JPS6096189A - Speed detector of wound-rotor induction motor - Google Patents

Abstract

PURPOSE:To inexpensively obtain a speed detector having high reliability by detecting the speed of a motor by the secondary voltage and the secondary frequency of the motor. CONSTITUTION:The secondary voltage of a motor is stepped down to a suitable value. A sinusoidal AC voltage which has less waveform distortion is obtained through a filter 7. To discriminate the positive or negative polarity, it is inputted to a comparator 8, which outputs a pulse of frequency inversely proportional to the speed of a motor, and when it is inputted to a frequency-voltage converter 9, its output becomes a voltage signal of the characteristic of the curve (a). This is inputted to a level converter 10 to obtain the characteristic of the curve (b). This becomes the signal proportional to the speed of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a speed detection device for a wound induction motor.

[Prior art]

A conventional device of this type is shown in FIG.

In the figure, (1) is a power source, (2) is a wound induction motor connected to this power source (1), and (3) is a finger speed generator directly connected to the shaft of the wound induction truss (2). It is. (4) is a power conversion device connected to the secondary side of the wound induction motor (2), and (5) is a control device for controlling this power conversion device.

Next, the operation will be explained. The wound induction motor (2) is supplied with a stain force from the power source (1) and rotates. In order to control the rotation speed, an output signal from a t-coupled generator directly connected to the shaft is inputted to a control device (5), and the power converter (4) is fully controlled to maintain a predetermined rotation speed. Here, as a means for detecting the total number of revolutions, a finger speed generator is used which generates a signal proportional to the number of revolutions.

Conventional speed detection equipment uses a finger speed generator that is directly connected to the rotating shaft of the motor, so it requires space to store such equipment in the upper shaft, and it is difficult to handle fluctuations in the shaft of the motor. A special joint was required so that the finger speed generator would not be affected.Furthermore, the conductor wire leading the output signal from the finger speed generator to the full control device had to be wired with special consideration so that it would not be affected by noise. was there.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the above-mentioned sub-))() by detecting the secondary voltage of the motor and obtaining a speed signal based on the frequency of the voltage. This paper proposes a complete speed detection device that does not rely on a special finger speed generator.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, the same reference numerals as in Figure 1 indicate the same parts, (6) is the sewing pressure device that detects the secondary voltage of the electric motor, and (7) is the electric motor secondary voltage detected by the transformer (θ). This is a filter for detecting all waveform distortion included in the voltage.

(8) is the ratio 1 for completely determining the polarity of the filter output voltage.
articulator, (9) is the frequency # which is converted into the output pulse k'rK pressure fu of the comparator (8), voltage converter, α1 is the level Jv
It is a degree conversion 1” road.

Next, the operation of the device configured as described above will be explained. The secondary voltage and secondary frequency of a wound induction motor are inversely proportional to the speed as shown in Figure 3. It has the characteristic that it becomes zero at maximum at synchronous speed.The secondary voltage of the motor is stepped down to an appropriate value via the transformer (6), but the voltage signal obtained here has a large waveform distortion. Therefore, it cannot be used for control as it is. By passing filter (7) to remove all waveform distortion, a sine wave AC voltage with less waveform distortion can be obtained. In order to distinguish between positive and negative polarity. When input to the comparator (8), a pulse with a frequency inversely proportional to the motor speed is obtained from the comparator output, and when this is input to the frequency-voltage converter (8), the output signal is as shown in Figure 3 ω. It becomes a characteristic voltage signal.

This is input to the level conversion circuit (9) to obtain the characteristics shown in Figure 3 (3). This is a signal proportional to the motor speed.

〔Effect of the invention〕

As described above, according to this invention, since the speed detection device of the motor is configured to detect the motor secondary voltage and secondary frequency, there is no need to attach a special finger speed generator to the motor. Moreover, there is no need for an external line for that purpose, and there is an effect that an inexpensive and highly reliable speed detecting device 6' can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a Glock diagram showing a conventional speed detecting device, Fig. 2 is a block diagram showing a speed detecting device according to an embodiment of the present invention, and Fig. 3 is a secondary voltage and secondary frequency of a wound induction motor. FIG. 2 is a characteristic diagram showing the characteristics of the speed detection signal obtained by the present invention. In the figure, (1) is a power supply, (2) is an induction motor, (4) is a power converter, (5) is a control device, (6) is a transformer, and (7) is a power converter.
) is a filter, (8) is a comparator, (9) is a frequency @ voltage converter, and α0 is a level converter. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1

Claims (1)

[Claims] A voltage detector that detects the secondary voltage of a wound induction motor, a frequency/voltage converter that generates a DC voltage proportional to the output frequency of this voltage detector, and a DC voltage of this frequency/voltage converter that changes the total motor rotation speed. A speed detection device for a wound induction motor, characterized in that it is equipped with a level converter t'' for adjusting the signal to be directly proportional to the signal.