阅读说明：本技术 用于监控变频器的运行的方法和变频器 (Method for monitoring the operation of a frequency converter and frequency converter ) 是由 J·布兰德 T·韦德迈尔 T·比西希 于 2019-11-26 设计创作，主要内容包括：一种用于监控变频器(1)的运行的方法,所述变频器被构造用于操控电动机(2),其中所述方法具有步骤：-产生用于所述电动机(2)的相对应的相线(2.1、2.2、2.3)的相电压(u1、u2、u3),-确定电压旋转场,-测量出现的相电流(i1、i2、i3),-根据所测量的相电流(i1、i2、i3)确定电流旋转场,-计算所述电压旋转场和所述电流旋转场之间的相位差和/或计算所述电压旋转场的频率和所述电流旋转场的频率之间的频率差,以及-当所述相位差超过相位差阈值时和/或当所述频率差超过频率差阈值时,确定差错状态。(Method for monitoring the operation of a frequency converter (1) which is designed for operating an electric motor (2), wherein the method has the steps: -generating phase voltages (u 1, u2, u 3) for corresponding phase lines (2.1, 2.2, 2.3) of the electric motor (2), -determining a voltage rotating field, -measuring the occurring phase currents (i 1, i2, i 3), -determining a current rotating field from the measured phase currents (i 1, i2, i 3), -calculating a phase difference between the voltage rotating field and the current rotating field and/or calculating a frequency difference between the frequency of the voltage rotating field and the frequency of the current rotating field, and-determining an error condition when the phase difference exceeds a phase difference threshold and/or when the frequency difference exceeds a frequency difference threshold.)

1. Method for monitoring the operation of a frequency converter (1) which is designed for operating an electric motor (2), wherein the method has the steps:

-generating phase voltages (u 1, u2, u 3) for corresponding phase lines (2.1, 2.2, 2.3) of the electric motor (2) on the basis of the nominal values of the phase voltages (u 1, u2, u 3),

-determining a voltage rotating field,

-measuring the occurring phase currents (i 1, i2, i 3),

determining a current rotating field from the measured phase currents (i 1, i2, i 3),

-calculating the phase difference between the voltage rotating field and the current rotating field and/or calculating the frequency difference between the frequency of the voltage rotating field and the frequency of the current rotating field, and

-determining an error status when the phase difference exceeds a phase difference threshold and/or when the frequency difference exceeds a frequency difference threshold.

2. The method of claim 1,

-determining the voltage rotating field according to the nominal values of the phase voltages (u 1, u2, u 3).

3. The method according to claim 1 or 2,

-generating phase voltages (u 1, u2, u 3) for corresponding phase lines (2.1, 2.2, 2.3) of the electric motor (2) by means of pulse width modulation with a variable duty cycle, wherein the voltage rotating field is determined according to the duty cycle of the pulse width modulation.

4. The method according to any of the preceding claims,

-performing an error handling, in particular preventing the generation of the phase voltages (u 1, u2, u 3), after the error condition has been determined.

5. The method according to any of the preceding claims,

-performing a safe torque shutdown function after determining the error condition.

6. The method according to any of the preceding claims,

-the frequency converter (1) has:

-a control unit (3),

-a power unit (4), and

at least one safety unit (5, 6),

-wherein the control unit (3), the power unit (4) and the at least one safety unit (5, 6) are coupled to each other via a communication channel (7) for exchanging data,

-wherein the nominal values of the phase voltages (u 1, u2, u 3) are transmitted from the control unit (3) to the power unit (4) via the communication channel (7),

-wherein the measured values regarding the measured phase currents (i 1, i2, i 3) are transmitted from the power unit (4) to the control unit (3) via the communication channel (7), and

-wherein the at least one safety unit (5, 6) is designed to evaluate the respective setpoint values of the phase voltages (u 1, u2, u 3) transmitted via the communication channel (7) and the measured values of the measured phase currents (i 1, i2, i 3) transmitted via the communication channel (7) for determining an error state.

7. A frequency converter (1) is characterized in that,

-the frequency converter (1) is configured for performing the method according to any of the preceding claims.

8. Frequency converter (1) according to claim 7,

-the frequency converter (1) has:

-a control unit (3),

-a power unit (4), and

at least one safety unit (5, 6),

-wherein the control unit (3), the power unit (4) and the at least one safety unit (5, 6) are coupled to each other via a communication channel (7) for exchanging data,

-wherein the nominal values of the phase voltages (u 1, u2, u 3) are transmitted from the control unit (3) to the power unit (4) via the communication channel (7),

-wherein the measured values regarding the measured phase currents (i 1, i2, i 3) are transmitted from the power unit (4) to the control unit (3) via the communication channel (7), and

-wherein the at least one safety unit (5, 6) is designed to evaluate the respective setpoint values of the phase voltages (u 1, u2, u 3) transmitted via the communication channel (7) and the measured values of the measured phase currents (i 1, i2, i 3) transmitted via the communication channel (7) for determining an error state.

9. Frequency converter (1) according to claim 8,

-the control unit (3) is configured for adjusting the phase currents (i 1, i2, i 3).

10. Frequency converter (1) according to claim 9,

the control unit (3) is designed to use the phase voltages (u 1, u2, u 3) as control variables for setting the phase currents (i 1, i2, i 3).

Technical Field

The invention relates to a method for monitoring the operation of a frequency converter and a frequency converter.

Disclosure of Invention

The object on which the invention is based is to provide a method for monitoring the operation of a frequency converter and a frequency converter, which enable reliable and cost-effective monitoring of the operation.

The invention solves this object by a method for monitoring the operation of a frequency converter according to claim 1 and a frequency converter according to claim 7.

The method is used for monitoring the operation of a frequency converter, which is designed for operating an electric motor. The motor may for example be a synchronous motor or an asynchronous motor.

In this method, the conventional phase voltage for the corresponding phase line or between the corresponding phase lines of the electric motor is generated on the basis of the associated setpoint value of the phase voltage. The amplitude and frequency of the phase voltage are generated, for example, on the basis of the setpoint values, so that a desired rotational speed of the electric motor and/or a desired torque of the electric motor occurs. Typically, three phase voltages are generated for three corresponding phase lines. In this connection, reference should also be made to the relevant technical literature.

As a further method step, a voltage rotating field is determined. In particular, the voltage rotating field is calculated from the nominal values of the phase voltages. In the determination of the voltage rotating field, reference should also be made to the relevant technical literature.

As a further method step, at least one phase current is measured, which flows in the phase line and occurs as a result of the phase voltage. In the case of a three-phase motor, it may be sufficient to measure two of the three phase currents, since the third phase current is computationally derived from the other two phase currents.

As a further method step, a current rotating field is calculated from the one or more measured phase currents. In this connection, reference should also be made to the relevant technical literature.

As a further method step, the phase difference between the voltage rotating field and the current rotating field and/or the frequency difference between the frequency of the voltage rotating field and the frequency of the current rotating field is calculated.

Finally, an error condition is determined if the phase difference or the value of the phase difference exceeds a phase difference threshold and/or if the frequency difference or the value of the frequency difference exceeds a frequency difference threshold.

The phase difference threshold and the frequency difference threshold may be absolute or relative values. The phase difference threshold and the frequency difference threshold may take into account a possible slip rate (Schlupf). The phase difference threshold and the frequency difference threshold may for example be in a range between 1% and 10% with respect to the phase of the voltage rotating field or with respect to the frequency of the voltage rotating field.

The position of the rotor of the electric motor is typically determined in applications with safety functions by means of a so-called safety transmitter system (geber system). With the aid of such a transmitter system, it is possible to determine the rotational speed and the angular position of the rotor. However, the transmitter system represents a space and cost factor. It is therefore common to abandon such transmitter systems in cost-critical facilities. However, this causes limitations in dynamics and accuracy, but this is acceptable in many applications.

Conventional synchronous or asynchronous motors are operated with a three-phase voltage rotating field, wherein the phase lines are indicated in the following figures with 2.1, 2.2, 2.3 (also conventionally referred to as U, V and W). Angular velocity of rotorAngular velocity of rotating field dependent on feed voltageOr the rotation frequency f. The phase currents i1, i2, i3 are generated in each of the 3 phase lines 2.1, 2.2, 2.3 by a voltage rotating field. For angular velocityIs applicable to。

In the case of synchronous motors, there is a strict ratio between the angular speed of the rotating magnetic field or voltage rotating field and the angular speed of the rotor. In the case of asynchronous machines, the angular velocity of the rotating magnetic field or of the rotating electrical voltage field is always higher than the angular velocity of the rotor during operation of the electric motor. The difference is described by the slip(s) and is required so that the asynchronous machine can apply torque. In this case, the slip during operation of the electric motor is always between 0 and 1. In the calculation of the mechanical rotational speed, the number of pole pairs (p) must still be taken into account.

Thus, for a synchronous machine, the following applies:

。

in the ASM case, the supplementary slip is still needed.

According to the invention, safety transmitter systems are now dispensed with, in which the frequency of the current rotating field and the frequency of the voltage rotating field are used for monitoring the operation of the frequency converter, for example for monitoring the angular speed of an electric motor operated by means of the frequency converter.

The voltage rotating field describes the operation of the voltage in the motor (Umlauf). In order to obtain a current alignment of the current vector and the voltage vector describing the current rotating field or the voltage rotating field, the current voltage value or the current value, respectively, is geometrically added.

Wherein。

In addition to amplitude information, valuesBut also angle information. For calculating the rotational speed, only the derivative of the angle may be determined. Instead of a voltage, a duty cycle may also be used for calculating the angular velocity in the voltage rotating field. The duty cycle and the voltage differ only in amplitude, which in turn has no effect on the angular speed.

In this case, a characteristic can be used in which the current and voltage (or duty cycle) contain the rotating field frequency, and with both values it is possible to determine the speed of the rotor with slip neglected.

It is therefore possible to construct a two-pass structure in order to monitor the angular speed of the rotor. In this case, the first channel constitutes a voltage rotating field and the second channel constitutes a current rotating field.

After determining the error condition, the frequency converter may be switched off, e.g. based on the functions STO, SS1, SLS, SMS and SDI.

The present invention is a low cost solution to the non-transmitter (geberlos) security technologies, especially to the functions SS1, SLS, SMS, SDI and SMS. Furthermore, it is possible to safely detect the output frequency even without additional sensor devices in the power output stage in the case of asynchronous motors. The invention thus makes it possible, in particular in the case of asynchronous machines, to implement a speed-dependent safety function without an additional feedback system.

The output frequency, i.e. the rotational speed of the motor, can be monitored by independently evaluating the phase angle of the current rotating field and the voltage rotating field. The monitoring can be carried out on a communication channel between the control unit and the power unit, wherein the voltage rotating field or the associated voltage space vector is formed by the setpoint values of the phase voltages from the control unit and the current rotating field or the associated current vector is formed by the measured values of the phase currents from the power unit.

For safety reasons, the two-pass characteristic, which is necessary, is achieved by monitoring two separate physical variables, namely on the one hand the angle of the voltage rotating field or voltage vector and on the other hand the angle of the current rotating field or current vector.

It is possible for the two monitoring units to monitor the angle of the voltage and current vectors and to initiate or maintain a safety state when the detected rotational speed is outside predefined limits.

For the detection of the rotational speed, no feedback system at the motor is required. Thereby costs in the system can be saved.

According to one specific embodiment, the voltage rotating field is determined as a function of the setpoint values of the phase voltages. In this connection, reference should also be made to the relevant technical literature.

According to one specific embodiment, the phase voltages for the corresponding phase lines of the electric motor are generated by means of pulse width modulation with a variable duty cycle, wherein the voltage rotating field is determined as a function of the duty cycle of the pulse width modulation. In this connection, reference should also be made to the relevant technical literature.

According to one specific embodiment, after the error state has been determined, an error processing is carried out, in particular the generation of the phase voltages and thus also the rotating field is prevented.

According to one embodiment, a Safe Torque-Off (Safe-Torque-Off) function is performed after the error condition is determined.

According to one specific embodiment, the frequency converter further comprises: for example, a control unit in the form of a microprocessor, a power unit and at least one safety unit, in particular exactly two safety units, which are independent of one another. The power unit may, for example, conventionally comprise an inverter with power semiconductors or the like, which is designed to generate phase voltages. The control unit, the power unit and the at least one safety unit are coupled to each other via a communication channel for exchanging data. The respective nominal values of the phase voltages are transmitted from the control unit to the power unit via the communication channel, wherein the power unit then generates the phase voltages according to the nominal value or nominal values. The measured values for the measured phase currents are transmitted from the power unit to the control unit via the communication channel. The at least one safety unit is designed to evaluate the one or more setpoint values of the phase voltages transmitted via the communication channel and measured values of the measured phase currents transmitted via the communication channel for determining an error state.

The frequency converter according to the invention is constructed for carrying out the above-described method.

According to one embodiment, the frequency converter has: for example, a control unit in the form of a microprocessor, a power unit and at least one safety unit, in particular exactly two safety units, which are independent of one another. The power unit may, for example, conventionally comprise an inverter with power semiconductors or the like, which is designed to generate phase voltages. The control unit, the power unit and the at least one safety unit are coupled to each other via a communication channel for exchanging data. The respective nominal values of the phase voltages are transmitted from the control unit to the power unit via the communication channel, wherein the power unit then generates the phase voltages according to the nominal value or nominal values. The measured values for the measured phase currents are transmitted from the power unit to the control unit via the communication channel. The at least one safety unit is designed to evaluate the one or more setpoint values of the phase voltages transmitted via the communication channel and measured values of the measured phase currents transmitted via the communication channel for determining an error state.

According to one specific embodiment, the control unit is designed to set the phase currents.

According to one specific embodiment, the control unit is designed to use the phase voltages as manipulated variables for phase current regulation.

Drawings

The present invention is described in detail below with reference to the accompanying drawings. In this case:

FIG. 1 shows highly schematically a drive system with a frequency converter and an electric motor operated by means of the frequency converter, and

fig. 2 shows a schematic block diagram of the internal structure of the frequency converter shown in fig. 1.

Detailed Description

Fig. 1 shows a highly schematic drive system with a frequency converter 1 and an electric motor 2 operated by means of the frequency converter 1.

The frequency converter 1 is designed to generate three phase voltages u1, u2, u3 for the corresponding phase lines 2.1, 2.2, 2.3 or between the corresponding phase lines 2.1, 2.2, 2.3 of the electric motor 2 and to measure the occurring phase currents i1, i2 and i 3. In this connection, reference should also be made to the relevant technical literature.

Fig. 2 shows a schematic block diagram of the internal structure of the frequency converter 1 shown in fig. 1.

With reference to fig. 2, the frequency converter 1 has a control unit 3, for example in the form of a microcontroller.

The frequency converter 1 furthermore has a power unit 4. The power unit 4 has a conventional inverter 8 for generating the phase voltages u1, u2 and u 3. Furthermore, the power unit 4 has a conventional current sensor 9, for example in the form of a shunt resistor. Phase flows i1, i2, and i3 are measured by means of current sensor 9. The power unit 4 furthermore has a control device 10, which controls all basic functions of the power unit 4. The power unit 4 furthermore has a Safe Torque Off (STO) circuit 11, by means of which Safe Torque Off circuit 11 an STO state can be caused. The inverter 8 is connected to the control device 10 via optocouplers 12 and 13. The current sensor 9 is connected to the control device 10 by means of an optional signal amplifier 14.

The frequency converter 1 furthermore has a first safety unit 5 and a second safety unit 6.

The control unit 3, the power unit 4 (galvanically isolated by the optocoupler 15), the first safety unit 5 and the second safety unit 6 are coupled to each other via a communication channel 7 for exchanging data. A point-to-point data connection between the two security units 5 and 6 is optionally provided.

The respective nominal values of the phase voltages u1, u2, u3 are transmitted from the control unit 3 to the power unit 4 via the communication channel 7. The measured values for the measured phase currents i1, i2, i3 are transmitted from the power unit 4 to the control unit 3 via the communication channel 7.

The safety units 5, 6 are each designed to evaluate, independently of one another, one or more setpoint values of the phase voltages u1, u2, u3 transmitted via the communication channel 7 and measured values of the measured phase currents i1, i2, i3 transmitted via the communication channel 7 for determining an error state.

For this purpose, the safety units 5, 6 determine a voltage rotating field as a function of the phase voltages u1, u2, u3 generated or to be generated, respectively. Furthermore, the safety units 5, 6 determine the current rotating field from the measured phase currents i1, i2, i3, respectively, and calculate the phase difference between the voltage rotating field and the current rotating field and/or the frequency difference between the frequency of the voltage rotating field and the frequency of the current rotating field, respectively. The safety units 5, 6 respectively determine an error status if the phase difference exceeds a phase difference threshold and/or if the frequency difference exceeds a frequency difference threshold.

If an error condition is determined in at least one of the safety units 5, 6, said safety units perform error handling independently of each other by signaling the safety torque Shutdown (STO) circuit 11: the STO condition is induced by appropriate operation of the inverter 8.

The security units 5, 6 may be arranged on a security circuit board 16. Accordingly, the control unit 3 may be arranged on the control circuit board 17. Finally, the power unit 4 may be arranged on the power circuit board 18.