JPS58192494A - Controller for induction motor - Google Patents

Abstract

PURPOSE:To effectively control the V/F ratio in response to the load of a motor and to stably control an inverter by altering the input voltage of an induction motor with the added output of the peak value of the output current of a converter and the voltage in response to the set speed. CONSTITUTION:A current detector 8 is provided between a converter 1 and an inverter 3, and the peak value of the output of the detector 8 is sampled and held by a sample-holding circuit 11. After the outputs of the circuit 11 and a speed setter 5 are added by an adder 9, it is supplied through an amplifier 10 to a phase control circuit 2, thereby controlling the converter 1.

Description

[Detailed description of the invention]

The present invention relates to an induction motor control device. In this control device, an NFG for efficient operation of an induction motor (hereinafter simply referred to as a motor) regardless of load fluctuations was invented by the present inventors and has been filed separately. Figure 1 shows the W1 configuration of this existing proposal, and P
S is the commercial power supply, and J! from the thyristor with the lFi humperter
! The voltage of the commercial power supply PS is input, and the thyristor is triggered by a pulse from the phase control circuit 2 to output a variable DC voltage. 3 is converter l
The DC voltage from the inverter is input via the DC bus 4, which is also a transistor (6 if converting to three-phase).
It generates three-phase AC voltage with a phase difference of 120 degrees from each other. Motor M is driven by this alternating voltage. The 5-speed speed setting device outputs an analog voltage a corresponding to the target rotation speed. The voltage oscillator 6 converts the voltage into a pulse having a frequency corresponding to the magnitude of the voltage σ. The future oscillation pulses are phase-split by the phase splitting circuit F, and the phase splitting circuit drives the transistors of the inverter 3, so that a three-phase AC voltage is generated. These configurations are similar to those already proposed in the well-known book as a pulse amplitude modulation motor drive. Insert -mrtwr detector (for example, resistor) 8 of DC path 4 -F. Then, the current signal C, the variable analog voltage a from the speed setting device 5, and the bias signal e are added by the adder 9 with the polarity shown, and the output is amplified by the amplifier 10. debt. Then, the amplified output of the lever is used as the input signal f to the phase control circuit 2, and depending on the magnitude of this signal f, the converter l is changed to c7)u! flf output voltage e control m-t
-x. According to the above HI3 configuration, when the rotation speed cliff is set by the speed crotch determiner 5, the setting I! An analog voltage a corresponding to the voltage a is output, and the frequency of the output from the inverter 3 is set to Vl according to the voltage a. Also, analog voltage (lid
It is added to the current signal C from the current detector 8 by the adder 9,
As a result, if the analog voltage a is larger than the current signal C, then i' of the converter l! [The converter l is controlled so that the flf output voltage decreases, and vice versa, the DC output voltage increases. As a result, the magnitude of the voltage from the inverter 3 is controlled. In other words, the ratio between the input voltage of the motor M and its frequency F, that is, v/F
Since VW is maintained, the motor M is supplied with an appropriate voltage according to the load and remains at rest. - Vintage drawing 2 shows the characteristic curve m of the line current of the motor M when the load of the motor M is constant, and the characteristic curve n of the current passing through the DC path 4, with respect to the ratio b. It's full of things. There is a large difference between the minimum point Cm of the wire electrician of the motor M and the minimum point Cn of the current IB (average current) flowing through the DC bus 4 and the current ratio, and this characteristic curve un is a forest that exhibits certain negative characteristics. In other words, in the region where the characteristic mm exhibits a positive characteristic, the characteristic 1anI/'i exhibits a negative characteristic +F, so! Even if feedback control is performed as shown in Figure 1, positive feedback will not occur (since stable control is possible). When the capacitance changes, the current flowing through the DC path 4 also changes by -F. Therefore, if the bias signal e is a book whose size corresponds to the motor capacity, then According to me, I expected stable control.'#!I happened to read the book and found the characteristic tune tsn as shown in Figure 2.
Since this minimum point Cnf;r exists, if the line voltage of motor M becomes excessive due to some disturbance, 4H from minimum point Cn
(lllK('Foot can occur. In this region, characteristic surface 1NJJnt;j has a positive characteristic, so when feedback control is performed as shown in Fig. This invention makes it possible to achieve stable control because there are times when the line voltage of the motor is excessive due to external disturbances, etc. Before explaining the embodiments of the present invention, the waveform of the current flowing through the DC bus 4 will be explained.
IT for time tK when the frequency F of is 3+IHz
This shows the waveform of the current flowing through the flf bus 4, (
A), (B), and (C) are cases where the load on the motor M is no load, rated load, and 150% load, respectively. T is a half period of the frequency F of the inverter 3, P (+ side) is the current on the negative side, and r (- side) is the current on the regenerative side. As will be understood from this, when there is no load, the peak current value is on the pFi- side, and when the load is applied, the peak current value is on the pfi- side,
Heavy load! (H8I, high. Figure 4 is the same. When the frequency F of the inverter 3 is set to 30H2, the V/F ratio of the peak current value p when the motor M is applied with the rated load force. This is a diagram showing the characteristics of the current passing through the first stream path 4.As will be understood from this, the peak current value p is the average fly (average current) of the current flowing through the first stream path 4.
While the characteristic curve n in FIG. 2 has a minimum value C, the characteristic curve n does not have an extreme value. WK Figure 5 shows motor M[f
i) Using the load with force λ as a parameter, the peak current p is plotted against the inno(-) frequency F. As can be understood from these characteristic diagrams, the peak current is the WA value fr. From the beginning, it is possible to control the /F ratio by using the beak electric current p instead of the characteristic curve n in Fig. 2, so that positive feedback can occur even in the order of overvoltage. If fk<, stable i control is possible.An embodiment of the present invention will be explained with reference to Fig. 146.The same reference numerals as in Fig. 1 are given in each hexagram.1.9 indicates the same or corresponding part. In this embodiment, a sample and hold circuit 11iiL11 is provided, into which the current signal C from the current detector 8 is input.Then, it is sampled at the rising edge of the output pulse b from the oscillator 6, and its sampling output d is Output + f. In addition, 7 phase splitting circuits operate at the rising edge of pulse b. Adder 9 # - t analog voltage a, sampling 11 output d
. The bias signals eft are added with the illustrated polarity, and the addition result is input to the amplifier 100. Part 7 is a time chart for explaining the operation of Fig. 6.
) Fi shows the case at rated load, in which case the lowest value of the current signal C from W flow test gain 8, that is, the peak current value Ip
Fi Same as Figure 3 (B) (positive*lK tomorrow, therefore, take the positive value of the sampling output dIfi. From this point, it can be seen that the load on the motor M has changed from the rated load to the light load. Suddenly, Figure 3 (A) shows that the peak current value becomes negative as shown in Figure 5. At this time, the sampling output d also becomes negative 11? as shown in Figure 1 (B), and the result is , ffH of the signal f is quite small and passes through a transient state +f.As a result, the phase control circuit 2 operates and the output voltage of the inverter 3 becomes low.
■//F ratio is carefully adjusted so that an appropriate voltage according to the motor MVC load is supplied (see Fig. 7 (C)). The above explanation was about the case where the load on the motor M becomes small, but the same applies even when the load on the motor M becomes small. In either case, the peak current value p#'iV/
Even if the F ratio is increased, it does not take an extreme value, so if this is added to the analog voltage a and the bias signal e using the adder 9, positive feedback can be achieved more than in the previously proposed configuration. Therefore, stable control is possible.A peak hold circuit may be used in place of the sample hold circuit #l'LK in the embodiment shown in the figure. As is clear from (A), the peak electric current?
Since the JF value exhibits flat characteristics at approximately 2QH2 or higher, there is a particular problem when operating the inverter at 20H7,' or higher.However, when operating at less than 2QH2, the rated load The peak current value Ip of
As the frequency F becomes low (and thick), an overvoltage is applied to the motor M in the configuration shown in Fig. 5. Fig. 8 solves this problem. In Fig. 14, the voltage 'f'
The current signal C from the iiF detector 8 is inputted to the sump Vhode circuit 1 via the limiter 12 . The IJ transmitter 12 has the peak current value (p) at rated load selected as the limit level V, and the input above the level vf is set to the limit level -+f. As a result, as shown in FIG. 7, the output of the limiter 12 is cut above the current signal C, and the output is sampled by the pulse b into the sample hole F circuit and held. Nafu. As a result, even if the motor M is loaded with a load that exceeds the rated load, the V/F ratio will remain large (but not

[For loads within the rated capacity of two
In this case, the V4 ratio can be properly controlled when the frequency F of the inverter 3 is about several H2. In other words, the motor M is operated at a higher efficiency. Next, Figure 5 (B) is a characteristic diagram of the peak lightning current p versus inverter frequency when the motor capacity is large (for example, 750 W or more).As will be understood from now on, the motor capacity has a large impact. In the case of no load or light load, the peak current Ip tends to increase in the negative direction as the frequency becomes low.At this time, the voltage applied to the motor becomes insufficient. This is obvious.In order to solve this problem, a separate sabre hold circuit 1 is shown in FIG.
1 and the adder 9, a suppression amount UPSP for suppressing the output (feedback amount) from the triple hold circuit 11 is provided, and its output d' is input to the adder 9. By providing such a suppression circuit SP and suppressing the amount of feedback when the frequency F becomes low in the case of no load or idle load, the no-load condition shown in Fig. 5 (B) can be suppressed. Or, the curve of the peak current p at light load may drop down (as a result, it approaches the direction of O as shown by the dotted line). As a result, the lack of voltage to the motor can be resolved. K
lk/', (with D suppression amount 7 Y tri, -+
y-y”v*j-Hold circuit 11 (or peak hold circuit) Connect a resistor with a resistance value smaller than the leakage resistance of this capacitor in parallel with the K-use +F capacitor to form a -F-F] , or the terminal voltage of the capacitor with the period 'f/- corresponding to the frequency F may be configured by a chopper circuit using pulses from a monostable circuit. However, it goes without saying that the present invention is applied to P, W, and M type inverters. By the way, in each H1 configuration described above, when the frequency F of the inverter 3 gradually changes, the phase The voltage vFi of the controlled converter 1 will hardly lag behind the change in frequency, but if the rate of change in the frequency F is relatively fast, the change in the voltage (2) may lag behind the frequency F. This occurs, for example, when the analog voltage C from the speed setting device 5 changes rapidly. If the control according to the embodiment shown in Fig. 1 is carried out when the value of The analog voltage σ from the speed setter 5 is multiplied by the comparator 13 and the integrator 4, and then input into the slow up/down circuit 15. The output j of the integrator 14 is input to the inverting terminal (←) of the comparator 13, and its output is input to the integrator 14. The output j of the integrator 14 is the non-inverting terminal (+) of the comparator
is input to the oscillator 6. The output j and the analog voltage a change in a step-like manner, and there are rapid changes. On the other hand, the output iFi of the comparator 13 remains high (crossover low) until the levels of the inputs applied to the inverting terminal and the non-inverting terminal match.
Ami on the level. This output is passed through an off-delay circuit #16 to a switch circuit 1 consisting of, for example, 7 automatic couplers.
7.18, and each switch circuit 1'7.18 is turned off during the period when this is at the H (crossover L) level. By turning off the switch circuit 11, the bias signal e is not input to the comparator 9, and by turning off the switch circuit 8, the output 41 from the sample ho 91 circuit 11 is input to the suppression circuit SP as shown in the figure.
is inserted, its output α') is input to the adder 9. When the analog voltage σ becomes low (and the output of the comparator 13 becomes zero, the delay operation of the off-delay circuit 16 ends, and its output l becomes zero, the rotational speed of the motor M becomes stable. +, so depending on the output l, each switch times UP1
7.181d is turned on, and the bias signal θ is input to the output d multiplied adder 9. The subsequent operation is the same as in each of the above-mentioned configurations, and as a result, the operation of the inverter 3 remains stable. As described in detail above, according to the present invention, the V/F ratio can be reliably controlled according to the motor load with a simple configuration, and the inverter can be controlled stably.

[Brief explanation of the drawing]

Figure 1 d is a circuit diagram of another proposal, Figure 2 is the characteristic curve diagram, and Figure 3 is a diagram of the same characteristic curve.
5 to 5 are waveform diagrams for instantaneous operation of the present invention, FIG. 6 is a circuit diagram showing an embodiment of the invention, FIG. 7 is a time chart for operation questions, and FIG. 8. FIG. 9 is a circuit diagram showing another embodiment of the invention. PS...Commercial DC power supply, M...Interlayer conduction motor,
1...Converter, 2...-phase side a times IF
, 3... Song inverter, 5... Speed setting device, 8
...Current detector, 9...Adder, 1
1...Bending sample hold times B, 12...Limiter, 15...Slow up/down circuit, sp
... Suppression circuit patent applicant Shinpo Kogyo Co., Ltd. name 1 Agent Yoshinobu Nakazawa ↓ 569- 2℃ Q- S H (A) (5) Shun □ [r ding]- ( C) Procedural amendment stamp) 1. Indication of the case 1982 Patent Application No. 75695
Name of No. 2 Invention Relationship with Induction Motor Control Device 3 Amended Person Case Patent Applicant 4th Attorney Address 731 Yoshimashoencho, Nishikyo-ku, Kyoto City: 1
, Name (6184) Patent attorney Kinnosuke Nakazawa
;1. . . 5 Date of amendment order Showa year, month, day
2 ``'16, Amendment. Subject Contents of the detailed description of the invention in the specification, each a of the claims, and the amendments to drawing 7 [1) Before ``thyristor'' on page 4, line 2 of specification 1, ``, e.g. ” is added. (2) Delete "This too" in line 7 of the same page. (3) Page 5, lines 12-16 [Result 1102. be done. ” should be corrected as follows. “If the added output increases, the DC output voltage from converter 1 will also increase, and if Kaga Sanno decreases in the sentence selection, the @ output voltage from converter 1 will also decrease.” (4) Same page 7, No. 15 Add "7F is constant" next to line 150H2J. (5) Same @ page 8, line 16 [Insert “or its vicinity” next to peak current 1 pJ. (6) Correct "Figure -15" in the negative second line of No. 11 to "Figure 6". C Power lFr1 Page 12, line 15, ``Naku Kali,'' is followed by the next sentence, ``Naku Kali,'' (8) On the same page, line 17, ``Insufficient'' is corrected to ``One under or under foot''. (9) Correct "Inverter 5" at the end of page 13 to "Converter 1". (10) "Comparator" in the 11th line of the 15th corner is "adder",
I am corrected. (11) Line 12 of the same page, “Inverter 3” is corrected by [Converter iJK. (13 The claims of the same patent are corrected as shown in the attached sheet. (13) Figures 1, 4, wi, 5, 6, 8 and 9 are corrected as shown in the attached sheet.゛Claims (1) A converter that inputs the voltage of a commercial AC power supply and converts it into a DC voltage, and a DC output voltage of the converter,
In an induction motor control device comprising an inverter that converts into an alternating current voltage with a frequency corresponding to a set speed, and an induction motor driven by the output of the inverter, the output current from the converter reaches a peak of 1! A hold circuit that holds the flow value or its vicinity, and an adder that adds the hold output of the hold circuit and a voltage according to the set speed are provided, and the input voltage of the induction motor is determined by the output of the adder. Modified induction motor control device (2) A converter that receives the voltage of a commercial AC power source and converts it into a DC voltage, and a DC output voltage of the converter,
In an induction motor control device comprising an inverter that converts into an alternating current voltage with a frequency corresponding to a set speed, and an induction motor driven by the output of the inverter, the output current from the converter is equal to or higher than the peak current value at the rated load. a limiter for rebuilding the limiter, a hold circuit for holding the lowest value of the output from the limiter, and an adder for adding the hold output of the hold circuit and a voltage according to the set speed; The input voltage of the induction motor is changed by the output of the induction motor! Motivation control device (3) A converter that inputs the voltage of a commercial AC power supply and converts it into a DC voltage, and a DC output voltage of the converter,
Induction motor 4iM 1111111111 that is connected to an inverter that converts it into an alternating current voltage with a frequency corresponding to a set speed, and an induction motor that is driven by the output of the inverter.
In the device, a hold circuit that holds a peak current value of the output Wi flow from the converter or its vicinity;
An adder is provided to add the hold output from the hold circuit and the voltage corresponding to the set speed after the change in the voltage generated according to the set speed is completed, and the output of the adder is used to control the motive control device (4). A converter that inputs the voltage of a commercial AC power supply and converts it to a DC voltage, and a DC output voltage of the converter,
In an induction motor control device comprising an inverter that converts the voltage into an alternating current voltage having a frequency corresponding to a set speed, and an induction motor driven by the output of the inverter, a hold circuit that holds the output voltage from the converter; A suppression circuit that suppresses the output of the circuit, and an adder that adds the output from the suppression circuit and a voltage according to the set speed are provided, and the input voltage of the vi induction motor is changed according to the output of the adder. Induction motor control device comfort + 0 1

Claims (4)

[Claims] (1) A converter that inputs the voltage of a commercial AC power source and converts it into a variable DC voltage; an inverter that converts the DC output voltage of the converter into an AC voltage with a frequency corresponding to a set speed; In an induction motor driven by an output and a Karanafu induction motor control device,
A hold circuit that holds the peak current value of the output voltage from the converter, and a sum adder that adds the hold output of the hold circuit and a voltage according to the set speed are provided, and the output of the adder is used to control the converter. An induction motor control device that controls the DC voltage from 'fF'. (2) Input the voltage of the commercial AC power supply, L7, and fl! to the variable DC voltage! In the simple induction motor control system M, which includes a double converter, an inverter that converts the DC output voltage of the converter into an AC voltage having a frequency according to a set speed, and an induction motor driven by the output of the inverter, Directly from the converter? A limiter that limits the peak current value of jIF current at rated load or more,
A hold circuit is provided to hold the lowest value of the output from the limiter, and an adder is provided for adding the hold output of the hold circuit and a voltage according to the set speed, and the output from the converter is determined by the output of the adder. Style I
I An induction motor control device that changes the pressure. (3) a converter that inputs the voltage of a commercial AC power source and converts it into a variable DC voltage VcV; In an induction motor control installation consisting of an induction motor driven by the output of an inverter,
A hold circuit holds the peak current value of the output current from the converter, and after the change in the voltage generated according to the set speed is completed, the hold output from the hold circuit and the voltage according to the set speed are controlled. Add′
The +F adder is used to change the DC voltage from the converter depending on the output of the adder for induction motor control snow making. (4) a converter that inputs the voltage of a commercial AC power source and converts it into a variable DC voltage; an inverter that converts the DC output voltage of the converter into an AC voltage with a frequency corresponding to a set speed; In an induction motor driven by an output of an inverter and a karanaf induction motor control device, r! r? A hold circuit that holds the peak current value of i1F current at rated load,
A suppression circuit for suppressing the output of the hold circuit and an adder for adding the output from the suppression circuit and a voltage according to the set speed are provided, and the DC voltage from the converter is increased by the output of the adder. The Ai 1 is equipped with an induction motor control.