JP2001175342A - Ac voltage regulating device and method for controlling the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of an arc when a relay is driven, to reduce the size of the relay and to prevent a device from being destructed due to overvoltage generated when power is restored. SOLUTION: The voltage regulating device is constituted of a transformer 2 inserting a secondary winding 2b into an AC line, an AC chopper 3 for outputting voltage to the primary winding 2a of the transformer 2, a normally opened relay MC1 inserted into the input line of the chopper 3 in series, a normally closed relay MC2 connected to the primary winding 2a of the transformer 2 in parallel, a voltage comparator 5 for judging the value of control voltage Vc outputted from a control power supply device 6, and a control device for controlling the chopper 3 and the relays MC1, MC2. When service interruption is generated, the chopper 3 is turned to an electrically direct sending state, the relays MC1, MC2 are driven, and when power is restored, the chopper 3 is driven after starting the drive of the relays MC1, MC2 and voltage is applied to the primary winding 2a of the transformer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying a stable AC voltage to a load while suppressing fluctuations of a received AC voltage.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC voltage regulator that saves power by stepping down and outputting a received AC voltage, and particularly relates to a technique for preventing the occurrence of an internal short circuit or an internal overvoltage of such an AC voltage regulator at the time of recovery from power failure.

[0002]

2. Description of the Related Art A conventional AC which adjusts a voltage applied to a load by inserting a secondary winding of a transformer into an AC circuit between a power supply and a load and adjusting a voltage applied to a primary winding of the transformer. FIG. 4 shows the voltage regulator. As shown in the figure, the output voltage is controlled by providing a plurality of taps on the primary winding of the transformer 12 inserted in the electric circuit, and connecting the taps to the switches S11 and S1.
2 to control. And the relay MC
Reference numerals 11 and MC12 are provided for establishing a direct feed state for supplying the power supply voltage to the load as it is, and a relay MC13 is provided for contact protection.

[0003] The control procedure of the AC voltage regulator shown in FIG.
It looks like this: (1) When returning to the voltage adjustment state from the power recovery (start of energization) or direct feed state, the initial state is: MC11 open, MC12 closed, MC13 open, S
11 open, S12 open Step 1: MC13 closed Step 2: [MC12 open] Step 3: MC11 closed Step 4: S11 closed Step 5: [MC13 open] (2) When entering the direct feed state from the voltage adjustment state, the initial state: MC11 closed, MC12 open, MC13 open, S
11 closed, S12 open Step 1: [MC13 closed] Step 2: S11 open Step 3: MC11 open Step 4: [MC12 closed] Step 5: MC13 open (3) In case of tap change, initial state: MC11 closed, MC12 open , MC13 open, S
11 closed, S12 open Step 1: [MC13 closed] Step 2: S11 open Step 3: S12 closed Step 4: [MC13 open] (4) When power failure occurs Initial state: MC11 closed, MC12 open, MC13 open, S
11 closed Step 1: MC11 open, MC12 closed, MC13 open, S
11 opening

[0004]

However, in the switching operation described above, the switching operation described in [] causes an arc, thereby impairing the contact reliability of the relay. In addition, since a large number of large relays must be used, it has been difficult to reduce the size of the device, and the operating noise of the relays has been loud. Furthermore, the number of operations is large,
Electrical and mechanical life was shortened. Also, in such a transformer series type AC voltage regulator, the load current flows through the secondary winding of the transformer at the same time as the power is restored,
Since a current according to the winding ratio tends to flow through the primary winding, an excessive voltage is generated at both ends of the primary winding unless a current path is formed between the primary windings of the transformer. There has been a problem that electronic devices connected between the wires are destroyed, the insulation of the transformer is deteriorated, and the device is broken down or its life is shortened.

[0005] In view of the above problems, the present invention suppresses the occurrence of arcs during the operation of the relay, enables the capacity of the relay to be reduced, and prevents the destruction of the device from an overvoltage generated when the power is restored. The task is to

[0006]

According to a first aspect of the present invention, there is provided an AC voltage regulating apparatus comprising: a secondary winding of a transformer inserted between a power supply of an AC circuit and a load; And an AC chopper provided between the primary windings of the transformer for controlling the output voltage of the AC chopper to keep the load voltage constant. A normally open contact provided in series with the input circuit of the AC chopper, A normally closed contact provided in parallel with the primary winding of the switch, a power failure detection means for detecting a power failure of the AC power circuit, and controlling the AC chopper, the normally open contact and the normally closed contact according to an output signal from the power failure detection means. And control means for starting and stopping the apparatus.

According to a second aspect of the present invention, there is provided a control method of an AC voltage regulator, wherein a secondary winding of a transformer is inserted between a power supply of an AC circuit and a load, and a power supply of the AC circuit and a primary winding of the transformer are provided. In an AC voltage regulator that keeps the load voltage constant by adjusting the output voltage of an AC chopper provided therebetween, a normally open contact provided in series with an input circuit of the AC chopper, and a parallel connection to a primary winding of a transformer are provided. A normally closed contact, a power failure detecting means for detecting a power failure of the AC power circuit, and controlling the AC chopper, the normally open contact and the normally closed contact according to an output signal from the power failure detecting means to start and stop the apparatus. A control method for an AC voltage regulating device comprising: a control unit for performing an operation, wherein when an energization is started or power is restored, a normally open contact and a normally closed state are established after an input cutoff and an output short circuit state of the AC chopper are established. Activate the device by activating the contacts and stop There when generated is characterized by normally open contacts, it stops to return the normally closed contact after enacted input shutdown and output short-circuit state of the AC chopper.

[0008] The state of the electrical direct delivery of the AC chopper is as follows.
A state in which the supply of power to the AC chopper is cut off and the primary winding of the transformer is short-circuited.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit block diagram of an AC voltage regulator according to the present invention, and FIG. 2 is a circuit diagram of a control power supply and a voltage comparator.

In the figure, 1 is an AC voltage regulator, 2 is a transformer, 3 is an AC chopper, 4 is a controller, 5 is a voltage comparator, 6 is a control power supply, and the transformer 2 is a secondary winding. 2
b is connected in series with the AC circuit between the power supply 9 and the load 10,
The voltage applied to the primary winding 2a of the transformer 2 is adjusted by the AC chopper 3 so as to keep the load voltage constant. The normally open contact MC1 of the relay is provided in series on the power supply line of the AC chopper 3, and the normally closed contact MC2 of the relay is provided in parallel on the primary winding 2a of the transformer 2.
Controls the relays MC1, MC2 and the switches S1, S2, S3, S4 of the AC chopper 3. The control power supply 6 outputs a control voltage, which is also a power supply for operation, to the control device 4 and the voltage comparator 5.

The operation of each section by the control device 4 will be described with reference to the timing chart of FIG. First, when energization starts or power is restored (points A and C), the relay MC1 opens and the relay M
C2 is closed and is set to a mechanical direct delivery state. And
When the energization starts, the control voltage Vc, which is the output voltage of the control power supply device 6, increases, and when the control voltage Vc reaches the control device operable voltage V1, the voltage comparator 5 outputs a power failure signal, and the AC chopper is in the electrical direct delivery state, that is, the switch. S1 or switch S4 is turned off, and switches S2 and S3 are turned on.
Incidentally, the voltage comparator 5 and the control power supply device 6 constitute a power failure detection means.

Then, the control voltage Vc rises and the voltage V2
, The power failure signal of the voltage comparator 5 is released, an operation command is issued to the relays MC1 and MC2, and after an operation time unique to the relay, MC1 and MC2 are inverted, and the mechanical direct transmission state is released. Further, after the elapse of the time t set in consideration of the operation time of the relay after the power failure signal is released, the AC chopper 3 shifts from the electrical direct feeding state to the voltage adjustment state, and starts the present apparatus. Therefore, the AC chopper is always in the state of direct electrical transmission during the operation of the relay.

Next, when a power failure occurs (point B), the control voltage V
When c decreases to V2, a power failure signal is output from the voltage comparator 5, and the AC chopper 3 instantaneously shifts to an electrical direct-feed state. This continues until the control voltage Vc drops to V1, and at the same time, a return command is issued to the relays MC1 and MC2.
After the lapse of the operation time unique to the relay, MC1 and MC2 perform the reversing operation, and the mechanical direct delivery state is established. However, the capacitance of the capacitor of the control power supply device is selected so that the control voltage Vc does not become V1 or less before the transition to the mechanical direct delivery state.

When the power outage time is short as shown at point D, and when the control voltage Vc falls below V2, the AC chopper 3 shifts to the electrical direct delivery state, and t seconds after the power outage is released, The AC chopper 3 shifts from the electrical direct delivery state to the voltage adjustment state. Furthermore, if the time during which the control voltage Vc drops to V2 or less is shorter than the operation time of the relay, the relays MC1 and MC2 do not reverse and do not enter the mechanical direct delivery state. Further, when the power failure is instantaneous and the control voltage Vc does not fall below V2 as shown at the point E, the AC chopper 3 continues the previous operation simultaneously with re-energization without shifting to the electrical direct feed state. .

As described above, the tap is not provided, the AC chopper, the control power supply device and the voltage comparator as the power failure detection means are provided, and the relay is controlled by the control device as the control means together with the two relays. The number of times of opening and closing can be greatly reduced as compared with the conventional operation only at the time of power failure occurrence and at the time of power failure recovery, so that the consumption of the relay can be reduced and the reliability of the device can be improved. In addition, since the number of times of opening and closing of the relay is reduced, the number of times of generation of operation noise can be reduced, and noise can be reduced. Further, since the number of relays is as small as two, miniaturization of the device can be promoted and reliability is improved.

Further, when shifting from the direct-feed state of the AC chopper to the voltage adjustment state, a waiting time t taking into account the operation time of the relay is set. That is, the input-side switching element of the AC chopper is in the cut-off state, and no arc is generated at the time of opening / closing without opening / closing of current. Also,
When the normally closed contact MC2 is opened and closed, the AC chopper connected in parallel is also in the direct feed state, and the output side switching element is energized. Therefore, although current is opened and closed, no voltage is applied between the contacts and arcing is prevented. it can. Therefore,
The wear of the contacts of the relay can be reduced, and the reliability of the device can be improved.

Further, the rated current of the relay is larger than the rated switching current, and the switching current must be applied in the prior art. However, in the present invention, the relay can be selected according to the rated switching current. It is possible to use a small-capacity (small) relay, which can promote the miniaturization of the device, reduce the operating noise of the relay, and reduce the noise of the device.

[0018]

As described in detail above, according to the AC voltage regulator of the first aspect, the control means controls the AC chopper and the normally open contact and the normally closed contact, so that a short circuit or an overvoltage at the time of recovery from a power failure can be achieved. It is possible to prevent the destruction of the device due to. In addition, there is no tap, and the opportunity for the normally open contacts and normally closed contacts to operate only when a power failure occurs and when the power failure recovers, the number of times of opening and closing can be greatly reduced compared to the conventional operation, reducing the consumption of relays. Reliability can be improved. By further reducing the number of times of opening and closing, the number of occurrences of operation noise can be reduced
It also contributes to lower noise.

According to the control method of the AC voltage adjusting device of the present invention, the input-side switching element is in the cut-off state because the AC chopper is always in the electrical direct delivery state when the normally open contact is opened and closed, and the current is opened and closed during the opening and closing. No arc is generated, and when the normally closed contact is opened and closed, the output switching element of the AC chopper connected in parallel is in a conducting state, and although current is opened and closed, no voltage is applied between the contacts and an arc is generated. Can be prevented. Therefore, the consumption of the relay contact can be reduced, and the reliability of the device can be improved. Furthermore,
As described above, the contact load at the time of normally-open and normally-closed contact switching can be reduced, so that the capacity and size of the relay can be reduced, which contributes to downsizing and noise reduction of the device.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an AC voltage regulator showing an example of an embodiment of the present invention.

FIG. 2 is a circuit diagram of a control power supply device and a voltage comparator of FIG. 1;

FIG. 3 is a timing chart showing the voltage of each part in FIG. 1 and the state of a contact;

FIG. 4 is a main part circuit diagram of a conventional AC voltage regulator.

[Explanation of symbols]

2. Transformer, 3. AC chopper, 4. Control device,
5. Voltage comparator, 6 Control power supply, 9 AC power supply, 10 load, MC1 relay (normally open contact), M
C2: Relay (normally closed contact), S1, S2, S3, S4
··switch.

Claims (2)

[Claims] A secondary winding of a transformer is inserted between a power supply of an AC circuit and a load, and an output voltage of an AC chopper provided between a power supply of the AC circuit and a primary winding of the transformer is adjusted. In an AC voltage regulator for maintaining a constant voltage, a normally open contact provided in series with an input circuit of the AC chopper, a normally closed contact provided in parallel with a primary winding of a transformer, and a power failure for detecting a power failure of the AC circuit. Detection means, and control means for controlling the AC chopper and the normally open and normally closed contacts in accordance with an output signal from the power failure detection means to start and stop the apparatus. AC voltage regulator. 2. A secondary winding of a transformer is inserted between a power supply of an AC circuit and a load, and an output voltage of an AC chopper provided between a power supply of the AC circuit and a primary winding of the transformer is adjusted. In an AC voltage regulator for maintaining a constant voltage, a normally open contact provided in series with an input circuit of the AC chopper, a normally closed contact provided in parallel with a primary winding of a transformer, and a power failure for detecting a power failure of the AC circuit. An AC voltage regulating apparatus comprising: detecting means; and control means for controlling the AC chopper and the normally-open and normally-closed contacts in accordance with an output signal from the power failure detecting means to start and stop the apparatus. When the energization is started or power is restored, after the input cutoff and the output short-circuit state of the AC chopper are established, the normally open contact and the normally closed contact are actuated to start the device, and a power failure occurs. When the input is cut off and the output is short A control method of an AC voltage regulator that returns to a normally open contact and a normally closed contact and then stops after establishing a short circuit state.