JPH087833Y2 - Motor starter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a starter for a three-phase induction motor, and is particularly suitable for operating a motor using a dedicated generator as a power source.

Conventional technology Although there are reactor starting methods as a starting method for a three-phase induction motor, when the direct-insertion starting is difficult, the star delta starting method, which can be realized at a relatively low cost, has been often adopted.

Problems to be solved by the invention In starting a star-delta of a three-phase induction motor, when switching from star connection to triangular connection, there is a secondary current that continues to flow in the rotor and a temporary current that flows from the power supply when switching. Depending on the phase relationship, a shocking large current may be required of the power supply in order to pull it into the synchronous state, and when the capacity of the power supply is insufficient due to the current, the voltage of all phases drops temporarily. In some cases, it was impossible to apply a sufficient voltage to the operation circuit due to a large degree. For this reason, the electromagnetic switch or the like in the operation circuit is insufficiently excited, and the object to be held by itself is separated, and the electric motor may be cut off to cause a trouble such as inability to operate. Such a phenomenon was particularly remarkable when a pump such as a sprinkler fire extinguishing facility was started by using a private power generator having a limited capacity, which was an emergency power source prepared for a power failure.

It would be convenient if the voltage of the operating circuit could be secured with a simple device.

Means for Solving the Problem A V-shaped connection in which only two sets of coils are connected using a timer or the like before starting the star-shaped connection, and after a required time of 21 has elapsed, and before shifting to the normal operation 23 of the triangular connection, Alternatively, for a single-phase load that requires a temporary period 22 in which the current flowing through a pair of coils is limited by a reactor or a resistor 19 and for which a particular voltage is to be secured, such as in an operating circuit, the power supply should be delayed from the one-phase directly connected to the coil of the motor. Supply. If an electromagnetic switch is obtained in which one of the three contact points is closed with a delay by using an oil dashpot structure, etc., the present invention can be realized in a circuit similar to a normal star delta starter. It is possible.

Action When switching from the star-shaped connection to the V-shaped connection by the method as described above, when trying to pull in the synchronous state, a large amount of current flows into the electric motor in the two phases in which the two sets of coils are directly connected, and as a result, The voltage drop of the other one phase connected to the operation circuit can be made smaller than that of the previous two phases. Therefore, the voltage required for the excitation of the electromagnetic switch etc. is secured, and the function of the operation circuit is made more reliable. Further, since the transition from the V-type connection to the triangular connection is performed without shutting off the power supply, the degree of requiring a shocking large current to pull in the synchronous state is small.

Embodiment An embodiment of the present invention will be described with reference to FIG. 1. In addition to a usual star-delta starting device for a three-phase induction motor, a timer 7 is provided in its operation circuit, and its contact or its contact 16
By the contact 10 of the electromagnetic switch 5 operated by, during the steady operation of the triangular connection among the three coils of the motor to be started 1, the current flow path of the one coil that is in parallel with the operation circuit is Let it form. Alternatively, when a current limiting reactor or a resistor 19 is inserted in the flow path, they are configured to be short-circuited.

However, the switches, etc. 18 are shown in the time chart of FIG.
When contact is made as shown at 20, the electromagnetic switch 2 is brought into a self-holding state by its contact 11. Then, the electromagnetic switch 3 is attracted and its contact 8 is brought into contact with the motor 1, so that the electric motor 1 is star-connected and the voltage is reduced. At the same time, the timer 6 starts counting time, and when the set time limit 21 is passed, the contact point to be contacted from 14 is changed.
By switching to 15, the excitation of the electromagnetic switch 3 is released, the electromagnetic switch 4 is attracted, the contact 9 is closed, and the contact 12
If a V-shaped connection that does not allow current to flow in the coil in parallel with the operation circuit, such as by self-holding, or if a reactor or resistor 19 is inserted, the current that flows in the coil is limited and the operation continues. At this time, the voltage effect of the contacted phase of the operating circuit is less than others. At the same time, the timer 7 starts counting time and continues this state for the set time period 22. After that, when the time is over, the contact 16 closes, and the electromagnetic switch 5 attracts it and holds it by the contact 13 for the purpose of further securing the contact.
When 10 is closed, the operation is shifted to the normal operation 23 of the triangular connection and continued until the switch 17 is turned off.

Effect of the Invention The present invention can be easily implemented by adding a small amount of material and man-hours to the conventional star delta starter, and has the following advantages.

The three-phase induction motor starts up and reduces obstacles such as difficulty in self-holding where it occurs due to insufficient excitation of the electromagnetic switch etc. of the operating circuit due to the voltage drop caused by a momentary large current required at the time of acceleration. Ensure functionality.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a time chart of the device according to the present invention. 1 …… Three-phase induction motor 2,3,4,5 …… Electromagnetic switch 6,7 …… Timer, 17,18 …… Switch 21 …… Star-shaped connection operation time 22 …… V-type connection operation time

Claims (1)

[Scope of utility model registration request] 1. In addition to a normal star-delta starter which operates three sets of coils of a three-phase induction motor by starting a star-shaped connection first and then switching to a triangular connection by operating the electromagnetic switches sequentially. Then, before entering the normal operation of triangle connection,
A V-type connection in which no current flows in one set of coils, or a temporary period in which the current flowing in one set of coils is limited to less than the current flowing in the other two sets by inserting a resistor or a reactor, and the operation is performed, An electric motor starter characterized in that power is supplied to an exciting part of a switch from one phase in which a coil is directly connected with a delay when switching to a triangular connection.