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Title:
ELECTRICAL AUTOMATIC TRANSFER SWITCH HAVING THERMAL OVERLOAD PROTECTION
Document Type and Number:
WIPO Patent Application WO/2007/035017
Kind Code:
A1
Abstract:
An electrical automatic transfer switch (100) having a thermal overload protection function is disclosed. The electrical automatic transfer switch (100) includes an electrical switch unit (30) formed of a semiconductor switching device, and an assistant switch unit (110) formed of a non-heating device connected with the same inparallel. A switching operation for a switch between a constant power and an emergency power is performed when the phase of a power voltage is zero using a semiconductor switching device (TR30). The continuous supply of power voltage is performed through an assistant switch unit (110). A heating phenomenon does not occur at a semiconductor switch device (TR30) by power supplied to the load after a switching operation is performed. A radiating plate is not needed, do that a small size system can be fabricated.

Inventors:
YOO KI-HYUN (KR)
Application Number:
KR2005/003853
Publication Date:
March 29, 2007
Filing Date:
November 14, 2005
Export Citation:
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Assignee:
HANKWANG ELECTRIC CO LTD (KR)
YOO KI-HYUN (KR)
International Classes:
H02H3/00; H02H5/00
Foreign References:
US20050057878A12005-03-17
US20040233602A12004-11-25
US20040172204A12004-09-02
US20030117761A12003-06-26
US20020117900A12002-08-29
US5784240A1998-07-21
US5739594A1998-04-14
US4405867A1983-09-20
Attorney, Agent or Firm:
LEE, Bong-Jin (642-1 Yeoksam 1-dong Gangnam-gu, Seoul 135-910, KR)
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Claims:

Claims

[1] An electrical automatic transfer switch having a thermal overload protection, comprising: a first rectifier which receives and rectifies a constant power and outputs a first power voltage Vl ; a second rectifier which receives and rectifies an emergency power and outputs a second power voltage V2; an internal voltage generator which receives the first and second power voltages and generates an internal operation power; a controller which detects whether a constant power has an error or not and outputs a first power voltage to a load when the constant power is normal, and outputs a second power voltage to the load when the constant power has an error; an electrical switch unit which performs a switching operation so that either a first power voltage or a second power voltage is supplied to a load in accordance with a control of the controller, and which performs a switching operation when the phases of the first and second power voltages is a zero point; and an assistant switch unit which includes a non-heating switching device designed to perform a switching operation in cooperation with the electrical switch unit so that either a first power voltage or a second power voltage is supplied to a load in accordance with a control of the controller, whereby the power supplied to the load is supplied through the electrical switch unit and then is supplied through the assistant switch unit after a certain time period.

[2] The switch of claim 1, wherein said electrical switch unit includes: a first switch unit which is connected between a first power voltage and a load and performs a phase-based switching control and includes four first switching modules which are switched at a point in which the phase of the first power voltage is zero; a first switch driving unit which drives a first switching module in accordance with a control of the controller; a second switch unit which is connected between a second power voltage and a load and includes four second switching modules which perform a switching operation at a point in which the phase of the second power voltage is zero; and a second switch driving unit which drives the second switching modules in accordance with a control of the controller.

[3] The switch of claim 2, wherein said assistant switch unit includes: a first assistant switch unit which includes four first latch modules connected with the four first assistant modules of the first switch unit in parallel; and

a second assistant switch unit which includes four second latch relay modules connected with four the four second switching modules of the second switch unit in parallel.

[4] The switch of claim 1, wherein when the assistant switch unit is turned on, it is turned on with a certain time difference interval as compared to the electrical switch unit, and when the assistant switch unit is turned off, it is first turned off with a certain time difference interval as compared to the electrical switch unit.

Description:

Description

ELECTRICAL AUTOMATIC TRANSFER SWITCH HAVING THERMAL OVERLOAD PROTECTION

Technical Field

[1] The present invention relates to an electrical automatic transfer switch (ATS), and in particular to an electrical automatic transfer switch having a thermal overload protection function capable of preventing a thermal overload of a semiconductor switching device used at an electrical switch unit for a switching transfer operation. Background Art

[2] An automatic transfer switch is a physical device designed so as to automatically transfer at least one load from a power to another power. As shown in Figure 1, an automatic transfer switch 2 is designed to supply a power from a constant power to a load 4 in the normal mode. When a constant power does not supply due to a failure or error, the automatic transfer switch 2 automatically transfers so as to supply a power from an emergency power to a load. Here, the constant power represents a commercial power, and the emergency power represents a common generation power or an emergency battery power.

[3]

Disclosure of Invention Technical Problem

[4] The automatic transfer switch has adapted a mechanical type. With the above mechanical type, it is impossible to enhance a transfer speed up to a desired speed due to a physical limit of a mechanical switch structure. In case of a mechanical type, a machine sound and an abrasion problem occur. In a worse case, a contact point may be melted.

[5] In addition, the loads may be damaged owing to a noise or an arc discharge which occurs during a transferring operation. In particular, a critical erroneous operation or critical damage may occur owing to a noise or arc discharge based on a load type. For example, in case of an automated or unmanned system, a worker may die due to an erroneous operation in a worse case. A defective product may be produced due to an erroneous operation of a controller which performs a numeric control at an automated fabrication line.

[6] The above problems occur due to a transfer operation irrespective of a phase of an input power. In order to overcome the above-described conventional problems, the applicant of the present invention filed an electrical automatic transfer switch with a Korean patent application number 10-2005-0002211 on January 10, 2005. The above

electrical automatic transfer switch is designed to transfer power at a point where a phase of an input power becomes zero during a transfer operation of an input power, so that a noise or arc discharge are inhibited, and a damage of a load is prevented.

[7] In addition, a semiconductor switching device, which has been used at an electrical automatic transfer switch, produces a heat during a power supply. As a semiconductor switching device generally used at an electrical automatic transfer switch, there is a triac. Since a triac is structurally constructed in such a manner that an anode and a cathode are formed with a PN junction of a five-layer structure, a lot of junction heat occurs due to a contact resistance at a junction portion. Here, a junction heat generated is l~2W per lA.

[8] A radiating plate should be used so as to cool heat generated at a semiconductor switching device. In case that a radiating plate is small or a heat exchange operation is not performed well, it is needed to perform ventilation by using a fan.

[9] However, an electrical automatic transfer switch is engaged at a power distribution panel, which is constructed in a sealed structure due to a physical characteristic of a power distribution panel, so that there is a problem for constructing a ventilation port or the like. Technical Solution

[10] Accordingly, it is an object of the present invention to provide an electrical automatic transfer switch which is capable of effectively preventing a heat generation of a semiconductor switching device adapted at an electrical automatic transfer switch.

[11] In order to achieve the above objects, there is provided an electrical automatic transfer switch having a thermal overload protection comprising a first rectifier which receives and rectifies a constant power and outputs a first power voltage Vl; a second rectifier which receives and rectifies an emergency power and outputs a second power voltage V2; an internal voltage generator which receives the first and second power voltages and generates an internal operation power; a controller which detects whether a constant power has an error or not and outputs a first power voltage to a load when the constant power is normal, and outputs a second power voltage to the load when the constant power has an error; an electrical switch unit which performs a switching operation so that either a first power voltage or a second power voltage is supplied to a load in accordance with a control of the controller, and which performs a switching operation when the phases of the first and second power voltages is a zero point; and an assistant switch unit which includes a non-heating switching device designed to perform a switching operation in cooperation with the electrical switch unit so that either a first power voltage or a second power voltage is supplied to a load in accordance with a control of the controller, whereby the power supplied to the load is

supplied through the electrical switch unit and then is supplied through the assistant switch unit after a certain time period.

[12] In the present invention, the electrical switch unit includes a first switch unit which is connected between a first power voltage and a load and performs a phase-based switching control and includes four first switching modules which are switched at a point in which the phase of the first power voltage is zero; a first switch driving unit which drives a first switching module in accordance with a control of the controller; a second switch unit which is connected between a second power voltage and a load and includes four second switching modules which perform a switching operation at a point in which the phase of the second power voltage is zero; and a second switch driving unit which drives the second switching modules in accordance with a control of the controller.

[13] In the present invention, the assistant switch unit includes a first assistant switch unit which includes four first latch modules connected with the four first assistant modules of the first switch unit in parallel; and a second assistant switch unit which includes four second latch relay modules connected with four the four second switching modules of the second switch unit in parallel.

[14] In the present invention, when the assistant switch unit is turned on, it is turned on with a certain time difference interval as compared to the electrical switch unit, and when the assistant switch unit is turned off, it is first turned off with a certain time difference interval as compared to the electrical switch unit.

[15]

Advantageous Effects

[16] As described above, the electrical automatic transfer switch 100 according to the present invention is switched so that the first power voltage Vl is supplied to the load 4 based on the power inputted from the constant power. If the constant power is not inputted or an over current occurs due to a certain reason, the electrical automatic transfer switch 100 is switched so that the second power voltage V2 is supplied to the load 4 based on the power inputted from the emergency power. Here, since the electrical switch unit 30 performs a switching on and off operation at a point in which the phase of the power voltage is a zero point, noises or arc discharges do not occur. Since the power supplied to the load 4 during the power supply is supplied through a corresponding latch relay, the heating phenomenon due to the semiconductor device does not occur.

[17] According to the electrical automatic transfer switch according to the present invention, the switching operation is electrically performed between the powers, so that a faster power switching operation can be performed. In addition, since the

switching operation occurs when the phase of the power voltage is a zero point, noises or arc discharges does not occur in the present invention. The power supplied to the load after the start of the switching operation is supplied through a corresponding latch relay, so that a heating problem does not occur by the semiconductor switching device. Therefore, a radiating plate is not needed in the present invention. Since the radiating plate is not used in the present invention, a small compact size system can be fabricated.

[18] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims. Brief Description of the Drawings

[19] Figure 1 is a block diagram illustrating an electrical connection structure of a conventional automatic transfer switch;

[20] Figure 2 is a circuit block diagram illustrating an electrical automatic transfer switch having a thermal overload protection function according to the present invention;

[21] Figure 3 is a view illustrating a construction of an electrical switch unit and an assistant switch unit of Figure 2; and

[22] Figures 4 and 5 are flow charts of a switching operation of an electrical switch unit and an assistant switch unit according to the present invention.

[23]

Best Mode for Carrying Out the Invention

[24] The preferred embodiments of the electrical automatic transfer switch having a thermal overload protection function according to the present invention will be described with reference to the accompanying drawings.

[25] Figure 2 is a circuit block diagram illustrating an electrical automatic transfer switch having a thermal overload protection function according to the present invention. As shown therein, an electrical automatic transfer switch 100 includes a first rectifier 10, a second rectifier 13, an internal power generator 20, an electrical switch unit 30, a controller 50, and an assistant switch part 110.

[26] A first connector 12 is connected with an input terminal of the first rectifier 10, and a second connector 15 is connected with an input terminal of the second rectifier 13 for receiving an emergency power. A first fuse 11 is connected between the input terminal

of the first rectifier 10 and the first connector 12, and a second fuse 14 is connected between the input terminal of the second rectifier and the second connector 15.

[27] Here, the first rectifier 10 receives and rectifies a constant power and outputs a first power voltage Vl to the internal power generator 20, the electrical switch unit 30 and the assistant switch unit 110, respectively. The second rectifier 13 receives and rectifies an emergency power and outputs a first power voltage V2 to the internal power generator 20, the electrical switch unit 30 and the assistant switch unit 110, respectively. The internal power generator 20 receives either a first power voltage Vl or a second power voltage V2 for thereby generating an internal operation power Vcc.

[28] The electrical switch unit 30 and the assistant switch unit 110 perform a switching operation so that either a first power voltage Vl or a second power voltage V2 is supplied to a load 4 in accordance with a control of the controller 50. In the switching operation, the electrical switch unit 30 performs a switching operation when the phases of the first and second power voltages Vl and V2 are zero.

[29] The assistant switch unit 110 operates in cooperation with the electrical switch unit

30. The power is supplied through the electrical switch unit 30 in a switching operation performed for a power supply. Next, the power is supplied to the load 4 through the assistant switch unit 110. When the power is supplied to the load 4 through the assistant switch unit 110, the power supply through the electrical switch unit 30 stops. So, the semiconductor switch device installed at the electrical switch unit 30 is not heated.

[30] Here, the controller 50 is designed so as to detect whether a constant power has an error or not and to control so that the first power voltage Vl is outputted to the load 4 when the constant power is normal. When the constant power has an error, a switching operation of the electrical switch unit 30 is performed so that the second power voltage V2 is supplied to the load. First and second photo couplers 16 and 17 are connected between the output terminals of the first and second rectifiers 10 and 13 and the controller 50, respectively. The controller 50 detects an output state of the first and second power voltages Vl and V2 through the first and second photo couplers 16 and 17.

[31] The electrical automatic transfer switch 100 may further include an over current detector 40 and an assistant contact unit 80. The over current detector 40 detects an over current state of a power voltage inputted from the electrical switch unit 30 into the load 4. When an over current is detected, an over current detection signal is inputted into the controller 50. The controller 50 controls a switching operation of the electrical switch unit 30 in response to an over current detection signal inputted, so that a power voltage inputted into the load 4 is switched. The assistant contact unit 80 includes first and second assistant contact points 82 and 84. Other units may be connected with the

first and second assistant contact points 83 and 84 when needed, so that they can cooperate based on a switching operation of the electrical switch unit 30.

[32] In addition, the electrical automatic transfer switch 100 includes a front panel 60 having an input unit 62, a state indication unit 64, and a state value indication unit 66. The input unit 62 is connected with the controller 50 and comprises a plurality of input switches for operating the electrical automatic transfer switch 100. The state value indication unit 64 is controlled by the controller 50 and indicates the state of the electrical automatic transfer switch 100 in numerals or characters. The state indication unit 66 indicates the operation state of the electrical automatic transfer switch 100 in a blinking method. The detailed operation of the above element is described in the Korean patent application No. 10-2005-0002211 filed on January 10, 2005.

[33] Figure 3 is a view illustrating a construction of an electrical switch unit and an assistant switch unit of Figure 2. As shown therein, the electrical switch unit 30 includes a first switch unit 31, a second switch unit 35, a first switch driving unit 33 and a second switch driving unit 37. Here, the first switch unit 31 is driven by the first switch driving unit 33 and performs a switching operation so that the first power voltage Vl is inputted into the load 4 or the input of the same is disconnected. The second switch unit 35 is driven by the second switch driving unit 37 and performs a switching operation so that the second power voltage V2 is inputted into the load 4 or the input of the same is disconnected.

[34] The first switch unit 31 is connected between the first power voltage Vl and the load 4 based on either a series connection or a parallel connection. The first switch unit 31 includes four first switching modules 32a, 32b, 32c and 32d, which are adapted to perform a switching control by the phases. The second switch unit 35 is connected between the second power voltage V2 and the load 4 based on either a series connection or a parallel connection. The second switch unit 35 includes four second switching modules 36a, 36b, 36c and 36d, which are adapted to perform a switching control by the phases.

[35] Each module of the first switching modules 32a, 32b, 32c and 32d is formed of a semiconductor switching device TR30, a photo coupler PC30 and a plurality of resistors R30, R31 and R32. Each module of the second switching modules 36a, 36b, 36c and 36d is formed of a semiconductor switching device TR35, a photo coupler PC35 and a plurality of resistors R35, R36 and R37. Here, the semiconductor switching devices TR30 and TR35 are preferably formed of a triac. The photo couplers PC30 and PC35 are preferably formed of a photo triac.

[36] The semiconductor switching device TR30 connected at each of the first switching modules 32a, 32b, 32c and 32d is connected between the first power voltage Vl and the load 4. In the photo coupler PC30, an anode terminal of the input terminal is

connected with the internal operation power Vcc, and a cathode terminal is connected with the first switch driving unit 33. An emitter terminal of the output terminal is connected with the first power voltage Vl, and a collector terminal is connected with a gate terminal of the semiconductor switching device TR30. With the above construction, the phase of the first power voltage Vl operates ON/OFF at the zero point.

[37] The semiconductor switching device TR35 connected at each of the second switching modules 36a, 36b, 36c and 36d is connected between the second power voltage V2 and the load 4. In the photo coupler PC35, an anode terminal of the input terminal is connected with the internal operation power Vcc, and a cathode terminal is connected with the second switch driving unit 37. In addition, an emitter terminal of the output terminal is connected with the second power voltage V2, and a gate terminal is connected with a gate terminal of the semiconductor switching device TR35. With the above construction, the phase of the second power voltage V2 operates ON/OFF at the zero point.

[38] The first switch driving unit 33 includes a transistor QA30 and resistors R33 and

R34, which are turned on and off in accordance with a first switching control signal from the controller 50. The first switch driving unit 33 drive the first switching modules 32a, 32b, 32c and 32d in response to a first switching control signal. The second switch driving unit 37 includes a transistor Q35 and resistors R38 and R39, which are turned on and off in response to a second switching control signal.

[39] The assistant switch unit 110 includes a first assistant switch unit 110a, and a second assistant switch unit 110b. The assistant switch unit 110 uses a non-heating switching device such as a latch relay, etc.

[40] The first assistant switch unit 110a includes four first latch relay modules RLlO,

RL20, RL30 and RL40 connected with the first switching modules 32a, 32b, 32c and 32d in parallel. The second assistant switch unit 110b includes four second latch relay modules RL12, RL22, RL32, and RL42 connected with the second switching modules 36a, 36b, 36c and 36d in parallel.

[41] The first and second latch relay modules RLlO, RL20, RL30 and RL40 and RL12,

RL22, RL32 and RL42 are formed of driving circuit for driving the latch relays, respectively. The latch relays are connected with corresponding semiconductor switching devices, respectively, and are turned on and off in response to first and second relay control signals inputted from the controller 50.

[42] The electrical switch unit 30 and the assistant switch unit 110 adapted to supply power to the load 4 operate in accordance with a control of the controller 50 as follows. The following switching operations are identically adapted to the operations of the first switching modules 32a, 32b, 32c and 32d, the second latch relay modules RLlO, RL20, RL30 and RL40, and the second switching modules 36a, 36b, 36c and

36d and the second latch relay modules RL12, RL22, RL32 and RL42.

[43] Figures 4 and 5 are flow charts for describing the switching operations of the electrical switch unit 30 and the assistant switch unit 110.

[44] As shown in Figure 4, the switching operation for supplying power to the load 4 is performed as follows. First, a corresponding semiconductor switching device of the electrical switch unit 30 is turned on in accordance with a control of the controller 50, so that a power is supplied to the load 4 in a step SlOO. The latch relay connected with a corresponding semiconductor switching device in parallel is turned on in a step SIlO. Power is supplied to the load through the latch relay. As the power is supplied through the latch relay, the semiconductor switching device is not heated. When the power is supplied to the load 4 through the latch relay, the semiconductor switching device is preferably turned on in a step S 120.

[45] Here, the semiconductor switching device and the latch relay are preferably turned on at a certain time difference between the semiconductor switching device and the latch relay. The controller 50 may be designed to output a control signal at a certain time difference interval or at the same time so as to control the semiconductor switching device and the latch relay. The latch relay is turned on after the semiconductor switching device is turned on because the latch relay is slower than the semiconductor switching device. Here, the time difference interval is about 40~50msec.

[46] As shown in Figure 5, the operation that the latch relay, which is currently supplying the power, is turned off so as to change the power supplied to the load will be described.

[47] First, a corresponding semiconductor switching device is turned on in a step S200.

[48] A reverse voltage is supplied to the turned-on latch relay, so that the latch relay is turned off in a step S210. The semiconductor switching device, which has been turned on, is turned off after about 40-50 ms in a step S220.

[49] The turning-on and turning-off operations of the semiconductor switching devices and the latch relays connected with the semiconductor switching devices are performed with certain time difference intervals so that the switching operations should be performed when the phase of the power voltage supplied to the load 4 is a zero point.

[50] In the transferring mode, the N-phase is first turned on, and then the power is turned on. In the turn-off mode, the power is first turned off, and the N-phase is turned off.

[51]

Industrial Applicability

[52] As described above, the electrical automatic transfer switch 100 according to the present invention is switched so that the first power voltage Vl is supplied to the load

4 based on the power inputted from the constant power. If the constant power is not inputted or an over current occurs due to a certain reason, the electrical automatic transfer switch 100 is switched so that the second power voltage V2 is supplied to the load 4 based on the power inputted from the emergency power. Here, since the electrical switch unit 30 performs a switching on and off operation at a point in which the phase of the power voltage is a zero point, noises or arc discharges do not occur. Since the power supplied to the load 4 during the power supply is supplied through a corresponding latch relay, the heating phenomenon due to the semiconductor device does not occur.

[53] According to the electrical automatic transfer switch according to the present invention, the switching operation is electrically performed between the powers, so that a faster power switching operation can be performed. In addition, since the switching operation occurs when the phase of the power voltage is a zero point, noises or arc discharges does not occur in the present invention. The power supplied to the load after the start of the switching operation is supplied through a corresponding latch relay, so that a heating problem does not occur by the semiconductor switching device. Therefore, a radiating plate is not needed in the present invention. Since the radiating plate is not used in the present invention, a small compact size system can be fabricated.

[54] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

[55]