JPH09285170A - Rapid stop device for induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform work for adding and installing a rapid stop device easily and in a sort time to a power supply circuit by outputting a DC damping current by operating conversion means in a state where a second contact is opened. SOLUTION: A stop switch 32 is manually pushed and a main contact 2 is opened, opening of the main contact 2 is detected by a current detector 6, a second contact 4 is opened 200msec later. A DC contact 3 is closed 320msec later. A thyristor 5 begins its operation 420msec later, a braking DC current is supplied to an induction motor 1 for rapidly stopping it. When the time set by a timer 8 elapses, the operation of the thyristor 5 stops, and the second contact 4 is closed 250msec later and the DC contact 3 is opened. By doing this, the work for rapidly adding and installing the rapid stop device to a power source circuit can be performed easily and in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quick stop device for an induction motor by DC braking, and relates to a device attached to an operation box not equipped with a quick stop device to add a quick stop function.

[0002]

2. Description of the Related Art A technique for rapidly stopping an induction motor by backflow braking or direct current braking is well known, and an operation box that can quickly stop the induction motor by incorporating a circuit for these rapid stops is also known. is there.

However, many induction motors for driving various types of equipment, which are intended to be small and inexpensive, do not have a quick stop device. There are also many demands for quick stop of the drive motor.

[0004] For example, generally-used general-purpose drilling machines often do not have a quick stop device provided on an induction motor for driving a spindle, but an index table for intermittently feeding a work to the table of such drilling machine. When a large number of drilling and tapping processes are performed by attaching a jig such as the above, the work efficiency greatly differs depending on the presence / absence of the quick stop device, so that it is necessary to additionally install the quick stop device.

As a quick stop device used when such a demand occurs, it is convenient to use a DC braking device using a thyristor. FIG. 4 shows an example of this type of conventional device, in which a quick stop device 11 is connected in parallel with a main contact 2 provided in the power supply circuit of the induction motor 1.
The quick stop device 11 is supplied with an alternating current from the primary side (power supply side) of the main contact 2, and when the main contact 2 is opened, a direct current generated by a thyristor built in the quick stop device 11 is supplied to the main contact 2. To the secondary side thereof to apply DC braking to the induction motor 1.

Such a quick stop device 11 is, of course, provided with a DC contact 3 for turning on / off the braking DC current. And the main contact 2 and the DC contact 3
Since there is a danger of serious accident if both and are closed at the same time, it is necessary to interlock the main contact 2 and the DC contact 3 with each other. Lock contacts 2b, 3b are shown.

[0007]

Among such interlock contacts, the interlock contact 2b interlocking with the main contact 2 needs to be opened and closed by the relay 2c of the main contact 2.
Since the interlock contact 3b on the DC contact side is connected in series with the relay 2c as the main contact, when the quick stop device 11 is additionally installed, the interlock contacts 2b and 3b are housed in the main contact 2 and its relay 2c. It must be additionally installed in the existing operation box.

However, the existing operation box usually does not plan to additionally accommodate such contacts, and in many cases these interlock contacts cannot be accommodated in the operation box. In addition, since it is necessary to interlock between the contacts in the existing operation box and the contacts in the additionally installed quick stop device in this way, the cable of the interlock circuit will be connected between them. There is a problem that the cabling when additionally installing the quick stop device is complicated and requires skill and time for the work.

SUMMARY OF THE INVENTION An object of the present invention is to obtain an induction motor quick stop device that can easily and quickly perform an installation work when an additional quick stop device is installed in a power supply circuit of an induction motor.

[0010]

A quick stop device 10 for an induction motor according to the present invention comprises a connection side terminal 21 connected to the primary side of a main contact 2 and a power supply side terminal 22 connected to a power supply side.
And a second terminal connected in series with the DC terminal 23 that is an output terminal of the braking current and the main contact 2 of the induction motor 1 that is the control target.
It incorporates a contact 4 and a DC contact 3 for turning on / off a DC current applied to the secondary side of the main contact 2 as in the conventional case. The DC current for braking is generated by the thyristor 5 which is supplied with the AC current from the primary side of the second contact 4. The device of the present invention has a built-in current detector 6 that detects whether or not current is flowing in the power supply circuit of the induction motor.
The current detector 6 is connected to the secondary side of the main contact 2,
The opening / closing of the main contact 2 is detected by the current detector 6. Further, the device of the present invention includes the first delay element 14 which opens the second contact 4 with a predetermined time delay when the current detector 6 detects the current off.

According to the second aspect of the present invention, the second contact 4 is opened after the second contact 4 is opened with a predetermined time delay.
The delay element 13 and the DC contact 3 are closed, and the trigger circuit 7 of the thyristor 5 is operated with a predetermined time delay.
Delay element 15 of

Thyristor 5 outputting a braking DC current
The operation can be stopped by detecting the rotation stop of the electric motor 1, but it is easy to set it by the timer 8 that can adjust the time. In this case, after the thyristor 5 has finished its operation, the DC contact 3 is opened with a predetermined time delay and then the second contact
A fourth delay element 16 is provided which closes the contact 4.

[0013]

The apparatus of the present invention, as shown in FIG. 3, disconnects the cable on the power supply side of the existing operation box 30 provided in the power supply circuit of the induction motor 1 for which the quick stop device is to be provided, and then makes a quick stop. It is installed by connecting the devices 10 in series and connecting the cable 23 for supplying a direct current to the electric motor side of the existing operation box 30. The electric motor 1 is turned on and off by the main contact 2 built in the existing operation box 30. When the main contact 2 is opened, the current detector 6 detects that the current on the secondary side of the main contact 2 is cut off, and after a predetermined time delay, the second contact 4 is opened to generate the DC braking current. Output. The above-mentioned time delay has a safety effect against the operation delay of the device and also has an effect of providing a dead zone in the operation. For example, rapid braking is prevented when the induction motor is switched from forward rotation to reverse rotation or when there is a momentary power failure.

According to the second aspect of the present invention, after the current detector 6 detects that the current on the secondary side of the main contact 2 has been cut off, a time delay is set between the respective operations, and the Two
The contact 4 is opened, the DC contact 3 is closed and the thyristor 5 is triggered. As a result, a large input current does not flow through the DC contact 3, so that the contact can be made small and obstacles due to device operation delay can be avoided. After the induction motor 1 is DC-braked,
After measuring the timing at which the electric motor 1 stops (by setting a timer, etc.), the trigger operation of the thyristor 5 is stopped, and the second contact 4 and the DC contact 3 are restored after a certain delay time.

According to the above structure, the main contact 2 and the DC contact 3
Since it is not necessary to interlock between the second contact 4 and the DC contact 3 if necessary, this interlock circuit can be built in the device in advance. , It becomes unnecessary to connect the cable for the interlock circuit when additionally installing the quick stop device. Further, since it is not necessary to attach anything to the existing operation box 30, there is no problem of storage space, the power circuit can be compactly assembled, and the risk of accident due to incorrect wiring during installation can be avoided as much as possible. it can. Further, since the second contact 4 and the DC contact 3 are both opened and closed in the state where no current is flowing, it is not necessary to consider the damage of the contact due to the arc, and the durability is sufficient even if a small contact is used. The device can be provided at low cost.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. An existing operation box 30 is provided in the power circuit of the induction motor 1, and the main contact 2, the main contact relay 2c, and the start switch 3 are provided in this operation box.
1 and a stop switch 32 are built in. The self-holding circuit provided in parallel with the start switch 31 is not shown. The quick stop device 10 of the present invention is interposed between the main contact 2 and the power source, and the connection-side terminal 21 of the quick stop device is connected to the primary side of the main contact 2 and the power-side terminal 2
2 is connected to the power supply.

The connection side terminal 21 and the power supply side terminal 22 are connected to each other by a power supply line 25 with the second contact 4 interposed in the apparatus. The direct current for the timer 8 and the thyristor trigger circuit 6 provided in the device is supplied by rectifying the alternating current obtained from the power supply line 25 by the rectifier 9. DC terminal 2
3 is connected to the secondary side of the main contact 2. Specifically, at the time of installation work, loosen the screw of the connection part of the cable connecting the main contact 2 and the induction motor 1, insert the other end of the cable 24 connected to the DC terminal 23, and then insert the screw. Just tighten it.

The quick stop device 10 is provided with a current detector 6 connected to the DC contact 23, and the second contact relay 4c 200 msec after the off detection signal of the current detector 6 is output. Delay circuit 14 for exciting
And a second delay circuit 13 for exciting the DC contact relay 3c 120 milliseconds after the second contact relay 4c is excited, and a trigger of the thyristor 5 100 milliseconds after the DC contact relay 3c is excited. A third delay circuit 15 is provided.

Further, a timer 8 for adjusting the operation time of the thyristor 5 is provided in the device, and 250 seconds after the operation of the thyristor 5 is stopped, the second contact relay 4c and the DC A fourth delay circuit 16 for demagnetizing the contact relay 3c is provided. The adjustment time of the timer 8 is set within the range of 1 to 7 seconds according to the operating environment of the induction motor 1. Note that the above delay time and timer setting time are merely examples, and are values that should be set as appropriate in consideration of relay operation delay and the like.

The operation of the device after the main switch 2 is opened by manually pressing the stop switch 32 is shown in the timing chart of FIG. After the opening of the main contact 2 is detected by the current detector 6, the second contact is made 200 milliseconds later.
The contact 4 opens and the DC contact 3 closes after 320 milliseconds. And thyristor 5 after 420 milliseconds
Starts its operation, supplies a direct current for braking to the induction motor 1 through the cable 24, and rapidly stops the motor 1. When the time set by the timer 8 has passed, the operation of the thyristor 5 is stopped, and 250 seconds later, the second thyristor 5 is stopped.
The contact 4 is closed and the DC contact 3 is opened. The restart A of the induction motor 1 is performed at the timing thereafter.
Even if the start switch 31 is pressed before the induction motor 1 is stopped to restart it, the induction motor 1 cannot be restarted because the second contact 4 is opened, which causes the main contact 2 to be restarted. It is a substantial interlock with the DC contact 3.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing the operation

[Fig. 3] Connection diagram for additional installation of the quick stop device

FIG. 4 is a block diagram showing a connection state of a conventional quick stop device.

[Explanation of symbols]

 1 induction motor 2 main contact point 3 DC contact point 4 second contact point 5 thyristor 8 timer 13 second delay element 14 first delay element 15 third delay element 16 fourth delay circuit 21 contact side terminal 22 power supply side terminal 23 DC terminal 24 Cable for DC

Claims (3)

[Claims] 1. A DC terminal (23) for outputting a DC braking current to an induction motor (1) to be controlled, a DC contact (3) for turning on / off a DC braking current output circuit, and an AC current for converting the DC current to a DC current. In a quick stop device for an induction motor equipped with a conversion means (5) for converting, a power supply side terminal (22) connected to the power supply side of the main circuit of the induction motor (1) and a primary side of the main contact (2). Connected side terminal (21), the second contact (4) connected between the power source side terminal (22) and the connection side terminal (21), and a current for detecting the drive current of the induction motor. After the detector (6) and the current detector (6) detect the current off, the second
A second contact with a delay element (14) for opening the contact (4)
A quick stop device for an induction motor, characterized in that the conversion means (5) is operated in a state where (4) is opened to output a DC braking current. 2. A DC contact with a predetermined time delay after the second contact (4) is opened with the delay time set by the delay element (14).
A second delay element (13) for closing (3), and a third delay element (15) for operating the conversion means (5) with a predetermined time delay after the DC contact (3) is closed. Induction motor quick stop device. 3. A time-adjustable timer (8) for setting the operation time of the conversion means (5), and opening the DC contact (3) with a predetermined time delay after the operation of the conversion means is completed and 2. The quick stop device for an induction motor according to claim 1, further comprising a fourth delay element (16) closing the second contact (4).