JPH0454890A - Apparatus for controlling induction motor and driving method thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an induction motor used in general industrial machinery, machine tools, etc.

[Conventional technology] Servo control devices conventionally used in machine tools, etc. require stable speed control from extremely low speeds to high speeds for rotational speed control and positioning control. A servo control device was used to perform vector control by feeding back speed values. However, recently, higher speed rotation has become required due to the workability of aluminum materials.

In this case, in a servo control device that controls an induction motor using feedback control, the output current detection timing leap is the same from low speed to high speed, so as the speed increases, the detected value within one cycle of the output current also decreases. The frequency becomes discrete, and the upper limit of the frequency that can be controlled by feedback is limited, and even if you try to increase the rotation speed above this, it is impossible to control it.

In this way, for ultra-high-speed rotating tilted walls to which servo control H1L cannot be applied, an inverter (an inverter device that operates under open-loop control by setting the ratio between the terminal voltage V of the induction motor and the drive frequency F to a predetermined ratio) has been used. ) was applied, but with an inverter, low-speed control and high-precision positioning were not possible.

In addition, in the servo control WST device, if an abnormality occurs in the feedback detector during operation, for example, if an abnormality occurs in the rotation detector, the actual speed or rotational position cannot be detected correctly, and the induction motor may run out of control or burn out. Because of these abnormalities, the base drive signal of the power transistor in the inverter circuit was cut off and the system stopped running. As described above, in the past, if an abnormality occurred in the feedback detector during operation, no consideration was given to continuing operation.

Furthermore, when constructing a material processing line using a large number of these induction motors and control devices, if an abnormality occurs in the feedback detector of any of them, a free-run stop process is performed. In controlling the film winding line, material shortages occur, which inevitably results in defective products. There was no way to continue operating these products, and the only option was to anticipate and deal with defective products.

[Problems to be Solved by the Invention] An object of the present invention is to provide an induction motor control device that can switch the operation mode of the control device depending on the field condition and continue operation in a wider range. More specifically, there are the following points.

l) To provide an induction motor control device that provides servo performance with excellent responsiveness at low speeds and can continue operating even at ultra-high speeds.

2) To provide an induction motor control device that can continue operation without stopping even if a feedback detector becomes abnormal.

3) When multiple induction motor control devices are used in a material processing line, even if a feedback detector error occurs in one of them, the operation mode of the other control devices can be switched without stopping the line. To provide an induction motor control system that allows continuous operation.

[Means for solving the problem] In order to achieve the above technology, two control calculation units, a feedback control calculation unit and a V/F control calculation unit, are provided to detect the operating state of the induction motor control device and generate a switching command signal. The feedback control and V
A switching control means for controlling switching of the /F control is provided.

[Operation] The operating state detection section monitors the control state of the induction motor and its control device, and outputs a switching command signal according to the operating state, so that the switching control means can be stably controlled depending on the operating state. Automatically switches to a possible operating mode (feedback control or V/F control).

[Embodiment] FIG. 7 is a block diagram showing an embodiment of the present invention. ]0] is a power converter that outputs an arbitrary variable frequency; 4 is an induction motor connected to the output of the power converter;
5 is a current detector that detects the current of the induction motor 4; 6 is a rotation detector that detects the rotation of the induction motor 4; 7 is a rotation speed command section that commands the rotation speed of the induction motor 4; 8 is the induction motor 4; A V/F control calculation unit that performs open-loop control of the
Reference numeral 9 inputs the value of the speed command unit 7 that commands the rotation speed of the induction motor 4, the feedback signal detected by the current detector 5, and the feedback signal detected by the rotation detector 6, and performs feedback control of the induction motor 4. 102 is a feedback control calculation unit 9 and V /F control calculation unit 8 signal is input, and based on the output of the operating state detection 11B 53, the signals of the feedback control calculation unit and the V/F control calculation unit are switched, and the signals are output to the power conversion device 101. It is a control means.

With this configuration, the induction motor control device 4
The operating state detecting section 33 that monitors the operating state of the feedback control calculating section 9 and the V/F control calculating section 8 determines switching between the feedback control calculating section 9 and the V/F control calculating section 8 based on signals such as the output frequency range and abnormality of the feedback control signal, and sends a switching command signal to the switching control means. 102. The switching control means 102 can switch the operating mode based on the signal from the operating state detection section 33. In this way, the operation mode (feedback control or V
/F i'J II), so operation can be continued stably.

Note that in order to set data so that the output of the power conversion device is continuous during switching, signals from the V/F control calculation section 8 and the feedback control calculation section 9 are exchanged through the switching control means 102.

An embodiment of the present invention will be described below with reference to FIG.

The main circuit that supplies power to the induction motor 4 is a three-phase AC power fi
converter section 2 that converts l into direct current, and converter section 2
The inverter section 3 converts the direct current output of the converter into variable frequency alternating current and supplies power to the induction motor. The converter section 2 includes six rectifier elements that perform full-wave rectification of three-phase AC, a current-limiting resistor R5 that limits the current when the three-phase AC power is turned on, and a smoothing capacitor C and a magnetic contactor connected through R5. It consists of 84. After the smoothing capacitor C is charged up through the current limiting resistor R3 after the power is turned on, the electromagnetic contactor 84 short-circuits the current limiting resistor by using the closing of the contact when the operation is delayed, and supplies power through the contact of 84 during energized operation. It is provided for.

The inverter section 3 is composed of six switching elements Q and a flywheel diode DF, and the converter section 2
Converts DC output to variable frequency AC. The current of the induction motor 4 is fed back to the control circuit by a current detector 5.

First, the operation of the feedback control calculation section when the rotation detector 6 is normal and the induction motor 4 is at a low speed will be described.

The software switches SWI and SW2 in the block diagram are in the off state (as shown in FIG. 1).The rotation speed of the induction motor 4 is detected by the rotation detector 6, and the current is detected by the current detector 5. Feedback control calculation Jl!
Sent to 9th. The feedback control calculation section 9 calculates the speed and current based on the command value of the speed setting 117, the speed detection value, and the current detection value, and
4, and the rotation angle Δθ per sampling for outputting the output angular frequency ω. These ω2 and Δθ are input to the three-phase PWM generation calculation unit 10, and a signal for controlling the on/off states of the six switching elements Q is output. This on/off state signal is amplified by the switching element drive circuit II and then transferred to the inverter section 3.
sent to. This signal turns the switching element Q on and off, converting the DC output of the converter section 2 into alternating current with a variable frequency.

Next, when the speed change range is large and high-speed operation is required with the rotational speed at opposite rpm, the primary output frequency of the induction motor becomes high, making it difficult to control the current using feedback control. For this reason, the speed-torque characteristic (N
-T curve), feedback control is performed at low speeds, and open loop control is performed by switching to V/F control at high speeds above the rotational speed N0. However, the rotation speed,
Only current detection is continuously performed by the feedback control calculation unit 9.

The switching operation from low speed to high speed is the same procedure as that for the detector abnormality shown in FIG. In Figure 2, the alarm process is activated when an abnormality occurs in the rotation detector, but in this case,
Activation may be performed by the output of the operating state detection section 33, which switches to feedback control operation when the rotation speed is below a certain predetermined rotation speed, and to V/P control operation when the rotation speed is equal to the predetermined rotation speed.

Conversely, the switching operation from high speed to low speed is as follows. 1st
The rotation angle Δ per sampling of the output voltage magnitude 1v11 of the V/F control calculation unit 8 and the output car order angular frequency ω
The data of θ is transferred from the soft switch SW2 to the feedback control calculation unit 9, and the initial positive value for switching to feedback control is calculated from the rotation speed and current value that were continuously detected even during ■/F control operation, and each value is is set in the corresponding calculation section shown in FIG. 5, and then the soft switch SWI is switched to the feedback control side. In addition, Figure 4 shows the hysteresis characteristic of the rotation speed N0 for switching between feedback control and V/F control (when the rotation speed increases, the switch is turned on at the rotation speed N0□, and when the rotation speed decreases, it is switched off at the rotation speed N02). ), and if you do this, N
Since switching chattering does not occur at o, it is possible to smoothly switch the control state.

A detailed block diagram of FIG. 1 is shown in FIG. The detailed operation of the feedback control calculation unit 9 will be explained with reference to FIG.

The output N, ゎ of the rotation detector 6 is input to the speed calculation unit 12 to calculate the rotation speed feedback signal N, and the difference between this Nt and the output of the speed setting device 7 is calculated by the subtraction unit 7 to perform a proportional calculation. section 13 and the integral calculation section 14. These signals are added by an adder 15 and limited by a limiter 16 to obtain a torque command, that is, a torque current command signal q11. On the other hand, the excitation magnetic flux command signal φ is generated by the magnetic flux setting unit 20 in which the relationship between the rotation speed feedback signal N and the magnetic flux φ is set to 1.
is output, and the magnetic flux current command signal 1d'' is obtained by multiplying by a coefficient 1 (□) in the excitation current setting section.In addition, the actual current of the UIIIW phase flowing through the induction motor 4, ■., Iw is detected by the current detector 6. , 28 sample and hold circuits, and then converted to a digital value by the A/D converter 29 alternately by the changeover switch 31. Furthermore, this value is converted from the alternating current amount by the output Δθ0. signal of the rotation angle calculation unit 27. The 3-phase/2-phase conversion calculation unit 30 converts it into a DC amount, and outputs it separately into an excitation current feedback Idf and a torque current feedback Iqf.This Idf, Iqf
are the command currents IQ" and Id", respectively, in the subtraction section 17.
and the difference between them is output. Among these signals, the torque current difference is subjected to proportional integral calculation by the proportional calculation section 22 and the integral calculation section 23, and is added 11115. After calculation is performed by the limiter section 16, the induced voltage is added by the induced voltage calculation section 32 to obtain the q-axis voltage command. (2) Obtain q1 and send it to the vector calculation section 26. Further, the excitation current difference is calculated by a proportional calculation section 24,
An integral calculation M25 performs a proportional-integral calculation, and the adder 15 and limiter 16 output a d-axis excitation voltage command Vd'', which is sent to the vector calculation unit 26.

In the vector calculation unit 26, Vd'', IV1al from q1
Calculate = + q, output to the soft switch SWI, and further calculate the current phase θ from ld”, ■q$
is calculated as shown below, and θ is output to the rotation angle calculation section 27.

On the other hand, as for the torque current signal Iq11, the slip angular frequency calculation unit 18 outputs the slip angular frequency ωS, and the rotation angular frequency output calculation unit 19 outputs the rotation angular frequency ωr from the speed feedback Nf. The adder 15 outputs the primary angular frequency ω1 for ωS and ω, which is sent to the already mentioned induced voltage calculation unit 32 and the rotation angle calculation unit 27, and the rotation angle calculation unit 27 outputs the rotation angle per sampling. do.

Reference numeral 8 in FIG. 5 shows details of the V/F II control calculation unit 8 in FIG.

The speed command signal is sent to the rotation angle calculation section 8-1 and the voltage calculation section 8-2.
The voltage calculation unit 8-2 outputs the voltage +Vl, l of the induction motor 4, and the rotation angle calculation unit outputs Δθ□. Reference numeral 33 denotes a control state detection section that constantly monitors whether the speed is low or high and whether the detector is abnormal or not, and outputs a signal to switch the soft switches SWI and SW2 depending on the state.

Next, the operation at the time of switching will be explained.

0) The operation when switching from low-speed range feedback fli'J control to high-speed range V/F control is almost the same as when switching due to detector abnormality (FIG. 2), which will be described later. In this case, the switching timing can be set using a detection signal of a predetermined frequency instead of the detector abnormality signal. In this way, the output voltage, frequency, and phase can be matched before and after switching, so switching can be performed without shock. can.

(2) Switching from V/F control in a high speed range to a feedback loop in a low speed range will be explained below in the order of (a) to (e).

(a) From the primary angular frequency ω at the final sampling of V/F control and the actual rotational angular frequency ω, the slip angular frequency is calculated as ωS=ω, -ω.

(b) The proportional integral calculation output of the speed control system, that is, the torque current command ■q1' is obtained from Iq''cx:ωS.

This is a case where the induction motor has constant torque, but the same calculation formula can be used for constant torque, although the calculation formula is different.

(c) Next, the proportional calculation section 13 and the integral calculation section 1 of the speed control system.
The initial value of 4 is set as follows when the speed control system is saturated and when the speed control system is in an unsaturated operating state.

a) When the speed control system is saturated (when the rotation speed changes rapidly) Setting value of proportional calculation section 13 = Iq11 Setting value of integral calculation section 14 = O b) When speed control system is unsaturated ( When the change in rotational speed is gradual) Feedback control is performed by setting the initial values such that the setting value of proportional calculation section 3 = 0 and the setting value of integral calculation section 14 = l q *.

As mentioned above, the initial values of the proportional calculation section 13 and the integral calculation section 14 differ depending on the operating state, but this is because the proportional section is dominant in the transient state, so the integral section is set to zero, and conversely, in the steady state, Since the steady-state error is corrected in the integral part, the proportional part is set to zero.

Next, the initial settings of the proportional calculation section 22 and the integral calculation section 23 of the current control system will be explained.

(d) The output current phase θ is obtained from the output current detection value (feedback value) at the final sampling in the V/F control operation.

(e) Obtain the output power factor angle ψ from the phase of the output voltage (command value VX) and the phase of the output current detected in (d) above.

(Go) From the sum of the current phase θε and the power factor angle ψ (θ+ψ), the value of the primary voltage V□ is determined as the d-axis voltage Vid and the Q-axis voltage ■1. ″

Vx,”=V, cos (θ+ψ)vl,”=
v, sin (θ + ψ) this v,
d, V1@'' are set in the proportional calculation section 22 and the integral calculation section 23 as follows depending on the current state.

a> When the current control system is saturated (when the current change is rapid) Setting value of the q-axis proportional calculation unit 22 =■.

〃 Setting value of integral calculation section 23 = O Setting value of the d-axis proportional calculation unit 24 = ■.

〃 Setting value of the integral calculation unit 25; O b) When the current control system is unsaturated (when the current change is gradual) Setting value of the q-axis proportional calculation unit 22 = 0 〃 Setting value of the integral calculation unit 23 = ■ 1- Setting value of d-axis proportional calculation unit 24 = 0 Setting value of integral calculation unit 25 = V□.

The initial value is set to switch from V/F control to feedback control, and since the current phase is performed continuously from V/F control, problems such as shock do not occur. The reason why the initial values of proportional and integral values are different depending on the state of the current is the same as that of the proportional integral value of the speed control system.

According to this embodiment, it is possible to switch from feedback control to V/F control, and vice versa, so when the speed change range is large, for example, V/F control at high speeds
pm high speed machining, and low speed 0.5rp orientation control used for positioning when changing tools on machine tools, etc.
This has the effect of allowing continuous operation even in a wide speed change range such as 1:100000.

Furthermore, by using this servo controller, inverter operation under V/F control is also possible without a speed detection cable. An excellent effect is that a single unit can be used for both feedback control when accuracy is required, and V/F control when accuracy is not required.

Next, a rotation detector 6 detecting the speed of the induction motor 4
The operation in the case where the feedback calculation section 9 is broken or the wiring to the feedback calculation section 9 is opened or shorted will be described.

A rotation detector installed in a place that outputs power such as an induction motor, for example a detector that outputs AB phase with a 90° phase difference, is made of electronic components and may be installed in a place with a poor atmosphere, In addition, vibrations and heat from machinery may also be applied, which may cause failures. At this time, the rotation of the induction motor 4 is unknown. If the normal wiring is open or short-circuited, no signal is sent, so the feedback control calculation section 9 detects that the rotation speed is zero.

Therefore, when a certain speed setting is given, feedback control works to keep the rotation of the induction motor 4 constant and to generate the maximum torque. For this reason, there is a possibility that the maximum current will flow through the induction motor 4 and it will eventually burn out. In order to prevent this, the control state detection section 33
After an abnormality is detected by When free-running occurs, material may run out due to the relationship between the front and rear flow lines, resulting in a defective product that cannot be used later.

In the present invention, as shown in FIG. 2, after detecting the occurrence of an abnormality in the rotation detector at sampling time 1n, the signal given to the induction motor 4 is changed to the value at the final sampling tn-x calculated by the feedback control calculation section 9. Soft switch SW in the diagram
2 to the V/F control calculation section 8 as an initial setting value, and after transferring the internal calculation data, the soft switch SWI
By turning on, it switches to the V/F control calculation section 8.

Since the output voltages v1 and Δθ are switched from the same value, no abnormal shock or the like will occur. After this, continue the operation or switch to emergency operation and set the speed setting device 7.
It is also possible to slowly lower the value of , lower the entire line, stop the line without running out of material, and then resume operation by the feedback control calculation unit 9 after taking measures to correct the abnormal location. In particular, if there is no need to stop the line, it is possible to continue operation.

This operation will be explained in more detail below in (1) to (3).

(+) Final sampling t during feedback control
A proportionality constant is determined from the relationship between the output frequency ω□' and the speed command N' at n-i.

(2) The output can frequency ω1 after switching to V/F control gives a -order angular frequency as ω1=1·N,8 for an arbitrary speed command N111.

(3) Next, for the primary voltage V□ of the induction motor, a proportional constant is determined from the output voltage 1' at the final sampling during feedback control and the speed command N'.

Next, calculate the negative voltage by setting V1 = k, ・N1'' for an arbitrary speed command N'. Note that the current phase at the time of switching is naturally controlled in accordance with the phase in the feedback control loop, so the torque There is no fear of shock.

According to this embodiment, it is possible to automatically switch to V/F control operation without using a detector and to perform continuous operation, which has an excellent effect of improving the safety and reliability of the system.

In addition, the controller part and induction motor are placed separately, and
If either is on the trolley, power is supplied to the induction motor by a pantograph or brushes, but since the rotation detector output signal is a weak electric wire, poor contact occurs in the brush configuration, resulting in frequent disconnection detection and free running. Even in such a case, switch to V/F control, so! Not only can this operation be continued for up to 30 seconds, but it is also possible to return to feedback control once the connection status returns to normal, which has the excellent effect of making this type of operation possible.

In this embodiment, the case where the rotation detector is abnormal has been described, but the current detector is abnormal and the torque detector J! when torque feedback control is being performed. This can be considered in the same way for normal situations, and is not limited to rotation detector abnormalities.

Next, FIG. 6 shows an embodiment of line control for multi-unit operation to which the present invention is applied.

Figure 6 shows the magnetic coating or processing line for film.
4 is a feeding machine, 35 is a winding machine, 36 is a pinch a-
It is la.

The overall line speed is set by a line speed setter 43, and a soft start circuit 41 gives acceleration/deceleration commands using a ramp function. Speed command is controlled & Il! The signal is input to the device 39-2 and drives the induction motor 4-2. Note that the speed of the induction motor 4-2 is fed back by the rotation detector 8-2, and the speed of the line is determined by the pinch roller 36. Next, in the winding 11135, the signal of the dancer roll is detected by a detector 38 such as Selsin, and feedback control is performed by subtraction 11B17 so that the induction motor 4-3 is slow when the dancer roll goes up, and is lost when it goes down. In the zero winding machine 35, the circumferential speed increases due to the thickening of the winding, so the dancer roll rises, and as a result, the induction motor 4-3 is controlled to slow down. At the sending out 34, the tension detector 37
The tension is detected by the tension amplifier 40, and the difference with the tension setter 42 is calculated by the subtraction unit 17, and the result is sent to the control j*1t39-1. The induction motor 4-1 is driven for pack tension control. Here, the rotation detector of the induction motor 4-2 fails and the control device 39-2
When switching to /F control, the broken line V/F shown in Figure 6
It is input to the V/P external switching signal of the control device of the F control controllability signal output 9-3, and forcibly switches the induction motor 4-3 to V/F control. Note that if this broken line connection is not made, switching will be done only by the control device 39-2, and the difference in response will appear as the upper and lower parts of the dancer roll, and the winder 3 will be switched to follow the slow-response induction motor 4-2.
The induction motor 4-3 of No. 5 is controlled.

As an application example, it is possible to match the response of an induction motor driven by another normal control device to the V/Fiti'ill response of a control device that has switched to V/F control due to an abnormality in the detector. It can also be done.

This is to change the responsiveness of the feedback control when the normal control device receives the V/F II control signal, so that the rotations of the plurality of induction motors coincide as a whole. In this case, the normal control device is V/F
By doing this without switching to V/F control operation, you can make even subtle adjustments that cannot be made with V/F control operation.

[Effects of the Invention] According to the present invention: l) It is possible to provide a control device for an induction motor with a wide speed change range, which can obtain servo performance with excellent responsiveness at low speeds, and can also be operated at ultra-high speeds.

2> Even if the rotation detector becomes abnormal, the operation can be continued without stopping.

3) When many induction motor control devices are used in a material processing line, even if a rotation detector error occurs in one of them, all control devices can be set to the same mode and the line can be stopped. It is possible to continue operation without any problems.

It has excellent effects.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram showing one embodiment of the present invention, and FIG.
The diagrams are the software processing diagram when the detector is abnormal in Figure 1, and Figure 3.
The figure is a diagram showing the control state switching slope in the shift range.
Figure 5 shows the hysteresis characteristics of switching timing.
The drawings are detailed diagrams of the control circuit of FIG. 1, FIG. 6 is a diagram showing one embodiment of the present invention, and FIG. 7 is a diagram showing one embodiment of the present invention. Explanation of symbols 1... Three-phase AC power supply, 2... Converter section, 3...
・Inverter section, 4... Induction motor, 5... Current detector, 6... Rotation detector, 7... Speed setting device, 8...
...V/F control calculation unit, 9...Feedback control calculation unit, 10...PWM generation calculation unit, 11...Switching element drive circuit, 12...Speed calculation unit, 13...
・Speed control section proportional calculation section, 14...Speed control section integral calculation section 15...Addition calculation section, 16...Limiter, 17
... Extermination calculation section, 18... Slip angle frequency calculation section,
19... Rotation angular frequency calculation section, 20... Magnetic flux setting section, 21... Excitation current setting section, 22... Current control q-axis proportional calculation section, 23... Current control q@integral calculation section , 24
...Current control d-axis proportional calculation section, 25...Current control d
Axis integral calculation unit, 26... Hector calculation unit, 27...
Rotation angle calculation unit, 28... Sample hold circuit, 29
. . . A/D converter, 30 . . . 3-phase/2-phase conversion calculation section, 31 . Feeding machine, 35... Winding machine, 36... Pinch roller, 37... Tension detector, 38... Angle detector, 39... Control device, 40... Tension amplifier,
41... Soft start circuit, 42... Tension setting device, 43... Line speed setting device, D... M flow element, 84... Magnetic contactor, 101... Power converter, 102 ...Switching control means, R5...Current limiting resistor, C
...Smoothing capacitor, Q...Switching element, D
F...Flywheel diode, SWI...Soft switch, SW2...Soft switch. ...3@AC i room source 3 - converter part 6 - - tributary soil detection 7 - -iL degree 2... converter part 4 - - induction tS support 6 - speed detection heat exchanger 3 Figure drawing (no change in content) Figure 5 Figure 5 Concave diagram Rich procedure amendment (method) % formula % Relationship to the case of the person who amends the induction motor control device and its operating method

Claims (1)

[Claims] 1. A power converter that converts to an arbitrary variable frequency, an induction motor that is connected to the output of the power converter and whose rotation is controlled, and a rotation detector that detects the rotation of the induction motor. ,
An induction motor control device comprising a control circuit that controls the induction motor by varying the output frequency of the power converter according to a rotation command, wherein the control circuit receives the rotation command and the output signal of the rotation detector. a feedback control calculation unit that generates a feedback control signal by inputting the rotation command; a V/F control calculation unit that receives the rotation command and generates an open-loop control signal; and detects the operating state of the induction motor control device and issues a switching command. A driving state detecting section that outputs a signal, and a switching control means that switches the signals of the feedback control calculating section and the V/F control calculating section based on the output of the driving state detecting section and outputs the signal to the power conversion device. An induction motor control device characterized by: 2. A power conversion device that converts to an arbitrary variable frequency, an induction motor that is connected to the output of the power conversion device and whose rotation is controlled, and a rotation detector that detects the rotation of the induction motor;
An induction motor control device comprising a control circuit that controls the induction motor by varying the output frequency of the power converter according to a rotation command, wherein the control circuit receives the rotation command and the output signal of the rotation detector. a feedback control calculation unit that receives the rotation command and generates a feedback control signal; a V/F control calculation unit that receives the rotation command and generates an open-loop control signal; and a V/F control calculation unit that receives a signal corresponding to the output frequency of the power converter. a driving state detection section that compares the magnitude with a predetermined switching reference frequency and outputs a switching command signal; and an output of the feedback control calculation section and the V/F according to the output of the driving state detection section. An induction motor control device comprising a switching control means for switching the output of the control calculation section and outputting the same to the power conversion device. 3. a power conversion device that converts to an arbitrary variable frequency; an induction motor that is connected to the output of the power conversion device and whose rotation is controlled; and a rotation detector that detects the rotation of the induction motor;
An induction motor control device comprising a control circuit that controls the induction motor by varying the output frequency of the power converter according to a rotation command, wherein the control circuit receives the rotation command and the output signal of the rotation detector. a feedback control calculation unit that generates a feedback control signal by inputting the rotation command; a V/F control calculation unit that receives the rotation command and generates an open-loop control signal; and a V/F control calculation unit that detects an abnormality in the rotation detector and generates a switching command signal. a driving state detecting section to output; an output of the feedback control calculation, an output of the V/F control calculating section, and an output of the driving state detecting section;
An induction motor control device comprising a switching control means for outputting an output of the V/F control calculation section to the power conversion device when an abnormality detection signal from the operating state detection section is received. 4. A power conversion device that converts to an arbitrary variable frequency, an induction motor that is connected to the output of the power conversion device and whose rotation is controlled, and a rotation detector that detects the rotation of the induction motor;
a feedback control calculation unit that inputs the rotation command and the output signal of the rotation detector to generate a feedback control signal; a V/F control calculation unit that inputs the rotation command and generates an open loop control signal; A V/F external switching signal receiving section that can command the /F control operation from the outside;
/F external switching signal and a signal from the rotation detector, and outputting a switching command signal for switching to V/F control when the rotation detector is abnormal or when the V/F external switching signal is received; The output of the feedback control calculation, the output of the V/F control calculation section, and the output of the operating state detection section are input, and the output of the V/F control calculation section is converted into the power according to the switching command signal of the operation state detection section. A plurality of induction motor control devices each having a switching control means for outputting an output to the device, and a V/F control in progress signal output unit that outputs a V/F control in progress signal when the rotation detector is abnormal and the V/F control is in operation. , the V/F control signal output section of at least one control device of the plurality of control devices is connected to the V/F external switching signal receiving section of at least one other control device of the plurality of control devices; An induction motor control system featuring: 5. a power converter that converts to an arbitrary variable frequency; an induction motor that is connected to the output of the power converter and whose rotation is controlled; a rotation detector that detects the rotation of the induction motor; a feedback control calculation section that inputs the output signal of the rotation detector and generates a feedback control signal; a V/F control calculation section that inputs the rotation command and generates an open loop control signal; and the induction motor control device. The power conversion device includes an operating state detection section that detects an operating state and outputs a switching command signal, and switches signals from the feedback control calculation section and the V/F control calculation section based on the output of the operation state detection section. When operating an induction motor control device having a switching control means for outputting an output to the step of initially setting the feedback control calculation unit or the V/F control calculation unit to which the switch is to be made; and the step of starting to output the calculation result of the control calculation unit to which the switch is to be made to the power conversion device after the initial setting is completed. A method of operating a featured induction motor control device.