DE102009020479A1 - Method for testing conductivity or insulation fault of laminated stack in e.g. squirrel-cage rotor of asynchronous electric motor, involves outputting indication signal when difference of output voltages of sensors exceeds preset value - Google Patents

Abstract

The method involves assembling a magnetic field (60) in a measuring object i.e. laminated stack (50). A measuring arrangement (100) with two magnetic field sensors i.e. Hall sensors, is moved over a measuring object surface and over length dimension of the object. Magnetic field strength at the measuring surface is detected in the length dimension, and an indication signal is output when a difference of output voltages of the sensors locally exceeds a preset value at a point of the length dimension. An independent claim is also included for a measuring arrangement for testing conductivity or insulation fault of a magnetisable measuring object.

Description

The The invention relates to a method and a measuring arrangement for checking the conductivity or insulation faults of a magnetizable, in a longitudinal dimension emphasized DUT, in particular a laminated core of an electric motor.

Short runner of electric motors consist of a cage (made of copper or aluminum) with short rings and a package of a plurality of electrical sheets that are electrically insulated against each other Shaft made of round steel are attached. The electrical conductors are lying in rod form in outwardly open grooves of the individual sheets. The conductors are parallel to each other, but inclined to the shaft and be frontal of a shorting plate or a shorting ring short-circuited, forming the so-called cage.

Of the during operation of the electric motor current-carrying cage should the electric current with the lowest possible resistance conduct. The electrical, mechanical and chemical properties the materials of a short-circuit runner determine the Quality (functional property) of an electric motor. at a change in material properties and / or damage of the cage deteriorate its properties.

Often errors in short-circuited runners are due to damage the sheets and / or the cage (as an aging phenomenon or manufacturing defects), so that insulation defects arise. It can cracks, connecting weakness of the ladder with each other and enrichment of alloy materials arise. By change the conductor property, the magnetic flux density change and the electrical properties in the affected area.

When electrical measurement, a comparative measurement can be performed become. In this case, a voltage is induced in the rotor cage by a coil and next to the induction surface by a secondary coil the voltage is determined. Here are the values of different Measurements compared. Although possible Differences are measured, but it can not depend on the type of Error can be deduced because the induced voltages just a global but not local picture of the runner cage supplies.

A method for measuring damage to a cage or to end plates of asynchronous motors, which is also used in the operation of the engine is in the WO 2006048470 A1 been presented. The method is based on the use of an introduced into the motor auxiliary coil on which an induced voltage can be tapped.

A method for detecting hot spots in a stator of an electric generator is in WO 2004081594 A1 specified.

task the invention is to provide a method and an arrangement, which are suitable insulation faults, especially in squirrel cage rotors of Determine electric motors.

The Solution of the problem can be found in the independent claims. Advantageous embodiments are formulated in the respective subclaims.

• – Aufbau eines Magnetfelds in dem Messobjekt,
• – berührungsloses Erfassen der Magnetfeldstärke an der Messobjektoberfläche in der Längsdimension mittels mindestens zweier, vorzugsweise als Hallsensoren ausgebildeter Magnetfeldsensoren, deren jeweiligen (Hall- oder) Ausgangsspannungen gegenpolig geschaltet sind, und eine Indikationsspannung (oder Fehlersignal) ausgegeben wird, wenn die Differenz der beiden Ausgangsspannungen lokal an einer Stelle der Längsdimension einen vorbestimmten Wert als voreinstellbare Empfindlichkeitsschwelle überschreitet, wodurch Inhomogenitäten der Magnetfeldstärke an der Messobjektoberfläche erfassbar werden.

The core of the method is that in order to check the conductivity or insulation errors of a magnetizable, stressed in a longitudinal dimension object to be measured, in particular a laminated core of an electric motor, such as rotor or stator, the following steps are:

• Construction of a magnetic field in the measurement object,
• - Non-contact detection of the magnetic field strength at the measuring object surface in the longitudinal dimension by means of at least two, preferably designed as Hall sensors magnetic field sensors whose respective (Hall or) output voltages are connected in opposite polarity, and an indication voltage (or error signal) is output, if the difference of the two output voltages locally at a position of the longitudinal dimension exceeds a predetermined value as a presettable sensitivity threshold, whereby inhomogeneities of the magnetic field strength at the measuring object surface can be detected.

A corresponding measuring arrangement on which the method is based, is also claimed. With such a measuring arrangement can be Error, for example, squirrel cage electrical Determine asynchronous motors. The measuring arrangement allows a localization of errors and conclusions on causes of errors. The measuring arrangement is particularly suitable for use in quality control in new production or maintenance companies of electrical Asynchronous motors.

in the The following are characteristics listed individually or in common to be claimed.

The Indication signal - as a voltage-path diagram - can displayed on a meter or on a storage device recorded and / or displayed.

The movement of the measuring arrangement on the measuring object surface can take place both in a first direction of the longitudinal dimension of the measuring arrangement and in the opposite direction, so that a dop peltes voltage-path diagram is created and can be evaluated. The measuring arrangement has a preferred geometric direction, which should be aligned as parallel as possible to the longitudinal direction of the measurement object.

In of the measuring arrangement are at least two magnetic field sensors (Hall sensors) either parallel next to each other in the longitudinal direction of the longitudinal dimension (Preferred direction), or side by side across the longitudinal direction the longitudinal dimension arranged.

In A further advantageous embodiment may be a first pair magnetic field sensors associated with a second pair of magnetic field sensors be. Both pairs are parallel in the preferred direction next to each other. Again, the output or Hall voltage of the first pair is the Output or Hall voltage of the second pair connected in opposite polarity and an indication signal is output when the difference of the both output voltages locally at a location of the longitudinal extent exceeds a predetermined value.

Preferably a measuring arrangement should be designed so that at least two magnetic field sensors on a support or bracket made of ceramic or plastic, and the measuring arrangement contactless over the target surface is movable.

In the measuring arrangement, the magnetic field sensors in through arranged magnetic conducting body formed magnetic circuits be. Such an arrangement may consist in that on one the measurement object surface side facing away from a two magnetic field sensors bridging Yoke made of a magnetic material, so that on the back of the measuring arrangement a magnetic flux over the yoke takes place.

Farther can on any of the front sides of the measuring arrangement every magnetic field sensor a magnetic-conducting magnetic leg be upstream. As front side the measuring arrangement is meant the side of the magnetic field sensors, which faces the measuring object. The magnetic field at the measuring object surface thus flows through a first magnetic leg, a first magnetic field sensor, a yoke, a second magnetic field sensor and a second magnetic leg. The cross section of the magnetic conductive body should substantially the surface of the sensor plate of a magnetic field sensor correspond.

In a further advantageous embodiment, the the Magnetic field sensors to the measuring object upstream magnetic legs be wedge-shaped. This is a measurement object facing end face of the wedge shape narrower, as a back surface facing the magnetic field sensors the wedge shape. The wedge-shaped magnet legs rejuvenate extending from the back surface covering the surface (the cross-section) of the sensor platelets have, to the end face down (on the surface of the test object). The face is usually rectangular, in which case the long side of the Rectangles to lie parallel to the preferred direction of the measuring arrangement comes.

a from two magnetic field sensors (Hall sensors) formed first pair of magnetic field sensors with magnetic legs and yoke can be a second Pair of also two magnetic field sensors with magnetic legs and Be assigned yoke. The pairs are parallel next to each other the carrier arranged, wherein for outputting a first indication signal the output or Hall voltages of the first pair of output or Hall voltage of the second pair are connected in opposite polarity.

A particularly preferred embodiment of a measuring arrangement lies in the fact that a compilation of two parallel juxtaposed Pairing magnetic field sensors on both sides parallel to the pairs of magnetic field sensors in each case a further compilation of two magnetic field sensors with magnetic legs and yoke on the support assigned. Again, the output or Hall voltages the first compilation of the output or Hall voltages of the other Compilation switched to opposite polarity. It comes to the issue of a Indication signal if the two output voltages differ.

The magnetically conductive magnet legs and the yokes should preferably be made of ferrite.

Two Magnetic field sensors (Hall sensors) can be used in a measuring branch a bridge measuring circuit lie, so that the difference value of the Output or Hall voltages via the bridge measurement circuit is dispensable.

When Magnetic field sensors can be integrated Hall generators, including amplifier module are used, which are arranged in the form of a chip on a support.

The Measuring arrangement can be used to test short-circuited runners be designed by electric motors as a mobile measuring device.

preferred Embodiments of the invention are illustrated in the figures, which show in detail:

1A and 1B an arrangement with two magnetic field sensors and spatial representation;

2A and 2 B another arrangement with four magnetic field sensors and spatial representation;

3A and 3B two views of a magnetic circuit with two magnetic field sensors;

4 a view of two parallel magnetic circuits;

5 a spatial view of four parallel magnetic circuits;

6 a circuit arrangement and

7 different constructions.

to Initiation of a measurement process becomes a magnetic field in a measurement object Preferably, the inventive Method (and arrangement) for testing short-circuited runners be used by electric motors. Therefore, to the shorting rings a short-circuit rotor connected to a constant current source. The transmitted electric current generates a magnetic field in the measurement object, wherein the laminated core of the squirrel cage of the magnetic fields is flooded. The magnetic flux density becomes at the surface the squirrel cage with the illustrated circuit arrangement measured with magnetic field sensors (Hall sensors). When a (described below) error signal is a fault in squirrel cage. Such a mistake can mean that an insulation fault between at least two electrical sheets is present, or that conductor elements of the squirrel cage are interrupted or that between them a bad (high-impedance) Contact is available

Current-carrying Conductors have a magnetic field 90 ° to the current direction around the Ladder around. Due to inhomogeneities of the conductivity in a conductor, for example by non-conductive inclusions in the conductor, the current threads do not run in the conductor homogeneous, especially not parallel. This can be a change the magnetic flux density at the surface of the conductor to lead. The present measuring arrangement is thus also suitable, by Scanning along the longitudinal direction of a conductor inhomogeneities to determine the conductivity in the conductor.

In the 1A . 1B . 2A and 2 B is an example of the invention in the measurement of a laminated core 50 an electric motor explained. In the grooves 52 of the laminated core 50 a squirrel cage are transverse to the electrical sheets ( 50 ) running ladder 54 , The magnetization of the squirrel cage rotor is generated by DC or AC voltage applied to both ends of the squirrel cage rotor. The laminated core is flooded by the magnetic field. The individual, mutually insulated electrical sheets are perpendicular to the axis of the squirrel cage rotor. The one in the leader 54 flowing electricity generates the magnetic field 60 ,

With the measuring arrangement 100 the surface of the squirrel cage contactlessly along a groove 52 sampled. The traversing of the measuring arrangement can be done manually, or be moved in automated form for routine investigations in the electric motor manufacturing, in which the measuring arrangement 100 is guided in a rack. Into the magnetic flux circuit 60 thus arrive - in the simplest case 1B - Formed as a Hall sensors magnetic field sensors H1, H2, which - in differential circuit against each other - deliver a measuring voltage within a presettable sensitivity of the measuring arrangement. During scanning, the measuring assembly is driven from the beginning to the end of a groove and back in one pass. The path of the measuring arrangement is then twice the groove length. The measurement values can then be recorded over time by a oscilloscope in a positive forward direction and in a negative direction in a forward measurement. The representation of the measurement signals is thus a path-time diagram. A direct comparison of both measurement paths allows the determination of whether a defect is present in the measurement object.

In the situation where the electric sheets 50 are neatly isolated against each other, and in the ladder 54 (Rotor bars, and short-circuiting rings) of the squirrel cage rotor have clean contacts (welding), resulting in a homogeneous magnetic field in strength and direction 60 on the surface of the squirrel cage. In the case of a fault of the squirrel cage rotor, which is an insulation defect between electric sheets or in a broken or high resistance contact between conductor elements of the squirrel cage rotor, the superficial magnetic field is 60 no longer homogeneous.

At defective areas cause increased eddy currents, the one change of an otherwise homogeneous magnetic field cause. Hall voltages of the two magnetic field sensors (Hall sensors) in Differential circuit result in a finite value. From the record, or in the simplest case from the consideration of a measuring instrument (Oscilloscope) can locate the location of the error.

The basic principle of the measurement arrangement for a magnetic flux density is that the off output or Hall voltages of two magnetic field sensors are connected in opposite polarity (see 4 . 5 and 6 ) and the difference of the output or Hall voltages is evaluated as a measurement signal. A homogeneous magnetic field at the surface of a test object does not provide a measuring signal with this measuring principle. A change (inhomogeneity) of the magnetic flux density at the surface of a DUT means that a difference in the output voltages of two pairs of opposite polarity switched magnetic field sensors arises.

Two magnetic field sensors (Hall sensors H1, H2) - as in 3A or 3B - Can be arranged in a bridge circuit, both magnetic field sensors in a bridge branch and two identical voltage sources in a second bridge branch. The resulting from the (superficial) magnetic field output or Hall voltages of the two in their polarity mutually connected magnetic field sensors H1, H2 is as a resultant (as a voltage difference) (for example U1 in 6 ) tapped at the output of the bridge circuit.

3A and 3B show a measuring arrangement ( 100 ), which is composed of only two Hall sensors H1, H2. To increase the sensitivity, it is recommended to use a measuring arrangement in which four Hall sensors H1 ... H4 are assembled according to the principle of a bridge circuit ( 4 . 5 and 6 ).

The invention goes into 3A and 3B from a measuring arrangement, in which the magnetic field exiting from the surface of the measuring object is closed via magnet-conducting bodies to form a flow-through circuit. To 3A includes the measuring arrangement 100 two magnetic legs 10'a . 12'a ; or - in 3B - 10a . 12a and a magnetic yoke 14a , The material of the magnetic body should have a very low and constant magnetic resistance. A remanence should be low (if possible not present). Preferably, ferrite is proposed as the material for the magnetic conductive bodies.

The 3A . 3B . 4 and 5 represent schematic views. There, the contacts (electrical supply and discharge lines) of the Hall sensors H1 ... H4 (for control voltage and for Hall voltage) are not shown. Furthermore, a carrier of the respective arrangement is not indicated. Spacers are present between the magnet-conducting bodies (also not shown). A measuring arrangement can be supported for example in an embedding of plastic (casting resin) or ceramic.

The front of the measuring arrangement lies in the 3 to 5 front, the back in the picture. The preferred direction of the measuring arrangement ( 3B : parallel to the edges of the wedge shape) is denoted by the reference L1-L1, a transverse extent (transverse to the edges of the wedge) L2-L2. The scanning of the measurement object is carried out without contact in the preferred direction L1-L1, so that the preferred direction with the longitudinal direction of the measurement object (position of the conductor 54 in the groove 52 ) coincides. However, it is also possible to make a scan in transverse extension.

The thickness of electrical sheets is relatively small for electric motors in the lower power classes; about 0.5 mm thick. Hall sensors with integrated digital amplifier module have a typical size of about 5 × 5 mm. Since the cross-section of such Hall sensors compared to the thickness of the electrical steel sheets is excessively large, it is proposed that the formation of the magnetic leg 10a . 12a adapt this geometric situation by forming the magnetic leg in a wedge shape. 3B shows such a modification of the arrangement of 3A in which the magnet legs are wedge-shaped. Starting from a cross-sectional area at the location of the Hall sensors H1, H2 (corresponding to the measuring surface of the Hall sensors) are the magnet legs 10a . 12a formed to the front and measuring range (L1-L1, or L2-L2) wedge-shaped tapered. The width of the front side 10S . 12S the magnetic leg 10a . 12a corresponds in this training about the thickness of the electrical steel sheets. The magnetic flux in the magnetic circuit 10a , H1, 14a , H2, 12a is essentially determined only by the leaking from a single electric sheet magnetic field.

4 shows an expanded measuring arrangement in which four Hall sensors H1 ... H4 are interconnected. The output voltage of the first pair of Hall sensors H1, H2 is reverse-connected to the output voltage of the second pair of Hall sensors H3, H4, and an error signal is output if the difference of the two indication voltages locally exceeds a predetermined value at a position of the longitudinal dimension of the measurement object.

Such an arrangement lends itself to because the Hall sensors can be interconnected in a bridge circuit. In such a measuring arrangement, the Hall voltages UH of the two Hall sensors H1 and H2 are in a first branch of a bridge circuit and the Hall voltages UH of the other two Hall sensors H3 and H4 in the second branch of the bridge circuit. The details of the bridge circuit are in 6 explained in more detail.

In 5 a particularly preferred arrangement is shown consisting of two magnetic circuits ( 10a . 14a . 12a and 10b . 14b . 12b ), as they are already in 4 are shown and in the two other magnetic circuits 10c . 14c . 12c and 10d . 14d . 12d are added laterally parallel. As in the previously discussed figures, there are four Hall sensors between the bodies 10a and 14a (H1), between 14a and 12a (H2), and between 10b and 14b (H3) and between 14b and 12b (H4). Not drawn, but there are still four Hall sensors between the bodies 10c and 14c , between 14c and 12c , and between 10d and 14d and between 14d and 12d , The first two magnetic circuits ( 10a . 14a . 12a and 10b . 14b . 12b ) serve - as I said - the "enlargement" of the flow cross-section on the measuring surface of the Hall sensors H1, H2. The magnetic circuits with the bodies 10c . 14c . 12c and 10d . 14d . 12d serve the magnetic shielding. The shielding achieves a reduction of the errors in the measuring range and an increase of the sensitivity.

In summary, it can be said about the measuring arrangements: There are at least two, preferably four, magnetic circuits parallel to each other. Each magnetic circuit comprises a first leg 10 (a, b, c, d), one perpendicular to the first leg 10 (a, b, c, d) arranged yoke 14 (a, b, c, d) and a second leg 12 (a, b, c, d) lying parallel to the first leg 10 (a, b, c, d), the second leg 12 (a, b, c, d) is again perpendicular to the yoke 14 (a, b, c, d).

The magnetic flux in each magnetic circuit passes through a first leg, a first Hall effect sensor, a magnetic yoke, a second leg, and the air space in front of the end faces of the two legs (front of the measuring arrangement), in which the measurement object is located. Each magnetic circuit is closed on the front of the measuring arrangement via a measuring object, or via an air gap located there. The respective first legs 10 (A, b, c, d) of a magnetic circuit are in a first plane, the respective second leg 12 (a, b, c, d) of a magnetic circuit lie in a second plane parallel to the first plane, the yokes 14 (a, b, c, d) lie in a common plane perpendicular to that of the legs 10 and 12 formed plane, so that a parallel arrangement of the magnetic circuits arises. Preferably, the legs 10a . 10b . 12a . 12b shaped so that it extends from the back of the flow on the side of the yoke to the leg end faces 10S . 12S taper, in particular tapering in a wedge shape, wherein in each case a first Hall sensor H1, H3 in an intermediate space 16 ( 5 ) between the flooding back of the first leg 10a . 10b and the associated yoke 14a . 14b and a second Hall sensor H2, H4 in a gap 16 between the back of the second leg 12a . 12b and the associated yoke 14a . 14b located.

The resulting from a magnetic field measuring voltages of two Hall sensors (H1, H2, H3, H4) of a magnetic circuit are in their polarity switched against each other. The resultant (voltage difference) we output as indication voltage.

The Resultant (voltage difference) (U1) of the first pair (H1, H2) the resultant (voltage difference) (U3) of the second pair (H3, H4) is switched in opposite polarity and it becomes a finite indication signal UM output when the difference between the two resultants (U1-U3) locally at a location of the longitudinal dimension a predetermined Value exceeds.

The 6 shows a circuit arrangement with eight magnetic field sensors H1 ... H8 according to the arrangement of 5 , As magnetic field sensors Hall generators are used, in which the Hall sensors are realized with an internal amplifier and a built-in differential amplifier on a chip. The Hall generators deliver a Hall voltage UH that is proportional to the magnetic flux density 60 is at the surface of the measurement object. The circuit arrangement is based on the known principle of a bridge measuring circuit (according to Wheatstone). In the bridge measuring circuit, at least four bridge links are interconnected, two of them in series and the series links in parallel. The measuring signal is determined in the diagonal path of the bridge. In the presented circuit arrangement, the bridge members are designed as Hall sensors (generators).

basics Details of a bridge circuit are for the Skilled and understandable, such as the use a harmonic-free DC power source for the control voltage US or the use of other amplifiers, the sensitivity increase the measuring arrangement. Because the fields to be measured usually weak, need to use amplifiers become. The Hall effect generators are in this circuit with a built-in amplifier running. The integrated Amplifier is located directly behind the Hall effect generators and is realized with a transistor circuit. The circuit arrangement can be designed as an analogue as well as a digital scarf device. The measuring voltages can be over operational amplifiers be prepared in digitized form.

In usually have commercial Hall sensors and amplifiers different base voltages and tolerances. To these differences compensate, the magnetic field sensors and amplifiers uniformly calibrated (calibrated). These are tuning potentiometers R1 (eg with 200 kOhm) used.

In the 6 described circuit arrangement consists of two bridge circuits. A first bridge circuit is used to measure the magnetic fields and the other bridge circuit is used for control and overview measurement. However, an overview measurement is not absolutely necessary for the actual measuring procedure.

The Hall sensors H1 with H2 are in the same measuring circuit and this applies also for H3 with H4, H5 with H6 and H7 with H8.

The Hall sensors H1, H3, H5, H7 are in the same magnetic field direction (exiting or entering magnetic field) and the Hall sensors H2, H4, H6 and H8 are in the opposite magnetic field direction.

To When the values in a measuring path are determined, the signal is switched to passed another potentiometer (R2) and recalibrated and continued on a differential amplifier (S3) passed.

In this step will be the differences in the gain factors the operational amplifier (S rows) compensates and the Values made comparable.

The Measuring circuits are calibrated to each other with the potentiometer R2 and the differences of the circuits to be measured are by differential amplifiers S3 determined as the potential difference between the indication signal UM - mass GRD and U2 - mass GRD output.

at The measurement of a constant and homogeneous field is determined by the circuit arrangement Signal with constant value output. At a difference (increase or attenuation) of the field changes leaking signal proportional to change in the measured Field. The steepness of the change depends on the settings of the Circuit and design dependent. The evaluation type of Measurement is not relevant here as it is done in different ways can be carried out.

The 7 shows various structures of measuring arrangements with magnetic field sensors. As should be apparent from the foregoing description, the structures differ in their complexity, and thus in the sensitivity of the evaluation of the measurements.

A

nur ein Magnetfeldsensor ohne Joch und ohne vorgelagerte Keilform; keine Vorzugsrichtung in Bezug auf einen stromführenden Leiter; der Magnetkreis liegt (mit Ausnahme des Magnetfeldsensors) vollständig in Luft;

B

zwei Magnetfeldsensoren in Reihe parallel zu einem stromführenden Leiter (ohne Joch und ohne vorgelagerte Keilform)

C

zwei Magnetfeldsensoren gegenüber quer zu einem stromführenden Leiter (ohne Joch und ohne vorgelagerte Keilform)

D

zwei Magnetfeldsensoren jeweils paarweise gegenüber quer zu einem stromführenden Leiter

E

ein Magnetfeldsensor (wie A) mit vorgelagerter Keilform

F

zwei Magnetfeldsensoren (wie B) mit vorgelagerten Keilformen

G

zwei Magnetfeldsensoren (wie C) mit vorgelagerten Keilformen.

H

zwei Magnetfeldsensoren jeweils paarweise (wie D) mit vorgelagerten Keilformen

I

zwei Magnetfeldsensoren überbrückt rückseitig mit einem Joch ohne vorgelagerte Keilform

J

zwei Magnetfeldsensoren überbrückt rückseitig mit einem Joch mit vorgelagerter Keilform

K

zwei Magnetfeldsensoren paarweise und paarweise überbrückt rückseitig mit einem Joch ohne vorgelagerte Keilform

L

zwei Magnetfeldsensoren paarweise und paarweise überbrückt rückseitig mit einem Joch mit vorgelagerten Keilformen (wie in 4)

The structures are described in tabular form:

A

only a magnetic field sensor without yoke and without upstream wedge shape; no preferred direction with respect to a current-carrying conductor; the magnetic circuit is completely in air (except for the magnetic field sensor);

B

Two magnetic field sensors in series parallel to a live conductor (without yoke and without upstream wedge shape)

C

Two magnetic field sensors opposite to a current-carrying conductor (without yoke and without upstream wedge shape)

D

two magnetic field sensors in pairs opposite each other across a current-carrying conductor

e

a magnetic field sensor (like A) with an upstream wedge shape

F

two magnetic field sensors (like B) with upstream wedge shapes

G

two magnetic field sensors (like C) with upstream wedge shapes.

H

two magnetic field sensors in pairs (like D) with upstream wedge shapes

I

Two magnetic field sensors bridge the back with a yoke without an upstream wedge shape

J

Two magnetic field sensors bridge the back with a yoke with an upstream wedge shape

K

two magnetic field sensors in pairs and in pairs bridged at the back with a yoke without an upstream wedge shape

L

two magnetic field sensors in pairs and in pairs bridged at the back with a yoke with upstream wedge shapes (as in 4 )

10 (a, b, c, d) 10'a

first leg

10S

front the first leg

12S

front the second leg

11a ... 11d

front the first leg

12 (a, b, c, d) 12'a

second leg

13a ... 13d

front the second leg

14 (a, b, c, d)

yokes

15

distance the first leg of second thighs

16

distance the leg of the associated yoke (gap)

50

Laminated core electrical sheets

52

groove

54

ladder

60

magnetic field

100

Measuring arrangement

H1 ... H4 ... H8

Magnetic field sensor, Hall sensor, Hall generator

L1 L1

preferred direction

L2 L2

transverse extension

R1, R2

Ausgleichpotentiometer

S, S2,

subtractor OP amplifier

GRD

ground potential

UH

Output voltage, Hall voltage

U1 ... U7

difference the Hall voltages

AROUND

indication signal

US

control voltage

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

• - WO 2006048470 A1 [0006]
• - WO 2004081594 A1 [0007]

Claims (16)

Method for checking the conductivity or insulation faults of a magnetizable, in a longitudinal dimension emphasized object to be measured, in particular a laminated core of an electric motor, with the following method steps - construction of a magnetic field ( 60 ) in the measurement object ( 50 . 52 ), - moving a measuring arrangement ( 100 ), which comprises at least two magnetic field sensors (H1, H2), via the measurement object surface and over the longitudinal dimension (L1-L1, L2-L2) of the measurement object ( 100 ), - detecting the magnetic field strength ( 60 ) at the measuring object surface in the longitudinal dimension (L1-L1; L2-L2), wherein the respective output voltages (U1, U3) of the magnetic field sensors (H1; H2) are connected in opposite polarity, and - an indication signal (UM) is output if the difference the two output voltages (U1, U3) locally exceeds a predetermined value at a position of the longitudinal dimension. Method according to claim 1, characterized in that that the indication signal (UM) is recorded. Method according to claim 1 or 2, characterized in that the movement of the measuring arrangement ( 100 , H1, H2) on the measurement object surface both in a first direction of the longitudinal dimension (L1-L1; L2-L2) and in the opposite direction. Method according to one of the preceding claims, characterized in that a first pair of magnetic field sensors (H1, H2) is associated with a second pair of magnetic field sensors (H3, H4), the parallel in the longitudinal direction next to each other, the magnetic field strength and that the output voltage (U1) of the first pair (H1, H2) of the output voltage (U2) of the second pair (H3, H4) with opposite polarity is switched and an indication signal (UM) is output when the difference between the two output voltages (U1, U3) locally at one Position of the longitudinal dimension exceeds a predetermined value. Measuring arrangement for carrying out a method according to one of the preceding claims, characterized that at least two magnetic field sensors (H1, H32) on a support are arranged, which over the measuring object surface is movable. Measuring arrangement according to claim 5, characterized in that that in the measuring arrangement, the at least two magnetic field sensors (H1, H2, H3, H4) in succession parallel to the longitudinal direction the longitudinal dimension (L1-L1; L2-L2) are arranged. Measuring arrangement according to claim 5, characterized in that that in the measuring arrangement, the at least two magnetic field sensors (H1, H2, H3, H4) side by side transversely to the longitudinal direction of the longitudinal dimension (L1-L1, L2-L2) are arranged. Measuring arrangement according to claim 6 or 7, characterized in that on a side remote from the measurement object surface side of the two magnetic field sensors (H1, H2) a two magnetic field sensors (H1, H2) bridging yoke ( 14a ) is arranged from a magnetically conductive material, so that on the side of the magnetic field sensors (H1, H2) facing away from the target surface, a magnetic flux through the yoke (FIG. 14a ) takes place. Measuring arrangement according to the preceding arrangement claim, characterized in that on the side of the magnetic field sensors (H1, H2) facing the measuring object surface each magnetic field sensor (H1, H2) has a magnetically conducting magnetic leg ( 10a . 12a ) is upstream. Measurement arrangement according to the preceding arrangement claim, characterized in that the magnetic legs upstream of the magnetic field sensors (H1, H2) ( 10a . 12a ) are formed in a wedge shape, so that one of the target surface directed to the target surface ( 10S . 12S ) of the magnetic leg ( 10a . 12a ) is narrower in wedge shape than a magnetic leg directed towards the back of the magnetic field sensors (US Pat. 10a . 12a ) in a wedge shape. Measuring arrangement according to the preceding arrangement claim, characterized in that a first pair of Hall sensors (H1, H2) formed by two magnetic field sensors with magnetic legs ( 10a . 12a ) and yoke ( 14a ) a second pair also of two Hall sensors (H3, H4) with magnetic legs ( 10b . 12b ) and yoke ( 14b ), which are arranged parallel to one another on a carrier, wherein the output or Hall voltage (U1) of the first pair (H1, H2) of the output or Hall voltage (U2) of the second pair (UH) for outputting a first indication signal (UH) H3, H4) is connected in opposite polarity. Measuring arrangement according to the preceding arrangement claim, characterized in that an arrangement of two parallel adjacent pairs of magnetic field sensors (H1, H2) on both sides parallel to the pairs of magnetic field sensors (H1, H2) each have a further arrangement of two magnetic field sensors (H3, H4 ) with magnetic legs ( 10b . 12b ) and yoke ( 14b ) are arranged on a carrier, and output voltages of the magnetic field sensors of the further arrangement are connected in antipole, so that the output voltage for outputting a second indication signal (UH) of the first pair of the output voltage (UH) of the second pair is connected in opposite polarity. Measuring arrangement according to one of the claims 8 or 9, characterized in that the magnetic conducting material ( 10a ... 10d ; 12a .. 12d . 14a ... 14d ) Are ferrites. Measuring arrangement according to one of the preceding arrangement claims, characterized in that the output voltage (UH) of two magnetic field sensors (H1, H2) in a first branch of a bridge measuring circuit and two comparison voltage sources in a second branch of the bridge measuring circuit lie and the indication voltage of the two magnetic field sensors (H1, H2) are tapped at the output of the bridge measuring circuit. Measuring arrangement according to one of the preceding arrangement claims, characterized in that the magnetic field sensors (H1 ... H8) as Semiconductor integrated Hall generators formed and including Amplifier module arranged on a support are. Measuring arrangement according to one of the preceding claims, characterized in that the measuring arrangement ( 100 ) is designed for testing short-circuit rotors of electric motors as a mobile measuring device.