CN104458894A - Detecting method and detecting device for T-shaped tail slot of magnetic poles and magnet yokes of high-speed hydrogenerator rotor - Google Patents

Abstract

The invention discloses a detection method and device for a high-speed hydraulic generator rotor magnetic pole magnetic yoke T tail slot. The detection method uses a magnet to magnetize the magnetic pole magnetic yoke T tail slot, and blocks the magnetic field lines passing through the surface of the T tail slot when there is a crack. , so that the magnetic flux in the magnetic circuit is distorted, causing part of the magnetic flux to escape from the surface of the T-tail groove, forming a leakage magnetic field in the space, using the magnetic sensor to obtain the magnetic flux leakage signal, and detecting the magnetic flux leakage signal through the magnetic flux leakage detector. The device includes a crack probe detection device, a guide bracket and a magnetic flux leakage detector. The crack probe detection device is installed on the guide bracket, and the crack probe detection device is connected with the magnetic flux leakage detector through a signal transmission line; The П-shaped magnet A on the guide bracket and the three-dimensional Hall probe, the three-dimensional Hall probe is connected to the signal transmission line through the signal terminal through the signal amplification and digital-to-analog conversion circuit.

Description

Detection method and device for high-speed hydraulic generator rotor magnetic pole yoke T tail groove

technical field

The invention relates to a detection method and a device for a T-tail groove, in particular to a detection method and a device for a T-tail groove of a rotor magnetic pole yoke of a high-speed hydraulic generator.

Background technique

The T-tail slot is a connection structure between the magnetic stage and the yoke of the hydraulic generator. It is made of silicon steel laminations with a thickness of 4mm. It bears a large alternating stress during the start-up and stop process, especially the stress value at the inner corner position. The largest, easy to initiate fatigue cracks, and there have been accidents where all the magnetic yokes of generators were replaced, resulting in huge direct and indirect losses. In order to ensure the safety of the T-tail groove connecting the magnetic pole and the yoke of the high-speed (500r/min) hydro-generator under long-term frequent start-stop conditions, it is necessary to perform crack detection on the T-tail groove of the magnetic pole yoke. The conventional non-destructive testing methods for detecting cracks include eddy current testing (ET), magnetic particle testing (MT) and penetrant testing (PT). All three methods can detect cracks on the surface of non-porous workpieces. In the conventional eddy current detection of cracks, although no detection fluid is used, there is no residual problem, but due to the strong "boundary effect" of the laminated silicon steel sheet on the eddy current signal, the crack eddy current signal is submerged in the background eddy current interference, and the signal-to-noise ratio is extremely low , cracks cannot be detected. For conventional magnetic particle inspection, water-based or oil-based magnetic suspension must be used. During the inspection, the magnetic suspension will enter the gap between the laminations and cannot be cleared out after the inspection. This will not only reduce the insulation of the magnetic grade yoke, but also cause pollution. In conventional penetrant detection of cracks, in addition to being unable to solve the problem of penetrant removal after detection, the re-seepage of residual penetrant in the lamination gap will greatly reduce the detection sensitivity, resulting in missed detection of cracks, which is also not applicable.

Contents of the invention

The object of the present invention is to provide a non-destructive testing method and device for the tail slot of the magnetic pole yoke T of the high-speed hydraulic generator rotor. The invention not only realizes the requirement of non-pollution, no residue and no reduction in insulation detection for the T tail slot of the magnetic pole yoke lamination structure, but also has high sensitivity and good accuracy, and fully meets the strict electrical and metal safety requirements of large hydroelectric generator sets The regulations improve the reliability of the operation of power generation equipment and are an important guarantee for the safety of hydroelectric generators.

The technical scheme of the present invention: the detection method of the T-tail groove of the rotor magnetic pole yoke of the high-speed hydraulic generator, which is characterized in that: the T-tail groove of the magnetic pole yoke is magnetized by a magnet, and the magnetic field lines passing through the surface of the T-tail groove are blocked when there is a crack , so that the magnetic flux in the magnetic circuit is distorted, causing part of the magnetic flux to escape from the surface of the T-tail groove, forming a leakage magnetic field in the space, using the magnetic sensor to obtain the magnetic flux leakage signal, and detecting the magnetic flux leakage signal through the magnetic flux leakage detector.

In the aforementioned detection method of the rotor magnetic pole yoke T tail groove of the high-speed hydraulic generator, the probe is sent to the detection position through the probe guide bracket, and the constant force structure is used to make the probe close to the surface under inspection, and the П-shaped magnet A magnetizes the detection position The ferromagnetic laminations generate an induced magnetic field. When the excited magnetic field lines encounter a crack at the tested position of the T tail groove, a leakage magnetic field will be formed at the crack. The leakage magnetic field is received by the magnetic sensitive element in the probe and converted into a digital signal. , through the magnetic flux leakage detector to process and display the signal of the crack leakage magnetic field, so as to determine whether there is a crack in the checked T tail groove.

In the aforementioned detection method for the T tail groove of the rotor magnetic pole yoke of the high-speed hydraulic generator, the method for determining whether there is a crack in the T tail groove under inspection is to place the three-dimensional Hall probe at the detection position through the guide bracket, and the three-dimensional Hall probe The Hall element Z in the probe is parallel to the plane of the magnetic pole yoke lamination, so that the X, Y, and Z direction signals of the three-dimensional Hall probe are all set to zero; when the ratio of the X direction signal to the Z direction signal strength is greater than or equal to 25: 1 or when the ratio of the Y-direction signal to the Z-direction signal intensity is greater than or equal to 50:1, it is judged that there is an abnormality on the laminated surface of the detected part.

In the aforementioned detection method of the rotor magnetic pole yoke T tail groove of the high-speed hydro-generator, the magnetic particle detection method is used to re-examine the position where there is an abnormal magnetic field; the magnetic particle detection method is carried out according to the following steps:

Clean the surface of the signal abnormal part in the magnetic flux leakage detection;

Turn on the power of the magnetic particle testing device;

Place the probe of the magnetic particle detection device on the surface of the abnormal part;

Slightly shake the magnetic suspension watering can, and evenly spray the magnetic suspension on the surface of the abnormal part;

The magnetic powder applied on the surface is adsorbed by the leakage magnetic field, and visually visible magnetic marks are formed under the ultraviolet light of 365nm wavelength, so as to confirm that there is a crack in the T tail groove of the tested magnetic pole yoke.

In the detection method of the aforementioned high-speed hydraulic generator rotor pole yoke T tail slot, the magnetic suspension is mixed by the following raw materials in parts by weight: 71-73 parts of ethanol, 16-18 parts of ethyl acetate, 2.5 - 3.5 parts of chloroform, 1.5-2.5 parts of acetone, 0.15-0.25 parts of fluorescent magnetic powder; the particle size of the fluorescent magnetic powder is 350 mesh.

Realize the detection device of the aforementioned high-speed hydraulic generator rotor magnetic pole yoke T tail slot detection method, which is characterized in that it includes a crack probe detection device, a guide bracket and a magnetic flux leakage detector, and the crack probe detection device is installed on the guide bracket. The probe detection device is connected with the magnetic flux leakage detector through a signal transmission line; the crack probe detection device includes a П-shaped magnet A and a three-dimensional Hall probe fixed on the guide bracket through an elastic member, and the three-dimensional Hall probe is arranged on the П-shaped magnet A. Between the two poles of the opening, and extending forward to the top of the slanted legs of the П-shaped magnet A, the three-dimensional Hall probe is connected to the signal transmission line through the signal terminal and the signal transmission line through the signal amplification and digital-to-analog conversion circuit.

In the detection device of the aforementioned high-speed hydro-generator rotor magnetic pole yoke T tail slot, the three-dimensional Hall probe is a three-dimensional magnetically sensitive Hall element array, which consists of three mutually perpendicular sheet-like Hall elements X, Y, and Z. Composed of components, three Hall elements are arranged in a T shape, which can simultaneously measure the magnitude and direction of the magnetic field in the three directions of XYZ.

In the aforementioned detecting device for the tail slot of the magnetic pole yoke T of the high-speed hydro-generator rotor, the guide bracket is provided with a handle for moving the guide bracket.

In the aforementioned high-speed water turbine generator rotor pole yoke T tail groove detection device, the П-shaped magnet A is a neodymium-nickel-cobalt permanent magnet, which is used to magnetize the part to be tested, and the two poles of the opening form a 45° slope Shaped, respectively attached to the two sides of the inner corner of the T tail groove

In the detection device of the aforementioned high-speed hydro-generator rotor magnetic pole yoke T tail groove, it also includes a crack magnetic particle detection device; the crack magnetic particle detection device includes a П-shaped magnet B, which is a neodymium-nickel-cobalt type permanent magnet, and is used to detect the position of the detected part. For magnetization, the two poles of the opening are formed into a 45° inclined plane, which are respectively attached to the two sides of the inner corner of the T tail slot;

A micro-LED ultraviolet lamp with a central wavelength of 365nm is fixed between the two stages at the opening of the П-shaped magnet B to excite fluorescent magnetic powder;

Power terminal, installed on the П-shaped magnet B, connected to the miniature LED type ultraviolet lamp;

DC power supply with on/off display and built-in battery to provide power for the UV lamp;

Flame-retardant power cord for connecting DC power supply and power terminals.

Compared with the prior art, the present invention detects the cracks in the T-tail groove of the magnetic pole yoke of the high-speed hydro-generator, timely discovers the dangerous cracks generated during the operation of the workpiece, and avoids the expansion of the cracks, threatening the safe operation of the unit. The invention not only realizes the requirement of non-pollution, no residue and no reduction in insulation detection for the T tail slot of the magnetic pole yoke lamination structure, but also has high sensitivity and good accuracy, and fully meets the strict electrical and metal safety requirements of large hydroelectric generator sets The regulations improve the reliability of the operation of power generation equipment and are an important guarantee for the safety of hydroelectric generators.

The invention adopts a special crack magnetic flux leakage detection probe for the T-tail groove, which integrates the functions of magnetization and three-dimensional magnetic field detection, and can detect the cracks of the magnetic pole yoke laminations sensitively and quickly without any influence on the electrical performance of the workpiece.

Through the characteristic comparison of the crack magnetic flux leakage signal in the XYZ three directions, the identification of the crack signal and the magnetic pole lamination gap signal is realized, and the problem that the conventional magnetic flux leakage method cannot detect the lamination crack is solved.

In order to ensure the accuracy and stability of the position of the magnetic flux leakage probe during the detection process, a special probe bracket and guide device are designed. This bracket also supports the rapid replacement of the probe to take into account the fluorescent magnetic particle detection.

Special crack fluorescent magnetic particle detection probe for T tail groove, and non-residual fluorescent magnetic powder formula that does not reduce the insulation performance of the workpiece, and the corresponding detection process has been formulated to realize the re-inspection of cracks and improve the high reliability of crack detection.

The invention can detect the cracks in the T-tail groove of the magnetic pole yoke of the high-speed hydraulic generator, and timely discover the dangerous cracks generated during the operation of the workpiece, so as to avoid the expansion cracks and threaten the safe operation of the unit. The invention can accurately and reliably judge the existence and equivalent depth of cracks in the T tail groove.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a structural schematic diagram of a crack probe detection device;

Fig. 3 is a structural schematic diagram of a three-dimensional Hall probe;

Fig. 4 is a schematic diagram of crack magnetic flux leakage detection state;

Fig. 5 is a structural schematic diagram of a crack magnetic particle detection device.

The marks in the drawings are: 1-magnetic flux leakage detector, 2-signal transmission line, 3-handle, 4-guiding bracket, 5-crack probe detection device, 6-elastic part, 7-magnetic pole yoke, 8-T tail Slot, 9-П-shaped magnet A, 10-signal terminal, 11-signal amplification and digital-to-analog conversion circuit, 12-three-dimensional Hall probe, 13-П-shaped magnet B, 14-power terminal, 15-miniature LED type ultraviolet lamp , 16-flame retardant power cord, 17-DC power supply.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but not as a basis for limiting the present invention.

Example. The detection method of the rotor magnetic pole yoke T tail groove of the high-speed hydro-generator is to send the probe to the detection position through the probe guide bracket, and use the constant force structure to make the probe close to the surface under inspection. The laminated sheets generate an induced magnetic field. When the excited magnetic field lines encounter a crack at the tested position of the T-tail groove, a leakage magnetic field will be formed at the crack. The leakage magnetic field is received by the magnetic sensitive element in the probe and converted into a digital signal. The magnetic detector performs signal processing and display on the leakage magnetic field of the crack, so as to determine whether there is a crack in the checked T tail groove.

The method for determining whether there is a crack in the checked T tail groove is, as shown in FIG. The planes are parallel; the X, Y, and Z direction signals of the three-dimensional Hall probe are all set to zero; when the ratio of the X direction signal to the Z direction signal strength is greater than or equal to 25:1 or the ratio of the Y direction signal to the Z direction signal strength When it is greater than or equal to 50:1, it is judged that there is an abnormality on the surface of the laminated sheet at the detected part.

Then use the magnetic particle detection method to re-examine the parts with abnormal magnetic field; the magnetic particle detection method is carried out according to the following steps:

Clean the surface of the signal abnormal part in the magnetic flux leakage detection;

Turn on the power of the magnetic particle testing device;

Place the probe of the magnetic particle detection device on the surface of the abnormal part;

Slightly shake the magnetic suspension watering can, and evenly spray the magnetic suspension on the surface of the abnormal part;

The magnetic powder applied on the surface is adsorbed by the leakage magnetic field, and visually visible magnetic marks are formed under the ultraviolet light of 365nm wavelength, so as to confirm that there is a crack in the T tail groove of the tested magnetic pole yoke.

The magnetic suspension is mixed by the following raw materials in parts by weight: 71-73 parts of ethanol, 16-18 parts of ethyl acetate, 2.5-3.5 parts of chloroform, 1.5-2.5 parts of acetone, 0.15-0.25 parts of fluorescent magnetic powder ; The particle size of fluorescent magnetic powder is 350 mesh. The boiling point of the magnetic suspension is lower than 80°C. Once applied, it will evaporate rapidly at room temperature in a short time without any liquid residue. The use process is as follows: The magnetic suspension should be prepared within 5 minutes before use, put into a closed pressure watering can, and the sensitivity should be checked on the 1mm wire groove on the crack test plate. The validity period of the magnetic suspension should not exceed 30 minutes. Observe under the ultraviolet lamp whether there are cracks and magnetic marks detected (cracks that absorb fluorescent magnetic powder will show bright yellow-green fluorescence under the irradiation of ultraviolet rays with a wavelength of 365nm). Preferably, the magnetic suspension is prepared by mixing the following raw materials in parts by weight: 72.8 parts of ethanol, 17 parts of ethyl acetate, 3 parts of chloroform, 2 parts of acetone, and 0.2 parts of fluorescent magnetic powder.

Using pole yoke lamination crack comparison test plate

Test plate material: silicon steel sheet; test plate thickness: 5mm

Test plate size: 240mm×225mm

Artificial defect: wire groove (simulated crack); processing method: EDM

#1 Test block: Groove size: depth 1.0mm; length 4mm; opening width 0.25mm

#2 Test block: Groove size: depth 2.0mm; length 4mm; opening width 0.25mm

#3 Test block: Groove size: depth 3.0mm; length 4mm; opening width 0.25mm

Use of crack comparison test plate:

Use the wire groove on the test plate to simulate the actual crack. If the signal strength of the actual crack measured by the detection device is consistent with the signal of the wire groove at a certain depth on the test board, then use the wire groove depth as the equivalent depth of the actual crack.

Before the magnetic flux leakage detection, the sensitivity verification and calibration of the magnetic flux leakage detection device shall be carried out on the test board;

After the crack detection, the crack signal found in the detection is compared and measured to determine the equivalent depth of the crack.

During the detection process, the sensitivity of the magnetic flux leakage and magnetic particle detection system can be verified and checked at any time.

Quality assessment and treatment of cracks:

assessment:

When the equivalent depth of the crack is 1mm~2mm, it is rated as Class I;

When the equivalent depth of the crack is 2mm~3mm, it is rated as Class II;

When the crack equivalent depth is greater than 3mm, it is classified as Class III;

deal with:

Class I defects, polished to eliminate;

For grade II defects, remove them by grinding and repair them to type C;

For Class III defects, replace the lamination or fill in the crack.

After all the defects are dealt with, the repaired part should be re-tested, and it can be put into use only after passing the test.

The detection device for realizing the above-mentioned high-speed hydraulic generator rotor pole yoke T tail groove detection method is composed as shown in Figure 1-5, including a crack probe detection device 5, a guide bracket 4 and a magnetic flux leakage detector 1, and a crack probe detection device 5. The device 5 is installed on the guide bracket 4, and the crack probe detection device 5 is connected with the magnetic flux leakage detector 1 through the signal transmission line 2; the crack probe detection device 5 includes a П-shaped magnet A9 fixed on the guide bracket 4 through an elastic member 6 and The three-dimensional Hall probe 12, the three-dimensional Hall probe 12 is arranged between the two poles of the opening of the П-shaped magnet A9, and extends forward to the top of the inclined plane of the two legs of the П-shaped magnet A9, and the three-dimensional Hall probe 12 passes the signal The amplification and digital-to-analog conversion circuit 11 is connected to the signal transmission line 2 via the signal terminal 10 . The three-dimensional Hall probe 12 can magnetize the part to be inspected, and simultaneously detect the magnetic field strength in the three dimensions of XYZ; the signal amplification and digital-to-analog conversion circuit 11 can simultaneously shape and transform the three groups of signals generated by the three-dimensional Hall probe 12 and Amplify, connect the signal terminal with the signal transmission line, and transmit the detection signal to the host of the magnetic flux leakage detector. The guide bracket can fix the crack probe detection device at the detection position, and apply constant force support to the crack probe detection device, so as to avoid excessive jumping and swinging of the probe during mobile detection.

The three-dimensional Hall probe 12 is a three-dimensional magnetically sensitive Hall element array, which is composed of three mutually perpendicular chip Hall elements X, Y, and Z. The three Hall elements are arranged in a T shape, and can simultaneously measure three XYZ elements. The magnitude and direction of the magnetic field in the direction.

The guide bracket 4 is provided with a handle 3 for moving the guide bracket.

The П-shaped magnet A9 is a neodymium-nickel-cobalt permanent magnet, which is used to magnetize the part to be inspected. The two poles of the opening are inclined at 45°, and are respectively attached to the two sides of the inner corner of the T tail groove.

It also includes a crack magnetic powder detection device; the crack magnetic powder detection device includes a П-shaped magnet B13, which is a neodymium-nickel-cobalt permanent magnet, used to magnetize the part to be inspected, and the two poles of the opening are in the shape of a 45° inclined plane, which are respectively aligned with the inner corners of the T tail groove. Fitted on both sides;

A micro-LED type ultraviolet lamp 15 with a central wavelength of 365nm is fixed between the two stages of the opening of the П-shaped magnet B13, and is used to excite fluorescent magnetic powder;

The power supply terminal 14 is installed on the П-shaped magnet B13, and is connected to the miniature LED type ultraviolet lamp 15;

DC power supply 17 with switch and shutdown display, built-in battery, provides power for micro LED type ultraviolet lamp 15;

The flame-retardant power cord 16 is used for connecting the DC power source 17 and the power terminal 14 .

The basic principle of the present invention: when the T-tail slot of the magnetic pole yoke is magnetized, the crack will block the magnetic field lines passing through the surface of the workpiece, and the magnetic flux in the magnetic circuit will be distorted, causing part of the magnetic flux to escape from the surface of the workpiece and form in space. Leakage magnetic field, use the magnetic induction element (probe) to obtain the signal, and through the processing of the magnetic flux leakage signal by the detector, determine the size and depth of the crack.

Claims (10)

1. the detection method of high speed magnet pole of rotor of hydraulic generator yoke T stern notch, it is characterized in that: by magnet magnetization magnetic pole yoke T stern notch, the magnetic line of force by T stern notch surface has been blocked when there is crackle, magnetic flux in magnetic circuit is distorted, cause part magnetic flux effusion T stern notch surface, form stray field in space, utilize magneto sensor to obtain magnetic leakage signal, and by Magnetic Flux Leakage Testing Instrument, magnetic leakage signal is detected.

2. the detection method of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 1, it is characterized in that: by probe guiding trestle, probe is delivered to detection position, and utilize constant force structure to make probe be close to subject face, the magnetization of П shape magnet A detects the ferromagnetism lamination at position, produce induced field, when the magnetic line of force excited runs into crackle on the tested position of T stern notch, stray field will be formed in cracks, stray field is received by the magneto sensor in popping one's head in and is converted into digital signal, by Magnetic Flux Leakage Testing Instrument, signal transacting and display are carried out to crack stray field, thus judge whether tested T stern notch exists crackle.

3. the detection method of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 2, it is characterized in that: the method whether tested T stern notch of described judgement exists crackle is, be placed in by guiding trestle by three-dimensional hall probe and detect position, the Hall element Z in three-dimensional hall probe is parallel with magnetic pole rim lamination plane; Make X, Y, Z tri-equal zero setting of direction signal of three-dimensional hall probe; When X-direction signal is more than or equal to 25:1 with the ratio of Z-direction signal intensity or when Y-direction signal is more than or equal to 50:1 with the ratio of Z-direction signal intensity, then judge that the laminate surface of detection site exists abnormal.

4. the detection method of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 3, be is characterized in that, then rechecked the position that there is anomalous field by magnetic powder detection method; Magnetic powder detection method is carried out in the steps below:

Snag clearly abnormal signal portion faces in Magnetic testi;

Open Magnetic testing installation's power source;

The probe of Magnetic testing device is placed in abnormal portion faces;

Weak vibrations magnetic flaw detection ink watering can, evenly sprays magnetic flaw detection ink at abnormal portion faces;

Be applied to the magnetic on surface by stray field absorption, under the ultraviolet illumination of 365nm wavelength, form visual visible magnetic trace, thus determine that detected magnetic pole yoke T stern notch exists crackle.

5. the detection method of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 4, it is characterized in that, described magnetic flaw detection ink is mixed by the raw material of following weight portion: 71-73 part ethanol, 16-18 part ethyl acetate, 2.5-3.5 part methenyl choloride, 1.5-2.5 part acetone, 0.15-0.25 part MPI fluorescent magnetic particles; MPI fluorescent magnetic particles granularity is 350 orders.

6. realize the pick-up unit of the high speed magnet pole of rotor of hydraulic generator yoke T stern notch detection method described in any one of claim 1-4, it is characterized in that: comprise crackle probe detector (5), guiding trestle (4) and Magnetic Flux Leakage Testing Instrument (1), crackle probe detector (5) is arranged on guiding trestle (4), and crackle probe detector (5) is connected with Magnetic Flux Leakage Testing Instrument (1) by signal transmssion line (2); Described crackle probe detector (5) comprises and is fixed on П shape magnet A (9) on guiding trestle (4) and three-dimensional hall probe (12) through elastic component (6), three-dimensional hall probe (12) is arranged between opening part the two poles of the earth of П shape magnet A (9), and extending out to forward the top of П shape magnet A (9) bipod inclined-plane extension, described three-dimensional hall probe (12) is amplified by signal and D/A converting circuit (11) is connected with signal transmssion line (2) through signal terminal (10).

7. the pick-up unit of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 6, it is characterized in that: described three-dimensional hall probe (12) is three-dimensional magnetosensitive Hall element array, be made up of the orthogonal sheet Hall element of X, Y, Z tri-, three Hall element landing tees are put, and can measure the magnetic field size and Orientation on XYZ tri-directions simultaneously.

8. the pick-up unit of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 6, is characterized in that: described guiding trestle (4) is provided with handle (3), for mobile guide support.

9. the pick-up unit of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 6, it is characterized in that: described П shape magnet A (9), for neodymium nickel cobalt type permanent magnet, for magnetizing tested position, opening the two poles of the earth pin inclined plane shape at 45 °, fits with T stern notch inside lock two sides respectively.

10. the pick-up unit of high speed magnet pole of rotor of hydraulic generator yoke T stern notch according to claim 6, is characterized in that: also comprise crackle Magnetic testing device; Crackle Magnetic testing device comprises П shape magnet B (13), is neodymium nickel cobalt type permanent magnet, and for magnetizing tested position, opening the two poles of the earth pin inclined plane shape at 45 °, fits with T stern notch inside lock two sides respectively;

Centre wavelength is the miniature LED type uviol lamp (15) of 365nm, is fixed between П shape magnet B (13) opening part two-stage, for fluorescence excitation magnetic;

Power supply terminal (14), is arranged in П shape magnet B (13), connects miniature LED type uviol lamp (15);

The direct supply (17) of belt switch and shutoff display, internal battery, for miniature LED type uviol lamp (15) provides power supply;

Anti-flammability power lead (16), for connecting direct supply (17) and power supply terminal (14).