Abstract:
This invention is based on the contents of the U.S. Pat. No. 5,831,349 and Chinese Invention Patent ZL94112284.0, ZL94114032.6 as their follow-up invention. The invention involves the technical schemes of several linkage apparatuses of AC two-wire solid-state switches. All of the AC two-wire solid-state switches of the linkage apparatuses must be the non-contact ON-OFF in the main circuits of the AC two-wire solid-state switches of the said three patents. This invention is intended to combine several or multiple the AC two-wire solid-state switches into linkage apparatus so that all of the said switches have consistently-combined ON-OFF actions, so that the application range of the AC two-wire solid-state switches is expanded from the single-phase circuit to three-phase circuit, from the low-voltage power grid to the high-voltage power grid.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention is based on the contents of Chinese Invention Patent ZL94112284.0, ZL94114032.6 and the U.S. Pat. No. 5,831,349 as their follow-up invention. 
         [0002]    This invention involves the technical schemes of several linkage apparatuses of AC two-wire solid-state switches. All of the AC two-wire solid-state switches of the linkage apparatuses must be the non-contact ON-OFF in the main circuits of the AC two-wire solid-state switches of the said three patents. In other words, the AC two-wire solid-state switches in this specification specially refers to the AC two-wire solid-state switches of the said three patents which used the non-contact ON-OFF in main circuit. 
         [0003]    At present, no prior art of the linkage apparatus of AC two-wire solid-state switches exists. Please refer to the said three patents&#39; documents for detailed background technology of the AC two-wire solid-state switches. 
       SUMMARY OF THE INVENTION 
       [0004]    This invention is intended to combine several or multiple the AC two-wire solid-state switches into linkage apparatus so that all of the said switches have consistently-combined ON-OFF actions, so that the application range of the AC two-wire solid-state switches is expanded from the single-phase circuit to three-phase circuit, from the low-voltage power grid to the high-voltage power grid. 
         [0005]    As a AC two-wire solid-state switch (hereafter referred to as “unit”) has only two external terminals, the linkage that is combined by multi-units can be classified into following three types according to their basic structures: linkage with multi-units connected in series to increase the working voltage, linkage with multi-units connected in parallel to increase working current, and three-phase linkage apparatus. The linkage with multi-units connected in parallel will not be included in this invention, because the corresponding external terminals of the units are equipotential, the ON-OFF control signal can be transmitted directly between the units need not any isolation, so its structure is relatively simple. The invention therefore will only involve three-phase linkage apparatus and linkage with multi-units connected in series. 
         [0006]    In this invention, all units in the linkage apparatus can be classified into two kinds: a sole unit which sends out the ON-OFF control signal initially on its own (hereafter referred to as the mastering unit) and the other units which accept the ON-OFF control signal (hereafter referred to as the controlled unit). The mastering unit can be independent operation on the single-phase AC circuit and have all of the control functions of the linkage apparatus; while the controlled units should complete the ON or OFF action after receiving the ON-OFF control signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows the unit connecting circuit diagram of a preferred embodiment of the three-phase linkage apparatus of this invention. 
           [0008]      FIG. 2  to  FIG. 4  shows the unit connecting circuit diagrams of three preferred embodiments of the linkage apparatus with multi-units connected in series of this invention. 
           [0009]      FIG. 5  to  FIG. 6  shows the simplified unit connecting circuit diagram of two preferred embodiments of the three-phase high-voltage multi-units linkage apparatus of this invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The invention will be detailed description with reference to the drawings and the embodiments as shown in the following: 
         [0011]    In  FIG. 1 , A, B, and C are the three units, P 1 , P 2 , P 3  and P 4  are the four photocouplers. The three-phase linkage apparatus is mainly composed of the said three units and four photocouplers, wherein, B is the mastering unit, A and C are the controlled units. In the circuit diagram of  FIG. 1 , S is the three-phase power supply, while L is the three-phase load. The six external terminals of the three units are connected to the three-phase power supply and the three-phase load respectively. In  FIG. 1 , b 2  is the common reference node of the internal control circuit of the mastering unit B, b 1  is the output terminal of the internal control circuit of the mastering unit B. When there are output signal in the internal control circuit of the mastering unit B, the main circuit bidirectional switching (MCBS) module in the mastering unit B is ON, that is, the mastering unit B is ON, otherwise, the MCBS module in the mastering unit B is OFF, or the mastering unit B is OFF. The mastering unit B also provides the short-circuit protection function. When it happens short-circuit fault in the external circuit of the mastering unit B, the short-circuit fault output signal on the secondary winding of the current mutual inductor via the bridge rectifying circuit enters into the short-circuit fault signal input terminal of the control circuit in the mastering unit B, result in the output signal of the internal control circuit disappears and the MCBS module is OFF, that is, the mastering unit B is from ON into OFF. In  FIG. 1 , b 4  is the short-circuit fault signal input terminal of the internal control circuit of the mastering unit B, while b 3  is a suitable positive level node as compared with the common reference node b 2 . In  FIG. 1 , a 4  is the common reference node of the internal control circuit of the controlled unit A, a 3  is the short-circuit fault signal output terminal on the divider which is connected to the secondary winding of the current mutual inductor via the bridge rectifying circuit in the controlled unit A; when it happens the short-circuit fault in the external circuit of the controlled unit A, this output terminal should have enough level short-circuit fault output signal; a 1  is a suitable positive level node as compared with the common reference node a 4 , a 2  is the ON-OFF signal input terminal of the internal control circuit of the controlled unit A, when this terminal gets the suitable level signal, the MCBS module in the controlled unit A is ON, that is, the controlled unit A is ON, otherwise, the MCBS module in the controlled unit A is OFF, that is, the controlled unit A is OFF. In  FIG. 1 , c 4  is the common reference node of the internal control circuit of the controlled unit C, c 3  is the short-circuit fault signal output terminal on the divider which is connected to the secondary winding of the current mutual inductor via the bridge rectifying circuit in the controlled unit C, when it happens the short-circuit fault in the external circuit of the controlled unit C, this output terminal should have enough level short-circuit fault output signal; c 1  is a suitable positive level node as compared with the common reference node c 4 , c 2  is the ON-OFF signal input terminal of the internal control circuit of the controlled unit C, when this terminal gets the suitable level signal, the MCBS module in the controlled unit C is ON, that is, the controlled unit C is ON, otherwise, the MCBS module in the controlled unit C is OFF, that is, the controlled unit C is OFF. 
         [0012]    As for the embodiment of  FIG. 1 , b 1  and b 2  are connected respectively to the light emitting diodes (LEDs) in the photocouplers P 1  and P 2  though current-limiting resistor R, while the terminal a 1  and a 2  and the terminal c 1  and c 2  are connected respectively to the photoconductive transistors in the photocouplers P 1  and P 2 , so when the internal control circuit of the mastering unit B has the output signal and the mastering unit B is ON, the output signal of the internal control circuit of the mastering unit B on b 1  and b 2  causes the LEDs in the photocouplers P 1  and P 2  lightened and the photoconductive transistors in the photocouplers P 1  and P 2  present a low resistance state, and the suitable positive level on a 1  and c 1  can reach a 2  and c 2  through their respective photoconductive transistors, so that the ON-OFF signal input terminals (a 2  and c 2 ) of the internal control circuits of controlled units A and C can get a suitable level signal, and the MCBS modules of controlled units A and C are ON, that is, the controlled units A and C are ON. Otherwise, when there is no output signal in the internal control circuit of mastering unit B and the mastering unit B is OFF, the LEDs in photocoupler P 1  and P 2  can not lighten, and the photoconductive transistors in photocoupler P 1  and P 2  present a high resistance state, and the suitable positive level on a 1  and c 1  can not reach a 2  and c 2  through their respective photoconductive transistor, so that the ON-OFF signal input terminals of the internal control circuits of controlled units A and C can not get the signal, and the MCBS modules in the controlled units A and C are OFF, that is, the controlled units A and C are OFF. Since via the signal transmissions of the photocouplers P 1  and P 2 , the three units A, B and C can have consistently-combined ON-OFF actions and thus complete the linkage of the three-phase units. 
         [0013]    As for the embodiment in  FIG. 1 , it has short-circuit protection function apart from the three-phase units linkage function. The embodiment can also act as the three-phase solid-state short-circuit protector, or three-phase solid-state breaker, in other words, when the short-circuit fault happens on the external circuits of any of the three units, the three units A, B and C can have consistently-combined OFF actions. As the mastering unit B itself has short-circuit protection function, when the short-circuit fault happens in the external circuit of the mastering unit B, it can OFF itself, and can result in the units A and C are OFF through the above said ON-OFF linkage function. Terminals a 3  and a 4 , terminals c 3  and c 4  are connected respectively to the LEDs in the photocouplers P 3  and P 4  though the current-limiting resistor R, when the short-circuit fault happens in the external circuits of unit A and/or unit C, terminals a 3  and/or c 3  have enough level the short-circuit fault output signal, so that the LEDs in the photocouplers P 3  and/or P 4  lightened, and the photoconductive transistors in the photocouplers P 3  and/or P 4  presents a low resistance state; and then the suitable positive level on the terminal b 3  can reach the short-circuit fault signal input terminal b 4  in the mastering unit B through the photoconductive transistors in the photocouplers P 3  and or P 4 , so that the MCBS module in mastering unit B is from cut-in to cut-off and the mastering unit B is OFF, and also the controlled units A and C are OFF at the same time through the ON-OFF linkage function of the mastering unit B to the controlled units A and C. Thus it can be seen, as for the embodiment in  FIG. 1 , when the short-circuit fault happens in the external circuit of any of the three units A, B and C, the three units A, B and C can have consistently-combined OFF actions, thus it completes the three-phase solid-state short-circuit protection function. 
         [0014]      FIG. 2  is the first embodiment of the linkage apparatus with multi-units connected in series of this invention. In  FIG. 2 , there are five units, respectively D, E, F, G, and H, wherein, D is the mastering unit, the left are the controlled units; as each unit has only two external terminals, so when the five units are connected in series, a new two-wire circuit is realized that has only two external terminals (T 1  and T 2 ). In  FIG. 2 , there are four photocoupleres, respectively P 5 , P 6 , P 7  and P 8 , terminals d 1  and d 2  are the output terminals of the internal control circuit of the mastering unit D, d 1  and d 2  are connected to the four LEDs in the four photocouplers P 5 , P 6 , P 7  and P 8  through current-limiting resistance R; terminals e 1 , f 1 , g 1  and h 1  are the suitable positive level nodes as compared with respectively four common reference nodes of the internal control circuits of the controlled units E, F, G and H; e 2 , f 2 , g 2  and h 2  are respectively the ON-OFF signal input terminals of the internal control circuits of the controlled units E, F, G and H; terminals e 1  and e 2 , f 1  and f 2 , g 1  and g 2 , h 1  and h 2  are connected respectively to four photoconductive transistors in the four photocouplers P 5 , P 6 , P 7  and P 8 . 
         [0015]    As for the embodiment of  FIG. 2 , when the internal control circuit of the mastering unit D has the output signal, the MCBS module in the mastering unit D is ON, that is, the unit D is ON, and the output signal on the terminals d 1  and d 2  causes four LEDs in the photocouplers P 5 , P 6 , P 7  and P 8  lightened and four photoconductive transistors in the photocouplers P 5 , P 6 , P 7  and P 8  present a low resistance states; therefore the suitable positive level of the terminals e 1 , f 1 , g 1  and h 1  can reach the terminals e 2 , f 2 , g 2  and h 2  through corresponding photoconductive transistor, so that the ON-OFF signal input terminals e 2 , f 2 , g 2 , h 2  of the internal control circuits of the controlled units E, F, G, H get suitable level input signals at the same time, and the MCBS modules in the controlled units E, F, G and H are ON, that is, the controlled units E, F, G and H are ON. Otherwise, when there is no output signal in the internal control circuit of the mastering unit D, the MCBS module in the mastering unit D is OFF, that is, unit D is OFF, and there is no output signal on the terminals d 1  and d 2 , the four LEDs in the photocouplers P 5 , P 6 , P 7  and P 8  can not lighten, and four photoconductive transistors in photocouplers P 5 , P 6 , P 7  and P 8  present a high resistance state, and the suitable positive level of the terminals e 1 , f 1 , g 1  and h 1  can not reach the terminals e 2 , f 2 , g 2  and h 2  through corresponding photoconductive transistor, so that the ON-OFF signal input terminals of the internal control circuit of the controlled units E, F, G and H can not get the input signal, the MCBS modules in the controlled units E, F, G and H are OFF, that is, the controlled units E, F, G and H are OFF. Thus it can be seen, through signal transfer of the photocouplers P 5 , P 6 , P 7  and P 8 , the five units D, E, F, G and H connected in series can have consistently-combined ON-OFF actions and thus complete the linkage of the multi-units connected in series, which is heightened the working voltage. 
         [0016]      FIG. 3  is the second embodiment of the linkage apparatus with multi-units connected in series of this invention. In  FIG. 3 , there are five units, respectively J, K, M, N, and Q, wherein, J is the mastering unit, the left are the controlled units; as each unit has only two external terminals, so when the five units are connected in series, a new two-wire circuit is realized that has only two external terminals (T 3  and T 4 ). In  FIG. 3 , there are four photocouplers, respectively P 9 , P 10 , P 11  and P 12 , terminals j 1  and j 2  are the output terminals of the internal control circuit of the mastering unit J, j 1  and j 2  are connected to the LED in the photocoupler P 9  through current-limiting resistance R; terminals k 3  and k 4  are the output terminals of the internal control circuit of the controlled unit K, k 3  and k 4  are connected to the LED in the photocoupler P 10  through current-limiting resistance R; terminals m 3  and m 4  are the output terminals of the internal control circuit of the controlled unit M, m 3  and m 4  are connected to the LED in the photocoupler P 11  through current-limiting resistance R; terminals n 3  and n 4  are the output terminals of the internal control circuit of the controlled unit N, n 3  and n 4  are connected to the LED in the photocoupler P 12  through current-limiting resistance R; terminals k 2 , m 2 , n 2 , q 2  are the suitable positive level nodes as compared with respectively the common reference nodes of the internal control circuits of the controlled units K, M, N and Q; k 1 , m 1 , n 1  and q 1  are respectively the ON-OFF signal input terminals of the internal control circuits of the controlled units K, M, N and Q; terminals k 1  and k 2  are connected to the photoconductive transistor in the photocoupler P 9 , terminals m 1  and m 2  are connected to the photoconductive transistor in the photocoupler P 10 , terminals n 1  and n 2  are connected to the photoconductive transistor in the photocoupler P 11 , and terminals q 1  and q 2  are connected to the photoconductive transistor in the photocoupler P 12 . 
         [0017]    As for the embodiment of  FIG. 3 , when the internal control circuit of the mastering unit J has the output signal and the MCBS module in the mastering unit J is ON, that is, unit J is ON, what&#39;s more, the output signal on the terminals j 1  and j 2  causes the LED in the photocoupler P 9  lightened and the photoconductive transistor in the photocoupler P 9  presents a low resistance state; and the suitable positive level of the terminal k 2  can reach the terminal k 1  through the photoconductive transistor in the photocoupler P 9 , so that the ON-OFF signal input terminal k 1  of the internal control circuit of the controlled unit K have a suitable level signal, the output terminals k 3 , k 4  of the internal control circuit of the controlled unit K has the output signal, the MCBS module in the controlled unit K is ON, that is, the controlled unit K is ON; what&#39;s more, the output signal on the terminals k 3  and k 4  causes the LED in the photocoupler P 10  lightened this moment and the photoconductive transistor in the photocoupler P 10  presents a low resistance state; and the suitable positive level of the terminal m 2  can reach the terminal m 1  through the photoconductive transistor in the photocoupler P 10 , so that the ON-OFF signal input terminal m 1  of the internal control circuit of the controlled unit M get suitable level signal, the output terminals m 3 , m 4  of the internal control circuit of the controlled unit M has the output signal, the MCBS module in the controlled unit M is ON, that is, the controlled unit M is ON; furthermore, the output signal on the terminals m 3  and m 4  causes the LED in the photocoupler P 11  lightened this moment and the photoconductive transistor in the photocoupler P 11  presents a low resistance state; and the suitable positive level of the terminal n 2  can reach the terminal n 1  through the photoconductive transistor in the photocoupler P 11 , so that the ON-OFF signal input terminal n 1  of the internal control circuit of the controlled unit N get suitable level signal, the output terminals n 3 , n 4  of the internal control circuit of the controlled unit N has the output signal, the MCBS module in the controlled unit N is ON, that is, the controlled unit N is ON; at the same time, the output signal on the terminals n 3  and n 4  causes the LED in the photocoupler P 12  lightened and the photoconductive transistor in photocoupler P 12  presents a low resistance state; and the suitable positive level of the terminal q 2  can reach the terminal q 1  through the photoconductive transistor in the photocoupler P 12 , so that the ON-OFF signal input terminal q 1  of the internal control circuit of controlled unit Q have suitable level signal, the output terminals of the internal control circuit of the controlled unit Q have the output signal, the MCBS module in the controlled unit Q is ON, that is, the controlled unit N is ON; Otherwise, when there is no output signal in the internal control circuit of mastering unit J, and the MCBS module in the mastering unit J is OFF, that is, the unit J is OFF, and there is no output signal on the terminals j 1  and j 2 , the LED in the photocoupler P 9  can not lighten, and the photoconductive transistor in the photocoupler  9  presents a high resistance state, and the suitable positive level of the terminal k 2  can not reach the terminal k 1  through the photoconductive transistor in P 9 , so that the ON-OFF signal input terminal k 1  of the internal control circuit of the controlled unit K can not get the signal, the MCBS module in the controlled unit K is OFF, that is, the controlled Unit K is OFF; and then the LED in the photocoupler P 10  can not lighten, and the photoconductive transistor in the photocoupler  10  presents a high resistance state; and the suitable positive level of m 2  can not reach m 1  through the photoconductive transistor in P 10 , so that the ON-OFF signal input terminals m 1  of the internal control circuit of the controlled unit M can not get the signal, the MCBS module in the controlled unit M is OFF, that is, the controlled unit M is OFF; in the same way, the LEDs in the photocouplers P 11  and P 12  can not lighten, and the photoconductive transistors in the photocoupler P 11  and P 12  present a high resistance state, the controlled units N and Q are both OFF. Thus it can be seen, through signal transfer of the photocouplers P 9 , P 10 , P 11  and P 12 , the five units J, K, M, N and Q connected in series can have consistently-combined ON-OFF actions and thus complete the linkage of the multi-units connected in series, which is heightened the working voltage. 
         [0018]      FIG. 4  is the third embodiment of the linkage apparatus with multi-units connected in series of this invention. In the  FIG. 4 , there are five units, respectively U, V, W, X and Y, wherein, U is the mastering unit, the left are controlled units; as each unit has only two external terminals, so when the five units are connected in series, a new two-wire circuit is realized that has only two external terminals (T 5  and T 6 ). In  FIG. 4 , terminals u 1  and u 2  are the output terminals of the internal control circuit of the mastering unit U, the terminals u 1  and u 2  are connected to the light emitting module LE through the current-limiting resistance R; OP 1 , OP 2 , OP 3  and OP 4  are four fibers; PC 1 , PC 2 , PC 3  and PC 2  are four photoconductive transistors; terminals v 2 , w 2 , x 2 , and y 2  are the suitable positive level nodes as compared with respectively the common reference nodes of the internal control circuit of the controlled units V, W, X and Y; terminals v 1 , w 1 , x 1  and y 1  are respectively the ON-OFF signal input terminals of the internal control circuit of the controlled units V, W, X and Y; terminals v 1  and v 2  are connected to the photoconductive transistor PC 1 , terminals w 1  and w 2  are connected to the photoconductive transistor PC 2 , terminals x 1  and x 2  are connected to the photoconductive transistor PC 3 , while terminals y 1  and y 2  are connected to the photoconductive transistor PC 4 . 
         [0019]    As for the embodiment of  FIG. 4 , when the internal control circuit of the mastering unit U has output signal and the MCBS module in the mastering unit U is ON, that is, unit U is ON, what&#39;s more, the output signal of the terminals u 1  and u 2  causes the light emitting module LE lightened, and the light shines four photoconductive transistors PC 1 , PC 2 , PC 3  and PC 4  through light propagation of four fibers OP 1 , OP 2 , OP 3  and OP 4 , so that the four photoconductive transistors PC 1 , PC 2 , PC 3  and PC 4  present a low resistance states; and the suitable positive level of the terminals v 2 , w 2 , x 2 , and y 2  can reach the terminals v 1 , w 1 , x 1  and y 1  through the four photoconductive transistors PC 1 , PC 2 , PC 3  and PC 4 , therefore the ON-OFF signal input terminals v 1 , w 1 , x 1 , y 1  of the internal control circuits of controlled units V, W, X and Y can get suitable level input signal, the MCBS modules in the controlled units V, W, X and Y are ON, that is, the controlled units V, W, X and Y are ON; otherwise, when the internal control circuit of the mastering unit U has no output signal and the MCBS module in the mastering unit U is OFF, that is, unit U is OFF, what&#39;s more, there is no output signal on the terminals u 1  and u 2 , the light emitting module LE can not lighten and the four photoconductive transistors PC 1 , PC 2 , PC 3  and PC 4  present a high resistance states; and the suitable positive level of the terminals v 2 , w 2 , x 2 , and y 2  can not reach v 1 , w 1 , x 1  and y 1  through the four photoconductive transistors PC 1 , PC 2 , PC 3  and PC 4 , so that the ON-OFF signal input terminals v 1 , w 1 , x 1 , y 1  of the internal control circuits of the controlled units V, W, X and Y can not get the input signal, the MCBS modules in the controlled units V, W, X and Y are OFF, that is, the controlled units V, W, X and Y are OFF. Thus it can be seen, through signal transfer of the light emitting module LE and four fibers OP 1 , OP 2 , OP 3 , OP 4  and the four photoconductive transistors PC 1 , PC 2 , PC 3 , PC 4 , the five units J, K, M, N and Q connected in series can have consistently-combined ON-OFF actions and thus complete the linkage of the multi-units connected in series, which is heightened the working voltage. 
         [0020]      FIG. 5  is the first embodiment of three-phase high voltage multi-units linkage apparatus of this invention. In  FIG. 5 , due to the large number of the units and their related devices involved, simplified diagram will be adopted here for illustration. In  FIG. 5 , A 1 , A 2 , A 3  . . . to An, B 1 , B 2 , B 3  . . . to Bn, C 1 , C 2 , C 3  . . . to Cn are respectively made up of n units into the three linkage apparatuses with multi-units connected in series, S is the three-phase power supply, L is the three-phase load. As each of the three linkage apparatuses is a two-wire circuit apparatus which has only two external terminals, it is the same with the embodiment of  FIG. 1 , the six external terminals of the three linkage apparatuses are respectively connected to the three-phase power supply and three-phase load. As shown in the  FIG. 5 , the solid line and the arrow indicate the route and direction which transmit ON-OFF control signal through photoelectric coupling, while the dotted line and the arrow indicate the route and direction which transmit the short-circuit fault signal through photoelectric coupling. In  FIG. 5 , B 1  is the mastering unit, others are the controlled units. The transmission of the ON-OFF control signal from B 1  to A 1  and B 1  to C 1 , and the transmission of the short-circuit fault signal from A 1  to B 1  and C 1  to B 1 , they are the same with the embodiment of  FIG. 1 . The transmission of the ON-OFF control signal from B 1  to B 2 , B 7 , B 12 , B 17 , etc. is the same with the embodiment of  FIG. 4 , this is a way using the non-metal fibers to transmit signals between units with many units in between will not cause generally voltage breakdown. The transmission of the ON-OFF control signal from A 1  to A 2 , A 7 , A 12 , A 17 , etc. and C 1  to C 2 , C 7 , C 12 , C 17 , etc. also adopts the same method as used in the embodiment of  FIG. 4 . The left transmission of the ON-OFF control signals, for example, from A 2  to A 3 , A 4 , A 5 , etc., from B 7  to B 8 , B 9 , B 10 , B 11 , etc., from C 17  to C 18 , C 19 , C 20 , C 21 , etc., adopts the same method as used in the embodiment of  FIG. 2 . 
         [0021]    As for the embodiment of  FIG. 5 , the transmission of the ON-OFF control signal starts from the mastering unit B, reaches to all the other units along the solid line and arrow level by level to several levels, thereby consistently-combined ON-OFF actions are realized. When there is short-circuit fault on the external circuit of A 1  or C 1 , the short-circuit fault signal can be transmitted from A 1  or C 1  to B 1 , as B 1  itself has short-circuit protection function, thus when any a phase external circuit of the three-phase external circuits has short-circuit fault, all the units can be consistently-combined “OFF”, therefore, this embodiment has the three-phase high voltage solid-state short-circuit protection function. 
         [0022]      FIG. 6  is the second embodiment of three-phase high voltage multi-units linkage apparatus of this invention. There is only one difference of this embodiment from the embodiment of  FIG. 5 , that is, the transmission of the ON-OFF control signal of the last level, for example, from A 2  to A 3 , A 4 , A 5 , etc. from B 7  to B 8 , B 9 , B 10 , B 11 , etc. from C 17  to C 18 , C 19 , C 20 , C 21 , etc, adopts the same method as used in the embodiment of  FIG. 3 . As the signal is transmitted between two adjacent units, the voltage breakdown of the photocoupler will not occur. As for the others of the  FIG. 6 , it is the same with that of the  FIG. 5  please refer to  FIG. 5 .