CN1945964A - Square-wave permanent magnet multiple frequency speed regulating synchronous cage motor - Google Patents

Abstract

This invention relates to a multi-frequency adjustable-speed motor, which derives a ration relationship of torque and rotor current to make the structure of the synchronous and asynchronous motors the same and simple as the cage motor, and increases the rated frequency when outputting rated voltage by one time, reduces the lead turn number of the stator winding of the cage motor to a half, increases the sectional area of lead by one time so as to increase the rated current and output rated power by one time.

Description

Square-wave permanent magnet multiple frequency speed regulating synchronous cage motor

Technical field

Multiplier speed regulating motor is a kind of improved frequency-conversion and speed-regulation motor, and this technology can make more than the cost drop by half of frequency-conversion and speed-regulation motor, and further increases work efficiency.

Technical background

Though present existing frequency-conversion and speed-regulation motor has the outstanding advantage of control mode and economize on electricity flexibly.But since when operation the rotatablely moving of rotor relative stator, make it was that the parameter of linear relationship transforms into non-linear relation originally.Caused the quantitative relationship of voltage in the voltage that can't find the solution in the rotor loop or electric current and the stator winding or electric current, so the function relation curve T=f (n) of torque T and rotation speed n can only be measured by experiment.This also just can't give full play to the sharpest edges of variable-frequency control technique.

The operation of actual motor is formed by three phases, and they are respectively: stall stage, start-up period, stable operation stage.And non-linear relation only just occurs at start-up period, still exists the linear relationship of parameter in stall stage and the stable operation stage.Only because the limitation of traditional concept is added the mistake that exists in the classical electromagnetic foundation theory, the rectifying effect of rotor loop can't be found when making motor stable operation.And the rectifying effect in rotor when rotation makes and only has direct current in the rotor loop, so rotor active power of output, no matter shaft power that Here it is is that synchronous machine or squirrel-cage motor are not always the case, and motor or generator also all produce torque by rectifying effect.And the non-linear relation of parameter dissolved by rectifying effect has become linear relationship.How does commutating electromotive force in the rotor loop form so? this intractable problem is discussed below.

For the correct problem that proposes above of answering, just must correct the mistake in the classical electromagnetic theory earlier, when correcting a mistake, just answer the process of the problems referred to above.

Substantive technology contents

Mistake in one law of magnetic induction

The law of electromagnetic induction that provides in the classical electromagnetic foundation theory is (1) formula:

U---induced electromotive force, ---magnetic flux, S---coil surrounds the magnetic circuit sectional area, and B---magnetic flux density is when B is SIN function, then

B＝B _MSinωt

Substitution (1) formula gets u=-s2 π fB _MCos ω t and transformer formula

Relatively differ N doubly.

And

Again with the definition of inductance coefficent L

Contradictory.Through audit, originally (1) formula and (2) formula all are wrong, must correct, and are rewritten as (3) formula and (4) formula respectively and are only correct.

L is the length of magnetic path, and inductance coefficent L is directly proportional with coil turn, rather than with square being directly proportional of coil turn.So Ampere circuit law $B=\mathrm{\μH}=\mathrm{\μN}\frac{i}{l}$ Also, also be applicable to alternating electromagnetic field simultaneously with law of electromagnetic induction contradiction not.

Another one gross error is exactly to be judged the direction of induced electromotive force by Lenz's law in the law of electromagnetic induction.The induced electromotive force that is the closed-loop path produces an induced current, and the rate of change of the magnetic flux that this electric current produces always hinders the variation of former magnetic flux, and this sense of current is exactly the direction of induced electromotive force.When ＞0, become the right-handed helix relation, when ＜0, become the left hand helix relation.

Faraday delivered the law of electromagnetic induction in 1831, and make after first generator model, obviously think the induction reactance of closure by mistake to be pure resistance in the rule of the judgement induced electromotive force direction that Lenz provides, therefore think induced current (exciting curent just) and induced electromotive force by mistake to be same-phase.Under technical conditions then, the phase difference that can't measure between induced electromotive force and the exciting curent is understandable, but has had the phase difference that is easy to measure the two behind the oscilloscope to be

Correct the mistake of Lenz's law but all have no talent, also nobody conscientiously judges the direction variation relation between the output voltage and rotor rotary pole, just phase relation in the electricity generator stator coil.This does not just still find the reason of the rectifying effect of rotor winding so far.

The rectifying effect of two rotor loops

Produce exciting curent and the magnetic flux same-phase of magnetic flux, so the two changes direction simultaneously, and vertical mutually, satisfy right-handed helix and concern.But induced electromotive force and exciting curent phase angle difference are

So can not change direction simultaneously between induced electromotive force and the magnetic flux, also just not exist the right hand or left hand helix to concern.So positive and negative can only or decline by the rising of magnetic flux of induced electromotive force judge, at first analyze the rectifying effect of single-phase generator rotor winding loop below for simplicity.

1 single-phase generator floating voltage

Magnetic flux density B in the positive and negative magnetic pole of generator amature is constant, is respectively B _mAnd-B _m, magnetic pole area S ₂Should equal magnetic circuit along the axial length l and rotor along the arc length τ on the circumference ₂Product

S ₂＝lτ ₂…………………………(5)

Same stator winding surrounds the area S of magnetic circuit ₁Should equal l with along diameter of stator bore arc length τ ₁Product

S ₁＝lτ ₁…………………………(6)

Because τ ₁＞τ ₂So the physical meaning that following said magnetic pole of the stator aligns with rotor magnetic pole is meant the state that the center line of magnetic pole coincides, come problem analysis with the pole center line as the reference point during rotor rotation.

Selected sub-winding is rich clockwise to begin to clock when the rotor negative pole aligns with the stator positive magnetic pole during stable operation to for just, so the magnetic flux that rotor passes the positive winding encirclement of stator magnetic circuit during l=0 is negative maximum value-B _mS ₁, the rotor rotation makes-B _mS ₁Be tending towards 0, when

The time pass that the magnetic flux of the positive winding of stator is positive and negative to be equated, cancel out each other and equal 0, the induced electromotive force u of stator winding equals 0 constantly at t=0, $t=\frac{T}{4}$ Constantly equal positive maximum U _m, so U is a SIN function

U＝U _mSinωt…………………………(7)

And what pass the stator winding magnetic flux is cosine function

＝- _mCosωt…………………………(8)

(8) formula and (7) formula are observed the law of electromagnetic induction.Magnetic flux  exists Commutation constantly, and induced voltage exists

Constantly do not change direction.

In time, magnetic flux  rises to positive maximum by 0, be that the positive magnetic pole rotor aligns with this forward stator winding magnetic circuit therefore, and the induced electromotive force of this stator winding drops to 0 by positive maximum, and U does not change direction.Therefore exist

In time, U and  promptly do not observe the right-handed helix relation, do not observe the left hand helix relation yet.If stator winding and external circuit are connected, so just have electric current and pass through, and electric current can be divided into active current and reactive current, analyze active current and reactive current produce induced electromotive force to the rotor winding relation below respectively.

The induced electromotive force that 2 stator active currents produce the rotor winding

Stator winding and external circuit pure resistance are connected the back and are formed active current, and therefore active current and voltage same-phase have following formula

i＝I _mSinωt…………………………(9)

Active power W=Ui=U _mI _mSin ²ω t gets

$W=\frac{U_m{I}_m}{2}(1-\mathrm{Cos}2\mathrm{\ωt})\·\·\·\·\·\·\left(10\right)$

There are two in the quantitative relation formula (10), first

Be the power of resistance consumption, second

It is the reactive power that exchanges between stator winding and the rotor winding.In the classical electromagnetic foundation theory with second careless having neglected.The corresponding relation of second of following surface analysis and rotor.

Active current is 0 at t=0 constantly, magnetic flux =0 of generation,

This magnetic flux rises to maximum  in time _m,

The rotor winding turns over constantly

The angle, the area that just in time surrounds the positive negative pole of stator respectively accounts for half, so the rotor winding exists

Constantly pass the magnetic flux sum and equal 0,

The magnetic flux that constantly passes the rotor winding is only maximum.Therefore the rate of change of magnetic flux exists in the rotor winding Double induced electromotive force U in time ₂Frequency double.But U ₂Equal the negative maximum value constantly at t=0,

Constantly equal 0,

Constantly rise to positive maximum, so should meet following relational expression.

U ₂＝-U _2mCos2ωt…………………………(11)

Attention: the magnetic flux of the magnetic flux that active current causes in the rotor magnetic pole, so it can not make that the current flux amount changes direction in the rotor, so U ₂Value is never greater than the excitatory direct voltage U of rotor ₄Value is worked as U ₂With U ₄When equidirectional, be equivalent to increase dc magnetizing voltage, and U ₂With U ₄In the time of in the other direction, be equivalent to reduce dc magnetizing voltage, average result is that dc magnetizing voltage is constant.When therefore generator is exported active current, do not need additionally to increase dc magnetizing voltage.And average direct current and U ₂Product just be equivalent to second phase in the active power.U ₂Value why so little, exactly because rotor magnetic circuit is full to be closed, thus permeability near with space permeability μ ₀Value very nearly the same, so the induction reactance of rotor winding is very little.

Reactive current makes the induced electromotive force that the rotor winding produces in 3 stators

Reactive current should be a cosine function, so relational expression is as follows:

i＝I _mCosωt…………………………(12)

Additional magnetic flux  and i that reactive current produces are synchronous, and at t=0 constantly, the magnetic flux  that reactive current causes is positive maximum  _m, at this moment rotor aligns with stator magnetic circuit, therefore the induced electromotive force U that causes in the rotor winding _2LEqual 0, magnetic flux decline U _2LBe negative value.When $t=\frac{T}{4}$ Constantly, the rotor winding turns over The angle, at this moment the positive and negative magnetic pole area of rotor winding and stator respectively accounts for the aligned in position of half, and the magnetic flux that therefore passes the rotor winding equals 0, and Reactive current also drops to 0 constantly, and the magnetic flux that causes also equals 0 simultaneously, so U _2L Constantly rise to the negative maximum value.Warp again

Arrive after time Constantly, the rotor winding turns over the π angle,

Constantly the rotor winding aligns with the stator negative pole, at this moment reactive current and change the negative maximum value simultaneously into by the additional magnetic flux of its generation.Negative negative for just, so this rotor winding aligns with the magnetic pole of positive maximum magnetic flux again, being equivalent to t=0 is equivalent constantly, so U _2LStill repeat later on

The Changing Pattern of time is negative value, so U _2lBe the direct current half-wave that is equivalent to after the rectification, can not change direction, the rectifying effect of Here it is rotor winding.

Known by last surface analysis: the additional magnetic flux that reactive current produces is always reverse with rotor direct current flux amount.When therefore exporting reactive current, generator must the compensating direct current exciting curent, improves the direct current flux amount, to offset reactive current to demagnetizing effect that rotor was produced, otherwise can reduce the output voltage of generator significantly, so reactive power to consume the generator installed capacity.But capacity current can be strengthened rotor direct current flux amount again, improves the idle ability of generator output.Generating state or electric motor state in addition, the phase place of its rotating speed and rotor relative stator winding can not change.Therefore the stator output voltage U is proportional to the direct current flux amount that the rotor dc magnetizing produces, and this direct current flux amount is enough big, and the synchronous machine output voltage will be higher than line voltage and outside active power of output, is in the generator state.Otherwise the direct current flux amount that produces when the rotor dc magnetizing is little, and the voltage of synchronous machine output will be lower than line voltage and absorb active power, is in electric motor state.

The spatial distribution of direct current flux amount in air gap in 4 rotor magnetic poles

The area that stator winding surrounds magnetic circuit is S ₁, S ₁Should equal magnetic circuit thickness l and extremely shared radian τ vertically ₁Product, and τ ₁Equal girth 2 π r and mutually the ratio of number of poles 2p, r is the garden radius, and p is a number of pole-pairs, then

$S_1=\frac{l2\mathrm{\πr}}{2p}\·\·\·\·\·\·\left(13\right)$

Pass stator winding magnetic flux maximum  _mEqual rotor dc magnetic flux density B and S ₂Product

Know by last surface analysis, Magnetic flux  in time _mDrop to 0, so ( _m-0) with

Ratio equal the coil-induced electromotive force of stator circle, multiply by total number of turns N and equal output voltage U, then

$U=4\mathrm{Bl\π}\frac{\mathrm{rN}}{p.\mathrm{\τ}}=\mathrm{NBlr}\frac{4\mathrm{\πf}}{p}\·\·\·\·\·\·\left(15\right)$

Generator uses the synchronous revolution of per minute, and this paper uses synchronous revolution and be designated as n each second _s, so each second synchronous revolution n _sEqual the ratio of supply voltage angular frequency f and number of pole-pairs p.

$n_s=\frac{f}{p}$

Substitution (15) formula gets

U＝4πNBlrn _s…………………………(16)

The same quantitative relationship of motional electromotive force U=Blv that adopts can derive (16) formula equally.The linear velocity v of a lead cutting magnetic line of stator equals angular speed 2 π n _sWith the product of radius r, with v=2 π n _sAmong the r substitution U=Blv, and N circle stator coil has 2N root lead cutting magnetic line, so can get

U＝4πNBlrn _s

As seen motional electromotive force is exactly another expression way of the law of electromagnetic induction.What deserves to be explained is, U=Blv with $U=-S\frac{\mathrm{dB}}{\mathrm{dt}}$ Compare, differ for AC sine wave

Phase angle difference, following surface analysis forms

The reason of phase angle difference.

Under the generator stable operation state, the rotary speed of rotor is stablized constant, and magnetic flux density B also is invariable, and therefore the output voltage U that provides by (16) formula should be the square-wave voltage of positive and negative alternate.How does sinusoidal waveform form so? originally the synchronous electric motor rotor winding surrounds the area S of magnetic pole ₂Surround the area S of magnetic group less than stator winding ₁, surrounds magnetic flux density B in the magnetic circuit and be only even distribution and maximum always because the rotor winding is a unicoil, and shared air gap of magnetic pole of rotor comprises the arc length that pole coil is shared along the arc length of circumference.So rotor flux density B presents Sine distribution along the circumference arc length, centerline B value is a maximum, and descends near 0 at magnetic pole and arranged on left and right sides boundary, Here it is in air gap sine space distribution relation.Therefore the density of stator winding cutting magnetic line is near 0 when t=0, and corresponding motional electromotive force U equals 0, and works as $t=\frac{T}{4}$ Moment stator winding cutting magnetic line density maximum, corresponding motional electromotive force μ equals maximum, is consistent with the phase place of induced electromotive force.So motional electromotive force is exactly an induced electromotive force, not only equal and opposite in direction, and phase place, frequency are all identical.But the magnetic flux in the t=0 stator winding encirclement constantly magnetic circuit remains maximum, so induced electromotive force can be not influenced owing to magnetic flux density in the air gap presents Sine distribution.

Known by last surface analysis: the B among the quantitative relation formula U=Blv of motional electromotive force is that SIN function distributes, and the phase angle postpones

Therefore become the cosine function relation, consistent with the induced electromotive force phase place.

The quantitative relationship of three interconnected cage motors

Know that by the front derivation motional electromotive force and induced electromotive force are the different expression-forms of the law of electromagnetic induction.Therefore adopting (16) formula to analyze interconnected cage motor has simplified a problem.Because the rotor squirrel-cage bar is to the axle center radius r ₂Though a corresponding shared separately radian of magnetic pole equates that the length that arc length differs equals the difference of girth and the ratio of number of magnetic poles 2p, for $\frac{2\mathrm{\π}(r_1-r_2)}{2p}=\frac{\mathrm{\π}(r_1-r_2)}{p},$ Add stator slot and be wider than the width of rotor squirrel-cage bar.Because the scope of revolutional slip is about 1.5%～5% during interconnected cage motor stable operation, the magnetic pole correspondence position only differs from 1.5%～5% scope so whenever circle, so little deviation can not influence the magnetic flux of stator and rotor magnetic circuit interlinkage, in other words by supply frequency $f=\frac{T}{2}$ The magnetic flux change value that produces in time can not reduce less than synchronous revolution n because of actual revolution n.So rotor bar is designated as U because of the electromotive force that electromagnetic induction produces still is directly proportional with synchronous revolution with this electromotive force _e, the U that produces in sliver _eSatisfy the following relationship formula

U _e＝4πBlrn _s…………………………(17)

The deviation of aliging with magnetic pole of the stator when rotor runs up to when enough big, the squirrel-cage bar of magnetic poles can be offset the position of a squirrel-cage bar simultaneously forward in the rotor, for example begin to constitute rotor magnetic circuit by the 1st to the 8th squirrel-cage bar, accumulate deviation so and then constitute this magnetic circuit when enough big by the 2nd to the 9th squirrel-cage bar, analogize in proper order, never because of actual revolution n less than the deviation that phase place appears in synchronous revolution n, therefore claim that actual revolution n is a plesiochronous mode.

The motional electromotive force that so actual revolution n produces is designated as U _r, then

U _r＝4πBlrn …………………………(18)

The pure resistance of rotor bar is R, then electric current I in the sliver ₂By following quantitative relation formula:

$I_2=\frac{U_e-U_r}{R}=\frac{4\mathrm{\πBlr}}{R}(n_s-n)\·\·\·\·\·\·\left(19\right)$

Thereby U _e-U _rBe that the half-wave waveform voltage is poor, because the rectifying effect of rotor bar can't change direction, so what flow through in the sliver is direct current, impedance yes pure resistance is when rotor revolution number during less than plesiochronous mode, just in the starting process, or during the stall state, the induction reactance in sliver loop just can work, and the sort of state is because rotating speed is low excessively, so U _rVery little, rotor current just can be provided by following formula.

$I_2=\frac{U_e-U_r}{X}\·\·\·\·\·\·\left(20\right)$

X is the induction reactance in sliver loop.After variable-frequency control technique occurs, just can enter plesiochronous mode from the starting beginning, therefore (20) formula is undebatable.1 sliver is subjected to the action of a magnetic field power F=BlI ₂, the total radical of rotor bar is N ₂, then

$F=\frac{4\mathrm{\π}{B}^2{l}^{2}r{N}_2}{R}(n_s-n)\·\·\·\·\·\·\left(21\right)$

Rotor torque T=Fr then

$T=\frac{4\mathrm{\π}{N}_2{B}^2{l}^2{r}^2}{R}(n_s-n)\·\·\·\·\·\·\left(22\right)$

Torque quantitative relation formula when (22) formula is exactly interconnected cage motor stable operation.

Electric current in the rotor bar is a pure resistance character, certainly I ₂The electric current that is folded in the stator winding has been exactly a real component, and real component electric current in the stator winding is designated as I _R, the stator winding total number of turns is N ₁Then

$I_R=\frac{4\mathrm{\π}{N}_2{B}^2{l}^2{r}^2}{N_{1}R}(n_s-n)\·\·\·\·\·\·\left(23\right)$

Shaft power is designated as W in the stator winding _R, then

$W_R={\mathrm{UI}}_R=\frac{{4\mathrm{\πN}}_2{B}^2{l}^2{r}^{2}U}{N_{1}R}(n_s-n)\·\·\·\·\·\·\left(24\right)$

In the stator winding exciting curent and loss current through Coordinate Conversion shown in figure-1-.

Loss power W ₁=R ₁I ₁ ², the loss voltage U ₁=R ₁I ₁Excitatory power $W_L={\mathrm{WL}}_1{I}_{L1}^2,$ Excitation voltage U _L=WLI _lShaft power $W_R={\mathrm{RI}}_{R2}^2,$ The shaft power voltage U _R2=R ₂I _R2, order respectively $\frac{U}{U_1}=K_1,\frac{U}{U_2}=K_2,\frac{U}{U_{R2}}=K_3,\frac{I_1}{I_{R1}}=K_1,$ $\frac{I_L}{I_L^{\′}}=K_2,\frac{I_{R2}}{I_R}=K_3,$ Then

$W_1=R_1{I}_1^2={\mathrm{UI}}_{R1}\·\·\·\·\·\·\left(25\right)$

$W_L={\mathrm{WLI}}_L^2={\mathrm{UI}}_L^{\′}\·\·\·\·\·\·\left(26\right)$

$W_R={\mathrm{RI}}_{R2}^2={\mathrm{UI}}_R\·\·\·\·\·\·\left(27\right)$

After above-mentioned Coordinate Conversion, with exciting curent, loss current, the shaft power electric current all becomes relation in parallel, and that corresponding all is supply voltage U.This is only the physical state of real interconnected cage motor.Fig. 1 circuit is the equivalent electric circuit of motor virtual condition.

Four three-phase doubling speed control interconnected cage motors

Quantitative relation formula (19) by the rotor bar electric current is known: during interconnected cage motor stable operation, rotor current is only regulated and control by the revolution difference between synchronous revolution and the actual revolution, when supply voltage improves or reduce, can only change the size of magnetic flux density B value, when the B value changes, revolution difference changes thereupon, makes rotor current I ₂Be not subjected to directly influencing of supply frequency f and change in voltage, so can significantly improve supply frequency f by variable-frequency control technique, and do not change supply voltage value, simultaneously the stator winding lead number of turn is reduced at double, and sectional area of wire increased exponentially, the interconnected cage motor rated current can increase exponentially like this.

Asynchronous motor electromagnetic power S equals induced electromotive force U _eProduct with rated current I and number of phases m.

S＝mU _eI…………………………(28)

Electromagnetic power S also can be by synchronous revolution n simultaneously _s, the motor stator inside diameter D square, stalk is to the product representation of length l, usage factor C

S＝CD ²ln _s…………………………(29)

Therefore the asynchronous motor electromagnetic power is directly proportional with supply frequency f, because f and n _sBe directly proportional f=n _sP, so when f doubled, the stator conductor sectional area increased and is twice, the number of turn reduces one times, resistance descends 4 times, so copper loss descends 4 times, when rated current increase be twice after, electromagnetic power increases and is twice, but copper loss is with original the same, so the efficient during less than rated current improves nearly one times.And motor copper consumption and size are all constant, be equivalent to motor rated power under the constant situation of raw material and double, so the cost drop by half.The loss of per kilogram copper conductor is 32 watts when the copper conductor current density is 4A, and the iron loss of silicon steel sheet per kilogram has only 1.2 watts, so after frequency doubled, iron loss increased little.Because rotor is direct current, can not cause iron loss, so generator loss mainly is copper loss, so motor efficiency can improve.4 pole motor supply frequencies are doubled, and synchronously revolution equates that with 2 pole motors cost is half of former 4 pole motors, reduces than former 2 pole motors that half is many, Here it is multiplier speed regulating motor.

Five two-phase square wave doubling speed control interconnected cage motors

Existing with the price height of capacity 2 pole motors than 4 pole motors, be exactly because 2 utmost points are bigger than the copper cash weight of 4 polar curves volume, because the two coil of wire number is identical with radical, but it is big that 2 polar curve wraparounds enclose the magnetic circuit area, therefore axial length equates and arc length is two times of 4 polar curves volume, so two polar curves volume uses copper cash many.Though two ultimate ratios, 4 pole motor sizes are little, though silicon steel sheet is light, there is not copper cash price height, the high reason of two pole motor costs that Here it is, visible number of poles can be saved copper conductor for a long time.If change 4 pole motors into 8 utmost points, stator is made of 16 grooves, 16 teeth, and rotor constitutes cage type short circuit 12 utmost point rotors by 12 slivers.Stator winding is two-phase 8 pole motors, and is constant when then revolution still keeps 4 utmost points if the specified output frequency of inverter is doubled, and can save copper cash about 25%, and efficient also improves simultaneously.When three-phase being changed into the two-phase quadrature coil of wire, import square-wave voltage, phase difference is still between the two-phase

Will form the square wave rotating magnetic field.The square wave magnetic flux density can improve 11%, knows that by (22) formula torque can propose 21%.Efficient improves the back can bring up to 30% again on 21% basis, so the total cost of two-phase 8 utmost point square wave interconnected cage motors descends 30%, efficient improves 21%, and revolution is constant.After converter technique is improved and become multiplier speed regulating motor in a word, can improve the multiple of frequency arbitrarily, reduce cost significantly, make its cost also lower than the cost of traditional interconnected cage motor and starting equipment sum, traditional interconnected cage motor will be eliminated.

Mistake in six ohm's law for magnetic circuit

Because the limitation of traditional concept, when the variable relation in the motor operation course is discussed, all the time adopt the relevant variable of stator, as: input voltage and frequency, electric current, and the magnetic flux of output variable and speed are always equaled torque by the product that the law of conservation of energy correlation is directly found the solution electric current and magnetic flux, and with rotor rotatablely move and relativeness has been ignored.In fact the independent system that rotatablely moves of rotor, these two have the system of relative motion should adopt coordinate transform to find the solution.Crucial the transforming into time in the coordinate transform of magnetic flux density spatial distribution sinusoidal variable through rotatablely moving of relativistic conversion is that the variable SIN function concerns, this transformational relation is actual to be exactly the origin that in the theory of relativity is become space-time the time as vector, and therefore the learning value of this transformational relation is discussed in a separate paper.

Magnetic flux density B will contradict with ohm's law for magnetic circuit with magnetomotive quantitative relationship in the air gap that provides by this paper.Magnetic flux  in the air gap or magnetic flux density B produce by magnetizing current M in magnetomotive force NI and the permeability magnetic material is common, but the magnetomotive force NI of effect air gap always equates with magnetizing current M that gas length is l ₀The time have the following relationship formula to set up

M＝NI …………………………(30)

Bl ₀＝M+NI…………………………(31)

Think in the classical electromagnetic theory that magnetic flux density is produced by the magnetomotive force in the magnetizing coil fully in the air gap, this and actual phenomenon are inconsistent.For example: the magnetizing current in the permanent magnet has magnetic flux distribution in a vacuum in the same old way, and the magnetizing current in the visible permanent magnet can distribute in a vacuum the state that corresponding just magnetomotive force NI equals 0.In fact put into the preferably proof that the phenomenon that just can strengthen the magnetic flux density of vacuum behind the magnetic core is exactly (30) and (31) formula in Tong Dian the ceases to be busy circle.Strict experimental results show that also is not difficult: take a contactor iron core that does not have short-circuited conducting sleeve, with gas length l ₀When being fixed as 1mm, by power frequency ac voltage, measure alternating voltage U and exciting curent value I to magnetizing coil, substitution transformer formula U=4.44NfSB just can calculate the magnetic flux density in the air gap.Magnetomotive force NI=400 ampere-turn in the time of can finding in the 1mm air gap, to occur B and equal 10,000 Gausses' magnetic flux density.

And the quantitative relation formula of air gap is as follows in the ohm's law for magnetic circuit:

Bl ₀＝NI

Think that the magnetomotive force when producing 10,000 Gauss's magnetic flux densities in the 1mm air gap is 800 ampere-turns, this is inconsistent with actual measurement.This mistake but exists in classical electromagnetic theory for a long time, and influences the result of calculation of motor air gap magnetic flux distribution.Owing to by the ohm's law for magnetic circuit of mistake magnetomotive value of air gap landing is increased and to be twice, therefore mistake is obscured rated current mutually with exciting curent, the exciting curent value correctly can't be made a distinction from load current value, also be hard to tell the right value of active current, so the relation of active current and stator current in the rotor can't be discussed in the conventional motors theory.Torque and rotation speed relation curve T=f (n) can't be found the solution.Also have other mistakes in the classical electromagnetic theory, in a separate paper, discuss.

Seven square-wave permanent magnet multiple frequency speed regulating synchronous cage motors

Know by preceding surface analysis: no matter be synchronous motor or asynchronous motor, all must there be the rotor bar current in loop that the additional magnetic flux that electric current in the stator winding produces is balanced out, the induced electromotive force that causes in the time of could guaranteeing the rotor field rotation is consistent with external power voltage, makes motor stable operation.Rotor core changed into to be become permanent magnet motor behind the permanent magnetism magnetic pole and equally also the rotor galvanic circle should be arranged, so the p-m rotor magnetic pole reduced exciting curent, so torque is big and most effective.Therefore synchronous permanent-magnet motor does not need the carbon brush arrangement of dc magnetizing, makes simple in structurely, has dwindled the synchronous motor volume, and makes the structure of itself and interconnected cage motor the same simple.

We know: synchronous motor overload capacity is big, most importantly rotating speed is fixed, and when adopting doubling speed control, its rotating speed can be determined and regulate and control in advance, accurately control is very favourable to realizing digitlization for this, very favourable for the high-quality precision and sophisticated technology device, so particularly the link control of production equipment of numerically controlled lathe and other automation equipments can realize setting parameter in advance, and increase substantially precision.And square wave permanent magnetic synchronous motor starting process is provided with squirrel-cage bar with the synchronous operation mode starting in permanent magnetism magnetic pole.Therefore the time of revolution can be accurately controlled in starting at the very start, and this is other synchronous motors technical performances that are beyond one's reach.How does square wave permanent magnetic synchronous motor so of the present invention start? this technical barrier is discussed below.

When in fact passing through direct current in the rotor bar, as long as the reversal in this sliver is in respectively in the positive and negative stator magnetic circuit, the direction of directed force F=BlI of the suffered stator magnetic flux density of sliver B is consistent so, and rotor will be always to a direction rotation so.If the quantity of rotor magnetic pole is below 1.5 times of stator one phase magnetic pole, when for example stator is two-phase 6 utmost points, so stator is 12 grooves, 12 teeth, and rotor should be 8 grooves, 8 utmost points, and rotor alternately is made of 4 positive poles, 4 negative poles respectively.Leave the groove of installing sliver between the positive and negative permanent magnetism magnetic pole, and make sliver form short-circuit loop.So just can overcome the dead-centre position of turning round between son and the stator, form the starting torque of synchronous operation mode simultaneously.

Because it is that every utmost point has only a coil that 12 grooves constitute the stator winding of two-phase 6 utmost points, when two-phase is passed through the square-wave voltage of positive and negative alternation, can form the square wave magnetic field of changeing by tooth spiral.Therefore the every utmost point width of 8 utmost point rotors is 1.5 times of stator per tooth width, and so sliver drops on respectively in the positive and negative magnetic pole of stator, the sliver electric current is subjected to stator field force direction unanimity, always rotates in the same direction as.The p-m rotor magnetic pole is square wave magnetic field, and requiring the stator magnetic flux density distribution so also should be square wave, and magnetic flux could make motor stable continuously like this.

The stator of electric current present type inverter forms the square wave magnetic flux in the variable-frequency control technique evolution, and rotor is when being squirrel-cage rotor, its rotor flux density spatial distribution still presents sinusoidal wave variation pattern, make the rotor rotation form the pulsating phenomenon, be exactly that the magnetic flux distribution shape is inconsistent, cause the discontinuous variation of magnetic flux distribution and the pulsating phenomenon occurs.

Square wave permanent magnetic synchronous motor magnetic pole of the stator of the present invention and rotor magnetic pole all are the square wave spatial distributions, and the every utmost point of stator is made of 2 teeth, shared radian is greater than shared radian of magnetic pole of rotor, so, there is towing leeway in rotor when rotation in the space, therefore stable, overload capacity can be eager to excel than three-phase synchronous motor, and starting torque is big, and is easy to use.When inverter output rated frequency improves three times, when promptly equaling three times of supply frequency 50 cycles and being 150 hertz, the motor revolutions per second is 50 commentaries on classics, double than 4 pole motor revolutions, rated power also doubles, add that the square wave magnetic flux density improves that the torque produced increases 21%, therefore total specified power improves 1.21 times, the efficient during output rated power improves more than 20%.

Description of drawings

Accompanying drawing 1 is the motor inductance equivalent circuit diagram.

Accompanying drawing 2 is two-phase square-wave permanent magnet multiple frequency speed regulating synchronous cage motor inverter schematic circuits.

Embodiment 1

Three-phase doubling speed control interconnected cage motor is to be made of special inverter and definite purpose motor.Special inverter is improved by former frequency control inverter and forms, frequency equals supply frequency f during former inverter output rated voltage, and the frequency during doubling speed control inverter output rated voltage will improve k doubly, k is the positive number greater than 1, therefore multiplier speed regulating motor inverter rated frequency equals kf, and output voltage equals the power supply rated voltage, because rated current also improves k doubly simultaneously, so output rated power improves k doubly, therefore the ability of the electronic switching device output current of inverter also will improve k doubly, but other vigour parts that use in the inverter can be constant.Definite purpose motor is to be improved by existing interconnected cage motor to form, improved method is: former threephase stator winding conducting wire sectional area is increased k doubly, and the number of turn reduces k doubly, because coil impedance and the number of turn square are directly proportional, be directly proportional with the frequency first power again, so coil impedance minimizing k doubly, and make rated current improve k doubly, conductor resistance reduce k square doubly, copper loss reduces k ²Doubly, the rotor bar sectional area suitably increases, and revolution improves k doubly, and rated power improves k doubly, and efficient also improves simultaneously, and motor other technologies parameter constant, cost decline k are doubly.Motor after the improvement can not directly connect with former power supply certainly and move because impedance reduces k doubly, also impossible employing former frequency control inverter, so must with the supporting use of doubling speed control special inverter.

Embodiment 2

Two-phase square wave doubling speed control interconnected cage motor is known by the motor torque quantitative relation formula that this paper provides, and torque and magnetic flux density B square are directly proportional, and improve B and can further improve stock utilization and efficient.When adopting the stator winding of two-phase omnidirectional distribution, can in this phase winding, not produce induced electromotive force owing to surround the other one positive and negative counteracting of magnetic flux that produces mutually in the phase winding, so do not disturb mutually between two phase windings, can not cause alternate energy exchange phenomenon yet, so during two phase windings input square-wave voltage, the energising angle can reach 180 °, and can will be every independent excitatory by a coil in extremely, overcomes the shortcoming that breadth coefficient that the employing parallel branch causes reduces utilance unshakable in one's determination.

When a magnetic pole was made of two teeth, a pair of magnetic pole was 4 teeth, and during two-phase orthogonal winding input square-wave voltage, in 4 teeth, having two teeth to keep B respectively is that positive and negative very big value is constant, and other two tooth B values are fast by just becoming negative and just being become by negative.4 spaces of teeth distribute, so the mean value of B is 0.75, improve 11% than sine-shaped mean value 0.64.Torque and B ²Be directly proportional, so two-phase square wave interconnected cage motor torque ratio threephase motor improves 21%, under the constant situation of raw material, cost descended 21% when efficient improved.

Improving one's methods of two-phase square wave mouse cage multiplier speed regulating motor is: change former three-phase 4 pole motor stators into 16 grooves, 16 teeth, and every 8 grooves that account for mutually, every utmost point accounts for two teeth, constitutes two-phase 8 pole motors.And the rotor bar number should equal 12, can overcome the dead-centre position like this, smoothly and steadily, can reduce leakage flux again when making starting, and is constant for other parameters and existing interconnected cage motor design parameter.

Improving one's methods of two-phase square wave mouse cage doubling speed control inverter is: the rated frequency during with output rated voltage improves 1 times, changes three-phase into two-phase, and when adopting symmetrical DC power supply, elementary diagram is shown in figure-2-.Only need 4 electronic switching devices, the output square-wave voltage, and just frequency is equal between the two-phase in the pressure regulation process, phase angle difference is

The restriction of vector correlation is not being arranged, controlling simplyr, total cost is also lower than three-phase multiplier speed regulating motor.Because k=2, frequency doubles, and electromotor series increases and is twice, so revolution is identical with former 4 pole motors.

If also wish to improve the ability of exerting oneself, so as long as on the basis of k=2, increasing the k value.When k=3, revolution is 1.5 times of former 4 pole motors, and other pole count motor are done similar processing and got final product.

Embodiment 3

Three-phase or single-phase rectifier power supply are added in the electrolytic capacitor C of two series connection ₀₁And C ₀₂Two ends constitute symmetrical DC power supply, intermediate contact and two-phase multiplier speed regulating motor stator coil L ₁And L ₂Join L ₁And L ₂Difference parallel capacitor C ₁And C ₂, C ₁And C ₂Capacity is less, L ₁And L ₂The other end is respectively through L ₁' and L ₂' series connection back and IGBT pipe G ₁And G ₃Series connection point and G ₂And G ₄The mid-series point joins G ₁, G ₂, G ₃, G ₄Difference parallel diode Z ₁, Z ₂, Z ₃, Z ₄And little capacitor C ₁', C ₂', C ₃＇, C ₄'.Little capacitor C ₁'-C ₄' capacity be C ₁And C ₂One of percentage of capacity gets final product.When IGBT electronic switching tube during with 16.6 kilo hertzs of pressure regulation of frequency, C ₁' and C ₂' and C ₃' and C ₄' can absorb L ₁' or L ₂The energy of ' release is worked as L ₁Or L ₂Release energy and can be through Z ₃, Z ₁Or Z ₄, Z ₂Release energy to power supply, so C ₁'-C ₄' can only charge once, return to the current potential of charging beginning then again, so G ₁-G ₄Be still low potential difference during connection, so four switching devices of IGBT disconnect or the always very low voltage of connection, are in the quasi-resonant switching state, have reduced the switch high-frequency loss.G ₁-G ₄Control signal is provided by programmable device B, respectively by P ₁, P ₂, P ₃, P ₄Output, the break-make of control IGBT.Programmable device carries out speed governing or starting multiplier speed regulating motor according to current value pressure regulation and frequency conversion that ammeter A records.

The rotor core that square wave permanent magnetic synchronizing and frequency doubling speed-adjusting cage motor needs only two-phase square wave interconnected cage motor makes permanent magnetic material into, after suitably magnetizing, form and get final product with the magnetic pole and the mouse cage shape sliver short-circuit loop of the identical number of teeth of two-phase square wave mouse cage multiplier speed regulating motor rotor, inverter still improves k doubly for the two-phase square wave frequency, other parameters are identical with existing above-mentioned interconnected cage motor design parameter, and synchronous motor reduces leakage flux as far as possible.Just become square wave permanent magnetic synchronizing and frequency doubling adjustable-speed motor after so improving.For example: when changing former three-phase 4 pole motors into two-phase 6 utmost points, then stator is 3 pairs of magnetic poles of 12 grooves, 12 teeth, and the rotor bar and the number of teeth are 8, and rotor formation 4 aligns, negative pole.When inverter output rated frequency is 120 hertz, revolution $n=\frac{f}{p}=40$ Change, output rated power improves 60%, if also want to improve revolution, rated frequency can be brought up to 150 hertz, and revolution can rise to 50 to be changeed, and output rated power can double.Other pole count motor are done similar processing and are got final product.

Claims (3)

1, the three-phase multiplier speed regulating motor is to be made of special inverter and definite purpose motor, frequency during the special inverter output rated voltage improves k doubly than the rated frequency f of former frequency control inverter, k is the positive number greater than 1, the ability of the output current of electronic switching device improves k doubly simultaneously, the sectional area of wire of the stator winding of definite purpose motor improves k doubly, the lead number of turn reduces k doubly, and the rotor wire sectional area suitably strengthens, and other design parameters are constant.

2, three-phase 4 pole motors can be changed into two-phase 8 utmost point square wave doubling speed control interconnected cage motors according to claim 1, stator slot, the number of teeth equals 16 respectively, whenever, constitute 4 by 8 coils and align, negative pole, rotor constitutes short-circuit loop by 12 mouse cage shape slivers, just form 12 teeth, negative pole, corresponding specified square-wave voltage value when doubling speed control inverter output rated frequency is 100 hertz, perhaps again rated frequency is further improved, the stator winding sectional area of wire and the number of turn improve multiple by frequency and do respective handling, become two-phase square wave mouse cage multiplier speed regulating motor, certainly motor also can adopt other numbers of poles, and the inverter rated frequency is done corresponding change.

3, according to claim 1, copy claim 2 to do similar processing, change the iron core in the rotor magnetic circuit into permanent magnetic material then, magnetize back formation just, negative pole, for example change former three-phase 4 pole motors into two-phase 6 utmost points, stator tooth, groove is respectively 12, and the rotor number of teeth and sliver number are respectively 8, forming 4 aligns, negative pole, when inverter output rated frequency was 120 hertz, rated revolution was the square wave permanent magnetic synchronous cage motor that per second 40 changes, and did respective handling when stator winding sectional area of wire and the number of turn improve multiple by frequency, certainly motor also can adopt other numbers of poles, and the inverter rated frequency is done corresponding change.

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