DE202018104332U1 - Circuit arrangement for overload protection of an EC motor - Google Patents

Abstract

Circuit arrangement (1) for overload protection of an EC motor (2) which is designed to be driven by a commutation electronics (4) operated at an intermediate circuit (3) with an intermediate circuit voltage U _ZK via an output stage (5)
a. a signal processing device (10) which is designed to process a detected signal (S _END ) representing the output stage current I _{END of} the output stage (5), a respective current motor phase voltage of the EC motor (2) and the current DC link voltage U _ZK ,
b. the signal processing device (10) has a comparator (20) which is designed to compare the signal (S _END ) corresponding to the output stage current I _END with a reference signal (S _REF );
c. a shut-off device (3, 6), which is designed to interrupt the power supply to the EC motor (2), depending on a shut-off condition comprising at least the comparison result of the comparator (10).

Description

The invention relates to a circuit arrangement for overload protection of an EC motor.

In electric drives and motors, it is almost inevitable that in the engine heat losses occur, which lead to an increase in temperature. Consequently, there is an upper limit temperature for the electric motor, and once this is exceeded, the motor may be damaged or fail.

The engine electronics, which typically consists of an input circuit, a DC link, the commutation and the power output stage z. B. a DC / AC converter, must be in accordance with the safety rules and regulations of the European Standard EN 60335-1 be designed so that the safety of the device is guaranteed and a protective device switches off when it reaches a high temperature, the device or the device. The stator temperature of the motor must not exceed a certain temperature.

It can come as a result of malfunction of the electric motor itself, but at an inadmissibly high temperature in the electric motor. Such cases occur at intended high loads on the machine, as in binding or z. B. in blockade of mechanics. Even dirty ventilation grilles on the electric motor can cause unwanted temperature increases. If the winding of the motor exceeds the allowable temperature, the electric motor will be damaged, which may result in failure of the entire machine and may lead to unsafe operating conditions, e.g. an insulating material fails. To protect the electric motor from overheating, it is therefore necessary to know the winding temperature.

There are currently solutions provided in the prior art, which z. B. provide the measurement of the winding temperature and have a shutdown, which triggers when the limit temperature is exceeded. Another known approach provides that the winding current is limited depending on the engine speed. The temperature increase of windings in motors is determined by the motor structure whose winding impedance and the winding current.

From the publication WO 93/23904 A1 is z. Example, a method for monitoring an electric motor in terms of thermal overload known. For this purpose, during the duty cycle of the electric motor, its power loss or a variable proportional thereto is calculated on the basis of measured motor data and then integrated. The integration value is compared with a predetermined threshold value, if the integration value exceeds a threshold limit value, the electric motor is switched off. According to this known method, environmental influences, which are partly responsible for the temperature behavior of the electric motor, are disregarded.

In other known methods which try to do without a temperature sensor, the current drawn by the electric motor is monitored. If the motor current exceeds the permissible continuous current for a longer period of time, the motor is switched off via the motor-protective circuit-breaker or in the case of variable-speed three-phase motors via the frequency inverter.

Other known methods for protecting an electric motor against overheating provide a temperature measurement by means of a temperature sensor, which is mainly installed in the motor winding. Thus, in known embodiments of motors with umstressten stators z. B. thermal switch used before the Umpressvorgang in the winding and the connecting leads connected to a circuit board. If the temperature determined in this way reaches a predefined, maximum permissible limit value in the vicinity of the motor winding, the shutdown of the electric motor is also initiated here. Such a method is known from the published patent application DE 199 39 997 A1 known.

The devices and methods known from the prior art have a number of disadvantages which present problems in practice. When using a temperature sensor, a sufficient insulating layer is required for electrical insulation between it and the winding. This insulating layer also represents a thermal insulation, which is why, especially in overload with high currents, a temperature difference between the electrically active part of the winding itself and the temperature sensor results. A delayed shutdown of the electric motor with existing overheating of the motor winding is the result. This effect is exacerbated by increased requirements for electrical insulation for personal protection. Moreover, the temperature is detected only at a single point of the winding via a temperature sensor built into the winding.

In a current monitoring only the motor current is also the further problem that depending on the motor voltage due to allowable reference values, the engine heating can not be optimally monitored, as result in a constant reference a non-constant shutdown depending on the operating point and drive level of the motor.

It is therefore an object of the present invention to overcome the aforementioned disadvantages and to provide a circuit arrangement and a method for the speed-independent protection of an electric motor, which can be realized inexpensively and reliably.

This object is achieved by a device according to claim 1.

A basic idea of the present invention is, in addition to the motor current, simultaneously to grasp the other relevant factors cumulatively to the motor current by means of a circuit arrangement designed according to the invention, in order to obtain a switch-off condition therefrom. In addition to the motor current, the motor voltage (motor phase voltage) and the DC link voltage are decisive for the stator heating.

1. a. eine Signalverarbeitungseinrichtung, die ausgebildet ist, zum Verarbeiten eines erfassten Signals „S_END“ repräsentierend den Endstufenstrom I_END der Endstufe, einer jeweils aktuellen Motorphasenspannung des EC-Motors und der aktuellen Zwischenkreisspannung U_ZK, wobei
2. b. die Signalverarbeitungseinrichtung einen Komparator aufweist, der ausgebildet ist das zum Endstufenstrom I_END korrespondierende Signal mit einem Referenzsignal „S_REF“ zu vergleichen;
3. c. eine Abschaltvorrichtung, die ausgebildet ist, abhängig von einer Abschaltbedingung, die wenigstens das Vergleichsergebnis des Komparators umfasst, die Stromversorgung zum EC-Motor zu unterbrechen.

According to the invention, therefore, a circuit arrangement for overload protection of an EC motor is provided, which is designed to be driven by a commutation electronics operated at an intermediate circuit with an intermediate circuit voltage U _ZK via an output stage, the circuit arrangement comprising:

1. a. a signal processing device, which is designed to process a detected signal "S _END " representing the output stage current I _{END of} the output stage, a respective current motor phase voltage of the EC motor and the current intermediate circuit voltage U _ZK , wherein
2. b. the signal processing device has a comparator which is designed to compare the signal corresponding to the output stage current I _END with a reference signal "S _REF ";
3. c. a shutdown device configured to interrupt the power supply to the EC motor depending on a shutdown condition including at least the comparison result of the comparator.

The magnitude of the final stage current, and hence the detected signal "S _END " representing the final stage current, is an essential indicator of the thermal overload of the motor. Since the reference value is an upper limit for the currently maximum permissible motor current, the reference value represents a dynamic reference value that changes in a manner corresponding to the variables motor phase voltage and intermediate circuit voltage.

In an advantageous embodiment, it is provided that the signal processing device has a signal input for the measured variables: motor phase voltage, output stage current I _END , intermediate circuit voltage U _ZK and an offset value (as auxiliary variable). On the input side, the signal processing device may have a filter for processing or filtering the data, and in particular for determining a reference value therefrom.

It is also advantageous if a low-pass filter filters at least the measured variable of the output stage current before a transmission of the signal obtained therefrom to the comparator.

Another advantage is an embodiment in which a comparator is provided downstream of an integrator, which is designed to delay the shutdown upon detection of a shutdown condition, until a predetermined number of shutdown instructions within a predetermined time interval are obtained by the comparator. The integrator thus has the property that the shutdown does not occur immediately when the signal for the power stage current "S _END " exceeds the reference value "S _REF ", but only after a series of such shutdown signals. Furthermore, the heating in the stator has a settling behavior and does not increase spontaneously. The integrator also reduces the influence of EMC.

In a preferred embodiment of the invention it is provided that a signal output of the signal processing device is provided in order to transmit a switch-off signal via a signal line to the output stage.

It is also advantageous if the disconnection device is arranged between the commutation electronics and the output stage or between the output stage and the EC motor, so that the motor is disconnected from its power supply before an unacceptable overheating of the stator has occurred without it being a temperature sensor requirement.

In a further advantageous embodiment of the invention it is provided that a measuring device for detecting the output stage current of the output stage is provided, which has a signal output for the measurement signal for transmission to the signal processing device.

Another aspect of the present invention relates to an application for overload protection of an EC motor, in particular by means of a circuit arrangement as described above. However, it is conceivable that the specific structure of the circuit arrangement deviates from the described arrangement even when using the method according to the invention.

1. a) Erfassen des Endstufenstroms I_END der Endstufe, einer Motorphasenspannung des EC-Motors und der Zwischenkreisspannung U_ZK,
2. b) Zuführen der im zuvor genannten Schritt a) erfassten Messgrößen an eine dazu ausgebildete Signalverarbeitungseinrichtung;
3. c) Bestimmen eines dynamischen Referenzsignals aus wenigstens einem der beiden Messgrößen: aktuelle Motorphasenspannung des EC-Motors und/oder aktuelle Zwischenkreisspannung U_ZK;
4. d) Kontinuierliches oder diskontinuierliches Vergleichen derjenigen Signale, die korrespondierend zum jeweils aktuellen Endstufenstrom I_END aus Schritt a) sind, mit dem gerade aktuell bestimmten Referenzsignal mittels des Komparators und Ermitteln daraus, ob eine Abschaltbedingung wegen zu hoher Motortemperatur vorliegt und optional
5. e) Erzeugen eines Abschaltsignals für die Abschaltvorrichtung, zur Unterbrechung der Stromversorgung zum EC-Motor, wenn eine Abschaltbedingung gegeben ist.

The application has the following steps:

1. a) detecting the output stage current I _{END of} the output stage, a motor phase voltage of the EC motor and the intermediate circuit voltage U _ZK ,
2. b) supplying the measured variables detected in the aforementioned step a) to a signal processing device designed for this purpose;
3. c) determining a dynamic reference signal from at least one of the two measured variables: current motor phase voltage of the EC motor and / or current intermediate circuit voltage U _ZK ;
4. d) Continuous or discontinuous comparison of those signals which are corresponding to the respective current output stage current I _END from step a), with the just currently determined reference signal by means of the comparator and determining whether a shutdown condition is due to high engine temperature and optional
5. e) generating a shutdown signal for the shutdown device, for interrupting the power supply to the EC motor, if a shutdown condition is given.

Further advantageously, the method is formed when an integrator is used, which forwards a switch-off signal to the switch-off device only after receipt of a predetermined number of switch-off instructions and only then takes place a switch-off.

It is also advantageous if in step b) additionally an offset in the form of a constant reference voltage as an auxiliary quantity is transmitted to the signal processing device, preferably to its input filter.

In a preferred embodiment of the method according to the invention, it is provided that in step c) for generating or determining a dynamic reference signal "S _REF " at least the following measured variables are processed and used: actual intermediate circuit voltage U _ZK , modulation level of the EC motor and an offset signal.

Other advantageous developments of the invention are characterized in the subclaims or are shown in more detail below together with the description of the preferred embodiment of the invention with reference to FIGS.

• 1 ein Blockschaltbild einer erfindungsgemäßen Vorrichtung und
• 2 ein Blockschaltbild der Signalverarbeitungseinrichtung zur Realsierung des Überlastschutzes.

Show it:

• 1 a block diagram of a device according to the invention and
• 2 a block diagram of the signal processing device for realizing the overload protection.

In the following, the invention will be described with reference to FIGS 1 and 2 explained in more detail, wherein like reference numerals refer to the same structural and / or functional features.

The 1 branches a block diagram of a device according to the invention with a circuit arrangement 1 for overload protection of an EC motor 2 , The EC engine 2 is on a conventional DC link 3 with a DC link voltage U _ZK operated commutation 4 via a power amplifier 5 connected to the commutation electronics 4 to be controlled.

The circuit arrangement 1 includes the realization of the overload protection, the signal processing device 10 adapted to process a detected signal S _END representing the final stage current I _{END of} the final stage 5 , a current motor phase voltage of the EC motor 2 and also the current intermediate circuit _voltage U _ZK .

Like in the 2 can be seen, the signal processing device 10 a filter TP, a comparator 20 , an integrator 30 , a module 40 for self-preservation and a signal output 10A on.

The comparator 10 is formed to compare the filter TP to the output stage current I _END corresponding signal S _END with a reference signal S _REF , as shown in the block diagram. The reference value or the dynamic reference signal S _REF is for this purpose from in the 2 processed input variables.

In the 1 are two exemplary shutdown devices 3 . 6 shown, which are each formed, depending on a shutdown condition, the power supply to the EC motor 2 either before or after the power amp 5 to interrupt. The final stage current I _END is connected to the measuring device 8th detected.

Furthermore, in the 2 to recognize that the signal processing device 10 at the signal input 10E the measured variables: motor phase voltage, output stage current I _END , intermediate circuit voltage U _ZK and an offset value are supplied.

The signal output 10A the signal processing device 10 can be a shutdown signal via the signal line 11 to the final stage 5 transfer.

The invention is not limited in its execution to the above-mentioned preferred embodiments. Rather, a modification is conceivable, which z. B. provides a further signal conditioning.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 93/23904 A1 [0006]
• DE 19939997 A1 [0008]

Cited non-patent literature

• Standard EN 60335-1 [0003]

Claims (7)

Circuit arrangement (1) for overload protection of an EC motor (2), which is designed to be driven by a commutation electronics (4) operated at an intermediate circuit (3) with an intermediate circuit voltage U _ZK via an output stage (5), comprising a. a signal processing device (10) which is designed to process a detected signal (S _END ) representing the final stage current I _{END of} the output stage (5), a current motor phase voltage of the EC motor (2) and the current intermediate circuit voltage U _ZK , where b , the signal processing device (10) has a comparator (20) which is designed to compare the signal (S _END ) corresponding to the output stage current I _END with a reference signal (S _REF ); c. a shut-off device (3, 6), which is designed to interrupt the power supply to the EC motor (2), depending on a shut-off condition comprising at least the comparison result of the comparator (10). Circuit arrangement (1) according to Claim 1 , characterized in that the signal processing device (10) has a signal input for the measured variables: motor phase voltage, output stage current I _END , intermediate circuit voltage U _ZK and an offset value. Circuit arrangement (1) according to Claim 1 or 2 , characterized in that a low-pass filter (TP) at least the measured variable of the output stage current before transmission of the signal obtained therefrom to the comparator (20) filters. Circuit arrangement (1) according to Claim 1 . 2 or 3 , characterized in that downstream of the comparator (20) an integrator (30) is provided, which is designed to delay the deactivation upon detection of a shutdown condition, until a predetermined number of shutdown instructions within a predetermined time interval are obtained from the comparator (20) , Circuit arrangement (1) according to one of the preceding claims, characterized in that a signal output (10A) of the signal processing device (10) is provided to transmit a switch-off signal via a signal line (11) to the output stage (5). Circuit arrangement (1) according to one of the preceding claims, characterized in that the cut-off device (3, 6) is arranged between the commutation electronics (4) and the output stage (5) or between the output stage (5) and the EC motor (2) , Circuit arrangement (1) according to one of the preceding claims, characterized in that a measuring device (6) for detecting the output stage current I _{END of} the output stage (5) is provided which has a signal output for the measurement signal for transmission to the signal processing means (10).

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