JPS61277390A - Controlling method for induction motor - Google Patents

Abstract

PURPOSE:To create an ideal curve and obtain the increasing brake force, by controlling a power converter in a range where the first phase potential and the third phase potential are higher than the second phase potential of an AC three-phase power source whose input is directed to the power converter. CONSTITUTION:So far as the power source waveforms of the first phase R, the second phase S, and the third phase T are concerned, in a range where the potential of the third phase T is higher than the potential of the first phase R and the second phase S, a control element TRCT is conducted to a control element TRCS. Also, in a range where the potential of the first phase R is higher than the potential of the second phase S and the third phase T, a control element TRCR is conducted to the control element TRCS.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a motor driving method for controlling the primary voltage of an induction/single motor using a voltage converter, and in particular, the present invention relates to a method for driving a motor that controls the primary voltage of an induction/single motor using a voltage converter. The present invention relates to a control method for an induction motor that obtains brake torque characteristics using a power converter using a power converter.

[Conventional technology]

Conventionally, induction motors (hereinafter referred to as I
The model shown in FIG. 3 is known as a model for controlling the -order can pressure (referred to as M).

Figure 3 is a known model diagram of IM-order voltage control, with R, S
, T are the 1st, 2m, and 3rd phases of a three-phase AC 'IC source, for example.
8, TRCa, Tl(ce, TRCT Ha2J
1aR.

This is a control element connected to the second phase S and the third phase T and having a power conversion function.

Since such connection configuration and speed control driving of the IM are well known, a detailed explanation thereof will be omitted.

Next, the case of obtaining brake characteristics in IMI driving will be explained with reference to FIG. 4.

Here, Fig. 4 (a) shows the power supply waveform, and Fig. 4 (b) shows the power supply waveform.
indicates the vector of the magnetic field.

Now, when generating a braking force on the rotating IM, if the control elements TRCa and TRCa are made conductive at the timing of section 2 of the power waveforms of the first phase R1, the second phase S, and the third phase T, the winding of the IM A current flows in one direction through the windings wU and Wv of SWυ, wv, and Ww, and the magnetic fields φU and φV generated by this ′1 current and their combined magnetic fields φ, φ′, and φ” become the vectors shown in the figure. .Here, the composite magnetic fields φ, φ', φ'' are in the low speed range and medium speed range of IM operation.

This is shown as a typical example in the high speed range.

Therefore, the IM can apply DC braking and generate braking force.

[Problem that the invention seeks to solve]

Generally, according to the conventional control method for obtaining the brake torque as described above, the torque-speed characteristic was as shown in FIG.

Figure 5 shows the braking characteristics obtained by the conventional method, where the vertical axis represents the rotational speed N of the IM, and the horizontal axis represents the driving torque (+
τ) and braking torque (-τ).

Here, BC is the brake curve.

In this way, the torque was drastically reduced in the high rotation range as represented by brake tune #BC.

As a solution to this problem, there is a known method of switching the braking method in high-speed ranges, but in that case there is a switching point, which causes problems such as discontinuities. Put it away.

In addition, if a control element is attached to the windings WU and WV to cause a large current to flow in order to increase the brake torque, it will not only be necessary to add a power cord, but will also complicate the element drive circuit. This resulted in a lack of reliability and increased costs.

[Structure of the invention]

The present invention has been made with attention to the above-mentioned points, and provides a method for realizing a simple device by skillfully increasing the brake torque without adding a power element or the like. . Hereinafter, the present invention will be explained based on the drawings.

Figure 1 (A), (r: 4 is shown similar to Figure 4 to facilitate understanding of the technical idea of the present invention, and Zl *
22 is the interval, φ! , φ2. φ1', φ2', φ1#,
φ- is the composite magnetic field.

In the figure, the same reference numerals as in FIG. 4 indicate parts having the same functions.

That is, to describe this with reference to FIG. 3, the first phase R
2 Control element TRCT and control element TRCs in section z1 of the power waveform of the second phase S and third phase T, and in section z of the power waveform.
2, the winding WU is made conductive between the control element TRCR and the control element TRCs.

When current flows through Wv and Ww, magnetic fields φU and
φV.

φW occurs.

Therefore, as respective synthetic magnetic fields, φ1 and φ2. φ1
' and φ2. φX and φ2 are obtained.

Therefore, what is shown in Figures 1 (a) and (c$) is, as is clear from the comparison with Figure 4 (a) and (c), an area where an approximately constant magnetic field is generated. The current flowing through the winding of the IM can be increased, and the IM can obtain an increased braking force.This is illustrated in FIG. 2.

FIG. 2 is a torque-speed characteristic diagram showing the brake characteristics obtained by the present invention, and BC' is a brake curve. In other words, in the brake curve BC', a mutually large braking torque is obtained particularly from the low speed range to the high speed range, and the high speed range characteristic provides an extremely large braking force compared to the conventional characteristic.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide an exceptional method of drawing an ideal curve and obtaining increased braking force using a conventional circuit configuration.

[Brief Description of the Drawings] Figures 1 and 2 are diagrams showing power supply waveforms and magnetic field vectors and torque-speed characteristic diagrams, which are shown to facilitate understanding of the technical concept of the present invention, and Figure 3 is an IM- Known model diagrams showing molding pressure control, FIGS. 4 and 5 are diagrams showing a single pressure waveform and a magnetic field vector, and a torque-speed characteristic diagram according to a conventional method. R, 8, T...'141 phase, 2nd phase of three-phase AC power supply. Third phase, TRrCn, TRCs, TRCT...
・・・Bidirectional three-terminal control element (control element), IM・
...Induction motor, Z. zl, Z2... section, φ, φ', φ″I ”'
t ”21 ””Z ”21 φt'. φ-・・・Synthetic magnetic field, BC, BC'・・・・・・
brake curve.

Claims (1)

[Claims] In a motor driving method in which the primary voltage of an induction motor is adjusted by a power converter to drive the motor, the first phase potential and the third phase potential are lower than the second phase potential of an AC three-phase power source input to the power converter. A method for controlling an induction motor, characterized in that the braking torque of the induction motor is obtained by controlling the power converter in a high-level section.