the monitoring structure in the drive. Here are a first converter unit 2 and a second transducer unit 12 intended. These converter units each carry out identical coordinate transformations of the input quantities U _q , U _d and γ _el into output quantities U _u , U _v and U _w . To the two converter units 2 and 12 close in each case balancing and limiting devices 20 respectively. 22 at. It is done after the coordinate transformation in the converter units 2 and 12 a symmetrization and limitation of the voltages, wherein first of all three voltages the same offset is subtracted. This offset results in:

U _u = U _u - Offset
U _v = U _v offset
U _w = U _w , - Offset

Before the three voltage values U _u , U _v , U _w a PWM modulator 24 are fed, they are limited to its allowable input range. The generated PWM signals become a power amplifier 26 whose output is connected to the motor terminals of the motor 4 connected is.

The on the coordinate transformation in the converter units 2 and 12 following operations do not contain trigonometric functions and therefore can not cause rotation. The pulse width modulation is carried out the difference to the coordination transformation and symmetrization not via software in the microprocessor but with counter modules. This counter logic can be integrated as a peripheral module with on the chip of the microprocessor or be arranged separately. Implementation in an FPGA (Field Programmable Gate Array) is advantageous. Neither fixed nor programmable logic operates on the basis of a program and therefore can not execute a wrong program in case of a malfunction. In particular, it can be ruled out that the PWM modulator, which is constructed on the basis of fixed or programmable logic, can of itself effect a rotation of the voltage vector. This also applies to the power level 26 which merely amplifies the PWM signals.

To ensure that the output voltage of the power amplifier exactly follows the commutation angle γ _el , according to the invention the correct software function of the first converter unit 2 supervised. This is done, as mentioned above, in which the coordinate transformation with the same input values in the second independent converter unit 12 is performed cyclically and the results are compared. For comparison, a comparison device 28 intended. Thus, both channels or both converter units monitor the angular velocities of γ _el , make a comparison with the other computer and each have their own Abschaltpfade. So it is, for example, as in 2 illustrated, possible to block the control signals for the power amplifier in the event of an error and thus the power supply for the three-phase machine 4 to interrupt. The reference number 27 refers to a differentiating element in which the angular velocity of the commutation angle γ is formed. This serves, as stated above, to monitor the rotational speed of a three-phase machine 4 , The reference number 30 denotes a security processor including the second converter unit 12 , the balancing and limiting device 20 , the differentiating member 27 and the comparison device 28 contains.

All Features disclosed in the application documents are considered to be essential to the invention as far as they are individually or in combination the prior art are new.

2

first converter unit

4

Phase machine

6

giver

9

Donors angle detection unit

10

Current detection unit

12

second converter unit

14

voltage regulators

15

differentiating element

16

current regulator

18

field controller

20 22

Symmetrierungs- and limiting device

24

PWM modulator

26

power amplifier

27

differentiating element

28

comparator

30

security processor

γ

angle of rotation or commutation angle

U _u , U _v , U _w ,

outputs

U ' _u , U' _v , U ' _w

outputs (transformed in the second converter unit 12)

U _q , U _d , γ _el

input variables

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10035783 A1 [0002]
• - DE 4330823 C2 [0003]

Claims (15)

Method for monitoring three-phase machines, wherein input variables (U _d , U _q , γ) of a first converter unit ( 2 ), and wherein one of these input variables is a commutation angle (γ) of a three-phase machine to be operated ( 4 ) and wherein the input variables (U _d , U _q , γ) in this first converter unit ( 2 ) are transformed into output variables (U _u , U _v , U _w ) and these output variables (U _u , U _v , U _w ) are fed to a three-phase machine for operating the same, characterized in that the angular velocity of the commutation angle (γ) is monitored and a further transformation of the input variables (U _q , U _d , γ _el ) into the output variables (U ' _u , U' _v , U ' _w for verifying the transformation in the first converter unit ( 2 ) is carried out. A method according to claim 1, characterized in that the further transformation of a second of the first transducer unit ( 2 ) independent converter unit ( 12 ) is carried out. Method according to at least one of the preceding claims, characterized in that for carrying out the transformation in the first converter unit ( 2 ) and for carrying out the transformation in the second converter unit ( 12 ) different data processing programs are used. Method according to at least one of the preceding claims, characterized in that the first converter unit ( 2 ) and the second transducer unit ( 12 ) differ from each other in at least one feature. Method according to at least one of the preceding claims, characterized in that in the first converter unit ( 2 ) transformed output variables (U _u , U _v , U _w ) and in the second converter unit ( 12 ) transformed output quantities (U ' _u , U' _v , U ' _w ) are compared with each other. A method according to claim 5, characterized in that the comparison of the output variables (U _u , U _v , U _w ) and (U ' _u , U' _v , U ' _w ) is not directly, but on the basis of the voltage angle, the ever from the three voltage values is formed. Method according to at least one of the preceding claims, characterized in that the first converter unit ( 2 ) and the second transducer unit ( 12 ) communicate with each other. Method according to at least one of the preceding Claims, characterized in that the commutation angle (γ) is determined by means of a transmitter. Method according to at least one of the preceding Claims, characterized in that the commutation angle (γ) is determined using a motor model. Method according to at least one of the preceding claims, characterized in that the second converter unit ( 12 ) several three-phase machines ( 4 ) supervised. Method according to at least one of the preceding claims, characterized in that input variables (U _q , U _d , γ _el ) cyclically in their entirety to the second transducer unit ( 12 ). Method according to at least one of the preceding claims, characterized in that the input variables (U _q , U _d , γ _el ) are sent sequentially to the second converter unit ( 12 ) be handed over. Device for monitoring the rotational speed of three-phase machines with a first converter unit ( 12 ), which input variables (U _d , U _q , γ) supplied to this first converter unit are transformed into output variables (U _u , U _v , U _w ), one of these input variables being a commutation angle (γ) of a three-phase machine to be operated ( 4 ) and the output variables are used for the operation of this three-phase machine, characterized in that the device has a second converter unit (14) which can be independently operated by this first converter unit (US Pat. 12 ), wherein the second converter unit also transforms the input variables (U _d , U _q , γ) supplied to this second converter unit into output variables (U ' _u , U' _v , U ' _w ), one of these input variables being the commutation angle (γ) of the to be operated three-phase machine ( 4 ) and that a comparison device is provided, which is the one of the first converter unit ( 2 ) output variables (U _u , U _v , U _w ) or derived therefrom with the parameters of the second converter unit ( 12 ) output variables (U ' _u , U' _v , U ' _w ) or from these derived characteristics. Device according to claim 13, characterized that the derived characteristic is um the angle of the voltage vector is that of the three voltage components is formed. Apparatus according to claim 13 or 14, characterized in that the device comprises a shut-off device, which the three-phase machine in response to a result of the comparison between the from the first converter unit ( 2 ) output variables (U _u , U _v , U _w ) and the output from the second converter unit ( 12 ) outputs output variables (U ' _u , U' _v , U ' _w ) to a safe state.