CN101465081A - Measuring-directly current type skin effect demonstration instrument - Google Patents
Measuring-directly current type skin effect demonstration instrument Download PDFInfo
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- CN101465081A CN101465081A CNA2007103019279A CN200710301927A CN101465081A CN 101465081 A CN101465081 A CN 101465081A CN A2007103019279 A CNA2007103019279 A CN A2007103019279A CN 200710301927 A CN200710301927 A CN 200710301927A CN 101465081 A CN101465081 A CN 101465081A
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Abstract
The invention discloses a direct-detection current type skin effect demonstration instrument which comprises a power supply, current detecting devices and a hollow conductor, wherein, the outer surface of the hollow conductor is continuous or an opening is formed on the outer surface of the hollow conductor, the two end points on the inner wall of the conductor and closest to the two connecting terminals outside the conductor are connected with a wire, the wire penetrates a perforated type Hall current detecting device, and the two connecting terminals outside the conductor are respectively connected with the power supply, and penetrate the other perforated type Hall current detecting device. By comparing the distribution rules of the centering current with the surface current under the action of the alternating-current with different frequency, the invention can intuitively and accurately demonstrate the skin effect. The power supply can adopt the alternating-current power supply with only hundreds of kilohertz, the obvious skin effect can be accurately demonstrated, and the fabrication cost is far lower than that of the dozens of MHz power supply of the prior skin effect demonstration instrument; and when the iron is adopted as the conductor, due to the high magnetic conductivity of the iron material, the same obvious effect also can be achieved when the alternating-current power supply with dozens of kilohertz, and the fabrication cost is further reduced.
Description
Technical field
The present invention relates to the instruments used for education field, particularly a kind of skin effect demonstration instrument.
Background technology
The skin effect principle is meant that steady current evenly distributes on the cross section of conductor.For exchange current, have self-induction electromotive force opposing electric current in the conductor and pass through, the size of this electromotive force is directly proportional with the interior magnetic flux that is cut of conductor unit time.Conductor with round section is an example, and more near the conductor center, the influence that is subjected to self-induction electromotive force is bigger; Near the conductive surface place, then be not subjected to the influence of its inner magnet line of force growth and decline, thereby self-induction electromotive force is less, this just causes convergence conductive surface place current density bigger.Owing to the raising of self-induction electromotive force along with frequency increases, skin effect also improves along with frequency and becomes more remarkable.
Net sectional area when skin effect makes in the conductor by electric current reduces, thereby makes its effective resistance become big.But naked eyes have no idea to observe, and can only lean on experimental verification, and the student also needs demonstration instrument to deepen the impression in learning process.At present, known skin effect demonstration instrument is to be connected in series two identical miniature bulbs in the center of the skin conductor that becomes respectively with surface location, when leading to direct current, two bulb brightness are identical, during indirect current, along with frequency improves constantly, darkness deepens for the bulb brightness at bonding conductor center, explanation is bigger than conductor " center electric current " at high-frequency ac electro ultrafiltration lower conductor " surface current ", proves skin effect with this.
But the problem that this method is deposited is the outside surface of conductor is continuous, terminals on any shaped conductors all can not really be connected to conductor, and " " center " measures conductor " center electric current ", and what in fact this mode of connection was measured is the summation of this path lower conductor center electric current and surface current.The light and shade that existing skin effect instrument makes bulb produce under high frequency changes and is actually the equivalent resistance difference of having utilized special conductor profile to cause the different surfaces current path, and the electromagenetic wave radiation energy loss makes the big phenomenon of equivalent electric resistive during high frequency.
With skin effect instrument shown in Figure 1 is example, the high-frequency ac power of casing 3 built-in direct supplys and frequency adjustable, two poles connects cylindrical conductor 5, and the cylindrical conductor root connects the two poles of the earth of surperficial pilot lamp 1 respectively, and the cylindrical conductor top center connects the two poles of the earth of center pilot lamp 2 respectively.When leading to direct current, the current path of surperficial pilot lamp 1 is two cylindrical conductor roots, lead and surperficial pilot lamp 1; The current path of center pilot lamp 2 is two whole cylindrical conductors, lead and center pilot lamp 2.Because DC current is that average flow is crossed conductor, the cross-sectional area of conductor of current path is long-pending very big, resistance is very little, though whole cylindrical conductor 5 current paths are longer, but the resistance of cylindrical conductor root and whole cylindrical conductor is all at the milliohm order of magnitude, the partial pressure difference that their resistance difference is brought can be ignored to the influence of two bulbs, so two bulb brightness are identical.During indirect current, along with frequency increases, overwhelming majority electric current is propagated along the cylindrical conductor surface, cause the current path sectional area sharply to reduce, equivalent resistance increases to ohm level, the partial pressure difference that cylindrical conductor root and whole cylindrical conductor resistance difference produce has influence on the dividing potential drop of two bulbs, especially at cylindrical conductor top end face 4, sharply dwindle to center terminals equivalent cross-sectional area by the periphery, current density sharply increases, and cause equivalent resistance to increase sharply, and high-frequency alternating current makes whole cylindrical conductor become antenna, to the space radiation electromagnetic wave, cylindrical conductor root off-energy is little, and dividing potential drop is less, and whole cylindrical conductor emittance is bigger, dividing potential drop is relatively large, changes owing to these reasons make two bulbs produce light and shade.
Make the skin layer enough thin because the frequency of alternating current must increase to, equivalent resistance just can have influence on the dividing potential drop of bulb, so can set up another wrong impression to the observer: think and only just skin effect can take place under tens mhz frequencys.And the difference of surface current and center electric current is little, because the electric current of bulb and not sum brightness are directly proportional, bulb is in hour wick temperature reduction of electric current, the wavelength of radiated electromagnetic wave increases, move to sightless infrared portion, more not luminous so become, in fact the electric current amplitude of variation is also little.Be characterized as example during with copper conductor generation skin effect, under the alternating current effect of 100KHZ, skin depth has only 0.21MM thick, that is to say in one deck conductor of the outermost 0.21MM degree of depth of conductor and concentrated 63% of whole electric currents, in the outer contact of 3 times of skin thickness 0.63MM that become, concentrated more than 95% of whole electric currents, 3 times of skin thickness that become have only 5% of total current with interior center conductor electric current, and strong skin effect has taken place when 100KHZ thus.
This shows, though skin effect can qualitative explanation high-frequency current have taken place during by conductor in the result that existing skin effect demonstration instrument causes, think skin effect only just takes place when tens of mhz frequencys are above but can be based upon the erroneous picture of conductor geometric center wiring measuring center electric current and mislead the observer to the observer, and " surface current " is more or less the same with " center electric current ", only can make bulb produce light and shade and change.That is to say, existing skin effect demonstration instrument only is to utilize skin effect to cause current concentration, the phenomenon that equivalent resistance increases is divided the resistance that varies in size for two resistances with conductor, and the inreal DISTRIBUTION OF CURRENT that causes owing to skin effect in the same conductor that discloses.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of measuring-directly current type skin effect demonstration instrument, be used to demonstrate the DISTRIBUTION OF CURRENT that causes owing to skin effect in the same conductor, accurately demonstrate skin effect intuitively.
The invention provides a kind of measuring-directly current type skin effect demonstration instrument, constitute by power supply, current sensing means and hollow conductor, described hollow conductor outside surface continuously or opening arranged, the two-end-point of outside two terminals of the most close this conductor of conductor inwall is connected with a lead, this lead passes a perforate Hall electric current detecting apparatus, outside two terminals of conductor are connected with power supply respectively, and pass another perforate Hall electric current detecting apparatus.
The present invention is divided into center branch road and surperficial branch road with conductor, insert current sensing means in the hollow conductor, the straight conductor center electric current of surveying, measure the total current that flows through conductor again, obtain the conductive surface electric current indirectly, the regularity of distribution of center electric current and surface current under the effect of contrast different frequency alternating current, thus skin effect can intuitively accurately be demonstrated.Can only qualitative checking skin effect thereby avoided in the prior art, and the problem of the DISTRIBUTION OF CURRENT that can't the quantitative measurment skin effect causes.
The present invention can adopt the AC power of hundreds of kilohertz, can accurately demonstrate out tangible skin effect, and its cost is far below tens of megahertz power supplys of existing skin effect demonstration instrument; And when the present invention adopts iron or other high magnetic permeability materials as conductor, use tens kilo hertzs AC power also can reach same obvious effects, and price further reduce cost far below non-ferrous metals such as copper materials.
Description of drawings
Fig. 1 is the structural drawing of existing skin effect demonstration instrument.
Fig. 2 is the principle assumption diagram of the embodiment of the invention.
Fig. 3 is the structural drawing of the hollow conductor part of the embodiment of the invention 1.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in further detail below in conjunction with accompanying drawing.
As shown in Figure 2, the embodiment of the invention is based on following principle: have a lead 26 to connect two ends in the hollow conductor 21 as Fig. 2 in the continuous airtight hollow conductor 21 of outside surface, formation center current branch.When these conductor 21 two ends terminals 24,25 feed electric current, electric current flows through center branch road and surperficial branch road respectively, because the supply frequency of using is lower, can ignore to the electromagnetic wave energy of space radiation is almost nil, so according to Kirchhoff's current law (KCL), total current=surface current+center branch current.The center electric current can directly be measured by sensor 22, and total current is directly measured by sensor 23, thereby obtains the surface electrical flow valuve indirectly.The ratio of center current value and surface electrical flow valuve under direct current and the different frequency alternating current relatively can accurately be demonstrated out the high-frequency ac current electric current and level off in conductor along the skin effect phenomenon of conductor outside surface transmission respectively.
Embodiment 1: Fig. 3 is the structure of hollow conductor part, hollow conductor chamber 31 is the barrel-shaped of back-off, top end face has two circular opens, one end of opening part and hollow conductor pipeline section 37 closely welds, the center Ampereconductors 33 that a U-shaped is arranged in two pipeline sections, with the pipeline section electrical isolation, center Ampereconductors 33 passes perforate hall current detector spare 310, two ends are threaded with the frustum of a cone 36, terminals 35 have been pressed solidly between top and the nut 34 on the frustum of a cone, terminals 35 are connected with power supply and pass another perforate hall current detector spare, measure total current.Signal transmitting module 38 is close to hollow conductor chamber 31 inwalls, is connected by lead 311 with perforate hall current detector spare 310, and signal coupling module 39 is relative across conductor casing with signal transmitting module, is close to the conductor casing outer wall.When two frustums of a cone 36 are pressed onto hollow conductor pipeline section 37 tops, when hollow conductor bottom surface 32 is gripping into the opening part in hollow conductor chamber 31, total is the continuous conductor of outside surface, the electric current that two terminals 35 flow through is flow through by conductor casing and center Ampereconductors 33 respectively, the center electric current is detected by perforate hall current detector spare 310, measuring-signal is passed to signal transmitting module 38 through lead 311, be transformed into magnetic signal and send to signal coupling module 39, the display centre current value is given the observer after reducing, another perforate hall current detector spare that is connected with terminals 35 is used for measuring total current, deduct the center current value, can obtain surface current indirectly.Increase the reason of hollow conductor pipeline section 37 in hollow conductor: conductor casing will guarantee certain thickness at least, satisfies under the certain frequency to reach several times of skin depths, flows through than multiple current; The ratio of center conductor sectional area and conductor casing sectional area will be tried one's best greatly when direct current, and the center current ratio is bigger when making direct current, and the center current ratio is die-offed during interchange; In the hollow conductor constant volume to be arranged, hold the center current sensing means; Packing into just to seal behind the current sensing means makes conductive surface continuous, and sealing part cannot flow through big electric current in order to avoid increase error; The conductor materials used is few as far as possible, to save cost.By above condition as can be known, if hollow conductor is made uniform shapes, can cause bigger waste, and error is increased, use this structure to put into hollow conductor chamber 31 to current sensing means, pipeline section is partly done to such an extent that try one's best narrowly to save cost, and the overwhelming majority of surface current is flow through by the top end face in hollow conductor chamber 31 during interchange, minimum by the electric current that the hollow conductor bottom surface is flow through, can ignore by sealing the error that contact resistance brings.Proof machine center electric current when direct current of doing accounts for more than 80% of total current in fact, accounts for about 5% of total current when exchanging 100KHZ, and strong skin effect has taken place.And this embodiment also embodies the notion of skin effect center electric current and surface current in form fully.
Embodiment 2: the signal transmitting module among the embodiment 1 38, signal coupling module 39 and hollow conductor bottom surface 32 are removed, directly the opening of lead 311 by hollow conductor chamber 31 passed, pass to display device display centre electric current.Though the conductor outside surface has extended to inside cavity by the opening part in hollow conductor chamber 31, but, alternating current in cavity, flows because being difficult to walk around opening, so the electric current that flows through from opening part is very little, be high-impedance state, influence to measurement result is very little, also can relatively accurately demonstrate skin effect.
In a word, the above is preferred embodiment of the present invention only, is not to be used to limit protection scope of the present invention.
Claims (6)
1, a kind of measuring-directly current type skin effect demonstration instrument, constitute by power supply, current detecting device and hollow conductor, it is characterized in that, described hollow conductor outside surface continuously or opening arranged, the two-end-point of outside two terminals of the most close this conductor of conductor inwall is connected with a lead, this lead passes a perforate Hall electric current detecting apparatus, and outside two terminals of conductor are connected with power supply respectively, and pass another perforate Hall electric current detecting apparatus.
2, measuring-directly current type skin effect demonstration instrument according to claim 1, it is characterized in that, when described hollow conductor outside surface consecutive hours, a described perforate Hall electric current detecting apparatus is made of perforate hall current detector spare and magnetic coupling signal transmission device spare, between described perforate hall current detector spare and the magnetic coupling signal transmission device spare for being electrically connected.
3, measuring-directly current type skin effect demonstration instrument according to claim 1 is characterized in that, when described hollow conductor outside surface had opening, the signal transmssion line of a described perforate Hall electric current detecting apparatus was passed by described opening.
According to claim 1,2 or 3 described measuring-directly current type skin effect demonstration instruments, it is characterized in that 4, described power supply is the high-frequency ac power that is lower than 300KHZ and frequency adjustable.
According to claim 1,2 or 3 described measuring-directly current type skin effect demonstration instruments, it is characterized in that 5, described power supply is by below the 300KHZ and the high-frequency ac power of frequency adjustable and can constituting with the direct supply that described high-frequency ac power switches.
According to claim 1,2 or 3 described measuring-directly current type skin effect demonstration instruments, it is characterized in that 6, described hollow conductor material is copper or iron.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007103019279A CN101465081A (en) | 2007-12-20 | 2007-12-20 | Measuring-directly current type skin effect demonstration instrument |
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| Application Number | Priority Date | Filing Date | Title |
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| CNA2007103019279A CN101465081A (en) | 2007-12-20 | 2007-12-20 | Measuring-directly current type skin effect demonstration instrument |
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| CN101465081A true CN101465081A (en) | 2009-06-24 |
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| CNA2007103019279A Pending CN101465081A (en) | 2007-12-20 | 2007-12-20 | Measuring-directly current type skin effect demonstration instrument |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109741669A (en) * | 2019-02-28 | 2019-05-10 | 中国地质大学（武汉） | The demonstrator of method demonstration skin effect based on equivalent measuring resistance |
| CN110288889A (en) * | 2019-07-30 | 2019-09-27 | 新疆工程学院 | A kind of homogeneous half space plane electric fields distribution characteristics experimental provision and experimental method |
| CN112014626A (en) * | 2020-08-10 | 2020-12-01 | 南京信息工程大学 | Skin effect measuring device and method |
-
2007
- 2007-12-20 CN CNA2007103019279A patent/CN101465081A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109741669A (en) * | 2019-02-28 | 2019-05-10 | 中国地质大学（武汉） | The demonstrator of method demonstration skin effect based on equivalent measuring resistance |
| CN110288889A (en) * | 2019-07-30 | 2019-09-27 | 新疆工程学院 | A kind of homogeneous half space plane electric fields distribution characteristics experimental provision and experimental method |
| CN110288889B (en) * | 2019-07-30 | 2024-06-04 | 新疆工程学院 | Experimental device and experimental method for uniform half-space plane electric field distribution characteristics |
| CN112014626A (en) * | 2020-08-10 | 2020-12-01 | 南京信息工程大学 | Skin effect measuring device and method |
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Open date: 20090624 |