JPS61227693A - Momentary generating torque measuring instrument for three-phase induction motor - Google Patents

Abstract

PURPOSE:To enable momentary generating torque to be directly found, by detecting space rotation current vector and space rotation magnetic flux vector, and by operating the space rotation vectors arithmetically. CONSTITUTION:Vector analysers 3, 7 for inducting space rotation current vector and space rotation magnetic flux vector respectively from two phase current and two-phase magnetic flux are provided. The values of the space rotation magnetic flux vector PSIs and the space rotation current vector Is obtained from the vector analysers 3, 7 are fed respectively to a Sinphi arithmetic unit 6 and a multiplier 8, and Sinphi (phi is space phase difference between vectors.) and ¦PSIs¦.¦Is¦ are obtained. The Sinphi found by the Sinphi arithmetic unit 6 is induced to a multiplier 10 via a counter 9 for multiplying the coefficient K1 corresponding to n(polar logarithm), and ¦PSIs¦.¦IS¦ found by the multiplier 8 is fed to the multiplier 10, and the mutual product is found to obtain momentary generating torque taue.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an apparatus for measuring instantaneous torque generated in an induction motor, particularly a three-phase squirrel cage induction motor.

(Prior Art) Various methods have been developed and used to measure the torque of an induction motor. The most common method is mechanical measurement, which measures the amount of torsional strain on the shaft and indirectly determines the amount of torque from this.

For example, in order to measure the instantaneous torque of an induction motor, a method is often used that takes advantage of the property that the torsion angle of the shaft is proportional to the torque, detects the torsion angle of the shaft, and measures the shaft torque. Since this method shows the shaft torque due to torsional vibration between the generated torque of the electric motor and the reaction torque of the load, it is not possible to directly obtain the instantaneous generated torque of the electric motor, and it is also difficult to actually measure the instantaneous generated torque using other methods. Met.

In this regard, the present applicant has discovered that the instantaneous torque generated by the motor can be easily determined by simply detecting the stator current, rotor current, and sine wave and cosine wave voltages with respect to the rotor position of the wound induction motor [ We filed an application for ``Instant Torque Measuring Device for Wound Induction Motor Using Space Rotating Current Vector'' (Japanese Patent Application No. 59-058154).

However, since the rotor current cannot be measured in squirrel cage induction motors, the device of the above-mentioned prior application was not applicable.

(Objective of the Invention) The present invention detects and calculates the stator side three-phase voltage and three-phase current, even in a three-phase squirrel cage induction motor in which the rotor current cannot be measured, and calculates the stator side space rotating current. The present invention aims to provide a measuring device that obtains the instantaneous generated torque of a three-phase squirrel cage induction motor by determining the vector and the spatially rotating magnetic flux vector.

(Structure of the Invention) The device of the present invention detects the three-phase voltage and three-phase current on the stator side of a three-phase squirrel-cage induction motor, and detects the two-phase voltage of the three-phase voltage when there is no normal zero phase. Detect the voltage and the two-phase current in the three-phase current, perform calculations to calculate the spatially rotating current vector and the spatially rotating magnetic flux vector, and then multiply by a predetermined coefficient to calculate the instantaneous generated torque. It is characterized by

(Effects) To further explain, the device of the present invention detects the stator winding current and winding voltage instead of indirectly measuring the instantaneous generated torque using the torsion angle of the rotating shaft as in conventional methods. This allows for direct measurement.

The instantaneous torque τ of an induction motor. Is it a spatially rotating magnetic flux vector? , and the spatial rotating current vector 1. It is proportional to the vector product of , and is expressed by the following equation (1).

Also, the generated torque τ. are the component space vectors I: L, I on the two-phase axes of the above magnetic flux vector and the above current vector.
It can be expressed in terms of the size of j, resulting in equation (2).

Furthermore, the generated torque τ. is the above spatial rotation vector ψ8.1
, and the spatial phase difference φ between them, which is given by equation (3).

τe: Kl l WS xim l --
---(1)・Kl I's l l Is 1stn
φ ----(3) Here, K1 indicates a proportionality constant and is equal to the number of pole pairs n.

If we use the spatially rotating magnetic flux vector and the spatially rotating current vector to measure the instantaneous generated torque of a three-phase squirrel cage induction motor, we can directly measure the instantaneous generated torque using equations (2) and (3). First, according to equation (3), it is possible to directly measure the magnitude of each spatial rotation vector and the sine value sinφ of the spatial phase difference φ between them.

Embodiments of the present invention will be described in detail below with reference to the drawings.

(Example) In FIG. 1, 1 and 2 are three-phase/two-phase converters, and currents tii',i, flowing through the three-phase stator windings are supplied from a three-phase induction motor (not shown).

iF and the phase voltage v, between the three-phase stator winding terminals.

": + vC according to the following equation (4), l 1' l = K2i" α a l 1' l = K3 (i' − i' ) −
1-(4) β bC I V'' I = K2V' α a IV, > l = 3 (V et -vs ) Display the space current vector and space voltage vector, K2 and K3 are both proportionality constants. If there is no normal zero phase, the values of iλ xA in the three-phase current and the two-phase voltages Vλ and VC in the three-phase voltage, respectively, except for the broken lines shown in Figure 1, are shown by the solid lines. By simply detecting, the spatial current vector 1:, I,; and the spatial voltage vector v:, v, ) of the two-phase axis can be determined from the following equation (5).

l''' I = K 21 m α a l 1'' l = K4i''+, i'' ---(
5) β ab l V" l = K, v' α a l V2 l = K4V2+, V,; here, K4
．． KS indicates a constant of proportionality. In this way, the two-phase spatial current vector obtained from the three-phase/two-phase converter 1 is expressed by I:ti,; and for the converter 2, v',
When expressed by v', α β A composite spatial current vector I3 and a composite spatial voltage vector vs as shown in FIG. 2 are obtained. Next, the space vector differential equation on the stator side of the induction motor is expressed by equation (6), and when the spatial magnetic flux vector ψ is determined from equation (6), equation (7) is obtained.

V, = R'! , +PW, -------(6) Here, R'' represents the stator winding resistance, and P represents the differential operator.

? , =f<V, -R"1.)dt---1-(
7) The spatial magnetic flux vector weight is the two-phase spatial voltage vector v from the converter 1 in Fig. 1; V, y is the magnetic flux calculator 4.
The spatial magnetic flux vector ψ,,V, on the two-phase axis is determined based on equation (7). The signals are further supplied to a vector analyzer (V, A,) 7 and synthesized as shown in FIG.

When three-phase AC voltage is applied to each phase winding of the stator and three-phase AC is caused to flow, the resultant space vector V,,I, and! , will be spatially rotated. Therefore, such synthetic space vectors will be referred to as a "spatial rotation voltage vector," a "spatial rotation current vector," and a "spatial rotation magnetic flux vector," respectively.

The instantaneous generated torque of a three-phase squirrel cage induction motor is proportional to the vector product of the spatially rotating magnetic flux vector ψ and the spatially rotating current vector I, as given by equation (1), and the calculation of the instantaneous torque is given by equation (2). and (3).

According to equation (2), the instantaneous generated torque is calculated by calculating the two-phase axial space current vector from converter 1, I, y, and the magnitude of the magnetic flux calculator based on equation (2), and then calculating the coefficient Kl. It is obtained by multiplying.

Next, the two-phase spatial voltage vector I to I/ from the converter 1 is supplied to the vector analyzer (V, A, ) 3, and the two-phase axial spatial magnetic flux vector, Ayu, ψ) from the magnetic flux calculator 4 is・Supply to analyzer (V, A,) 7. For each vector analyzer 3 and 7, the following (8)
Based on each term of the equation, the spatial rotation vector 1 shown in FIG.
and Cao are found.

Also, since the instantaneous value L + ψ1 of the spatial rotation vector is given by the following equation (9), the spatial rotation vector I
,,? , the magnitude of the two-phase axis space vector is shown in Figure 2 and (8
) are respectively expressed as the following equation 01.

1111100 The relationship of this α1 formula is the generated torque τ. By substituting into equation (2), the following round equation is obtained.

r. −, lψ1I−IISI−[sinφj8・co
sd, 5-cosφis””φ91S co-, 1Fji
ll5i [:5in(φis-φ9s month-, I1
1yo 1-IIsI ・[Sinφko
--- (11) Therefore, the (8
) is supplied to the sinφ calculator 6 and the multiplier 8 as shown in the figure to calculate the values of each term in the equation (3).・II- are obtained respectively.

Furthermore, sinφ calculated by the sinφ calculator 6 is n
(N'
By supplying sl·ll81 to the multiplier 10 and calculating the product between them, the instantaneous generated torque τe can be obtained according to equation (3), that is, equation 00.

According to the present invention configured as described above, by detecting a spatially rotating current vector and a spatially rotating magnetic flux vector for the stator winding of a three-phase induction motor, and performing calculations on these spatially rotating vectors, The instantaneous generated torque can be directly determined, and the instantaneous generated torque of the induction motor can be calculated moment by moment.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a configuration example of an instantaneous torque measurement device for a three-phase induction motor, and Figure 2 shows the spatially rotating current vector and spatially rotating magnetic flux vector of the stator windings obtained by the vector analyzer. FIG. 3 is a vector diagram showing an example of a vector relationship of spatial rotation voltage vectors. 1.2... Three-phase/two-phase converter 3.7... Vector analyzer 4... Magnetic flux calculator 5... Generated torque calculator 6... Sinφ calculator 8.10... Multiplier 9...Coefficient unit ρ-axis

Claims (1)

[Claims] 1. A three-phase/two-phase converter that converts the three-phase voltage and three-phase current of the stator winding of a three-phase induction motor into two-phase voltage and two-phase current, respectively, and a normal zero-phase converter. includes a converter that detects two-phase voltage of the three-phase voltage and two-phase current of the three-phase current of the stator winding and converts from three-phase to two-phase if there is no Further, a magnetic flux calculator calculates two-phase magnetic flux from the converted two-phase voltage and two-phase current, and a vector derives a spatially rotating current vector and a spatially rotating magnetic flux vector from the two-phase current and two-phase magnetic flux, respectively. - an analyzer, a sine value calculator that calculates a sine value corresponding to the spatial phase difference between the spatially rotating current vector and the spatially rotating magnetic flux vector, a multiplier that calculates the product of the magnitudes of the spatially rotating vector, and a predetermined A device for measuring instantaneous torque generated in a three-phase induction motor using a stator side spatial rotating current vector and a spatial rotating magnetic flux vector, characterized in that the instantaneous generated torque is calculated by multiplying by a coefficient of , and the product with the sine value. 2. A three-phase/two-phase converter that converts the three-phase voltage and three-phase current of the stator winding of a three-phase induction motor into two-phase voltage and two-phase current, respectively, and when there is no normal zero phase. It includes a converter that detects the two-phase voltage in the three-phase voltage and the two-phase current in the three-phase current of the stator winding, and converts the three-phase to two-phase, and further converts the converted two-phase. a magnetic flux calculator that calculates two-phase magnetic flux from voltage and two-phase current; a vector analyzer that derives a spatially rotating current vector and a spatially rotating magnetic flux vector from the two-phase current and two-phase magnetic flux, respectively; a sine value calculator that calculates a sine value corresponding to the spatial phase difference between the rotating current vector and the spatially rotating magnetic flux vector; a multiplier that calculates the product of the magnitude of the spatially rotating vector; The instantaneous generated torque is calculated by multiplying it with the above sine value, and the two-phase current and two-phase magnetic flux converted into two-phase are calculated by calculating each component of the spatially rotating current vector and the spatially rotating magnetic flux vector on the two-phase axes that are orthogonal to each other. Since it is a space vector, there is a multiplier that calculates the product of the magnitude of the first axis space vector of the spatial rotation magnetic flux vector and the magnitude of the second axis spatial vector of the spatial rotation current vector, and a multiplier that calculates the product of the magnitude of the on-axis space vector and the magnitude of the first on-axis space vector of the spatial rotation current vector; a subtracter that subtracts the value obtained by the multiplier described later from the value obtained by the multiplier; Measurement of instantaneous torque generated in a three-phase induction motor using a stator-side space rotating current vector and a space rotating magnetic flux vector, characterized in that it is also equipped with a τ_e calculator that can calculate the instantaneously generated torque by multiplying by a coefficient. Device.