JPS6110986A - Starting method of induction motor - Google Patents

Abstract

PURPOSE:To obtain a large starting torque by flowing an exciting current larger than a normal value to form an internal magnetic flux larger than that at normal time, then returning the exciting current to the normal value and simultaneously flowing a torque current. CONSTITUTION:When a switch 32 is closed, a large exciting current set value is applied, sufficiently larger internal magnetic flux PHI0 than that at normal time is formed, and then the switch 32 is opened, switches 33a/33b/33c are ON/OFF/ON. Then, an exciting current command value decreases to normal value, and a torque current iq is applied. Since the internal flux PHI0 formed previously remains at this time, a starting torque equal to the product of the flux PHI0 and the torque current iq is generated to start an induction motor 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a method for starting an induction motor suitable for use in equipment that requires a large starting torque, such as an air-powered vehicle. [Prior Art] In recent years, With the development of power conductor elements such as thyristors, inverters have become widespread, and in the field of variable speed drive systems, where DC motors have traditionally been used, OT variable speed drive devices consisting of "inverter + induction/motor" are being developed one after another. It has been adopted. However, in applications that require a very large starting torque, such as 4-air vehicles, there are only a few examples of its use. This is because the starting torque (static torque) of an induction motor is higher than that of a series-wound DC electric machine.
This was because it was difficult to produce.

Against this background, recently vector side legs have been used as a method to obtain stable static torque in induction/yon motors, and vector control of VCIL/Yonta C
The purpose is to separate the current component into two orthogonal components, d and the torque current component Iq, and apply each component independently to obtain a custom order equivalent to that of the page flow gth machine.

Figure 3 is a Pronk diagram showing the general structure of a conventional vector damping device, and is quoted with some changes from page 133 of "Motor Drive Electronics", edited by Naohiko Ueyama, 1st edition (published by Ohmsha). It is. In this figure, [
3 is a DC' power source; 3 is an inverter that converts the AC into DC and controls the rotation of the induction motor 4; 5a is a speed detector for the induction motor 4; and 5 is a speed detection circuit.

The output of the speed detection circuit 5 (actual rotational speed of the inductor mortar 4) ω゛m is the summation point 7 and the automatic field weakening control 9
from the automatic field weakening @9, the actual rotational speed ωm
A magnetic flux command value determined by f is output. Moreover, the parameter table outputted from the summing point 7 is as follows.

The torque command value becomes large after being converted by the speed amplifier [0]
Fire wave number command 1st shift, )s and excitation current command value 1d are calculated (for these waveforms, see Figure 4
NeojS = [(τ÷h)÷5L”) X kLz
−・−・・−(21+ (1−) L,: Induction motor 40 Secondary self-inductance M: Induction motor 4's secondary mutual inductance R2: Inductance motor 4's 2?: Resistance These calculated values iQ, +d, ωS and the actual rotational speed 'ωml obtained from the speed detection circuit 5 are inputted to the coordinate conversion circuit 20, and the resulting output is the 3-phase "turbulent flow command iu* t iv” + iw” VT flow control circuit/21fK: Supplies to the inverter 3 with a valve.

Thus, the amplitude and frequency of the current 1 supplied to the induction motor 4 are sequentially controlled, and the speed of the induction motor 4 is controlled.

In FIG. 1, 22 is a current detector, which detects the primary current of the induction motor 4.

[Problem that the invention seeks to solve]

By the way, in the conventional vector control device described above, as shown in FIG. 4, since the motor internal magnetic flux Nt' is controlled to be constant, the maximum output current Imax of the inverter 3 is determined. However, the maximum value of the output torque of the induction motor 4 ``7:max'' is limited to the same value from a stationary state to a steady speed.

Therefore, even if you are in a load system that requires a large amount of torque only at startup, you need an induction motor and inverter that can always produce the torque required for startup (even within the constant torque range). It was so hot,
As shown in Fig. 5, even though the steady load torque is small, if the required starting torque '11'' IO is too large, the inductor motor is larger than the maximum steady output torque '7: maX75; c10. I had to use a person who could control this Q) Inno Kuichita.

This invention attempts to solve the above-mentioned problem of ignition. [Means for solving the problem] In order to solve the above-mentioned problem, this invention aims to solve the above-mentioned problem. The first step is to flow a current to form a larger internal magnetic flux than in a steady state, and the second step is to flow a torque current at the same time as returning the excitation current to the steady state value.
[Operation] At the stage when the excitation current is returned to the steady value and the torque current is applied, a large internal magnetic flux remains, so this and the torque '
A large starting torque can be obtained by using the current.

More specifically, the present invention utilizes the following facts.

(1) The motor internal magnetic flux f should be delayed by a predetermined time constant T with respect to the excitation current id. Ding, that is, 1 of the indakun yong motor? :K (stator), 2i'lX: (Mutual inductance between rotor 9 &M, secondary leakage inductance is 13.Secondary resistance is bird.

The following equation holds true: S: Love 2 S Operator (2) The motor generated torque T is proportional to the torque current lq when the motor internal magnetic flux f is present at all times. In other words, if the number of pole pairs of the induction motor is A, then T = J:' j iq (6)
becomes.

(3) The ratio of excitation current to the rated current of an inductor motor is usually about 1/3 for small motors, and further decreases as the motor size increases. Also, during normal use, the motor core is not energized to saturation, which can increase internal magnetic flux. This is especially true for vector control motors.

For the above reasons, when starting the motor, by continuing to flow an excitation current id as large as the inverter current response allows for a certain period of time or more, the motor internal magnetic flux φ is made larger than the steady state, and then the torque current iq is increased. Chemical engineering and excitation current at the same time! d. When switching to the steady state value, the torque generated by the product of the internal S magnetic flux f formed by the current at the limit of the inverter and the inverter's original torque current 1q is generated until the internal magnetic flux φ is attenuated. .

Large starting torque can be obtained.

〔Example〕

The present invention will be described in detail below with reference to one drawing.

FIG. 1 is a block diagram showing the formation of an embodiment of the present invention, and parts corresponding to those in FIG. 3 are given the same reference numerals.

The difference between this embodiment and the conventional device shown in FIG. To obtain the magnetic flux command value φ from +d, (5
) equation, that is, the following equation is used. Reference numeral 3 in FIG. 1 is a calculator that performs this calculation.
The switch 32 (shown as an open contact) and the switch 33b (a normally closed contact) are supplied with the excitation current command value (indicated by
Appetizer + d (Hereafter, this is fp (Id c
] is also supplied to the arithmetic unit 15 by controlling the switch 33C (normally closed contact).

Further, a switch 33a (
A single open contact) is inserted, and the calculation di? The output r of 31 is supplied to arithmetic units it and 13. In addition, the above switch 3
3a to 33c are designed to be interlocked.

The operation of the above embodiment will be briefly described with reference to the waveform diagram in FIG.

Now, when the switch 32 is turned on at time t shown in FIG.
0 and 3L. In this case, switch 33
Since a is in the open state, 5 Torque flow command 11 section iq'
= o, and the calculator 20 outputs the electrical connection 1, which is i"-1do", while the one-stop frequency command 1 (1
7s' is also a lily. In addition, since the rotational speed ωm is also zero, the one-rotation frequency ridge command one-direction ω is also zero, and the induction motor 4 has a non-rotating internal magnetic flux f [hereinafter referred to as f]. ] is formed. This internal magnetic flux fo
is the excitation T4 flow combined value id according to the relationship of equation (5).

The internal magnetic flux f. I also have a correspondingly large value. Furthermore, the magnetic flux command value r has a similar waveform.

In this way, the internal magnetic flux f is sufficiently strong compared to the steady state. is formed, and when the switch 32 is turned off at time t2 in Fig. 2 and the switches 33a/33b/33C are turned on/off/on, the excitation peak/bottom combination command value Id water decreases to the steady value idc. At the same time, the torque index value 'C'
and the torque center combination value iq corresponding to the magnetic flux command value ψ
and 1st direction frequency command ωS ρ) are calculated, and these are input to the coordinate conversion circuit 20 together with the actual rotational speed ωm obtained from the speed detection circuit 5, and the three-phase current command iu''
,iv”.

The command value iq<,
A torque current lq equal to +d energy causes an excitation current 1d to flow into the inductor/yeon motor 42.Here, at time t2, the internal magnetic flux f formed in the light. remains, so this i. A starting torque equal to the product of the torque current 1q and the torque current 1q is generated, and this reaches the maximum starting torque shown in FIG. 2 (G), and the induction motor 4 is started. Then, the internal magnetic flux f has a time constant ′r
As the torque decreases, the torque approaches a steady one-direction C, and eventually the internal magnetic flux f, the torque, and the alignment frequency ff
According to this embodiment, m5 reaches the dK value.
An internal magnetic flux f that is one wave larger is created by flowing a large excitation current ido that is at the limit of the current capacity. ? forming the torque current Iq, and at the same time transmitting the excitation current command 1st shift from IdO to IdO.
Since dCVC and I/I are changed, the internal magnetic flux f. A person can obtain a small starting torque of 4 until it decays.

〔Effect of the invention〕

As explained above, the present invention allows a human-like mobilizing current to flow from a fixed coil within the normal output of an innocent to form an internal magnetic flux more than in a steady state, and then.

By excitation mJ and returning the Ji current to a steady value, the torque current was made to flow 1" at the same time, so a large starting torque could be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram shown in Embodiment 91J of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 3 is a waveform diagram for explaining the operation of the embodiment. Structure of conventional vector system O11 device
, FIG. 4 is a waveform diagram for explaining the operation of the device, and FIG. 5 is a block diagram showing the required starting torque 'T: 1
FIG. 3 is a diagram showing the relationship between o and steady load torque. 3. Inverter, 4. Induction motor (induction motor).

Claims (1)

[Claims] In an induction motor whose rotation is controlled by a vector control inverter, a first step of flowing an excitation current larger than a steady value within the maximum output of the inverter to form a larger internal magnetic flux than in a steady state; A method for starting an induction motor, comprising a second step of returning the torque current to a steady state value and simultaneously supplying a torque current.