JPH01214286A - Idling state detector for induction motor - Google Patents

Abstract

PURPOSE:To detect the idling state of an induction motor without mechanically direct coupling of the motor with an equipment or the like by calculating and detecting the presence or absence, rotating speed and direction of an idling of the motor based on the remaining voltage of the motor. CONSTITUTION:Rectifiers 12a-12c respectively half-wave rectify the remaining detected voltages U-phase-W-phase by a transformer 11. Exclusive OR gates 12e, 12d respectively take exclusively logic sum of the outputs from the rectifiers 12a-12c. A presence/absence-of-idling and rotating speed detector 12f calculates the presence/absence and rotating speed of an idling of an induction motor 3 based on a pulse signal S4 relative to the frequency of remaining detected voltages from the gate 12e. An idling direction detector 12g detects the rotating direction of the idling of the motor 3 based on signals S1-S3 relative to the phase order of the remaining detected voltages from the rectifiers 12a-12c.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting the idling state of an induction motor, that is, the presence or absence of idling, the number of rotations, and the direction of rotation.

[Prior Art] Fig. 3 is a block diagram showing an induction motor system equipped with a conventional induction motor idling state detection device. In the figure, 1 is a power breaker, 2 is an induction motor drive control device, and 3
4 is an induction motor, 4 is a load machine driven by the induction motor 3, and 5 is an induction motor 3. A rotary generator serving as an idling state detection device directly connected to the rotating shaft of the induction motor 3 to detect whether or not the load machine 4 is idling; 6 a switch for sending an operation start command to the induction motor drive control device 2; 7 is an induction motor 3.7 by a rotary generator 5. This is a starting interlock circuit that applies an interlock even if there is a command to start operation from the switch 6 when idle running of the load machine 4 is detected.

Next, the operation will be explained.

Generally, depending on the type of the load machine 4 or the induction motor drive control device 2, there are cases where the load machine 4 or the induction motor 3 cannot be started when it is idling, or it may not be possible to start only when the load machine 4 or the induction motor 3 is idling.

Therefore, in such a system, the rotary generator 5 and the starting interlock circuit 7 are provided as described above. Thereby, the presence or absence of idling is detected from the presence or absence of an output from the rotary generator 5 directly connected to the induction motor 3. and,
When it is in the idling state, the starting interlock circuit 7 is operated by the output from the rotary generator 5, and the induction motor drive control device 2 prevents the induction motor 3 from starting even if there is a command to start operation from the switch 6. It has become.

Conventionally, in addition to the rotary generator 5 described above, a mechanical zero speed switch that uses rotational centrifugal force is installed on the rotating shaft of the induction motor 3, and the zero speed switch detects when the rotation is stopped. Devices that detect the presence or absence of idling are also used.

[Problems to be Solved by the Invention] Since the conventional induction motor idling state detection device is configured as described above, the rotary generator 5. No matter which zero speed switch is used, each device is connected to an induction motor 3 (
Alternatively, it is necessary to directly connect mechanically to the rotating shaft of the load machine 4), and it may be difficult to install it to existing equipment, which poses a problem in compatibility with existing equipment.

This invention was made to solve the above-mentioned problems, and it is possible to detect the idling state due to residual voltage in the induction motor in a simple and reliable manner without directly mechanically connecting equipment to the induction motor. An object of the present invention is to obtain a idling state detection device for an induction motor as described above.

[Means for Solving the Problems] The idling state detection device for an induction motor according to the present invention includes a voltage detection means for detecting the residual voltage of the induction motor, and a voltage detection means for detecting the residual voltage in the induction motor based on the frequency of the detected residual voltage by the voltage detection means. The motor is equipped with idling state detection means for calculating the presence or absence of idling and the number of revolutions, and detecting the rotational direction of idling in the induction motor from the phase order of the detected residual voltage.

[Function] In the idling state detection device for an induction motor according to the present invention,
The residual voltage in the induction motor is detected by the voltage detection means, and based on the detected residual voltage, the idling state detection means calculates and detects the presence or absence of idling in the induction motor, the number of rotations, and the direction of rotation. As a result, there is no need to directly mechanically connect equipment to the induction motor as in the past, and the idling state of the induction motor can be detected by electrically connecting the voltage detection means and the idling state detection means. Ru.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case will be described in which the present invention is applied to an induction motor system similar to the conventional one, and in the figures, the same reference numerals as described above indicate the same parts, so the explanation thereof will be omitted. .

In FIG. 1(a), 11 is a transformer (voltage detection means) for detecting the residual voltage in the induction motor 3;
is a idling state detection means, and this idling state detection means 12
is constructed as shown in FIG. 1(b).

That is, in FIG. 1(b), 12a and 12b.

12c is a rectifier that half-wave rectifies the U phase, ■ phase, and W phase of the residual voltage detected by the transformer 11, and 12d is a rectifier 1.
Exclusive O that takes the exclusive OR of the outputs from 2b and 12c
R gate, 12e is the output from rectifier 12a and exclusive O
The exclusive OR gate 12f calculates the exclusive OR with the output from the R gate 12d, and calculates the presence or absence of idling in the induction motor 3 and the rotation speed based on the pulse signal S4 regarding the frequency of the detected residual voltage from the OR gate 12e. 12g is the rectifier 12a to 12.
Signals 81 to S3 regarding the phase sequence of the detected residual voltage from c
This is an idle rotation direction detection circuit that detects the rotation direction of idle rotation in the induction motor 3 based on the following.

Next, the operation of the apparatus of this embodiment will be explained with reference to FIG.

In general, even if the induction motor 3 is in a power supply cut-off state according to a command from the induction motor drive control unit W2, residual magnetic flux is generated when the induction motor 3 is idling, so that it generates a residual voltage, albeit a small amount. The present invention focuses on this point.

In other words, the residual voltage during idling is detected by the transformer 11,
The detected residual voltage is input to the idle state detection means 12. The detected residual voltage input to the idling state detection means 12 is applied to the rectifiers 12 a and 12 b for each U phase, ■ phase, and W phase, respectively.
, 12 c, and the signals S L, S 2 .
It becomes S3. , and these signals S L,
S2. S3 is logically operated by the exclusive OR gates 12d and 12e to extract the portion of the U phase, ■ phase, and W phase in which only the stuttering phase is in the output state 1, and the detection as shown in FIG. 2 is performed. Pulse signal S4 regarding the frequency of residual voltage
is obtained and input to the idling presence/rotation speed detection circuit 12f.

In this idling presence/rotation speed detection circuit 12f, the presence or absence of idling in the induction motor 3 is detected by the presence or absence of generation of the pulse signal S4, and the idling rotation speed is detected by counting the number of pulse signals S4. become.

On the other hand, the signals Sl, S2, 83 are input to the idling rotation direction detection circuit 12g, and in this idling rotation direction detection circuit 12g, the signals SL, S2. By detecting the input order of S3, the rotational direction of the idle rotation is detected. In other words, the phase rotation order during normal rotation and idle rotation is U.

Since the signals from the rectifiers @12a to 12c are S L, S2. The inputs are input to the idling rotation direction detection circuit 12g in the order of S3, while the phase rotation order during reverse idling is u, w, v, so the rectifiers 12a to 1
The signals from 2c are S L, S 3. It is input to the idle rotation direction detection circuit 12g in the order of S2.

In this way, according to the device of this embodiment, various devices etc. are not mechanically connected directly to the induction motor 3 as in the conventional case.
By electrically connecting the transformer 11 and the idling state detection means 12, the idling state of the induction motor 3, that is, the presence or absence of idling, the number of revolutions, and the direction of rotation, can be easily and reliably detected. In addition to being extremely easy to install into existing equipment, there is also the advantage that the device can be configured at a low cost.

[Effects of the Invention] As described above, according to the present invention, the idling state detecting means determines whether or not the induction motor is idling based on the residual voltage detected by the voltage detecting means.

Since the configuration is configured to detect nine rotational speeds, the rotational state of the induction motor can be detected easily and reliably, and the device can be installed extremely easily and inexpensively in existing equipment.

[Brief explanation of the drawing]

FIG. 1(a) is a configuration diagram showing an induction motor system equipped with an induction motor idling state detection device according to an embodiment of the present invention, and FIG. 1(b) shows the configuration of the idling state detection means in the above embodiment. FIG. 2 is a detailed circuit diagram, FIG. 2 is a timing chart for explaining the operation of the above embodiment, and FIG. 3 is a configuration diagram showing an induction motor system equipped with a conventional induction motor idling state detection device. In the figure, 3 - induction motor, 11 - transformer (voltage detection means), 12 - idling state detection means. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In order to detect the idling state of the induction motor, a voltage detecting means for detecting the residual voltage of the induction motor, and a frequency of the residual voltage detected by the voltage detecting means, calculate the presence or absence of idling in the induction motor and the rotation speed, and the above-mentioned method. An idling state detection device for an induction motor, comprising idling state detection means for detecting the direction of idling in the induction motor from the phase order of detected residual voltages.