JPH06113575A - Star-delta start control circuit for motor - Google Patents

Abstract

PURPOSE:To provide a star-delta start control circuit for motor which allows continuous operation of motor in delta connection with no trouble upon recovery from instantaneous power interruption. CONSTITUTION:A main electromagnetic contactor 88 and electromagnetic contactors 6, 19 corresponding to star and delta connections are connected with the main circuit of an induction motor IM. The motor is started in star connection through the use of a star-delta timer 2 and eventually switching is made to delta connection operation upon elapse of a predetermined time limit. A holding circuit for exciting the main magnetic contactor 88 under the throw-in conditions of the electromagnetic contactor 19 for delta connection is provided as a control means for sustaining delta connection of the motor and restarting the motor on condition that the time to be elapsed after instantaneous power interruption before recovery therefrom is within the reset time of the star-delta timer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a Y-phase three-phase induction motor.
△ (Star Delta) Start control circuit.

[0002]

2. Description of the Related Art First, a conventional three-phase induction motor Y
-Δ The start control circuit is shown in FIG. The instrument numbers shown in the figure are based on the JEM (Japan Electrical Manufacturers' Association standard) automatic control instrument numbers. In the figure, to start the induction motor IM, the distribution breaker MCCB connected to the power supply open circuit is turned on, and then the push button switch PB (ON) is pushed. As a result, the Y-Δ timer 2 is energized, and the Y-Δ timer 2 is turned on first.
The electromagnetic contactor 6 for Y connection is excited and turned on by the output of, and the main electromagnetic contactor 88 is turned on to start the electric motor IM by Y connection. The main electromagnetic contactor 88 is held by itself. Then, when the Y-Δ timer 2 operates in a timed state after a fixed time period, the Y-connecting electromagnetic contactor 6 is opened, and then the Δ-connecting electromagnetic contactor 19 is turned on to switch the electric motor IM to the Δ-connecting operation. During operation, the Y-Δ timer 2 is held by the auxiliary contact of the main electromagnetic contactor 88, and the Δ connection electromagnetic contactor 19 is kept closed.

In addition, the start control circuit is provided with a restart relay 62 for a time-delaying operation as a measure against momentary power failure of the electric motor, and the time-delaying contact of the restart relay 62 is provided in the holding circuit of the Y-Δ timer 2. It is connected in parallel with the contact.
When a power failure occurs after the start of the electric motor, the electromagnetic contactor (return operation time is about 20 ms) opens,
The Y-Δ timer (recovery operation time is about 100 ms) recovers, but if power is restored before the restart relay 66 returns to the time limit, the Y-Δ timer 2 is re-energized through the time-reset contact of the restart relay 66. As a result, the motor IM
Restart in the order Y- [Delta] as described above. However, when the power failure time is prolonged longer than the time limit of the restart relay 66, it is necessary for the maintenance personnel to turn on the push button switch PB (ON) again to start the electric motor.

[0004]

By the way, in the motor start control circuit shown in FIG. 2, when a very short momentary power failure occurs during the Δ operation of the motor, which is extremely rare, the following occurs. There may be some problems. That is, if the power failure time from the occurrence of power failure to power recovery is longer than the recovery operation time of the electromagnetic contactor (about 20 ms) and shorter than the recovery operation time of the Y-Δ timer (about 100 ms), the main electromagnetic The contactor 88 and the electromagnetic contactor 19 for connecting [Delta] are restored and opened, but the Y- [Delta] timer 2 does not reach the reset operation. For this reason, when the Y-Δ timer 2 is energized again by the holding operation of the restart relay 62 after the power is restored, the electromagnetic contactor 19 for Δ connection is excited, but the main electromagnetic contactor 88 remains open. Therefore, the electric motor IM is not restarted. Therefore, in this case, the maintenance personnel presses the push button switch PB (ON) again to start the operation.

The present invention has been made in view of the above points, and an object thereof is to solve the above-mentioned problems, and in the case of a momentary power failure during the operation of the electric motor, the electric motor can be left in a Δ connection after the power is restored. Y of the electric motor that enables continuous operation without
-To provide a starting control circuit.

[0006]

In order to achieve the above object, in the start control circuit of the present invention, when the power source is momentarily interrupted during operation after the motor is started, the power failure time until power recovery is Y- A control means for holding the electric motor in the Δ connection and restarting the motor is provided under the condition within the reset time of the Δ timer.

Further, the control means is constructed as a holding circuit for exciting the main electromagnetic contactor under the condition that the connecting magnetic contactor is turned on, and the time-delaying contact of the restart relay provided as a measure against momentary power failure is set to Y. -There is an embodiment in which it is connected to the holding circuit of the timer.

[0008]

[Operation] With the above configuration, the motor is in operation (△ connection)
If the instantaneous power failure that occurs in 1) recovers before the Y-Δ timer returns, the Δ connecting electromagnetic contactor is closed and the main electromagnetic contactor is reclosed through the auxiliary contact of the electromagnetic contactor. Therefore, the electric motor restarts with the Δ connection.
Moreover, in this case, since the power failure time is a short time within 100 ms and the electric motor continues to rotate by inertia, even if the electric motor is not restarted from the Y connection, the continuous operation can be performed with the Δ connection.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which instruments corresponding to those in FIG. 2 are designated by the same reference numerals. That is, FIG. 1 has basically the same configuration as the start control circuit of FIG. 2, but particularly for the self-holding contact connected to the exciting coil of the main electromagnetic contactor 88, the Y-connecting electromagnetic contactor 6 is connected. A holding circuit is configured by additionally connecting the auxiliary contact of the Δ connecting electromagnetic contactor 19 in parallel with the auxiliary contact.

With this configuration, when an extremely short-time instantaneous power failure occurs during operation of the electric motor IM, the Y-Δ timer 2
If the power is restored within the recovery operation time of Y, the Y-Δ timer 2 is energized through the timed return contact of the restart relay 62, thereby closing the Δ connection electromagnetic contactor 19 and assisting the electromagnetic contactor 19. The contact (contact 19 connected to the holding circuit of the main electromagnetic contactor 88) is closed, and the main electromagnetic contactor 88 is reclosed. Therefore, the electric motor IM, which has continued to rotate by inertia during a power failure, does not start from the Y connection again, but restarts with the Δ connection and continues to operate.

[0011]

As described above, according to the Y-.DELTA. Starting control circuit of the present invention, even when an extremely short momentary power failure occurs within the recovery operation time of the Y-.DELTA. Timer while the motor is running. The electric motor can be restarted with the Δ connection and continuous operation can be performed without the trouble that the automatic restart of the electric motor cannot be performed, whereby the reliability of the Y-Δ start control circuit can be improved.

[Brief description of drawings]

FIG. 1 is a Y-Δ starting control circuit diagram of an electric motor according to an embodiment of the present invention.

FIG. 2 is a conventional Y-Δ starting control circuit diagram of an electric motor.

[Explanation of symbols]

 IM induction motor PB push button switch 2 Y- △ timer 6 Y connection electromagnetic contactor 19 △ connection electromagnetic contactor 62 restart relay 88 main electromagnetic contactor

Claims (3)

[Claims] 1. A Y-.DELTA. Starting control circuit for an induction motor, comprising:
Connect the main electromagnetic contactor to the main circuit of the motor, and each electromagnetic contactor for starting and operation switching corresponding to Y connection and △ connection,
In the case where the Y- △ timer is used to start the motor with the Y connection and the operation is switched to the △ connection after a fixed period of time, when the power supply momentarily fails during operation after starting the motor, the power failure time until power recovery A Y-Δ start control circuit for an electric motor, comprising control means for holding the electric motor in a Δ connection and restarting the electric motor under conditions within a return time of the Y-Δ timer. 2. The Y-.DELTA. Starting control circuit according to claim 1, wherein a holding circuit for exciting the main electromagnetic contactor is provided as a control means under the closing condition of the .DELTA. Connecting electromagnetic contactor. Y- △ start control circuit. 3. The Y-.DELTA. Starting control circuit according to claim 1, wherein a restart relay is provided as a measure against momentary power failure, and the time delay return contact of the restart relay is connected to the Y-.DELTA. Timer holding circuit. Y- △ start control circuit of the characteristic motor.