CN102841123A - Measuring device and measuring method for trap parameter of solid dielectric material - Google Patents
Measuring device and measuring method for trap parameter of solid dielectric material Download PDFInfo
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- CN102841123A CN102841123A CN2012103232336A CN201210323233A CN102841123A CN 102841123 A CN102841123 A CN 102841123A CN 2012103232336 A CN2012103232336 A CN 2012103232336A CN 201210323233 A CN201210323233 A CN 201210323233A CN 102841123 A CN102841123 A CN 102841123A
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Abstract
The invention discloses a measuring device and method for a trap parameter of solid dielectric. The solid dielectric material is charged by using a three-electrode corona discharge system; a material sample to be tested is placed below a single-needle electrode and a metal mesh electrode; the sample is adhered to a metal disc electrode through conductive silicone grease and is charged by the three-electrode system; after charging is ended, an external voltage is removed, and short circuit discharge is performed to remove surface free loads; surface potential of the measured sample is attenuated; and the trap energy level and the trap density parameter of the material can be calculated through a signal conditioning circuit and a data acquisition system. The measuring device comprises a constant temperature box, the three-electrode coronate charging system, a surface potential measuring system, a sample preheating system, a rotary electrode and a temperature and humidity control system. The invention provides an effective analysis means for research in representation of an aging condition of a polymer insulating material and an aging rule of polymer by the trap parameter and research in aspects such as a solid dielectric surface electrification phenomenon and surface flashover performance influence.
Description
Technical field
The invention belongs to dielectric substance Trap Characteristics field of measuring technique, relate to a kind of solid dielectric material measuring trap parameter device and measuring method.
Background technology
Insulating material of polymer has excellent dielectric properties such as high such as direct current resistance, that dielectric loss is low, good thermal stability and good machining property, thereby be widely used in the electric insulation field.But along with the raising of voltage class of electric power system and the development of direct current transportation technology; The space charge effect problem of polymer insulation is outstanding day by day; Cause the distortion of polymeric material internal electric field thus; Cause the development of shelf depreciation and electric branch, thereby cause the polymeric material problem of aging, how to suppress and the space charge eliminated in the polymer insulation has become domestic and international electric insulation hot research fields.
At present a lot of about the research of polymkeric substance agine mechaism, wherein more representational is the thermoelectron initiated polymerization thing degraded theory of people such as the Tu Demin proposition of Canadian Gao Guanzhi (Kwan-Chi Kao) and domestic Xi'an Communications University.Under high electric field action; Electrons/is injected into the polymkeric substance from electrode through Schottky effect (Schottky effect) or Fowler-Nordheim effect (Fowler-Nordheim effect); Owing to have a large amount of trap states in the energy gap of material forbidden band; The mean free path of electrons/is short, is therefore captured by trap very soon and forms space charge.Going into of space charge sunken/recombination process in, when electric charge was moved to low-energy state by high-energy state, unnecessary energy shifted to another electronics through non-forms of radiation, made the latter become thermoelectron.Thermoelectron with enough energy will cause molecular degradation and form a large amount of macromolecular radicals, will further cause free chain reaction, cause the further degraded of polymkeric substance.Thermionic generation and thermionic energy are decided by the density and the degree of depth of trap, change the trap depth or the density of polymkeric substance, just can change thermionic formation probability and energy.Therefore the injection of space charge, to move, go into sunken/detrapping, process such as compound and material internal Trap Characteristics closely related; Therefore Trap Characteristics such as energy level, the density etc. of measurement and analysis of material have crucial meaning for the space charge formation of material and the ageing state sign and the assessment of inhibition mechanism and polymeric material.
On the other hand; Since in the vacuum along the voltage breakdown of face insulation bulk breakdown voltage far below the insulator material; The vacuum edge flashing phenomenon is restricting the raising of vacuum insulation performance always for a long time; Increase vacuum equipment volume and expense, greatly limited the miniaturization and the practicalization of high power pulse equipment.Vacuum insulation is with existing a large amount of defectives usually in inorganic material or the organic composite material, these defectives are arranged etc. from the atom of crystal defect, impurity and amorphous domain is mixed and disorderly usually.The existence of a large amount of defectives makes material internal and surface form a large amount of local attitude energy levels, i.e. trap.The trap of material surface can cause material surface charged inhomogeneous, and then distortion internal field, and the injection of trapped charge and dispose procedure also can produce material impact to the edge flashing phenomenon in addition.Dielectric Trap Characteristics and surface charging characteristic receive extensive concern for a long time always, think that the surface flashover characteristics of medium is closely related under itself and the vacuum condition.
Application number is the test that 200710017229.6 Chinese patent disclosed " a kind of method of testing of polymeric material trap parameters " is applicable to the polymeric material trap parameters; For the inorganic insulating material that belongs to the solid dielectric material, test then is difficult to carry out like the trap parameters of aluminium oxide, processable ceramic etc.
People such as a champion of Xi'an Communications University think that the trap of different energy levels possibly have different contributions to the flashover progress; The low-lying level trap discharges after catching electric charge easily in short-term; Be prone to cause flashover discharge (viewpoint that Lee of North China Electric Power University becomes banyan and Ding Li to be good for is consistent therewith); And have certain effect for the secondary that suppresses material surface than the deep level trap; Density through improving deep trap can improve edge flashing voltage to a certain extent, but since trapped charge to the distortion effect of electric field, in case can make flashover takes place after follow-up flashover take place easily.Zhang people such as champion and think that also trap parameters possibly be except that parameters such as surface resistivity, specific inductive capacity, to influence one of the insulating material flashover voltage more parameter of intrinsic.
Based on above-mentioned analysis; Trap Characteristics very influences the dielectric and the flash-over characteristic of solid dielectric material significantly; And possibly become a kind of solid dielectric material property characterization parameter of more intrinsic, the trap parameters of therefore measuring and analyze solid insulating material has crucial meaning.
Canadian Xi Mengsi people such as (J.G.Simmons) proposed in the seventies in last century, can obtain the trap parameters of its any energy level through the current attenuation characteristic of excited target material under isothermy.The hot detrapping process of charge carrier under constant temperature that this theory is captured by trap after based on the insulating material excited target thought that the trap charge carrier that is in shallow trap in the medium discharges earlier, and is in the back release of deep trap; Hot release current time to time change under constant temperature, this electric current has reflected the regularity of distribution of trap level.Its advantage is that without any need for the distribution of traps a priori assumption isothermal decay current of measurement concerns the distribution of traps that can directly reflect material over time.Under electric field, inject the space charge position distribution form that charge carrier forms based on solid dielectric in addition, can distinguish electronics and hole trap through surface measurements potential decay characteristic, thereby obtain the single carrier trap information.
Summary of the invention
The problem that the present invention solves is to provide a kind of solid dielectric material measuring trap parameter device and measuring method; Both be applicable to inorganic insulating material; Like the test of insulating material traps such as aluminium oxide, processable ceramic, also be applicable to the test of insulating material of polymer trap simultaneously.
The present invention realizes through following technical scheme:
A kind of solid dielectric material measuring trap parameter device comprises the three electrode corona charhing units and the surface potential attenuation measurement unit that are arranged in the constant temperature oven;
Described three electrode corona charhing units comprise rosette electrode, wire netting electrode and pin electrode from top to bottom, rosette electrode grounding wherein, and the wire netting electrode is connected with dc charging power supply with the bias direct current power supply respectively with pin electrode;
Described surface potential attenuation measurement unit comprises the condenser type static probe that is arranged on the insulating support, and condenser type static probe also is connected with signal condition module, data acquisition module and processes and displays module in turn;
Sample to be measured is arranged on the rosette electrode, also is connected with the rotatable metal heating box below the rosette electrode; When electric charge injected, sample was positioned at the below of wire netting electrode; When the surface potential decay detected, sample rotated to the below of condenser type static probe.
Described rosette electrode comprises the copper disc electrode and the aluminium disc electrode of fixed connection, and the copper disc electrode is placed on the aluminium disc electrode, and the surface finish that the copper disc electrode is connected with sample is handled; Sample and copper disc electrode are bonding through the conduction silicone grease.
The diameter of described copper disc electrode is Φ 100～120mm, thickness 8～10mm; The diameter of aluminium disc electrode is Φ 200～250mm, and thickness 8～10mm, both eccentric distances are 60～80mm; Pin electrode is a stainless pin, and the needle point radius-of-curvature is 3～5 μ m, and the stainless (steel) wire that the wire netting electrode is tightened for the aluminum annulus, its diameter are Φ 80～100mm.
Described condenser type static probe is adjustable with the distance of specimen surface, and data acquisition module carries out uninterrupted sampling and record automatically to the surface potential decay of sample.
Be provided with temperature and humidity control device in the described constant temperature oven, temperature control equipment comprises thermopair that is arranged in the METAL HEATING PROCESS box and the quartzy infrared heating pipe that is arranged in the constant temperature oven, is connected with temperature control equipment after thermopair and the quartzy infrared heating pipe parallel connection; Humidity conditioner comprises the drying agent that is arranged in the constant temperature oven.
A kind of solid dielectric material measuring trap parameter method based on said device may further comprise the steps:
1) sample to be tested that the back side is scribbled the conduction silicone grease is bonded on the rosette electrode, in the face of the one side of wire netting electrode keeps clean, closes the constant temperature chamber door;
2) to after the sample preheating, on the wire netting electrode, apply dc offset voltage earlier, apply DC charging voltage to pin electrode then, three electrode corona charhing units produce corona discharge to the sample iunjected charge; After the time iunjected charge of setting finishes, remove DC charging voltage earlier, after remove dc offset voltage;
3) cover aluminium foil and short circuit dischange at specimen surface, remove surperficial free charge;
4) behind the surperficial free charge of removal; The rotating metallic disk electrode; The specimen surface electric charge is injected the central area to be moved under the condenser type static probe; Adjustment condenser type static probe and specimen surface distance, the surface potential decay of sample is obtained by condenser type static probe, samples and record through signal condition module and data acquisition module input processes and displays module then; Draw the trap density that the different energy levels of going out of sample distribute through isothermal current attenuation Theoretical Calculation.
Described preheating be with sample at 50～60 ℃ of following preheating 20～30min, preheating is through the thermopair that is arranged in the METAL HEATING PROCESS box heat to be provided.
Described dc offset voltage is+2kV or-2kV, DC charging voltage is+10kV or-10kV;
After applying voltage, corona discharge takes place at the needle point place of pin electrode, air is produced charging point by ionization, forms ionized region around the needle point; Charged ion drifts about to specimen surface through the wire netting electrode under electric field action; Charged ion forms uniform charge shift district between wire netting electrode and sample; The electronics of charged ion is captured by the trap states of specimen surface, thereby obtains uniform surface charging effect.
The time of described iunjected charge is 1～10min, after iunjected charge finishes, covers aluminium foil and short circuit dischange 0.5～1min at specimen surface, removes surperficial free charge;
Described condenser type static probe remains 2～3mm with the specimen surface distance, and the sampling time of surface potential decay can be designed according to sampling request.
Theoretical according to the isothermal current attenuation, the charge carrier that case hot discharges is trapization no longer, trap level E
tAnd isothermal current density, J and trap density N
tRelation be:
Applied voltage removes the decay of back surface potential and the relation of current density, J is:
E wherein
tBe trap level, k is the Boltzmann constant, and T is an absolute temperature, and γ is the electronic vibration frequency, and t is the time; J is the isothermal current density, and q is an electron charge, and d is the thickness of sample, f
0(E) be the initial occupation rate of trap, N
t(E
t) be the trap energy distribution function; ε
0Be permittivity of vacuum, ε
rBe the relative dielectric constant of dielectric material, V
s(t) be surface potential, the energy of electron trap is to calculate zero point at the bottom of with conduction band, and the energy of hole trap is to calculate zero point with the top of valence band;
At first calculate the isothermal decay current by surface potential, can calculate the trap density that different energy levels distribute according to formula (1) again according to formula (2).
Compared with prior art, the present invention has following beneficial technical effects:
Solid dielectric material measuring trap parameter device and method provided by the invention; Be based on isothermal current attenuation theory and calculate the trap level and the trap density parameter of sample, wherein the surface potential that electric charge injects and surface potential attenuation measurement unit detects after electric charge injects of sample is decayed through three electrode corona charhing units.Theoretical according to the isothermal current attenuation, in the surface potential isothermal attenuation process, the electric charge that is in shallow trap in the medium discharges earlier, and discharges after being in the electric charge of deep trap.Hot release current time to time change under steady temperature, this change in current has reflected the regularity of distribution of trap level.Through specimen surface potential decay characteristic under the isothermy, can calculate the isothermal decay current, and and then calculate the trap level and the trap density parameter of sample.The present invention both had been applicable to inorganic insulating material, like the test of insulating material traps such as aluminium oxide, processable ceramic, also was applicable to the test of insulating material of polymer trap simultaneously.
Solid dielectric material measuring trap parameter device and method provided by the invention, injecting at electric charge is to obtain uniform surface charging effect: the rosette electrode can guarantee abundant iunjected charge through after the preheating during charging.Applying under the high pressure effect, corona discharge takes place at the needle point place, thereby air is being produced a large amount of charging points by ionization, forming ionized region around the needle point.To apply reverse voltage is example; Negative ion drifts about to specimen surface through the wire netting electrode under electric field action; Because the Electric Field Distribution between wire netting electrode and the following rosette electrode is more even; Negative ion can form uniform charge shift district between wire netting electrode and sample, the electronics in the negative ion will be captured by the trap states of specimen surface, thereby can obtain uniform surface charging effect.
The attenuation characteristic of surface potential is affected by environment greatly; And solid dielectric material measuring trap parameter device and method provided by the invention; In constant temperature oven, carry out, can keep the temperature strictness constant, and be lower than 40% through placing solid drier control constant temperature oven internal relative humidity.
Solid dielectric material measuring trap parameter device and method provided by the invention; Under DC electric field, inject the space charge position distribution form that charge carrier forms based on solid dielectric; Think that surface potential is mainly determined by specimen surface layer charge (electronics or hole); Therefore can distinguish electronics and hole trap through surface measurements potential decay characteristic, thereby obtain the single carrier trap information.
The present invention has good stability and the strong advantage of anti-electromagnetic interference (EMI), and collocation rationally, and is easy to operate.For the Trap Characteristics of studying the solid dielectric material provides the theory and technology support; Can be the aging rule research of trap parameters characterize polymers insulating material aging performance and polymkeric substance, and Solid Dielectric Surface electrification phenomenon and a kind of effective analysis means is provided to the research of aspects such as edge flashing performance impact.
Description of drawings
Fig. 1 is the structural representation of measurement mechanism of the present invention;
Fig. 2 is the surface potential curve (for applying positive polarity voltage) of polyester (PET) insulation film of the present invention's measurement;
Fig. 3 is the surface potential curve (for applying reverse voltage) of polyester (PET) insulation film of the present invention's measurement;
The trap level distribution plan of the polyester that Fig. 4 measures for the present invention (PET) film;
The Al that Fig. 5 measures for the present invention
2O
3The trap level distribution plan of thin slice.
Wherein, 1 is dc charging power supply; 2 is the bias direct current power supply; 3 is pin electrode; 4 is the wire netting electrode; 5 is sample; 6 is the rosette electrode; 7 is the METAL HEATING PROCESS box; 8 are condenser type static probe; 9 is the signal condition module; 10 is signal acquisition module; 11 is the processes and displays module; 12 is constant temperature oven, and 13 is insulating support.
Embodiment
Below in conjunction with concrete embodiment the present invention is done further detailed description, said is to explanation of the present invention rather than qualification.
Referring to Fig. 1, a kind of solid dielectric material measuring trap parameter device comprises the three electrode corona charhing units and the surface potential attenuation measurement unit that are arranged in the constant temperature oven 12;
Described three electrode corona charhing units comprise rosette electrode 6, wire netting electrode 4 and pin electrode 3 from top to bottom, and wherein the rosette electrode grounding 6, and wire netting electrode 4 is connected with dc charging power supply 1 with bias direct current power supply 2 respectively with pin electrode 3;
Described surface potential attenuation measurement unit comprises the condenser type static probe 8 that is arranged on the insulating support 13, and condenser type static probe 8 also is connected with signal condition module 9, data acquisition module 10 and processes and displays module 11 in turn.
Concrete, constant temperature oven 12 is of a size of 400 * 400 * 400mm, also can confirm the concrete structure size according to the working condition of reality.Constant temperature oven is made up of base, casing cover, top cover three parts, and the detachable and combination of three makes things convenient for the closed test system assembles.The casing front be designed with can folding chamber door, make things convenient for personnel operation.
Being set to of described three electrode corona charhing units: there is the rosette electrode 6 of ground connection constant temperature oven 12 inside; Fixing below the rosette electrode 6 with rotatable metal heating box 7; Have above through the bonding insulation sample 5 of conduction silicone grease; The top of rosette electrode 6 is provided with pin electrode 3 and wire netting electrode 4, and is connected to dc charging power supply 1 and bias direct current power supply 2 respectively;
Further, pin electrode 3 is a stainless pin, needle point radius-of-curvature 5 μ m; The stainless (steel) wire of wire netting electrode 4 for tightening with the aluminum annulus, mesh size 0.6 * 0.6mm, net diameter of phi 100mm; The rosette electrode 6 of ground connection is for comprising copper disc electrode and aluminium disc electrode.The copper disc electrode is last, diameter of phi 120mm, thickness 10mm; The aluminium disc electrode is following, and diameter of phi 250mm, thickness 10mm, both eccentric distances are 60mm, through bolt.The polishing of copper electrode fine in surface is to guarantee sample and electrode good electrical contact property.
Being set to of described surface potential attenuation measurement unit: be provided with insulating support 13 in the constant temperature oven 12, installing condenser type static probe 8 on this insulating support 13, the distance on condenser type static probe 8 and sample 5 surfaces is through the adjusting mechanism accurate and adjustable; Condenser type static probe 8 links to each other with constant temperature oven 12 outside signal condition module 9, data acquisition module 10 and processes and displays modules 11 successively; Data acquisition and recording system can carry out uninterrupted sampling and record automatically to surperficial potential decay.
The signal that signal condition module 9 is nursed one's health is the surface potential signal of decay by a certain percentage of condenser type static probe 8 outputs, meets the simulating signal of data acquisition module 10 sampling requests through filtering and amplification output; 10 pairs of analog signal samplings of data acquisition module and convert digital signal into, the input computer unit.Processes and displays module 11 is a computing machine, mainly through software the digital signal of input is shown and stores.
Further, condenser type static probe (8) is adjustable with the distance on sample (5) surface, and data acquisition module (10) carries out uninterrupted sampling and record automatically to the surface potential decay of sample;
Concrete, described condenser type static probe remains 2～3mm with the specimen surface distance, and the sampling time of surface potential decay can be designed according to sampling request.
Further; Be provided with the sample pre-heating system in the constant temperature oven 12; Be fixedly connected with heating of metal box 7 through bolt below the aluminium disc electrode of rosette electrode 6, METAL HEATING PROCESS box 7 is of a size of 250 * 250 * 20mm, and the hole is got through at METAL HEATING PROCESS box center; Blind hole is beaten at center, the aluminium disc electrode back side, and both connect with bolt.2 of the thermopairs of METAL HEATING PROCESS box 7 inner placement series connection, heat electrode the back that is connected with the temperature control systems that are arranged on constant temperature oven 12 outsides, thereby to the sample preheating, to guarantee the injection of electric charge.
The rotation of sample is moved and is in the constant temperature oven 12: the bottom design at heating of metal box 7 has metal rotary disk, and metal rotary disk is fixedly connected with heating of metal box 7 and top rosette electrode 6 thereof through bolt, and the rosette electrode 6 that can be grounded rotates freely.Said parts all are placed on the metal aluminum sheet platform with the insulation support, and the rotational structure design can realize the position angle adjusting of sample, can be implemented in injection of sample electric charge and surface potential attenuation measurement two states and freely switch down.
Because the surface potential attenuation characteristic of solid dielectric material receives temperature, humidity effect very big, is provided with temperature and humidity control system in the constant temperature oven 12, system design has the precise dose control system, and temperature control precision is ± 0.1 ℃.Indoor design has two heating sources in the constant temperature oven 12, and the one, be placed on the thermopair in the METAL HEATING PROCESS box, can carry out preheating to the aluminium disc electrode of rosette electrode 6 and top sample thereof; The 2nd, be placed on the quartzy infrared heating pipe in the constant temperature oven 12, can realize even heating to air in the casing.Two heating source parallel connections, and unification is controlled by temperature controller.Humidity control is controlled through placing transformer special drying agent silica gel in the case, and humidity generally is controlled at below 40%, meets the demands.
The attenuation characteristic of surface potential is affected by environment greatly, so experiment is carried out in constant temperature oven 12, keeps the temperature strictness constant in the experimentation, and is lower than 40% through placing solid drier control constant temperature oven 12 internal relative humidities.
Solid dielectric material measuring trap parameter method based on said device may further comprise the steps:
1) sample to be tested that the back side is scribbled the conduction silicone grease is bonded on the rosette electrode, in the face of the one side of wire netting electrode keeps clean, closes the constant temperature chamber door;
2) to after the sample preheating, on the wire netting electrode, apply dc offset voltage earlier, apply DC charging voltage to pin electrode then, three electrode corona charhing units produce corona discharge to the sample iunjected charge; After the time iunjected charge of setting finishes, remove DC charging voltage earlier, after remove dc offset voltage;
Concrete, with the conduction silicone grease sample 5 being attached on the rosette electrode 6, pin electrode 3 is 2cm with wire netting electrode 4 distances; Wire netting electrode 4 is about 1cm with sample 5 distances; Pin electrode 3 applies+10kV or-10kV DC charging voltage, wire netting electrode 4 applies+2kV or-dc offset voltage of 2kV, each iunjected charge time is 1～10min; Heating disk electrode to 60 ℃ during charging is to guarantee abundant iunjected charge.
Applying under the high pressure effect, corona discharge takes place in pin electrode 3 at the needle point place, thereby air is produced a large amount of charging points by ionization, forms ionized region around the needle point.To apply reverse voltage is example; Negative ion drifts about to sample 5 surfaces through wire netting electrode 4 under electric field action; Because the Electric Field Distribution between wire netting electrode 4 and the following rosette electrode 6 is more even; Negative ion can form uniform charge shift district between wire netting electrode 4 and sample 5, the electronics in the negative ion will be captured by the trap states on sample 5 surfaces, thereby obtain uniform surface charging effect.
3) cover aluminium foil and short circuit dischange at specimen surface, remove surperficial free charge;
Concrete; After sample 5 electric charges inject and finish; Remove DC charging voltage and dc offset voltage successively,, keep short circuit dischange 0.5～1min (about 1min is good) to remove the free charge (non-trapped charge) of specimen surface deposition at sample 5 surface coverage aluminium foil and short circuit dischanges.
4) behind the surperficial free charge of removal; The rotating metallic disk electrode; The specimen surface electric charge is injected the central area to be moved under the condenser type static probe; Adjustment condenser type static probe and specimen surface distance, the surface potential decay of sample is obtained by condenser type static probe, samples and record through signal condition module and data acquisition module input processes and displays module then; Draw the trap level and the trap density parameter of sample through isothermal current attenuation Theoretical Calculation.
Concrete, behind the short circuit dischange, rotation grounded metal disk electrode 6 moves to condenser type static probe 8 times with the specimen surface zone of charging, and adopts the surface potential decay of non-contact mode measuring sample, and condenser type static probe 8 is 2mm with the distances on sample 5 surfaces.After the signal of condenser type static probe 8 outputs is nursed one's health by signal condition module 9; In the data acquisition module 10 that access links to each other with computing machine; Just can carry out continuous sampling to the surface potential of sample 5; The sampling time of surface potential decay can be designed according to sampling request, generally data acquisition system (DAS) is set at per 1～5s (specifically adopting 1s) once sampling in the experiment.
Theoretical according to the isothermal current attenuation, in the surface potential isothermal attenuation process, the electric charge that is in shallow trap in the medium discharges earlier, and discharges after being in the electric charge of deep trap.Hot release current time to time change under steady temperature, this change in current has reflected the regularity of distribution of trap level.Through the 5 surface potential attenuation characteristics of sample under the isothermy, can calculate the isothermal decay current, and and then calculate the trap level and the trap density parameter of sample 5.
Theoretical according to the isothermal current attenuation, the charge carrier that case hot discharges is trapization no longer, trap level E
tAnd isothermal current density, J and trap density N
tRelation be:
Applied voltage removes the decay of back surface potential and the relation of current density, J is:
E wherein
tBe trap level, k is the Boltzmann constant, and T is an absolute temperature, and γ is the electronic vibration frequency, and t is the time; J is the isothermal current density, and q is an electron charge, and d is the thickness of sample, f
0(E) be the initial occupation rate of trap, N
t(E
t) be the trap energy distribution function; ε
0Be permittivity of vacuum, ε
rBe the relative dielectric constant of dielectric material, V
s(t) be surface potential.The energy of electron trap is to calculate zero point at the bottom of with conduction band, and the energy of hole trap is to calculate zero point with the top of valence band.
At first calculate the isothermal decay current by surface potential, can calculate the trap density that different energy levels distribute according to formula (1) again according to formula (2).
Solid dielectric material measuring trap parameter method and system of the present invention both had been applicable to inorganic insulating material, like the test of insulating material Trap Characteristics such as aluminium oxide, processable ceramic, also were applicable to the test of insulating material of polymer Trap Characteristics simultaneously.
The concrete testing result according to said method is following:
As shown in Figure 2 is positive polarity surface potential die-away curve (60 ℃ of preheat temperatures, charging voltage+10kV, the bias voltage+2kV of polyester (PET) film; Duration of charging 1min, 70 ℃ of decay temperature), horizontal ordinate is the time; Unit is s, and ordinate is the surface electrical place value, and unit is V.
Shown in Figure 3 is the negative polarity surface potential die-away curve (charging voltage-10kV, bias voltage-2kV, duration of charging 1min, 70 ℃ of decay temperature) of polyester (PET) film, and ordinate is the absolute value of negative potential.
Fig. 4 is that the trap level of polyester (PET) film distributes, and horizontal ordinate is the trap level level, and unit is eV, and ordinate is a trap density, and unit is (eV)
-1m
-3
Theoretical according to above-mentioned isothermal current attenuation, by positive and negative polarity surface potential attenuation law among Fig. 2, Fig. 3, hole, the electron trap energy level that can obtain polyester (PET) film respectively distribute, and be as shown in Figure 4.
Fig. 5 is Al
2O
3The trap level of thin slice distributes, and horizontal ordinate is the trap level level, and unit is eV, and ordinate is a trap density, and unit is (eV)
-1m
-3
Claims (10)
1. a solid dielectric material measuring trap parameter device is characterized in that, comprises the three electrode corona charhing units and the surface potential attenuation measurement unit that are arranged in the constant temperature oven (12);
Described three electrode corona charhing units comprise rosette electrode (6), wire netting electrode (4) and pin electrode (3) from top to bottom; Rosette electrode (6) ground connection wherein, wire netting electrode (4) is connected with dc charging power supply (1) with bias direct current power supply (2) respectively with pin electrode (3);
Described surface potential attenuation measurement unit comprises the condenser type static probe (8) that is arranged on the insulating support (13), and condenser type static probe (8) also is connected with signal condition module (9), data acquisition module (10) and processes and displays module (11) in turn;
Sample to be measured (5) is arranged on the rosette electrode (6), also is connected with rotatable metal heating box (7) below the rosette electrode (6); When electric charge injected, sample (5) was positioned at the below of wire netting electrode (4); When the surface potential decay detected, sample rotated to the below of condenser type static probe (8).
2. solid dielectric material measuring trap parameter device as claimed in claim 1; It is characterized in that; Described rosette electrode (6) comprises the copper disc electrode and the aluminium disc electrode of fixed connection, and the copper disc electrode is placed on the aluminium disc electrode, and the surface finish that the copper disc electrode is connected with sample is handled; Sample (5) is bonding through the conduction silicone grease with the copper disc electrode.
3. solid dielectric material measuring trap parameter device as claimed in claim 2 is characterized in that the diameter of described copper disc electrode is Φ 100～120mm, thickness 8～10mm; The diameter of aluminium disc electrode is Φ 200～250mm, and thickness 8～10mm, both eccentric distances are 60～80mm; Pin electrode (3) is a stainless pin, and the needle point radius-of-curvature is 3～5 μ m, and the stainless (steel) wire that wire netting electrode (4) is tightened for the aluminum annulus, its diameter are Φ 80～100mm.
4. solid dielectric material measuring trap parameter device as claimed in claim 1; It is characterized in that; Described condenser type static probe (8) is adjustable with the distance on sample (5) surface, and data acquisition module (10) carries out uninterrupted sampling and record automatically to the surface potential decay of sample.
5. solid dielectric material measuring trap parameter device as claimed in claim 1; It is characterized in that; Constant temperature oven is provided with temperature and humidity control device in (12); Temperature control equipment comprises thermopair that is arranged in the METAL HEATING PROCESS box (7) and the quartzy infrared heating pipe that is arranged in the constant temperature oven (12), is connected with temperature control equipment after thermopair and the quartzy infrared heating pipe parallel connection; Humidity conditioner comprises the drying agent that is arranged in the constant temperature oven (12).
6. the solid dielectric material measuring trap parameter method based on the said device of claim 1 is characterized in that, may further comprise the steps:
1) sample to be tested that the back side is scribbled the conduction silicone grease is bonded on the rosette electrode, in the face of the one side of wire netting electrode keeps clean, closes the constant temperature chamber door;
2) to after the sample preheating, on the wire netting electrode, apply dc offset voltage earlier, apply DC charging voltage to pin electrode then, three electrode corona charhing units produce corona discharge to the sample iunjected charge; After the time iunjected charge of setting finishes, remove DC charging voltage earlier, after remove dc offset voltage;
3) cover aluminium foil and short circuit dischange at specimen surface, remove surperficial free charge;
4) behind the surperficial free charge of removal; The rotating metallic disk electrode; The specimen surface electric charge is injected the central area to be moved under the condenser type static probe; Adjustment condenser type static probe and specimen surface distance, the surface potential decay of sample is obtained by condenser type static probe, samples and record through signal condition module and data acquisition module input processes and displays module then; Draw the trap density that the different energy levels of going out of sample distribute through isothermal current attenuation Theoretical Calculation.
7. solid dielectric material measuring trap parameter method as claimed in claim 6 is characterized in that, described preheating be with sample at 50～60 ℃ of following preheating 20～30min, preheating is through the thermopair that is arranged in the METAL HEATING PROCESS box heat to be provided.
8. solid dielectric material measuring trap parameter method as claimed in claim 6 is characterized in that, described dc offset voltage is+2kV or-2kV, DC charging voltage is+10kV or-10kV;
After applying voltage, corona discharge takes place at the needle point place of pin electrode, air is produced charging point by ionization, forms ionized region around the needle point; Charged ion drifts about to specimen surface through the wire netting electrode under electric field action; Charged ion forms uniform charge shift district between wire netting electrode and sample; The electronics of charged ion is captured by the trap states of specimen surface, thereby obtains uniform surface charging effect.
9. solid dielectric material measuring trap parameter method as claimed in claim 6; It is characterized in that the time of described iunjected charge is 1～10min, after iunjected charge finishes; Cover aluminium foil and short circuit dischange 0.5～1min at specimen surface, remove surperficial free charge;
Described condenser type static probe remains 2～3mm with the specimen surface distance, and the sampling time of surface potential decay can be designed according to sampling request.
10. solid dielectric material measuring trap parameter method as claimed in claim 6 is characterized in that, and is theoretical according to the isothermal current attenuation, and the charge carrier that case hot discharges is trapization no longer, trap level E
tAnd isothermal current density, J and trap density N
tRelation be:
Applied voltage removes the decay of back surface potential and the relation of current density, J is:
E wherein
tBe trap level, k is the Boltzmann constant, and T is an absolute temperature, and γ is the electronic vibration frequency, and t is the time; J is the isothermal current density, and q is an electron charge, and d is the thickness of sample, f
0(E) be the initial occupation rate of trap, N
t(E
t) be the trap energy distribution function; ε
0Be permittivity of vacuum, ε
rBe the relative dielectric constant of dielectric material, V
s(t) be surface potential, the energy of electron trap is to calculate zero point at the bottom of with conduction band, and the energy of hole trap is to calculate zero point with the top of valence band;
At first calculate the isothermal decay current by surface potential, can calculate the trap density that different energy levels distribute according to formula (1) again according to formula (2).
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