CN102761096A - Undervoltage-overvoltage protection device and method - Google Patents

Abstract

The invention provides an undervoltage-overvoltage protection device. The protection device comprises a trip coil (210) connected with a power supply line and used for keeping a trip state when the line is undervoltage, an overvoltage detection circuit (240) used for generating an overvoltage protection triggering signal when detecting that the voltage of the line exceeds a preset threshold, and a control device (250) used for being in response to the overvoltage protection triggering signal and allowing the two ends of the trip coil to be undervoltage, so that the trip coil executes a trip action. The protection device can achieve undervoltage and overvoltage double protection only by using the trip coil, so that the cost is lowered, and the size of the protection device is greatly reduced.

Description

Undervoltage-overvoltage protection device and method

technical field

The invention relates to an undervoltage-overvoltage protection device and method, in particular to a device and method for dual protection of undervoltage and overvoltage using a single tripping coil. the

Background technique

Generally speaking, the voltage on the power supply line is not a constant value, and it may fluctuate correspondingly due to the change of the load. Once this voltage fluctuation (such as undervoltage or overvoltage) on the power supply line exceeds the range that the electrical equipment can withstand, it will have an adverse effect on the electrical equipment, or even cause damage to the electrical equipment. Therefore, undervoltage protection or overvoltage protection devices are usually used to ensure that the electrical equipment is used in a normal power supply state. the

Undervoltage protection generally means that when the voltage of the power supply line is lower than a predetermined threshold (for example, lower than 80% of the nominal voltage), the protection device automatically cuts off the power supply line, and when the line voltage returns to the normal range, the protection device can be activated again. Manual recovery. Relatively speaking, overvoltage protection means that when the line voltage exceeds a predetermined value (for example, 10% higher than the nominal voltage), in order to prevent damage to the electrical equipment, the protection device also automatically cuts off the line, and when the line voltage returns to normal It can be restored manually. the

The current undervoltage-overvoltage protection devices on the market mainly use two separate tripping coils to respectively realize undervoltage and overvoltage detection and protection actions. FIG. 1 exemplarily shows a schematic diagram of a conventional undervoltage-overvoltage protection device 100 . As shown in FIG. 1 , the power supply lines L (live line) and N (neutral line) are used to provide electric energy to the electrical equipment 150 . The protection device 100 is arranged on the electrical equipment side, and includes two tripping coils 110 and 120 and an overvoltage detection device 140 . These two tripping coils are used to perform tripping action when undervoltage or overvoltage is detected respectively. The tripping action of the tripping coils 110 and 120 further drives the circuit breaker 130 in a mechanical transmission manner to disconnect the electrical connection of the power supply line to the electrical device 150 . the

Specifically, in FIG. 1 , both ends of the trip coil 110 are connected to lines L and N. As shown in FIG. When the line voltage V is lower than a predetermined threshold Vmin (ie, undervoltage), the push rod in the tripping coil 110 is at position 2, ie, in a tripped state, thereby making the circuit breakers on lines L and N in an open state. When the line voltage V rises to a normal range, the push rod in the tripping coil 110 changes from position 2 to position 1, so that the circuit breaker 130 is closed and the line is turned on. The trip coil 120 is connected to an overvoltage detection circuit 140 for detecting whether the line voltage is overvoltage. When the overvoltage detection circuit 140 detects that the line voltage V is normal, the push rod in the tripping coil 120 is at position 1, so that the circuit breaker 130 remains closed and the power supply line is turned on. When the overvoltage detection circuit 140 detects that the line voltage V exceeds a predetermined threshold Vmax, it outputs an overvoltage protection trigger signal, so that the push rod in the tripping coil 120 changes from position 1 to position 2, that is, enters the tripping state, This in turn causes circuit breakers 130 on lines L and N to disconnect the power supply. the

Adopting the structure shown in Figure 1 can realize double protection of undervoltage and overvoltage. However, it can be seen from FIG. 1 that this undervoltage-overvoltage protection device requires two independent tripping coils to realize undervoltage and overvoltage protection respectively. However, due to the characteristics of its mechanical structure, each tripping coil is relatively large in size and high in cost, especially compared with electronic components. This shortcoming obviously cannot meet the miniaturization and low-cost requirements of the current protection device. Therefore, the existing undervoltage-overvoltage protection device needs to be further improved. the

Contents of the invention

An object of the present invention is to provide a small, low-cost undervoltage-overvoltage protection device and method. For this reason, the present invention proposes a device and method for realizing undervoltage-overvoltage dual protection by using a single tripping coil. Because the undervoltage-overvoltage protection device only includes one tripping coil, it is obviously superior to the existing undervoltage-overvoltage protection device with double tripping coils in terms of volume and cost. the

In order to achieve the above object, the undervoltage-overvoltage protection device proposed by the present invention includes: a tripping coil connected to the power supply line for tripping when the line is undervoltage; an overvoltage detection circuit for detecting When the line voltage exceeds a predetermined threshold, an overvoltage protection trigger signal is generated; the control device is configured to respond to the overvoltage protection trigger signal to cause undervoltage at both ends of the trip coil, so that the trip coil performs a trip action . By adopting this protection device, only one tripping coil can be used to realize the double protection of undervoltage and overvoltage, thereby reducing the cost and greatly reducing the size of the protection device.

According to one aspect of the present invention, the control device is a switch device connected in parallel with the trip coil, and the switch device is closed in response to the overvoltage protection trigger signal. Optionally, the switching device may be a transistor, a field effect transistor, a thyristor or a valve, or any other controllable switching device. the

According to yet another aspect of the invention, the undervoltage-overvoltage protection device preferably requires electrical isolation between the switching device and the overvoltage detection circuit. The advantage of this is that it can avoid undesired malfunction or damage caused when the power supply of the trip coil is different from the power supply of the overvoltage detection circuit. Preferably, optocouplers or relays are used to achieve electrical isolation. the

According to another aspect of the present invention, the switching means for short-circuiting the trip coil in response to the overvoltage protection trigger signal may include two transistors. The two triodes are always one conducting and the other being closed during operation, thereby ensuring that the tripping coil is only forcibly short-circuited by the switching device in the event of an overvoltage. In addition, the overvoltage detection circuit may include a comparator, a voltage detection chip, or any other device capable of determining overvoltage. the

The invention also proposes an undervoltage-overvoltage protection method. The method includes: using a tripping coil, the tripping coil is in a tripping state when the power supply line is undervoltage; detecting whether the line voltage exceeds a predetermined threshold; when detecting that the line voltage exceeds the predetermined threshold, causing the The tripping coil performs a tripping action due to undervoltage at both ends. the

Preferably, the method also makes the two ends of the trip coil undervoltage by short-circuiting the two ends of the trip coil. More preferably, the method further comprises electrically isolating said detection operation and said operation of causing undervoltage across said tripping coil from each other. The galvanic isolation is achieved, for example, using optocouplers or relays. the

Description of drawings

The following drawings are only intended to illustrate and explain the present invention schematically, and do not limit the scope of the present invention. in,

Fig. 1 shows the schematic diagram of existing undervoltage-overvoltage protection device;

Fig. 2 exemplarily shows a schematic structural view of an undervoltage-overvoltage protection device according to an embodiment of the present invention;

Fig. 3 shows the circuit schematic diagram of the undervoltage-overvoltage protection device according to one embodiment of the present invention;

FIG. 4 shows a schematic circuit diagram of an undervoltage-overvoltage protection device according to yet another embodiment of the present invention. the

Explanation of reference signs:

100 Existing undervoltage-overvoltage protection device

110 tripping coil

120 tripping coil

130 circuit breaker

140 Overvoltage detection circuit

150 electrical installations

130 circuit breaker

200 Undervoltage-overvoltage protection device

240 overvoltage detection circuit

250 Controls

300 Undervoltage-overvoltage protection device

340 overvoltage detection circuit

350 Switchgear

360 optocoupler

400 Undervoltage-overvoltage protection device

440 overvoltage detection circuit

450 Switchgear

460 relay circuit

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described with reference to the accompanying drawings. the

FIG. 2 exemplarily shows a schematic diagram of an undervoltage-overvoltage protection device 200 according to an embodiment of the present invention. As shown in FIG. 2 , a protection device 200 according to an embodiment of the present invention includes a single tripping coil 210, an overvoltage detection circuit 240 and a control device 230. When the tripping coil 210 of the protection device 200 performs a tripping action, it can drive the circuit breaker 130 to disconnect or conduct the power supply connection. Only one trip coil 210 is used in the protection device 200 to control the circuit breakers 130 on lines L and N (eg the main contacts of the miniature circuit breaker MCB). When an undervoltage occurs, the tripping coil 210 performs a tripping action in a manner similar to that of the tripping coil 110 in FIG. 1 and causes the circuit breaker 130 to disconnect the power supply. When an overvoltage occurs, the tripping coil 210 is tripped due to undervoltage driven by the overvoltage detection circuit 240 and the control device 250 , so that the circuit breaker 130 is disconnected from the power supply. In this way, only one tripping coil can be used in the present invention to realize double protection of undervoltage and overvoltage. the

Specifically, in FIG. 2 , both ends of the tripping coil 210 are connected to the lines L and N on the electrical equipment side. When the line voltage V, that is, the voltage across the trip coil 210, is lower than a predetermined threshold Vmin, the push rod in the trip coil 210 is in position 2, the tripped state, thereby causing the circuit breaker 130 on the line to remain open , the power supply is interrupted. When the line voltage V (the voltage across the trip coil 210 ) reaches or exceeds the predetermined threshold Vmin, the push rod in the trip coil 210 changes to position 1, so that the circuit breaker 130 on the line is closed and the power supply line is turned on. If the line voltage V drops below Vmin again after the line is turned on, the tripping coil 210 enters the tripping state as described above, thereby realizing undervoltage protection. the

For the overvoltage condition, the overvoltage detection circuit 240 in FIG. 2 detects whether the line voltage V exceeds a predetermined threshold Vmax. If it exceeds, the overvoltage detection circuit 240 outputs an overvoltage protection trigger signal to the controller 250 . In response to this trigger signal, the controller 250 causes the voltage across the trip coil 210 to drop below the threshold Vmin (ie, to an undervoltage state), thereby causing the trip coil 210 to trip due to the undervoltage. This tripping action of the tripping coil 210 in turn causes the circuit breaker 130 on the line to open, thereby realizing overvoltage protection. the

Using the protection device 200 shown in FIG. 2 can realize the dual function of undervoltage-overvoltage protection through only a single tripping coil 210, so that the size and cost of the protection device 200 can be reduced to meet the current miniaturization requirements. need. the

In FIG. 2, the overvoltage detection circuit 240 and the controller 250 can be realized by various devices. For example, the control device 250 can be a switch device, which can be closed in response to the overvoltage protection trigger signal of the overvoltage detection circuit 240 , that is, the two ends of the tripping coil 210 enter an undervoltage state due to a short circuit. Optionally, the control device 240 may also reduce the voltage across the tripping coil 210 to below Vmin through a triggerable voltage conversion circuit (such as a transformer device). In addition, the control device 250 can also be realized by using other triggerable step-down circuits well known to those skilled in the art. the

FIG. 3 shows a circuit diagram of an undervoltage-overvoltage protection device 300 according to an embodiment of the present invention. In the protection device 300, the tripping coil 210 is a low-voltage coil, the control device 250 is implemented as a switch device 350, and the overvoltage detection circuit 340 is implemented as a voltage detection chip U3. The switch device 350 is realized by a combination of transistors Q1 and Q2, for example. In addition, an isolation device 360 such as an optocoupler is added between the overvoltage detection circuit 340 and the switching device 350 to provide electrical isolation between the undervoltage protection and the overvoltage protection. the

Specifically, as shown in FIG. 3, on one branch, the rectified (U1) line voltage V1 is applied to both ends of the trip coil L1 (210). When the line voltage V1 is lower than a threshold voltage Vmin, the tripping coil L1 is in a tripped state, and then prompts the circuit breaker 130 (not shown in FIG. 3 ) to be turned off, realizing undervoltage protection. the

On the other branch in Fig. 3, the line voltage V2 after rectification (U4) is applied to the divider resistors R3-R6. The voltage detection chip U3 (optionally, it may be a comparator) obtains the divided voltage V3 from the resistor R6, and compares it with a threshold voltage Vmax. If the comparison result is that V3 is greater than Vmax, U3 outputs an overvoltage protection trigger signal at its output terminal 4, such as a high level. This high-level signal is applied to the base of the transistor Q3 connected in series with the light-emitting diode in the optocoupler U5, so that Q3 is turned on. The conduction of Q3 causes the light-emitting diode in U5 to work, and the corresponding photosensitive semiconductor tube to conduct, and then the output terminal ( V4 ) of the optocoupler U5 outputs a low level to the switch device 350 . On the contrary, if the comparison result is that V3 is smaller than Vmax, that is, there is no overvoltage, U3 outputs a low level at its output terminal 4 . This low level makes Q3 cut off, which in turn causes the optocoupler not to work, that is, the photosensitive semiconductor tube of optocoupler U5 is turned off, and V4 is high. Thus, the overvoltage protection trigger signal generated by the overvoltage detection circuit is transmitted to the switch device 350 in an electrically isolated manner through the optocoupler U5. the

In the example of FIG. 3, the switching device 350 is composed of Q1 and Q2. The base of Q1 is connected to the output terminal V4 of the optocoupler U5, the base of Q2 is connected to the collector of Q1 and connected to the line voltage V1 via the resistor R12. Therefore, when V4 is high (when no overvoltage occurs), Q1 is turned on and Q2 is turned off, that is, the tripping coil L1 works normally. When V4 is low (overvoltage protection triggers), Q1 is off and Q2 is on. At this time, due to the conduction of Q2, the two ends of the trip coil L1 are forcibly short-circuited, so that the trip coil L1 trips due to undervoltage, and then prompts the circuit breaker 130 to disconnect the power supply connection to realize overvoltage protection. the

In the example shown in FIG. 3 , the switch device 350 is realized by a triode. However, those skilled in the art should understand that the switch device can also be realized by using, for example, field effect transistors, silicon controlled rectifiers, electronic tubes, relays and the like. Moreover, the optocoupler used for electrical isolation shown in FIG. 3 can also be replaced by other electrical isolation devices, such as magnetic couplers or relays. the

FIG. 4 schematically shows an example of using a relay as the electrical isolation device in FIG. 3 . Different from FIG. 3 , in FIG. 4 , electrical isolation is realized by a relay circuit 460 between the switching device 450 and the overvoltage detection circuit 440 . the

Specifically, on one branch, the rectified line voltage V1 is applied to both ends of the trip coil L1 (210). Similar to before, the tripping coil L1 performs a tripping action when V1 is undervoltage, and then causes the circuit breaker 220 to open. the

On the other branch, the rectified voltage V2 is added to the series branch of the voltage dividing resistors R2 and R3, so that the voltage detection chip U5 can obtain the divided voltage V3 from the resistor R2. The voltage detection chip U5 compares V3 with a predetermined threshold Vmax. If the comparison result is that V3 is less than Vmax, U5 outputs a low level, indicating that no overvoltage occurs. If the comparison result is that V3 is greater than Vmax, U5 outputs a high level, that is, an overvoltage protection trigger signal. the

At the same time, the rectified voltage V2 is applied to the series branch composed of resistors R4, R5 and Zener diode D10, so as to supply power to the relay circuit 460 from D10. The relay circuit 460 includes a relay K1 and a transistor Q1 connected in series with it, and the base of Q1 is connected to the output terminal of U5. When U5 outputs a low level, Q1 is turned off, so the branch where the relay K1 is located remains disconnected, the relay K1 does not work, and the switch device 450 remains disconnected. When U5 outputs a high level (overvoltage protection trigger signal), Q1 is turned on, so that relay K1 is energized and trigger switch device 450 is closed. That is to say, in response to the overvoltage protection trigger signal of the overvoltage detection circuit 440, the switch device 450, driven by the relay K1, causes the tripping coil 210 to trip due to a short circuit at both ends, and then the circuit breaker 130 is disconnected to realize the overvoltage Protect. the

In the example shown in FIG. 4 , the relay K1 acts as a galvanic isolation device between the overvoltage detection circuit 440 and the switching device 450 . However, those skilled in the art can understand that other devices known in the art (such as magnetic coupling, etc.) can also be used to achieve this electrical isolation. the

As shown in Figures 2-4, the protection devices 200, 300, and 400 proposed by the present invention are formed according to the following design idea, that is, a single tripping coil is used to make it in the tripping state when the power supply line is undervoltage; Whether it exceeds a predetermined threshold; when it is detected that the line voltage exceeds the predetermined threshold, an undervoltage is caused at both ends of the tripping coil, so that the tripping coil performs a tripping action. Preferably, the two ends of the trip coil are undervoltaged by short-circuiting the two ends of the trip coil. More preferably, the detection operation and the operation of causing an undervoltage across the trip coil are electrically isolated from each other. This galvanic isolation is achieved, for example, using optocouplers or relays. the

The above-mentioned design idea proposed by the present invention can ensure the dual protection of undervoltage and overvoltage under the condition that only a single tripping coil is applicable, so this design idea can reduce the volume of the undervoltage-overvoltage protection device, which is suitable for current The need for miniaturization. At the same time, the above-mentioned design idea is easy to realize, and can be realized only by low-cost electronic components, thereby reducing the equipment cost while reducing the volume. the

It should be understood that although this description is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description of the description is only for clarity, and those skilled in the art should take the description as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art. the

The above descriptions are only illustrative specific implementations of the present invention, and are not intended to limit the scope of the present invention. Any equivalent changes, modifications and combinations made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the protection scope of the present invention. the

Claims (15)

1. An undervoltage-overvoltage protection device (200, 300, 400) comprising:

the single trip coil (210) is connected to the power supply line and is in a trip state when the line is under-voltage;

an overvoltage detection circuit (240, 340, 440) for generating an overvoltage protection trigger signal upon detecting that the line voltage exceeds a predetermined threshold;

and the control device (250, 350, 450) is used for responding to the overvoltage protection trigger signal to enable the two ends of the trip coil to be undervoltage, so that the trip coil executes tripping action.

2. The undervoltage-overvoltage protection device of claim 1, wherein said control device (250, 350, 450) is a switching device (350, 450) connected across said trip coil and closing in response to said overvoltage protection trigger signal.

3. The undervoltage-overvoltage protection device of claim 2, wherein the switching device (350, 450) is electrically isolated from the overvoltage detection circuit (340, 440).

4. The protection device of claim 3, wherein the overvoltage detection circuit (440) is electrically isolated from the switching device (450) by a relay (K1).

5. The protection device of claim 4, wherein the relay (K1) drives the switching device (450) closed in response to the over-voltage protection trigger signal.

6. The protection device of claim 5 wherein said relay (K1) is connected in series with a transistor (Q1), said transistor Q1 being conductive in response to said over-voltage protection trigger signal to drive said relay into operation.

7. A protection device according to claim 3, wherein said overvoltage detection circuit (340) is electrically isolated from said switching device (350) by an opto-coupler (360).

8. The protection device of any of claims 1-7, wherein the switching device (350, 450) comprises any of a triode, a field effect transistor, a thyristor, a valve, and a relay.

9. The protection device of claim 8, wherein the switching device (350) comprises two transistors (Q1, Q2), a first transistor (Q1) having a base for receiving the over-voltage trigger signal, a second transistor (Q2) having a base connected to a collector of the first transistor and to a power supply via a resistor, and a collector and an emitter of the second transistor (Q2) being connected across the coil of the coil trip (210), respectively.

10. The protection device of claim 1, wherein the over-voltage detection circuit (340, 440) comprises a comparator or a voltage detection chip.

11. The protection device of claim 1, wherein the trip coil (210) is a low voltage coil.

12. A method of performing under-voltage-over-voltage protection, comprising:

using a single trip coil, wherein the trip coil is in a trip state when a power supply line is undervoltage;

detecting whether the line voltage exceeds a predetermined threshold;

and when the line voltage is detected to exceed the preset threshold value, the two ends of the tripping coil are under-voltage, so that the tripping action is executed.

13. The method of claim 12, wherein the under-voltage across the trip coil is caused by shorting across the trip coil.

14. The method of claim 12, further comprising electrically isolating said detecting operation and said undervoltage-causing operation across said trip coil from each other.

15. The method of claim 14, wherein the electrical isolation is achieved using an optocoupler or a relay.

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