JPS58139662A - Torque measuring device for ac rotary machine - Google Patents

Abstract

PURPOSE:To accurately obtain a true torque together with its instantaneous value by calculating and measuring the torque produced from a terminal voltage and current on the basis of a torque producing principle of an AC rotary machine. CONSTITUTION:Voltage detectors 61, 62 respectively detect line voltages of two phases which are supplied to a motor 11. Current detectors 63, 64 detect line currents which are supplied from a power source 51 to the motor 11. These detected outputs are inputted through an A/D converter 71 a buffer memory 72 to a memory 73. A computer 74 processes data which are read out from the memory 73, calculates the torque of the motor 11, and outputs the result to an external output device 75.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torque measuring device that can accurately measure torque, including instantaneous values, generated by an AC rotating machine such as a large induction motor.

Conventionally, to measure torque in motors such as electric motors, the main method has been to mechanically measure the torque actually taken out from the output shaft. An electric dynamometer or the like was used, and a device like the one shown in Figure 1 was used in relatively large machines.

In Fig. 1, 11 is the electric motor as it is the object to be measured, and 21
3 is a torque detector, 31 is a load absorbing device, and 41.42 is a coupling.

The torque detector 21 is connected to the electric motor 1 via a coupling 411.
1, and an output shaft coupled to the input shaft of the load absorbing device 31 via the coupling 42. The amount of displacement due to torsion between the output shaft and the output shaft is now detected as torque.
The torque generated by the electric motor 1 can now be measured.

However, if the electric motor 11 to be measured becomes larger in capacity, there is a problem in that it becomes quite difficult to measure the torque using the apparatus shown in FIG. In particular, induction motors (hereinafter referred to as
If you try to measure the torque characteristics from startup to constant speed, such as the starting torque of an IM, it will be extremely difficult to measure the torque characteristics, such as the starting torque of the IM. In addition, the couplings 41 and 42 become larger, and the load absorbing device 31 in particular requires a device that is as large and heavy as the motor 11 to be measured, or even more so, and the cost required for measurement becomes enormous. It's put away.

In addition, in IMs, the starting current usually reaches several times to several tens of times the rated current, which requires an enormous amount of power supply equipment, and it is difficult for IMs to run the starting current for a long time in order to improve torque measurement. There are also problems such as the risk of thermal breakdown due to the temperature rising rapidly.Furthermore, as the torque is measured by the torque detector 21, it is difficult to detect the torque that is lost inside the IM. Not only is this impossible, but there is also torque that is converted into inertial energy of the torque detector 21, load absorber 31, and even the IM rotor itself, making it difficult to measure instantaneous torque and causing serious measurement errors. In the end, the torque measuring device shown in FIG. 1 has the disadvantage that it cannot accurately measure torque t such as IM in all cases.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to
The true torque t generated by a multi-phase AC rotating machine such as the To provide a torque measuring device dt that can be used to measure torque.

In order to achieve this object, the present invention provides an alternative method for measuring the torque t of an AC rotating machine to be measured mechanically at its output shaft, based on the torque generation hydraulics of the AC rotating machine. The generated torque is calculated and measured from the flow '1.

Hereinafter, an embodiment of the torque measuring device for an AC rotating machine according to the present invention will be explained with reference to the drawings, but first, the principle of torque measurement according to the present invention will be explained.

The AC rotating machine whose torque is to be measured is a two-phase IM.
Assume that the stator has an unbalanced two-phase winding, and the rotor has a balanced two-phase winding, and the axis of the coil is fixed as shown in FIG. From Figure 2, '8M -'IM @'IM + M
Md-θ"Rd-MMq, cos(9Q'e> ・
IBQ ・−・−・−(t)'SA = Lsr'
8A + 'A/"(90") "'na+M,
Q wound-・Todoroki, ・・・・・・・・・(3)'Rd”L
Rd ”Rd + 'dM ”” 11M+MdA equipped (
90-Li・・・・・・(3) FR1=LR4・i
n, -MqM (90"-#)・18 + MQA o
″−°transmitter ・・・・・・・・・(4) However, '8M #'!iA '' Stator O8M * 8)
dlj a O magnetic flux linkage 'Rd e 'Rq '' Rotor OR41R4s'SM I 'B□: Stator 8M
, S person winding current "Rd t IHq: Stator dog,
R-wire current L8M tLEA ``Stator winding 8M,
8A self-inductance LR: rotational prewinding IIIRd, ~ρ self-inductance MMd: 8 Mutual inductance between M and R1-line MAd-m: Sm and Rd " MMq9MqM: SM and 'FLq# M49MqM: The magnetic flux linkage of each coil can be expressed by the mutual inductance between SA and the 84 windings.

Furthermore, hAma −Mdw = MMQ −MqM = MM
R”=・−・・・・・・・・・・・・・・・・(5) Nmud
−・nimu=MAq;Hatom=MAR”−”’−”Four rules−
Since the relationship (6) holds true, equations (1) to (4) indicate that the total magnetism and energy of the stain motive force are proportional to the product of the magnetic flux linkage and current of each coil, so the following equation holds true.

tJm-4(LsM)SM+LIA”8A+
LH"Rd+LH'Bq)+ (MMl'1M'Rd
+MAR'8A'Rq) -'-(M Knee'Rq-
MAR'8A'lq)''θ... (7) Torque T generated by the electric motor Fi is expressed by differentiating equation (7) with respect to angle 0.

T-one snore--a#” (MMl import M'Rd +MAR'8A'l
q) i'(MMR'IM'Bq'All'
gA'Rd)−'°°(8) In the above equation, (1) to (4
) and (5) and (6), we get (8)
The formula can be written as the following formula.

Here, if the winding ratio of the 8A% wire and the 8M winding is tkω. Therefore, . Here, if the slit dimensions and coil end shape of 8M and 8A*# are the same, equation (11) becomes 0. Therefore, the torque T becomes the following equation.

T--1mmFiAK+1g+*Fsuk@' ・-
・・・・＜12）Furthermore, FIA, F, and M can be expressed by the following formula.

'IM' J(U IM -rt*MlaM) dt
・−・−・−・−・−＜13）FIA-5(Usmu-r
ah isn) d t-・・−・−・−・−・−・
(14) Here, UIIM, oIIm: SM, SA are the resistances of the coil terminals r1Ml'lA"'.

Therefore, equation (12) is further expressed as T vm kωllll S(ogM −reMi
ew )dt-,,11M J(U8A-rgAi
8A) di ・−・−・(15).

Therefore, from this equation (15), the terminal voltage of the motor,
If you measure the stator coil current [you can see that you can measure the torque.

The present invention is designed to measure torque based on the electromagnetic relationship in an AC rotating machine as shown above, and is based on the nine principles expressed by equation (15) to determine the terminal voltage, current, and winding of the motor. Embodiments of the invention will now be described with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which 51 is a two-phase AC power supply;
61.62 is a voltage detector, 63.64 is a current detector, 7
1 is an analog/daisymel converter (referred to as A/D), 7
2 is a buffer memory, 73 is a digital memory, 74 is a computer, and 75 is an external output device. The electric motor 11 to be measured is the same as that shown in Fig. 1.Previously, the pressure detectors 61 and 62 detect the two-phase line voltage and the nine-phase voltage supplied to the electric motor 11 from the power source 51. Detect each. Then, at this time, the detected phase voltage signal is isolated from the input of the motor 11 using an insulating amplifier or the like as necessary.

The current detectors 63 and 64 detect the line current supplied to the motor 11 from the power supply 51, that is, the current of each phase since it is two-phase.

At this time, if necessary, a detector called DCCT or the like is used to obtain an isolated signal from the input of the motor 11.

Therefore, the A/D 71 is continuously supplied with signals representing the instantaneous values of voltage and current of each phase of the A/D 71, and these are converted into digital signals at predetermined sampling times. is output from.

Buffer memory 72 receives digital signals y-, s obtained from A/D 71 and representing nine phase voltages and phase currents.

It acts as a store.

The digital signal stored in the buffer memory 72 is taken out in predetermined amounts, for example, every IK word, and transferred to a digital signal 73. As a result, the digital memory 73 receives, for example, the following data.

That is, the electric motor 11 whose torque is to be measured is started by applying voltage from the power source 51, and thereafter, digital data representing the voltage and current of each phase is stored for the entire time until the electric motor 11 reaches a steady rotational speed. .

The calculator 74 processes the data thus read out from the digital memory 73 to calculate the torque of the electric motor 11. First, the calculator 74 stores the resistance value r8mtrsM of the stator winding of the electric motor 11, and Motor data such as the winding ratio of the stator windings are input, and detection sensitivities by the detectors 61 to 64 are also input.

Next, before voltage is applied to the electric motor 11, (13)
Since the magnetic flux linkage number of the stator winding shown in equation (14) is O, F, Mu, and FgM10 are cleared accordingly.

After that, the following equation is calculated for each sampling time Δ in seconds.

'IM='IMo' (08M1-18M18 group)
Ne... - (16) F8Ai = 'go
+ (U 8Air!IM'11M
1) Δt −−−−−°°°−(17) Here, the subscript l means the fifth sampling, and the subscript O indicates the value one value before the mth sampling point.

Subsequently, the torque T can be calculated using the values calculated by equations (16) and (17).

The torque determined in this way is the electromagnetically generated torque at each instant. Therefore, this embodiment is extremely effective when an instantaneous value of the torque generated by the electric motor 11 is required, for example, when a transient torque when a voltage is applied or a true generated torque such as pulsating torque of the electric motor is required. .

Next, an example of the results of torque measurement according to this implementation/column is shown in FIGS. 4 to 8.

The electric motors measured were small model machines, 41st, 4th and 5th.
The figure shows fixed prewinding, voltage waveform 101 and current waveform 1 of 118M.
03, and FIGS. 6 and 7 are illustrative examples of the '1 pressure waveform 102 and current waveform 104 K of the stator winding SA, respectively.
The torque measurement results in this case are shown in FIG. 8, showing up to an instant of 1K.

The results shown in Fig. 8 are in very good agreement with the results obtained using a normal torque detector within a range of 5 [accuracy]. Therefore, it is understood that this difference of 5 [long] approximately corresponds to the normally considered torque loss within the electric motor, and therefore, the torque measurement according to this embodiment is sufficiently reliable.

By the way, in the embodiment shown in FIG. 3, the digital memory 73
The data read therefrom is processed by a computer 74 to calculate torque. However, if the processing speed of the computer 74 is sufficiently fast, it is possible to calculate the torque without using this digital memory 73t.
It is also possible to input the data from 2 to the computer 74 as is, have it immediately output from the external output device 75, and obtain a printed result.

Furthermore, in the embodiment described above, data is input from the state before voltage is applied to the motor 11.

However, in many actual motors, it is often possible to obtain voltage and current values as repetitive waveforms, that is, alternating voltage and alternating current.

Therefore, in such a case, the present invention may be configured so that the torque is measured by the following process.

That is, the digital memory 73 has at least i? It takes in signals for more than one cycle and processes the time for one arbitrary cycle. (13), (14) at any time, when t=eQ
If the constants of integration in the equation are CM and C, then 'FsiM=Dio
'(Usr-r!1MtgM)dt + CM --
-----C19) FIA -fO(UIIA -7'g
AigA ) dt + CA = (20) In order to find this constant of integration, first set CM = CM = 0 and integrate the results of equations (19) and (20) for one cycle time # USMI oin* 18MI i8
If A has only an alternating current component and no direct current component, then from any time 1-0 to time 1-1 of one cycle, '8
M e 'IA will also be a networking event only. Utilizing this fact, the integral constant CMeC1 is determined. In other words, CMtC
If the values obtained by further integrating ψM and φm obtained as A'to for one cycle are Φm and ΦM, then ΦM=-CMt ・・・・・・・−1・・−・
・−・・・・・・(21) Φ person = −CAt ・・
・・・・・・・・・・・・−・−・・・・・・・・・・(2
2), C,=-ΦM/l ・・・・・・・・・・・・・・・
・−・・・−・・・・・・ (23) Cmu=-ΦA/l
・・・・・・・・・・・・－・・・・・・・・・
...-... (24), therefore, (23)#
Using the integral constant determined by equation (24), F, F
can be calculated.

8M 8M According to this embodiment, the following advantages can be obtained.

First, it is possible to use a device that integrates the A/D 71 and the buffer memory 72, for example, a low-cost digital memory commonly known as a wave memory.
However, in this case, it is sufficient to simply store at least one cycle's worth of data from an arbitrary time, and the capacity of this wave memory is sufficient if it has two words, making further cost reduction possible.

In addition, transient phenomena can be solved as long as information beyond time that can be determined by the above-mentioned integral constant is stored.
For example, for the transient torque when the voltage is suddenly changed, it is sufficient that the information for at least one cycle before the voltage is suddenly changed and the information after the voltage is suddenly changed are the same. This makes it possible to determine the integral constant for one cycle using the method described above and calculate the torque from the integral constant. Therefore, even the transient torque itself can be accurately measured.

Next, in the above embodiment, all the data representing the phase voltage, phase current, etc. of the motor 11 is processed as a digital signal, but the present invention is not limited to this, and may be processed as an analog signal as it is. An embodiment of the present invention using such analog processing is shown in FIG.

In FIG. 9, 81 to 84 are amplifiers, 85.86 and 92 are adders, 88.89 is an integrator, and 90.91 is a multiplier.

Amplifiers 81 to 84 are connected to voltage detectors 61 and 62 (31st %l).
) and current detectors 63 and 64 (same), and furthermore, for amplifiers 81 and 84, the gain is set to compensate for the resistance of the stator winding (i.e.)
On〆rgMmiserable♂Vr8m is set to +i gain.

The gain of the integrator 88 is set to a value of (-0·r−M), and the gain of the integrator 89 is set to a value of [(1/ω·16M).

Therefore, the output of the adder 92 is the torque T based on equation (16), and it is possible to measure the torque torque including the instantaneous value.

Furthermore, in the above embodiments, the number of phases of the motor to be measured is two, but the present invention is not limited to this, and can also be implemented on a three-phase motor. - This case will be explained below.

First, in Fig. 3, since the motor 11 is a three-phase motor, the detectors 61 to 64t are replaced with ones that correspond to three-phase voltages and currents, so that the three-phase phase voltages and phase currents can be detected. do.

Furthermore, in a three-phase electric motor, the stator windings are symmetrical, so ω=1 in equation (15).

Therefore, now, the total phase voltages of each phase are Ua and UbOc, respectively.
If the phase currents are i, tb, iC, then the following relationship is obtained.

”IM　rl1M’1M Ji11A　　rllAiilA Here, rl is the resistance value of the stator coil.

Next, by substituting these relationships into equation (15) and arranging them, we get:
...The torque T is obtained as (29), and when this is replaced by the line voltages Uab, Udc, and Oca, the torque T at this time is ``ib<(UcB'-(ic + 'a) r @
)dt+xcS(Uab-(ia+iB)r
It can be obtained as a I dt "=" (30).

Therefore, in the above embodiment as well, by detecting the terminal voltage and current of the three-phase motor and performing calculation processing using equation (29) or (30 times), it is possible to arbitrarily obtain the instantaneous value of torque. Further, according to the present invention, it is possible to measure the instantaneous torque of any AC motor, even for multi-phase motors other than two-phase and three-phase, as long as the terminal voltage and current can be detected. I understand.

Next, the effects of the torque measuring device according to the present invention are enumerated as follows.

It is possible to measure torque without any special equipment as long as the motor constant (armature resistance) is known.For example, even if it is a large induction motor, if the terminal voltage and current of the motor can be detected. Torque can be measured.

2. It is possible to measure the instantaneous value of the torque generated by an electric motor based on electromagnetic theory. Ninthly, for example, if a torque detector is attached to the electric motor and the torque output to the outside can be detected, only the internal loss torque of the electric motor can be isolated.

3. Not only the torque generated by the electric motor but also the torque of the generator can be measured in exactly the same way.

4. Even if the capacity of the electric motor is different, torque can be measured simply by changing the sensitivity of the voltage detector or current detector. Therefore, there is no need to prepare a load absorbing device or a torque detector tube depending on the capacity of the object to be measured.

5. Since it is possible to obtain the true instantaneous generated torque of the electric motor, the true characteristics of the electric motor are better than the conventional method of detecting critical torque by subtracting the internal loss torque.

It becomes easier to understand the characteristics of the electric motor, such as by being able to accurately understand the stress inside the electric motor (for example, shaft stress).

6. Addition of a torque detector 1 Since it is not necessary, torque can be measured no matter what state the motor or generator is in.
For example, it is possible to measure the torque when the device is actually installed and in use, and therefore, it is also possible to easily measure the torque of equipment that is used in a sealed state.

As explained above, according to the present invention, it is possible to accurately measure the instantaneous value of torque by simply detecting the terminal voltage and current of a motor to be measured, thereby eliminating the drawbacks of the conventional technology. Therefore, it is possible to provide a torque measuring device for an AC rotating machine that can obtain the above-mentioned effects at low cost.

[Brief explanation of drawings]

Figure 1 is a block diagram showing an example of a conventional torque measuring device, Figure 2 is an explanatory diagram used to understand the operating principle of the present invention, and Figure 3 is an embodiment of the torque measuring device for an AC rotating machine according to the present invention. Block diagrams showing Fig. 4, Fig. 5, 6th factor, 7th factor
8 is a waveform diagram for explaining the present invention in detail, and FIG. 9 is a block diagram showing another embodiment of the present invention. 11... Electric motor to be torque measured, 51... AC power supply, 61.62... Voltage detector, 63.64...
1st current detector, 71...analog-to-digital converter,
(AAS72...Buffer memo v173...Digital memory 74...Computer %I5...External output device. 1st mouth 2nd figure 3rd figure 4th figure 5th figure 6th figure 7th figure Figure 8 Figure 9

Claims (1)

[Claims] 1. A torque measuring device for an AC rotating machine equipped with a polyphase electric machine prewinding IiI, comprising: signal detection means for detecting phase voltage and phase current for each phase of the armature winding; a first calculation means for obtaining a voltage signal by subtracting a voltage drop due to a phase current in the phase from the phase voltage of the phase detected by the means;
and second calculation means for obtaining a magnetic flux signal representing the number of magnetic fluxes interlinking with a phase current of a phase different from the above-mentioned phase by integrating the voltage signal. A third calculation means is provided for obtaining a torque signal representing the torque generated by the phase current by multiplying the magnetic flux signal and the phase current value of the specific phase, and adds this torque signal by the number of phases. 9. A torque measuring device for an AC rotating machine, comprising: calculating the torque of the AC rotating machine by calculating the torque of the AC rotating machine. 2. Claim 1, further comprising: an analog-to-digital converter receiving the phase voltage and phase current from the signal detecting means as input; and a digital memory receiving the output of the converter as input; Torque is 1! by processing the signal read from ! :A torque measuring device for an AC rotating machine, characterized in that it is configured to calculate the torque. 3. In claim 2, the above Iα digital memory t is configured with a memory capable of storing the phase voltage and phase current for at least one cycle period of the power supply frequency, and is an integral number used for arithmetic processing. is configured to be calculated by integrating one cycle of the phase voltage and phase current.1
Torque measurement device for AC rotating machines. 4, 4IiFF - in claim 2 or 3. A torque measuring device for an AC rotating machine, characterized in that the sampling time and sampling period of the analog-to-digital converter are maintained at constant values. 5. In claim 1, the above-mentioned 1st and 2nd.
A torque measuring device for an AC rotating machine, characterized in that the third calculating means and the third calculating means are respectively constructed of analog calculating means. 6. ! ! ! ft [analog memory that stores the outputs of the signal detectors in the desired range 5th term! Provided. A torque measuring device for an AC rotating machine, characterized in that the device is configured to perform arithmetic processing on the output tube of the analog memory.