JPS5923090B2 - Tap-switching automatic voltage regulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic voltage regulator that adjusts voltage by providing a tap in the shunt winding of an autotransformer and switching the tap with an electromagnetic contactor.

Figure 1 shows a conventional example, in which 4 is an autotransformer;
1 indicates the series winding, and nl indicates the number of turns. Similarly, 42 is a shunt winding, 42A, 42B, and 42C are taps provided in the shunt winding, and n2 to n4 are windings between the taps in the shunt winding.

1a and Ib are the contacts of the first electromagnetic contactor, 2a and 2b are the contacts of the second electromagnetic contactor, and 3a and 3b are the contacts of the third electromagnetic contactor, where a is a normally open contact and b is a normally closed contact. It shows the contact points.

5 is a resistor, E1 is an input voltage, and E2 is an output voltage.

Each of the electromagnetic contactors described above is operated by a control circuit (not shown).

Needless to say, the control circuit controls the first to third electromagnetic contactors so that they do not close at the same time. To explain the mode of control, when only contact Ib is closed, the output voltage E2 is: E2 E1 × When only contact 2a is closed, the output voltage E2 is 15n
1+n2+n3 E2=E1× When only the contact 3a is closed (n2+n3 n1+n2), the output voltage E2 becomes E2×E0×, so by appropriately selecting the number of turns n1 to n4 (20), a desired voltage value can be obtained.

The first to third electromagnetic contactors are electromagnetic contactors that have a structure in which both the normally open and normally closed contacts are closed in the process of each contact operating from open to close and from close to open. are using.

The ON and OFF states of the normally open and normally closed contacts 25 are illustrated in Figure T. When the magnetic contactor is attracted, the normally open A contact turns ON before the normally closed B contact turns OFF, and then the B contact turns OFF. Turn off. On the other hand, when falling, the B contact opens first.
After turning N, the a contact turns off. This type of contact 30 action is called an overlap type relay. An example of the tap switching state is shown in FIG. 1 from taps 42B to 42C.
FIGS. 2 to 6 are diagrams illustrating the case of switching to. That is, when the contact 2a is closed, the shunt winding 3542 is connected to the power supply at the tap 42B as shown in FIG. 2, and when switching from the tap 42B to the tap 42C, the second electromagnetic Contactor operating coil -
A-coo excitation is released.

In that case, the A and B contacts of the electromagnetic contactor overlap as mentioned above, so when the contact 2a is in the closed state, the contact 2b is closed first and the shunt winding is shorted through the resistor 5, as shown in FIG. Therefore, a current ISl flows through the short circuit. After that, when the contact 2a is completely opened, the shunt winding is not connected between the power supply terminals and the resistor 5
Since a short circuit is formed through the series winding, a current 1S2 sufficient to cancel the ampere turn caused by the load current 2 flowing through the series winding flows, thereby preventing overexcitation of the iron core. Next, when the operation coil of the third electromagnetic contactor is excited, the contact 3a is closed before the contact 3b is opened, and a short circuit current 1S3 flows through the resistor 5, as shown in FIG. is completed and the connection of the tap 42C is obtained as shown in FIG. Conversely, the movement from tap 42C to tap 42B follows the completely reverse order from FIG. 6 to FIG. 2. The basic operations of the other taps are exactly the same. resistance 5
An appropriate value such as Is, , Is3 is selected so that the short circuit current does not become excessive. During the tap switching process in a conventional tap switching circuit, the state shown in Figure 4 occurs, that is, as described above, the shunt winding is not connected between the power supply terminals, but a part of the shunt winding is short-circuited through the resistor. If the load current 12 is zero, that is, in a no-load state, the output voltage E
2 becomes E2+E, and when the load current 12 is flowing, a short circuit current 1S2 flows, and the output voltage E2 becomes E2<E1 due to the voltage drop between the resistor 5 and the impedance of the shorted shunt winding.

That is, each time the tap is switched, the output voltage becomes lower than the input voltage once, and the voltage fluctuates much larger than the step voltage width. FIG. 8 shows the relationship between the input/output voltage characteristics of each tap and the output voltage fluctuation when switching the taps. Such large voltage fluctuations at the time of tap switching cause an unpleasant flickering sensation in the case of electric lamp loads, and impede the supply of high-quality electricity. Also, when the state changes from the state shown in FIG. 4 to the state shown in FIG. At the moment when the tap of the winding is connected to the power supply terminal by the magnetic contactor contact, a large excitation inrush current flows through the shunt winding to the magnetic contactor contact, which may cause welding damage to the contact.

In order to suppress this excitation inrush current, it is necessary to make the magnetic flux density of the autotransformer sufficiently low, and the iron core of the autotransformer must be made much larger than that of a normal transformer. These phenomena occur every time the tap is switched. The present invention connects the shunt winding and the power terminal by a series connection body of the other normally open or normally closed contact of each magnetic contactor connected to each tap of the shunt winding and a resistor. The present invention is intended to eliminate the drawbacks of the conventional method, and embodiments of the present invention will be described below.

FIG. 9 shows an embodiment of the present invention, which corresponds to the conventional circuit shown in FIG.
Figures 10 to 1 are diagrams explaining the case of switching to C.
This is Figure 4.

That is, when the contact 2a is closed, the shunt winding 42 is connected to the power supply at the tap 42B as shown in FIG. 10, and the output voltage E2 is E2=E1×? Then,
When switching from tap N2+N3 tap 42B to tap 42C, the control circuit first de-energizes the operating coil of the second electromagnetic contactor.

In that case, since there is overlap in the magnetic contactor, the first
As shown in Figure 1, when the contact 2a is closed, the contact 2b is closed first, and then when the contact 2a is completely opened, the shunt winding 42 is connected to the power supply terminal through the resistor 5, and the current flows as shown in Figure 12. 1r flows. Output voltage E2nl+ in this state
Is N2+N3 E1×? It is the value obtained by subtracting the slight voltage drop between the resistance due to the current 1r and the impedance of the N2+N3 shunt winding.

Next, when the operation coil of the third electromagnetic contactor is excited, the first
As shown in FIG. 3, the contact 3a is closed before the contact 3b is opened, and a short circuit current 1s flows through the resistor 5. Then, the next instantaneous contact 3b completes opening, and the connection of the tap 42C is obtained as shown in FIG. 14, and the output voltage E2 is E2=E1×n.
1+N2? becomes.

Therefore, in the tap switching process, the output voltage E2 never becomes lower than the input voltage E1 as in the conventional case, and the output voltage fluctuation becomes a step voltage width as shown in FIG.

Further, since the shunt winding is always connected to the power supply terminal during the tap switching process, there is no excitation inrush current flowing as in the conventional case. Conversely, the movement from tap 42C to tap 42B follows the completely reverse order from FIG. 14 to FIG. 10. The basic operation is the same for other taps.
The value of the resistor 5 may be selected appropriately to prevent short-circuit currents such as Ir and Is from becoming excessive and to prevent the output voltage drop from becoming large in the state shown in FIG. 12.
Further, the position of the connection body between the electromagnetic contactor contact and the resistor between the power supply terminal and the shunt winding can be arbitrarily selected so as to minimize the output voltage fluctuation when switching each tap. Next, the contacts 1a and 1b of the electromagnetic contactor will be explained. Contact 1a, together with contacts 2b and 3b and resistor 5, is used to prevent the shunt winding 42 from being disconnected from the power supply even temporarily when switching from tap 42A to 42B or from tap 42B to 42A. is the same as that explained in FIGS. 11 to 13.

Also, its purpose is when switching from tap 42A to 42B when there is no connection body between contacts 1a, 2b, 3b and resistor 5.
Both contacts may be temporarily open, disconnecting the shunt winding 42 from the power source, or both contacts may be closed, shorting the N4 portion of the shunt winding 42. In the former case, when the load current is flowing, all of the current becomes an excitation current, the iron core becomes extremely saturated, and a high voltage with a sharp waveform is induced in the shunt winding 42, causing the insulation of the shunt winding 42 to deteriorate. leading to destruction. On the other hand, in the latter case, there is a possibility that the winding N4 may be short-circuited and burnt out. Further, the point that only the tap 42A uses the normally closed contact 1b of the electromagnetic contactor will be explained as follows.

This is to create a circuit configuration as shown in Figure 9 in the event that all the magnetic contactors become de-energized due to some kind of accident.For example, contact 1b is connected to the connecting body part that includes tap 42A contact 1a1 and resistor 5. In such a case, the resistor 5 is connected to the power supply through the resistor 5, and if the accident condition continues for a long time, the resistor 5 may burn out, and a large-capacity resistor is required to prevent this.

Fig. 15 shows another embodiment in which the number of taps is 4. In the figure, 14 is an autotransformer, and 141 is its series winding.
indicates the number of turns.

142 is also a shunt winding, 142A, 142B, 14
2C represents a tap provided in the shunt winding, and Nl2 to Nl4 represent the number of turns between each tap in the shunt winding.

11A, llb are first electromagnetic contactors, 12a, 12b are second electromagnetic contactors, 13a, 13b are third electromagnetic contactors, 14a, 14
b is each contact 5 of the fourth electromagnetic contactor, and the relationship between A and b is the ninth
Same as in the figure.

15 is a resistance.

Now, when only contact 11b is closed, the shunt winding is not excited from the power supply terminal and is short-circuited, so there is only a slight voltage drop between the input and output, equal to the impedance voltage drop of the autotransformer. It is E2. Next, when only the contact 12a is closed, the output voltage E2 is E2=ElXll
l+112+113+114, only contact 13a is closed N
When l2+Nl3+Nl4, the output voltage E2 is E
2=ElXshiγ translation? If only the two-way contact 14a is closed, the output voltage E2 of Nll+Nl2 is E2=E1×? becomes.

Nl2 This is basically the same as shown in the embodiment even if the number of taps is changed.

Note that the contact 11b is connected to the shunt winding 142 which is disconnected from the power supply.
Short-circuit the windings Nl3 and nl4, which are part of the contact 12a.
, 13a, 14a is prevented from dielectric breakdown of the shunt winding 142 due to opening of the terminals 13a, 14a. On the other hand, the contact 11a constitutes a connection body that temporarily connects the shunt winding 142 to the power source when the state shown in FIG. 15 changes to the state in which the tap 142A is connected by the contact 12a. The operation during tap switching is similar to that of the contact 2b in FIGS. 11 to 13. As above, the contacts 11a and 11b of the electromagnetic contactor
As explained in FIG. 9, although it is not essential, it is preferable to have it. Although the present invention is a simple circuit as described above, the shunt winding is not disconnected from the power supply terminal even momentarily during the tap switching process of the autotransformer, so output voltage fluctuation is reduced. A highly reliable (/pulse voltage regulator) is obtained in which no excitation inrush current flows.

[Brief explanation of the drawing]

Figure 1 is a conventional circuit diagram, Figures 2 to 6 are conceptual diagrams explaining an example of the operation in Figure 1, Figure 7 is a diagram explaining the contact operation of a magnetic contactor, and Figure 8 is a diagram explaining an example of the operation in Figure 1. Fig. 1 is a diagram showing input/output voltage characteristics and output voltage fluctuations when switching taps, Figs. 9 and 15 are circuit diagrams showing embodiments of the present invention, and Figs. It is a conceptual diagram explaining an example of operation.

Claims (1)

[Claims] 1. An autotransformer with multiple taps on the shunt winding,
A plurality of electromagnetic contactors are provided, each having a normally open contact and a normally closed contact such that a state exists in which these contacts are both closed during the opening/closing operation, and whether the plurality of magnetic contactors are normally open or One of the normally closed contacts is connected between each of the above taps and the power terminal, and the series connection body of the other contact of each of the magnetic contactors and the resistor is connected between the above power terminal and the shunt winding. A tap-switching automatic voltage regulator that is connected to the position where the output voltage fluctuation when switching line taps is minimized.