DE202019101710U1 - Device for detecting a Windungsschlusses a stator coil - Google Patents

Abstract

Evaluation device for detecting a short circuit in a stator coil (10) of an electrical machine, wherein the evaluation device has a wire loop (20) and an evaluation circuit (30) for detecting the induced in the wire loop (20) voltage U _ind , wherein the wire loop (20) is wound around the stator coil (10), wherein the stator coil (10) ends two measuring terminals (M1, M2) is formed, with which two input terminals (SENS1, SENS2) of the evaluation circuit (30) are connected and wherein the evaluation circuit (30) at least an operational amplifier (OP) for amplifying the voltage signal, a comparator (K) for comparing the detected voltage signal with a reference signal and a flip-flop IC (IC) for evaluating the result of the comparator (K) to generate a signal when the induced voltage U _ind detected in the wire loop (20) is smaller by a predetermined factor k than a target limit value of a desired value Reference voltage U _soll .

Description

The invention relates to a device for detecting a Windungsschlusses a stator coil, in particular a stator coil of a rotating field machine.

Winding closures can occur in coils of electric machines both in the stator and in the rotor winding. A winding short or winding closure in a stator winding is to be understood as meaning an electrical short circuit between two or more windings of a stator winding.

For monitoring and troubleshooting electrical drives, including an electric motor, a number of diagnostic functions are required. As a rule, short circuits to ground and supply are detected. The detection of a Windungsschlusses in the coils of the electric machine is possible in principle by measuring the ohmic resistance at the phases of the electric motor. However, this resistance is generally very small so that line impedances or contact resistance on (plug) connections can falsify the measurement result and are therefore inaccurate. Furthermore, if a (partial) short circuit occurs between two phases or within the phase of the electrical machine, then this is often not detected, or at least not clearly detected.

From the EP 1 312 929 A1 For example, a method for monitoring electrical insulation of a rotor of an electric machine is known. In this case, a magnetic field of two coils is detected, which are connected in series with a rotor winding. By changing the magnetic field of the two coils can be closed to a change in state of the insulation, such as a short circuit.

From the DE 10 2008 017 900 A1 For example, a method for detecting a fault in a rotary field machine is known. In this case, a flow-forming current component is subjected to a frequency analysis.

From the DE 10 2009 004 556 A1 It is known that in a PWM controlled electric machine, by observing a current ripple resulting from the PWM voltage circuit, partial winding conclusions can be detected.

Another solution for the detection of Windungsschlüssen in the rotor winding is for example from DE 10 2009 003 549 A1 known. In this case, a search coil is used, which is arranged in the air gap in close proximity to the surface of the rotor. Winding closures in the AC windings of the stator can be detected by asymmetries in the electrical currents of different winding phases or parallel-connected winding branches. However, this has the disadvantage that other deviations from the ideal state of the electrical machine, such as an ovality of the stator, can also lead to such asymmetries. This makes it very difficult to separate the two effects in this way.

Another known method for detecting turns in the stator used flow measuring coils, the two coil legs are guided in the Nutverschlusskeilen two grooves and thus cover a certain area of the stator laminated core in the circumferential direction. A disadvantage of this method is that these measuring coils can be installed only with considerable effort in an existing machine.

Further disadvantages of known methods can be seen in the fact that only winding faults and turns can be detected with sufficient reliability only from about 10% share of the complete winding. However, it would be desirable to have a detection in a single turn conclusion between two winding wires.

The invention is therefore based on the object to overcome the aforementioned disadvantages and to provide a simple and inexpensive to implement solution for the detection of winding faults.

The object is achieved by the features of claim 1.

A basic idea of the present invention relates to the utilization of the effect of the stray field change due to a winding closure and its evaluation with an evaluation circuit.

According to the invention an evaluation device for detecting a Windungsschlusses in a stator coil of an electric machine is proposed, wherein the evaluation device comprises a wire loop and an evaluation circuit for detecting the induced in the wire loop voltage U _ind , wherein the wire loop is wound around the stator coil, wherein the stator coil forms two measuring terminals at the ends, with which two input terminals of the evaluation circuit are connected and wherein the evaluation circuit at least one operational amplifier for amplifying the voltage signal, a comparator for comparing the detected voltage signal with a reference signal (setpoint signal) and a flip-flop IC for evaluating the result of the Comparator has to signal generate when the induced voltage U _ind detected in the wire loop is smaller by a predetermined factor k than a target limit value of a reference reference voltage U _soll .

In an advantageous embodiment, it is further provided that in the evaluation circuit, an LED is further provided, which lights when falling below the target limit value of the induced voltage U _ind , in particular permanently lit. It can then be recognized visually by a person in a simple manner during operation of the electric machine a Windungsschluss.

In a preferred and advantageous embodiment of the evaluation device, it is provided that the output of the comparator is connected to an input of the flip-flop IC in order to be able to evaluate the result of the comparator directly. The evaluation can alternatively z. B. also be done by means of a microcontroller.

In a likewise preferred embodiment of the evaluation device, it is provided that an input of the operational amplifier is connected to one of the ends of the wire loop. It would also be conceivable in the monitoring of a plurality of stator coils with an evaluation device that the ends of the respective coils are connected to the inputs of a single evaluation circuit separable and switchable via a switching device, so that in each case only the coil can be monitored, which is currently active with the Evaluation circuit is connected while the separate wire loops are inactive. In this way, a cost-effective evaluation device can be provided, which monitors a plurality of stator coils.

In a particularly advantageous embodiment of the evaluation circuit, it is provided that the factor k> 1.5, preferably greater than 2. This clearly makes it possible to detect a turn short and to distinguish it from potential voltage ripples.

Another aspect of the present invention relates to a method for detecting a Windungsschlusses in a stator coil of an electrical machine, wherein the stator coil has two terminals and is acted upon by these with an electrical AC voltage, wherein around the monitored stator coil around a wire loop is wound the end forms two measuring terminals, which are connected to an evaluation circuit for detecting the induced in the wire loop voltage U _ind , wherein the evaluation circuit is formed based on the height or the peak values of the currently detected induced voltage U _ind to detect a short circuit in the stator coil. This takes place in that the evaluation circuit is designed as described above or is alternatively designed such that a setpoint-actual value comparison, preferably over a longer time of the peak values of the current induced voltages to the induced voltage in the error-free state (ie without a short-circuit) the turns is performed.

Next advantageous is the method when the evaluation circuit is a quotient between the reference reference voltage U _soll , which corresponds to the induced voltage in the wire loop in the absence of a Windungsschlusses in a stator coil and the currently detected in the wire loop induced voltage U _{ind is} formed and is evaluated whether this quotient is greater than or less than a predetermined factor k and depending on the presence or absence of a Windungsschlusses is closed.

Furthermore, it can be provided that a comparison table is stored in a system memory in which each k value is assigned the amount of a turn conclusion in terms of its amount. For example, with a factor k = 1.5, only two turns could be short-circuited, whereas with factor k = 6, 20% of the turns already have a short circuit. In this way, it is not only possible to deduce the actual presence of the factor k, but also the extent of the existence of a short circuit.

It is particularly advantageous with the idea of the invention that the method can be carried out on a stator coil of an electrical machine during the operation of the electrical machine. Thus, there is the possibility of continuous operation monitoring and early detection of problems with winding faults.

Another aspect of the present invention relates to an electrical machine, in particular electric induction machine comprising an evaluation device as described above.

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 eine schematische Ansicht einer Statorspule mit einer Drahtschlaufe ausgebildet als Messwicklung;
• 2 eine Auswerteschaltung gemäß einer beispielhaften Ausführungsform und
• 3 eine Messkurve der induzierten Spannungen mit und ohne Windungsschluss.

It shows:

• 1 a schematic view of a stator coil with a wire loop formed as a measuring winding;
• 2 an evaluation circuit according to an exemplary embodiment and
• 3 a measuring curve of the induced voltages with and without short circuit.

In the following, the invention will be described with reference to FIGS 1 to 3 explained in more detail, wherein like reference numerals in the figures indicate the same functional and / or structural features.

In the 1 is a schematic view of a stator tooth 2 with a stator coil 10 shown. The stator coil 10 has two connections ( 10a . 10b ) to the stator coil 10 to energize. Around the stator coil 10 is a wire loop 20 formed wound as a measuring winding. The stator coil forms 10 two measuring connections at the end M1 . M2 made to connect with in the 2 illustrated evaluation circuit 30 are provided.

The 2 shows only an example of an evaluation circuit 30 according to an embodiment of the invention. The evaluation circuit 30 can also be realized alternatively with the same basic functions, the proposed evaluation circuit 30 represents a particularly efficient and cost-effective variant. The evaluation circuit 30 has, among other things, conventional electronic components, such as resistors R , Capacitors C , Counter S which require no further explanation and must be adapted to the application. The connection 31 is connected to the ground potential GND.

The evaluation circuit 30 and the wire loop 20 together form an evaluation device. The in the 2 shown evaluation circuit 30 has two connections 31 . 32 for applying a voltage, wherein the terminal 32 a terminal for a reference voltage level forms z. For a 5V voltage, which is a comparator K the circuit is supplied.

The wire loop 20 comes with their connection-side ends M1 . M2 at the two input terminals SENS1, SENS2 of the evaluation circuit 30 connected. The evaluation circuit 30 also has an operational amplifier OP for amplifying the induced voltage signal from the wire loop 20 which is connected to an input of the comparator K to be led.

After comparing the detected voltage signal with the reference signal, the output signal of the comparator K fed to a flip-flop IC. An output of the flip-flop IC is further provided with an LED D1 connected, which _{falls below} the set limit value of the induced voltage U _ind permanently lit as long as the measurement takes place.

The 3 shows a trace of the induced voltages U _ind with and without winding closure, the solid curve represents the case in which no turn conclusion is present. The ordinate here represents an exemplary dimensionless value for the voltage amplitudes and peak values of the measured induced voltages U _ind , which in the undisturbed case (without winding short circuit) has approximately the magnitude 6.5. If there is one turn, this peak drops to about 2.5. Thus, a factor K of 2.6 was obtained.

An automatic shutdown of the engine via an electrical shutdown device, such. B. a relay would also be advantageous.

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

• EP 1312929 A1 [0004]
• DE 102008017900 A1 [0005]
• DE 102009004556 A1 [0006]
• DE 102009003549 A1 [0007]

Claims (6)

Evaluation device for detecting a short circuit in a stator coil (10) of an electrical machine, wherein the evaluation device has a wire loop (20) and an evaluation circuit (30) for detecting the induced in the wire loop (20) voltage U _ind , wherein the wire loop (20) is wound around the stator coil (10), wherein the stator coil (10) ends two measuring terminals (M1, M2) is formed, with which two input terminals (SENS1, SENS2) of the evaluation circuit (30) are connected and wherein the evaluation circuit (30) at least an operational amplifier (OP) for amplifying the voltage signal, a comparator (K) for comparing the detected voltage signal with a reference signal and a flip-flop IC (IC) for evaluating the result of the comparator (K) to generate a signal when the induced voltage U _ind detected in the wire loop (20) is smaller by a predetermined factor k than a target limit value of a desired value Reference voltage U _soll . Evaluation device according to Claim 1 , characterized in that in the evaluation circuit (30) further comprises an LED (D1) is provided which lights when falling below the desired limit value of the induced voltage U _ind , in particular permanently lit. Evaluation device according to Claim 1 or 2 , characterized in that the output of the comparator (K) is connected to an input of the flip-flop IC (IC). Evaluation device according to one of the preceding Claims 1 to 3 , characterized in that an input of the operational amplifier (O) is connected to one of the ends (M1, M2) of the wire loop (20). Evaluation device according to one of the preceding claims, characterized in that the factor k> 1.5, preferably greater than 2. Electric machine, in particular electric induction machine comprising an evaluation device according to one of Claims 1 to 5 ,

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