CN1025761C - Method for measuring inductance of d.c motor rotor loop or plane-wave reactor - Google Patents

Abstract

The present invention relates to a method for measuring a rotor loop or a smoothing reactor of a direct current motor by utilizing the actually measured waveform of pulsating current. The method of the present invention comprises the following procedures: 1) measuring the resistance R of a rotor loop; 2) measuring the input voltage V of a rectification circuit; 3) measuring the average value I<D> of the pulsating current; 4) measuring the output voltage V<D> of the rectification circuit; 5) determining the initial value i (o) of the pulsating current; 6) computing a control angle A; 7) determining the values of parameters of C, P, D, W, B, K, M, S and G; 8) computing inductance L. The method has the advantages of convenient use and higher accuracy of the calculated inductance value.

Description

Method for measuring inductance of d.c motor rotor loop or plane-wave reactor

The present invention relates to a kind of method of measuring the DC motor rotor loop inductance, particularly a kind of method of utilizing the pulsating current measured waveform to measure DC motor rotor loop or smoothing reactor inductance.

When DC current power supply that direct current motor is provided by Dyn., under stable state, its electric current is generally constant.Modern age is owing to rectifier power source (or stabilized voltage supply) occurred, and rectifier power source is easy to use, thereby most of direct current motor is powered by rectifier power source.But because rectifier power source is a kind of pulsafeeder, its size of current also has the cycle to change, and also can occur changing discontinuous phenomenon sometimes.For making electric current continuous, the motor smoothing reactor of also need connecting.Because have the variation (di/dt) of electric current, the inductance value of accurately measuring DC motor rotor loop or smoothing reactor is more and more important.

For the inductance value of little impedance, when the electric current that flows through hour, can measure with electric bridge.For the inductance measurement under the situation that is operated in large current load, use following several method usually:

1) DC-method.This method is in the two ends of rotor or smoothing reactor impact one direct current low-voltage, and measures the escalating rate of its DC current, and during measurement, motor must swash (excitation), thereby rotor stopper securely.So the size of the inductance of asking is obtained by the escalating rate of impressed voltage divided by electric current.But, this method not only need the harder power supply of external characteristics promptly in experimentation impressed voltage can not change but also the process of the test complexity.

2) magnetic flux mensuration.This method is with an ancillary coil and is coupled together by the rotor (pivot) of measured motor, forms an electric bridge, has also formed a magnetic flux chain simultaneously, and input current is from I ₁Change to I ₂So, measure inductance L=(△ Φ)/(△ I) (wherein, △ I=I of the above-mentioned rotor loop of variation △ Φ of the magnetic flux in the above-mentioned magnetic flux chain again with a fluxmeter ₁-I ₂).This method is owing to the measuring process complexity, thereby use is not too convenient.

3) AC method.This method is adopted by most of motor manufacturing firm usually.It is to add a power frequency ac voltage at the two ends of rotor or smoothing reactor

, motor-field is swashed (encouraging), measure its electric current

So, the inductance L of asking= $\frac{\sqrt{{\mathrm{(V/I)}}^2{\mathrm{-<figure-callout\; id="2"\; label="R"\; filenames="911093656\_DRIMG1.png,911093656\_DRIMG2.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}}{\omega }$ , wherein ω is an alternating voltage

Frequency, R is the resistance value of rotor loop.But this method still has two shortcomings: (1) when the frequency of external voltage not simultaneously because the influence of eddy current, the inductance value of measurement has error; (2), thereby, certain defective is arranged in theory to measuring the inductance under the dc pulse load (electric current) because this method relatively is suitable for measuring the inductance under the alternating voltage.Certainly will increase the error of measuring like this.

4) revised AC method.IEC had recommended a kind of revised AC method again in 1988.This method be with by measured motor as generator, its rated current is I _D, and with this electric current as DC component, in addition provide an AC compounent with an alternator, its value is 20 percent of rated current, as if providing the voltage of AC compounent to be

, electric current is

Between phase angle be θ, then the inductance L of asking= This method has been owing to provide a DC component, and pre-determined the magnetic saturation of tested inductance, thereby further remedied the theoretic defective of AC method.But; Use this method must be equipped with the complicated testing equipment of a cover, and DC component I _DMust preestablish, and the magnetic saturation of test defined has a threshold quantity, thereby can not random variation, but, the actual DC component of motor load (being the average current value of direct current generator) is a random variation, be that magnetic saturation is at random, so this method can not be simulated actual condition fully.In addition, the frequency of the alternating voltage that uses is power frequency (50Hz or 60Hz), but the frequency of the dc pulse electric current that supplies is not limited to power frequency, for example the frequency of three-phase fully-controlled SCR is 300Hz, frequency difference, the eddy current of generation are also just different, certainly will influence the precision of measurement.

The present invention is intended to overcome the shortcoming of above-mentioned all methods, and a kind of method that can measure DC motor rotor loop and smoothing reactor inductance under any load current is provided.

When direct current motor provided power supply (stabilized voltage supply) by rectification circuit, motor manufacturing firm will measure following several parameter when delivery test usually: a) ac output voltage of rectification circuit

; B) DC voltage of rectification circuit output that is to say the input voltage V of direct current generator _D; C) the average current I during motor load _D(D. C. value); D) rotor resistance in circuit R.Even certainly above parameter motor producer does not provide, the user also can measure easily.If when power supply was the SCR rectification circuit power supply, its pilot angle A can consult relevant controllable silicon handbook and try to achieve.The pilot angle A=Cos of three-phase thyristor bridge rectifier power source for example ^-1

Pilot angle A has directly influenced the whether continuous of pulsating current.Can try to achieve pulsating current i(t by equivalent electrical circuit), wherein,

, then this differential equation separates i(t) functional relation be i(t)=f (R, E, A, i(0),

, B, L, F(ω t)) ... (A)

In the following formula (A), R, A, E(E=V _D-I _DR) described above.B is a constant, and it depends on which kind of rectifier power source of use.For example, to three-phase full-controlled rectifier bridge formula rectifier power source B=(π)/3, t is the time independent variable, and L=(R)/(ω) tgF, if obtain the initial current i(o of pulsating current), F, L can obtain.In fact ask inductance L very complicated by following formula (A), be difficult to sometimes obtain, so we can provide the continuity of the electric current of power supply to obtain inductance L.

When rectification pulsating current consecutive hours,, i(o is arranged then because the cycle of pulsating current is τ)=i(τ) certain actual value, so

i（τ）＝i（o）＝f〔R，E，A，i（o），V _m，B，L，F（ωτ）〕……（B）

Because following formula (B) is an implicit function, thereby can not ask L with analytical method.But, can adopt graphical method to ask L.Also can obtain L if use a computer.

When the rectification pulsating current is discontinuous, initial current i(o)=0, each pulsation of current working time of this moment, establishing the above-mentioned pulsation time was T, then less than period tau

0＝i（T）＝f〔R，E，A，i（0），V _m，B，L，F（ωT）〕……（c）

In fact, the power supply of direct current generator use at present has (1) three-phase fully-controlled rectifier power source usually; (2) three-phase half controlled bridge formula rectifier power source; (3) single-phase full-controlled bridge rectifier power source; (4) single-phase half-controlled bridge-type rectifier power source; (5) three-phase zero formula rectifier power source; (6) side is by (copped wave) power supply; (7) diode bridge rectifier power source (inductance of main lining wave reactor).The present invention is directed to above-mentioned seven kinds of rectifier power sources, on the basis of (A), (B) two formulas, concluded the general formula of the inductance of asking DC motor rotor loop or smoothing reactor:

〔i（o）R+V _D-I _DR〕〔1- $e^{-\frac{C}{\mathrm{tg\; F}}}$ 〕＝V _mCosPF｛DSin（W+A-PF）-Sin（B+A-PF） $e^{-\frac{C}{\mathrm{tg\; F}}}$ +KSinF. $e^{\frac{\mathrm{-M}}{\mathrm{tg\; F}}}$ +S· $e^{-\frac{G}{\mathrm{tg\; F}}}$ ｝……（D）

Wherein E is the back electromotive force and the E=V in loop _D-I _DR,

So the method for measurement DC motor rotor loop provided by the invention or smoothing reactor inductance may further comprise the steps:

(1) direct current generator is linked to each other with rectifier power source;

(2) measure DC motor rotor loop or smoothing reactor resistance in circuit R;

(3) measure the alternating voltage that rectification circuit (power supply) is imported

, and by formula V _m= $\sqrt{2}$

Obtain the maximal value V of voltage _m;

(4) measure the mean value I of the rotor pulse current of flowing through _D;

(5) determine the initial current i(o of pulsating current);

(6) the pilot angle A of calculating SCR rectification circuit;

(7) according to the value of the continuity of the pilot angle A of silicon controlled rectification power source, electric current, selectivity constant C, P, D, W, B, K, M, S, G; And

(8) by formula (i(o) R+V _D-I _DR) (1- $e^{-\frac{C}{\mathrm{tg\; F}}}$ 〕＝V _mCosPF

｛DSin（W+A-PF）-Sin（B+A-PF） $e^{-\frac{C}{\mathrm{tg\; F}}}$ +KSinF. $e^{\frac{\mathrm{-M}}{\mathrm{tg\; F}}}$ +S· $e^{-\frac{G}{\mathrm{tg\; F}}}$ ｝

Try to achieve F, so the tgF of the inductance L of asking=(R)/(ω).

Above-mentioned parameter C, P, D, W, B, K, M, S, G, E, A depend on the characteristic of rectification circuit (power supply), these characteristics comprise: the size of the continuity of pulsating current, pilot angle A and the characteristic of direct current, these characteristics comprise: the size of the continuity of pulsating current, pilot angle A and the type of the employed rectifier power source of direct current generator.

What particularly point out is, obtains its function i(t in value substitution row (A) formula with the inductance L asked) in the current value i(t of point of some ₁), i(t ₂) ... i(t _n), whether coincide according to above-mentioned point then with the actual arteries and veins shape of arteries and veins shape streaming current, can verify or judge the accuracy of the inductance value of asking.

Method provided by the invention has the following advantages:

(1) this method can measured under the load current arbitrarily; Institute's inductance biography value precision of asking is higher, and can verify its accuracy;

(2) measure conveniently, do not need special measurement and equipment thereof, and can when motor moves, measure.

Fig. 1 is the synoptic diagram of the measurement mechanism that does not comprise smoothing reactor of method use provided by the invention;

Fig. 2 is the synoptic diagram of the measurement mechanism that comprises smoothing reactor of method use provided by the invention;

Fig. 3 is the waveform synoptic diagram of square wave rectifier power source;

Fig. 4 is the oscillogram of the first embodiment of the present invention by the pulsating current of oscillograph demonstration; And

Fig. 5 is the oscillogram of the second embodiment of the present invention by the pulsating current of oscillograph demonstration.

Engaging accompanying drawing below is described further method of the present invention.

Fig. 1 is the synoptic diagram of the measurement mechanism that does not comprise smoothing reactor of method use provided by the invention.Less when direct current generator power, when not needing smoothing reactor, can use device as shown in Figure 1.Among Fig. 1, terminals of the end points a of rectifier power source 1 and the rotor (or pivot) of direct current generator 2 link to each other, and its end points b links to each other with the terminals e of shunt 3, and another terminals of DC motor rotor link to each other with the terminals f of shunt 3.Direct current generator 2 has the load (not shown), and shunt 3 is used for the photoelectricity oscillograph or through A/D converter

Fig. 2 is the measurement mechanism synoptic diagram that comprises smoothing reactor that method provided by the invention is used.Different with Fig. 1 is to be connected to a smoothing reactor 4 between the end points a of direct current generator 2 and rectifier power source, so that pulsating current i(t) keep continuously, thus make direct current function operate as normal.

It must be noted that, use device shown in Figure 1, use method provided by the invention can obtain the inductance of direct current generator 2 rotors, and use device shown in Figure 2, then obtain the inductance of the series loop of direct current rotor 2 and smoothing reactor 4.In fact, if in the device of Fig. 1, DC generator 2 is replaced by smoothing reactor 4, and makes the back electromotive force E=0 in the formula (D), i.e. V _D-I _DR=0 then can obtain the inductance of smoothing reactor.

Fig. 3 is the voltage oscillogram of square wave (copped wave) rectifier power source.In fact can draw its three time constant T by calculating or by the oscillogram direct current measurement ₁, T ₂Value with period L.

Be the table 1-1 of the value of parameters C, P, D, W, B, K, M, S, G in seven kinds of silicon controlled rectification power sources commonly used below.Can from table 1-1, find the value of above-mentioned parameter by the type of the continuity of the pilot angle A of silicon controlled rectification power source, pulsating current and rectifier power source, see table

Table 1-1

Parameters C P D W B K M S G

Power supply

Electric current is continuous

A＜ (π)/6 2/3 π 1 1 5/6 π (π)/6 0 0

Three-phase zero formula electric current is continuous

π 10 (π)/6 1 A-(π)/6 0 of rectifier power source A＞(π)/6 2/3

Electric current is discontinuous

A＞ (π)/6 5/6 π-A+ωT 1 0 (π)/6 1 ωT 0

Continuous ω (the T of square wave power electric current ₁+ T ₂) 00

01 ω T ₂

Discontinuous ω (the T of (copped wave) electric current ₁+ T) 00 (π)/4 01 ω T

Continuous π 11 π 000 of single-phase full control electric current

The discontinuous ω T 11 ω T 000 of rectifier power source electric current

Continuous π 1001 A 0 of single-phase half-controlled electric current

The discontinuous π of rectifier power source electric current-A+ ω T 10001 ω T 0

Diode is single-phase

Continuous π 11 π 000 of bridge rectification power electric current

The three-phase full-controlled bridge electric current is (π)/3 00, (π)/3 11 (2 π)/3 continuously

The discontinuous ω T 11 ω T+ (π)/3 (π)/3 00 of formula rectifier power source electric current

Electric current is continuous

And π 11 2/3 π (π)/3 1 (π)/3+A 0 of A＜(π)/3 2/3

The three-phase half controlled bridge electric current is continuous

(2 π)/3 1001 A-(π)/3 0 of formula rectifier power source and A＞(π)/3

Electric current is discontinuous

And A＞(π)/3 π-A+ ω T 1001 ω T 0

Below in conjunction with Fig. 3 and Fig. 4 two embodiment of the present invention are described respectively.

The direct current generator that the first embodiment of the present invention is measured is Z ₂Type, its Specifeca tion speeification is: power P=2.75/3.4/4.7KW, change whole n=1220/1450/2500 rev/min, voltage V=175/220/320V, the silicon controlled rectification power source that uses is the three-phase thyristor bridge rectifier power source.By installation drawing shown in Figure 1, at first measure: rotor resistance in circuit R=0.995 Ω; Input voltage

=212V, then maximal value V _m= $\sqrt{2}$

=299.8V; The mean value I of pulsating current _D=14.8A; VD V between a.b _D=220V; We can obtain the pilot angle A of this rectification circuit by above-mentioned data, the formula A=Cos that is provided by the controllable silicon handbook ^-1 Get A=39.76 °, obtain the waveform of pulsating current as shown in Figure 4 by the photoelectricity oscillograph that is connected with shunt.From oscillogram, try to achieve initial current i(o)=8.8.2A is by table 1 ^-1L=(π)/3, P=1 as can be known, D=1, W=(2 π)/3, B=(π)/3, K=0, S=0 is so try to achieve F=68.89019 ° or 1.202361rad, the then inductance L=8.203mH that asks by formula (D).

In order to judge the accuracy of described inductance value L, asking inductance value L=8.203mH can be updated in (A) formula, can try to achieve pulsating current i(t) for example eight of some values, as

i（t ₀）＝i（.0000000）＝8.2A

i（t ₁）＝I（0.0004167）＝15.13959A

i（t ₂）＝i（.0008333）＝15.13959A

i（t ₃）＝i（.0012500）＝17.26004A

i（t ₄）＝i（.001667）＝18.23914A

i（t ₅）＝i（.0020833）＝17.92703A

i（t ₆）＝i（.0025000）＝16.20567A

i（t ₇）＝i（.0029167）＝12.98256A

i（t ₈）＝i（.0033339）＝8.199985A

Above-mentioned value is pointed out on the coordinate of Fig. 4, shown in the ⊙ of Fig. 4, the point of its value representation and curve i(t as can be seen) coincide basically, consider computer error, can be sure of that institute's inductance L of asking is very accurate.

The direct current generator that the second embodiment of the present invention is measured is Z ₂Type, its Specifeca tion speeification is: power P=0.8KW, change whole n=1500 rev/min, voltage V=220V.The rectifier power source that uses is single-phase half-controlled bridge-type rectifier power source.Above-mentioned direct current generator is connected by Fig. 1 with rectifier power source, measures loop resistance R=5119 Ω then, voltage V=220V, then maximal value V _M= $\sqrt{2}$

=311.127V, the mean value I of pulsating current _D=4.2A, the output voltage V of rectification circuit _D=71V; Try to achieve pilot angle A=Cos so consult the controllable silicon handbook ^-1(71/ (0.45 * 220)-1)=106.4 °; The waveform of the pulsating current as shown in Figure 5 that is shown to by the oscillograph that links to each other with shunt 3 as can be known electric current continuously and initial current i(o)=0, by table 1-1, can check in the value of following parameters, i.e. C=2, P=1, D=0, B=0, K=1, M=A, S=0 is so try to achieve inductance L=55.0756mH.

By the waveform of the pulsating current of figure shown in (5) this pulsating current i(t as can be known) to can be two parts be i ₁(t) and i ₂And i (t), ₂(o)=i ₁((π-A)/(ω)), so asking L=55.07056mH substitution (A) formula is tried to achieve:

i ₁（t ₀）＝i（.0000000）＝0

i ₁（t ₁）＝i（0.00010222）＝4.067167

i ₁（t ₂）＝i（0.0030667）＝7.792159

i ₁（t ₃）＝i（.0040889）＝7.068013＝i ₂（to）

i ₂（t ₁）＝i（0.0011822）＝5.323028

i ₂（t ₂）＝i（0.0023644）＝3.76216

i ₂（t ₃）＝i（.0035467）＝2.365978

i ₂（t ₄.＝i（.0047289）＝1.117108

i ₂（t ₅）＝i（.0059111）＝5.722046E-66

The point of above-mentioned value representation is put on the coordinate diagram of Fig. 5 shown in figure " ⊙ ", these point and i(t as can be known) curve is very identical, illustrate the inductance value of asking very accurate.

By top description, we can know that the frequency order of the method for the invention can do some variation, can change arbitrarily to (6) as step (2), reach purpose of the present invention equally.

Claims (5)

1, a kind of measured waveform that utilizes pulsating current is measured the method for DC motor rotor loop inductance, it is characterized in that it may further comprise the steps:

(1) direct current generator is connected with rectifier power source;

(2) input ac voltage of measurement rectifier power source

, try to achieve the maximal value V of this alternating voltage thus _m=

(3) resistance R of measurement rotor loop;

(4) measure the DC voltage V that rectifier power source is exported _D

(5) the mean value I of the electric current of measurement rectifier power source output _D

(6) determine the initial current i (o) of pulsating current;

(7) determine rectifier power source pilot angle A;

(8) determine the value of constant C, P, D, W, B, K, M, S, G according to power supply characteristic; And

(9) by formula [i (o) R+V _D-I _DR] [1-e-(C)/(tgF)]=V _mCosDF{DSin (W+A-PF)-Sin (B+A-F) e-(C)/(tgF)+KSinFe-(M)/(tgF)+Se-(G)/(tgF) } ... (D)

And L=(R)/(ω) tgF ... (H)

Try to achieve the inductance L in DC motor rotor loop.

2, a kind of measured waveform that utilizes pulsating current is measured the method for the loop inductance of smoothing reactor, it is characterized in that it may further comprise the steps:

(1) smoothing reactor is linked to each other with rectifier power source;

(2) input ac voltage of measurement direct supply

, obtain the maximal value V of this alternating voltage thus _m= $\sqrt{2}$

;

(3) measure resistance in circuit R;

(4) measure the DC voltage V that rectifier power source is exported _D;

(5) the mean value I of the electric current of measurement rectifier power source output _D;

(6) the initial current i(o of measurement pulsating current);

(7) determine rectifier power source pilot angle A;

(8) determine the value of constant C, P, D, W, B, K, M, S, G according to the characteristic of rectifier power source; And

(9) by formula (i(o) R) (1- $e^{-\frac{C}{\mathrm{tg\; F}}}$ 〕＝V _mCosDF·｛DSin（W+A-PF）-Sin（B+A-F） $e^{-\frac{C}{\mathrm{tg\; F}}}$ +KSinF $e^{-\frac{M}{\mathrm{tg\; F}}}$ +S $e^{-\frac{G}{\mathrm{tg\; F}}}$ ｝……（D）

And L=(R)/(ω) tgF ... (H)

Try to achieve the inductance L in smoothing reactor loop.

3, the method for claim 1, it is characterized in that above-mentioned rectifier power source is three-phase zero a formula rectifier power source, arbitrary power supply in square wave power, single-phase full-controlled rectifier power supply, single-phase half-controlled rectifier power source, diode single-phase bridge rectification power supply, single-phase full-controlled bridge rectifier power source and the three-phase half controlled bridge formula rectifier power source.

4, method as claimed in claim 1 or 2, when rectifier power source is three-phase fully-controlled rectifier power source and electric current consecutive hours, C=in the above-mentioned constant (π)/3, P=1, D=1, W=2/3 π, B=(π)/3, K=0, S=0.

5, method as claimed in claim 1 or 2, when rectifier power source is single-phase half-controlled bridge-type rectifier power source and power supply consecutive hours, C=2 in the above-mentioned constant, P=1, D=0, B=0, K=1, M=A, S=0.

Images