JPH0116356Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a power supply switching circuit for receiving power from two systems.

In a system consisting of a group of electric motors, there is a method of temporarily inserting a resistor or reactor between the busbars at the time of switching in order to reduce the inrush current that occurs when switching the power supply and the generation of excessive torque caused by it. FIG. 1 shows an example of this conventional method, in which the power receiving switches 1 and 2 are always operated in the "closed" state, the bus bar communication switch 3 is "open", the auxiliary switch 15 is "open", and the bus bar 8 , 9 are each operated by separate power sources. When switching the power supply due to a power outage or the like, first open one of the power receiving switches 1 or 2, close the auxiliary switch 15, and connect the bus bars 8 and 9 with the resistor or reactor 14 for a short time. Thereafter, by closing the busbar communication switch 3, transient torque and rush current caused by residual voltage are suppressed, and instantaneous power switching is performed.

Therefore, in order to effectively suppress the above transient torque and inrush current, it is necessary to use a resistor with an impedance matching the capacity of the motor group 10, 11, or 12, 13 connected to the switching side bus 8 or 9. vessel,
Or it is necessary to select a reactor. However, in a system consisting of a large number of electric motors, the operating pattern is not constant, the number of electric motors connected to the switching bus is not constant, and the total load capacity changes. Therefore, there is a problem in that a single resistor or reactor cannot always effectively suppress the transient torque and rush current that occur during switching.

The present invention was developed in view of the above-mentioned problems, and an object of the present invention is to provide an instantaneous power switching circuit free from the above-mentioned drawbacks, which can always effectively suppress the transient torque and inrush current that occur during switching, regardless of the operating pattern. do.

The present invention will be explained below with reference to the drawings. FIG. 2 shows an embodiment of the present invention, and in the drawing, a controllable variable resistor or variable reactor 22, 23 and an auxiliary switch are used for the busbar connection switch 3 in a conventional instantaneous power supply switching circuit. The devices 24 and 25 connected in series are connected in parallel. 20,
21 are these variable resistors or variable reactors 2
This is a newly installed control device to control the impedances of Nos. 2 and 23. This control device 20,2
1 inputs the total current of the motor groups 12, 13, or 10, 11 connected to the No. 2 bus 9 or the No. 1 bus 8 via the instrument current transformer 27 or 26, and inversely proportional to the current value. The impedance of the variable resistor or variable reactor 22 or 23 is controlled so as to

In such a configuration, each switch operates as follows. That is, when the No. 1 power supply fails, first open the power receiving switch 1, then close the auxiliary switch 25, then close the busbar communication switch 3, and finally close the auxiliary switch 25. By opening the switch, the power supply switching is completed. Also, 2
If the number power supply fails, first open the power receiving switch 2, then close the auxiliary switch 24, then close the busbar connection switch 3, and finally open the auxiliary switch 24. By doing this, the power supply switching is completed.

As a result of the above, the impedance of the variable resistor or reactor 22 or 23 is
It is always adjusted to a value suitable for the capacity of 2, 13 or 10, 11, and it is possible to always effectively suppress transient torque and rush current that occur during switching, and to perform instantaneous switching.

In this way, according to the present invention, an effective instantaneous power switching circuit can be provided.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a conventional instantaneous power switching circuit, and FIG. 2 is a system diagram of an instantaneous power switching circuit showing an embodiment of the present invention. 1, 2, 3, 4, 5, 6, 7...Switch, 8,
9... Bus bar, 10, 11, 12, 13... Electric motor, 14... Resistor or reactor, 15, 2
4, 25... Auxiliary switch, 20, 21... Control device, 22, 23... Variable resistor or variable reactor, 26, 27... Instrument current transformer.

Claims (1)

[Scope of utility model registration request] A normally closed first power receiving switch 1 that opens and closes the connection between the first bus bar 8 and the No. 1 power system, and a normally closed second power receiving switch 2 that opens and closes the connection between the second bus bar 9 and the No. 2 power system. , a normally open busbar communication switch 3 that opens and closes the connection between the first busbar 8 and the second busbar 9, and a busbar communication switch 3 that is closed in the event of a failure; and a first variable impedance connected in parallel with the busbar communication switch 3. 22 and a first series circuit of the normally open first auxiliary switch 24, a first instrument current transformer 26 for measuring the current value of the No. 1 power supply system; A second series current transformer 27 for measuring the current value of the power supply system, a second variable impedance 23 connected in parallel with the busbar communication switch 3, and a second auxiliary switch 25 that is always open. a circuit, a first control device 20 that controls the second variable impedance 23 so as to be inversely proportional to the current value measured by the second instrument current transformer 26, and the first instrument current transformer 27.
a second control device 2 that controls the first variable impedance 22 so as to be inversely proportional to the current value measured by the second control device 2;
1. An instantaneous power switching circuit comprising: