JPS59156172A - Starting method of induction motor - Google Patents

Abstract

PURPOSE:To obtain a starting method of an induction motor capable of operating by saving energy in high efficiency by flowing an exciting current larger than the prescribed value after inputting a start command. CONSTITUTION:When a start instruction is outputted from a start instructing circuit 11, a speed command N* and a manetic flux command PHI* are respectively outputted from a speed instructing circuit 12 and a magnetic flux instructing circuit 22. A speed controller 13 outputs a torque current command If* in response to the deviation between the speed command N* and a speed signal N and a magnetic flux controller 23 outputs an exciting current command Im* in response to the deviation between the command PHI* and a magnetic flux PHI. An oscillator 18 outputs 2-phase sinusoidal waves sin W1t, cos W1t oscillated by the primary angular frequency command W1* obtained by adding a slip angular frequency command Ws* obtained by dividing an exciting current command Im* by a torque current command It* and the speed signal N. The primary current calculator 19 outputs the primary current command i* of the AC of an induction motor 3 in response to Im*, It*, sin W1t, cos W1t.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a method for controlling the 4-way crowd. especially,
Regarding how to start it.

[Conventional J branch technique]

If vector control is applied to the four induction motors, it is possible to perform a high l core response speed control; similar to the swinging of a DC motor. It's up! The same goes for emergency situations, and when a start command is received, the vehicle can immediately accelerate to the commanded speed.

In order to make the starting characteristics similar to those of the DC type exciter, vector control is performed so that a single bundle of motors is established prior to the starting command. Therefore, an exciting current that generates a predetermined magnetic flux, that is, a direct current, is passed through the motor.

After establishing magnetic flux and receiving a start command, torque is generated by the product of this magnetic flux and secondary current, and the electric machine is started immediately.

However, this method has the following drawbacks. In other words, since DC current is applied to establish magnetic flux prior to the startup command,
Loss occurs in the motor and converter, which reduces the overall efficiency and goes against energy conservation. This decrease in efficiency could not be ignored, especially for rolling mills that require constant starting and stopping.

[Purpose of the invention]

An object of the present invention is to provide a method for starting a single induction motor that is efficient and capable of energy-saving operation.

[Summary of the invention]

The key feature of the present invention is that an excitation current larger than a predetermined value is caused to flow after a startup command is received.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the invention. In the figure, is AC power supply 1 connected to PWM inverter 2? Feed squid. i) The WM inverter 2 converts the AC Mt voltage of the AC Ichihara 1 into a variable voltage, variable frequency AC, and supplies the induction motor 3 with power. The Liao conductive electric exciter 3 (is connected to the P'Vli inverter 2, and is rotated by an alternating current determined by the voltage and frequency that generates the required torque. The rotational speed is detected by a speed detector 4 attached to the shaft, and the detection value is N.

Start and stop commands are sent from the start command circuit 11 to 1°0-21.
Output as a direct signal. , the speed command circuit 12 and the magnetic flux command circuit 24 are connected to the output of the start command circuit 119, and output a speed command N and an excitation current command □, respectively. The speed control circuit 13 receives the deviation between the speed detection J34 and the speed command circuit 12 as input, and outputs a signal according to the deviation.

The output is the effective part of the primary current of the induction motor 3, that is, the torque current command 1. becomes.

On the other hand, the magnetic flux command Φ from the magnetic flux command circuit 22 and the magnetic flux Φ calculated by the magnetic flux calculation circuit 24 are input to the magnetic flux control circuit 23, and the output thereof is the reactive component of the primary current of the induced tomographic rock 3. In other words, the excitation current command becomes ``Y''.

The magnetic flux control circuit 23 is connected to the primary '6 current computation circuit 19 and the magnetic flux computation (9) path 24. Magnetic flux calculation circuit 24
is the excitation current command ■. The magnetic flux of the induction motor 3 is calculated from . The magnetic flux calculation circuit 24 has a magnetic flux control circuit 23 and a division r325.
connected to.

A speed control circuit 13 and a magnetic flux calculation circuit 14 are inputted to the detachment motor 25, and a command Ws for the total angular frequency of the induction motor 3 is inputted.
Output a signal. The adder 17 receives the divider 25 and the speed detector 4 as input, and outputs a command W1 of the -included angular frequency. The oscillator 18 is connected to the adder 17 and generates a two-phase sine wave 5IIIWI t * which oscillates at its command frequency .
Output CQS WHt. - The next current calculation circuit 19 is the distance cutting 1-qt times H: @ 13, the excitation current command circuit 1
4. It is connected to the generator H and B generator 18, and outputs the AC primary current command i of the output device 3 based on the output signal of the generator 18. The 1E current detector 2o detects the output current of the P'WM inverter 2, that is, the primary current of the i-conductor 3. Detection value! shall be. The current control circuit 21 inputs the deviation of the primary current arithmetic circuit 19 and the current surge generator 20, and operates the PWM inverter 2 ((
Let them input.

Next, the operation of the circuit shown in FIG. 1 will be specifically explained.

1a of Lebel' is issued as a start command from the start-Jij order circuit 11. The output signal N of the speed command circuit 12 and the 1-man command circuit 22 is from zero to a certain value]* degrees and the magnetic flux. Take orders. The speed control circuit 13 is N.
! :The magnetic flux control circuit 23 outputs the torque current command Itchi according to the deviation of
The magnetic flux calculation circuit 24 operates according to the deviation of the excitation current and outputs a command Im'' for the excitation current.The magnetic flux calculation circuit 24 calculates the magnetic flux Φ of the induced quadruple bale 3 by calculating the signal L''. Here, T is 1 shift, which is approximately equal to the time constant of the secondary circuit of the induction section 1 and the excitation section 3.
Similarly, M is the excitation intance. The splitter 25 outputs the command Ws+ of the four waves of Susashi angle according to the command. Adder 17 performs the following operation.

W1+=ws* 10N ・・・・・・・・・・・・
・・・・・・・・・(3) And the source oscillator is sin w
A sine temporary signal of Wlt is output at the port. In this way, the primary station wave number of induction and d-excitation 3 can be interpreted.

The one-force, -order diversion circuit 19 calculates the three-phase primary dU-cho command, but -I is also a component. i blue 6
,・fday*i=L5ulWlt+Ircosw,
t=1.5ill (WHL10) ・・・・・・・・・
・−・・・・・・・・・ Perform all vector calculations in (4). In this way, when the current command I is output, the maximum value l of the current becomes equal to 1 due to the control system m.

FIG. 2 shows operating waveforms when operating as described above.

(a) shows the output signal of the start command circuit 11, that is, the output signal of the speed control circuit 12 and the magnetic flux calculation circuit 22, which are the speed command N" and the magnetic flux command Φ. (b) shows the speed opening side 1 With the torque command ■, which is the output signal of the circuit 13,
Start at t = = t, Ji Command Into Old Mugi is speed command circuit 1
The signal applied to the limiter No. 3 is output. (C) is the excitation current command ■ which is the output of the magnetic flux control circuit 23. When the activation command is issued, a signal applied to the limiter of the magnetic flux calculation circuit 23 is output. (d) shows the magnetic flux Φ which is the output signal of the magnetic flux calculation circuit 24. (e) shows the slip angular frequency command Wε which is the output signal of the divider 25, and (5) shows the speed N.

According to the embodiment shown in FIG. 3, as can be seen from FIG. Figure (d)
As shown in , the magnetic flux Φ rises quickly and torque is generated quickly. As a result, it is possible to improve the start-up of the speed N immediately after the starting command is entered. Therefore, the time required for the speed N to rise to a predetermined value can be shortened. Furthermore, since no current is passed when the guiding and exciting rock 3 is stopped, the coupling efficiency of the system can be improved.

FIG. 3 shows a modification of the invention. In this example, PWΔ・
■Effective when there is no margin for the output current of the inverter 2. The lJ mitter f151I control circuit 26 has a magnetic flux side (af
1 circuit 23 is connected, and the value of the limiter 27 of the speed control circuit 13 is changed in response to the excitation wake flow command + 1 fan. The limiter 27 is connected to the limiter control circuit 26, and the maximum limit of the speed control circuit 13 is determined according to its output.

The circuit of FIG. 3 operates as follows. The limiter control circuit 26 determines the maximum value of the torque (flow command), that is, the limiter j'jj'j, l t m II X + as follows.

Po゛ ≠23 It□E = Me IIn,! -Iyo ・・・・・・・・・
(6) Here, ■, □x are the maximum allowed currents of the UPWM inverter 2. )A! , the limiter value of the limiter 27 of the degree control circuit 13 is positive or negative ■. It is set to be 8x.

FIG. 4 shows its operating waveform. (a> is the output signal of the start command circuit 11, that is, the output 1a of the speed command circuit 12.
No. N indicates the output signal Φ'' of the magnetic flux command circuit 22. (b
) is the output signal Iw'' of the speed command circuit 13, that is, the limiter 27, and after applying the start command with 1=1, the signal applied to the limiter 27 of the speed fδU control circuit 13 is output until t-13. The value is 1.≦t≦t, then (6
) is obtained from the equation □8I, and when t2≦tit3, Tt, , +a- is determined from the rated value of the induction exciter 3. (C) is the output signal of the magnetic flux control circuit 23, which operates under the limiter of the magnetic flux control circuit 23 immediately after the start command is issued. (d) shows the magnitude of the primary current calculated by equation (5), 1=1.
During the period from t2 to t2, the command 1°68' for the maximum value of the primary current is output.

As can be seen from Fig. 4(d), the magnitude of the -order flow does not exceed its maximum value 1111+1;C'', so
The output capacity of PWM inverter 2 will not increase.
Furthermore, as shown in FIG. 9 (9), in the section where the start command is issued, an excitation current command larger than that at the rated time is issued, so that the magnetic flux can be built up quickly.

In addition, when the induction turtle exciter 3 is stopped, no 7th order current is passed, so it is possible to save energy.

Note that in the above example, an analog circuit was used for the explanation, but it goes without saying that a microcomputer may also be used.

〔Effect of the invention〕

According to the present invention, excitation 1 can be achieved even when stopped in vector control.
This eliminates the uneconomical nature of using the L flow.
It is possible to increase the overall efficiency during operation. Furthermore, starting characteristics can also be improved, and transient characteristics almost the same as DC motors can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one practical example of the present invention, and Fig. 2 is a block diagram of a practical example of the present invention.
3 is a block diagram of another example of the present invention, and FIG. 1 is an explanatory diagram of the operation of FIG. 3. fl Mouth 20 Perforation 3 figure

Claims (1)

[Claims] 1. An induction fE motor driven by a seven converter that outputs an alternating current with a variable voltage and four variable frequencies, and the gravity converter; A method for starting an induction 1D motor, which is characterized in that a large excitation current is passed through the rated plate after a starting command for the induction motor is issued, in a method in which control Aj is divided into a sluice current and a torque current perpendicular to the magnetic flux. .