Patent Publication Number: US-2023147732-A1

Title: Load test device and cap of load test device

Description:
TECHNICAL FIELD 
     The present invention relates to a load test device. 
     BACKGROUND ART 
     Conventionally, as in Patent Literature 1, a dry load test device that performs a load test for a generator has been proposed. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2010-25752 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     Since a high voltage current flows through a load test device, it is desirable to find any failure in any of the members constituting the load test device as early as possible. 
     Therefore, an object of the present invention is to provide a load test device and the like capable of finding a failure at an early stage. 
     Solution to Problem 
     A load test device according to the present invention includes: a resistor unit that includes a plurality of resistors that receive supplied power and a wall that holds opposite ends of each of the plurality of resistors; and an insulating cap that is attached to a portion of a terminal of the resistor that protrudes from the wall. 
     The cap is composed of a material that is deformed by heat. 
     When a temperature of the terminal becomes equal to or higher than a first temperature, the cap is deformed by the heat and detached from the terminal. 
     In a case where the nut is loose, the resistor may generate more heat than in a normal state as compared with a case where the nut is sufficiently fastened. 
     In a case where the resistor generates more heat than in a normal state, the cap is deformed by the heat and detached from the terminal. For this reason, for example, when the resistor generates more heat than in a normal state, it is possible to easily visually recognize a situation in which the resistor generates heat from the outside due to deformation of the cap and detachment of the cap from the terminal. 
     That is, it becomes possible to detect a failure of the load test device at an early stage. 
     The load test device may further include a cover that is attached to a frame holding the resistor unit and protects an exposed portion of the terminal of the resistor that protrudes from the wall. 
     The cover is composed of a transparent material or a translucent material. 
     By providing the cover, it is possible to prevent dust or the like from entering from the outside and adhering to the terminal or the like. 
     As the cover is composed of a transparent material, it becomes possible to visually recognize a region where the terminal is located inside the load test device from the outside. 
     The cap may include a tubular portion that covers the exposed portion of the terminal that protrudes from the wall, and a lid portion that is provided at one end portion of the tubular portion and faces a distal end of the terminal. 
     A distance between the cover and the terminal may be larger than a sum of dimensions of the tubular portion and the lid portion in a height direction. 
     The distance between the terminal and the cover is larger than a dimension of the cap in the height direction (the sum of the dimensions of the tubular portion and the lid portion in the height direction). Therefore, a space where the cap deformed by heat falls downward is sufficiently secured. 
     By comparing the terminal from which the cap is detached with the terminal covered with the cap, it becomes possible to easily determine a resistor in which a failure has occurred. 
     The cap may be composed of a material that becomes a first color at a temperature equal to or higher than the first temperature and becomes a second color different from the first color at a temperature lower than the first temperature. 
     Since the color of the cap changes by heat, it is possible to easily visually recognize, for example, a situation in which the resistor generates heat from the outside by the color change when the resistor generates more heat than in a normal state. 
     The load test device may further include a first detection unit that acquires information regarding at least one of a temperature, a humidity, a sound, a vibration, an impact, a discharge voltage, or a smell of a region where the terminal and the cap are located inside the frame. 
     The first detection unit may be electrically connected to at least one of other devices included in the load test device. 
     At least one of transmission of the information acquired by the first detection unit to an external device or control of stopping power supply to the resistor unit based on the information acquired by the first detection unit may be performed. 
     The first detection unit detects a temperature, a humidity, a sound, a vibration, an impact, a discharge voltage, a smell, or the like, and thus, in a case where there is an abnormality in the load test device, it becomes possible to stop (perform off control) application of a voltage to the resistor or notify an external device based on these pieces of information. 
     The first detection unit may include a display unit that emits light based on the information acquired by the first detection unit. 
     The display unit emits light based on the information acquired by the first detection unit, so that the information regarding whether or not an abnormality has occurred in the load test device can easily be visually recognized from the outside. 
     The load test device may further include: a first device including a first communication unit that transmits at least a first signal; and a second device including a second communication unit that receives at least the first signal. 
     The first device and the second device may be arranged in a positional relationship in which at least one of a region where the terminal and the cap are located or a region where a relay for controlling power supply to the resistor unit is located is sandwiched. 
     At least one of transmission of information regarding radio waves of the signal received by the second communication unit to an external device, control of stopping power supply to the resistor unit based on the information regarding the radio waves of the signal received by the second communication unit, or light emission based on the information regarding the radio waves of the signal received by the second communication unit may be performed. 
     The load test device may further include: a first device including a first communication unit that transmits at least a first signal; and a second device including a second communication unit that receives at least the first signal. 
     The second device may transmit a second signal. 
     The first device may receive the second signal. 
     The first device and the second device may be arranged in a positional relationship in which at least one of a region where the terminal and the cap are located or a region where a relay for controlling power supply to the resistor unit is located is sandwiched. 
     At least one of transmission of information regarding radio waves of the first signal received by the second communication unit and information regarding radio waves of the second signal received by the first communication unit to an external device, control of stopping power supply to the resistor unit based on the information regarding the radio waves of the first signal received by the second communication unit and the information regarding the radio waves of the second signal received by the first communication unit, or light emission based on the information regarding the radio waves of the signal received by the second communication unit and the information regarding the radio waves of the second signal received by the first communication unit may be performed. 
     The load test device may further include an ultrasonic sensor that detects ultrasonic waves. 
     At least one of transmission of information acquired by the ultrasonic sensor to an external device or control of stopping power supply to the resistor unit based on the information acquired by the ultrasonic sensor may be performed. 
     In a case where deterioration such as carbonization of the inside of the relay of a relay unit, contamination of an insulator, generation of a leakage current, a failure of the resistor, or the like has occurred, ultrasonic waves may be emitted from a portion where a failure has occurred. Therefore, by detecting the ultrasonic waves and making the ultrasonic wave be audible or visible, it becomes possible to find a failure of the load test device  1  at an early stage. 
     The load test device may further include: a conversion unit that converts a frequency of a signal obtained by the ultrasonic sensor into a frequency in an audible range; and an output unit that outputs a signal obtained by conversion performed by the conversion unit as a sound. 
     The load test device may further include a second detection unit that is attached to a specific portion of the load test device and is composed of a member whose color changes according to a state of the specific portion. 
     The second detection unit may be provided at the specific portion that is visible from the outside through the cover in a state not electrically connecting to another device included in the load test device. 
     Similarly to the first detection unit, the second detection unit acquires information such as a temperature. 
     The second detection unit is not electrically connected to and does not communicate with another device. 
     Therefore, the second detection unit can be more easily arranged in a complicated load test device having many wirings as compared with a detection member that is electrically connected to or communicates with another device, such as the first detection unit. 
     The cover may vibrate based on electromagnetic waves generated from the resistor. 
     The cap may include a tubular portion whose opposite ends are opened. 
     The terminal may be inserted into one end portion of the tubular portion in a state where the other end portion of the tubular portion is opened. 
     A load test device according to the present invention includes: a resistor unit that includes a plurality of resistors that receive supplied power and a wall that holds opposite ends of each of the plurality of resistors; and an insulating cap that is attached to a portion of a terminal of the resistor that protrudes from the wall. 
     The cap is deformed by heat and is detached from the terminal when a temperature of the terminal becomes equal to or higher than a first temperature, and/or the cap becomes a first color when the temperature of the cap becomes equal to or higher than the first temperature, and becomes a second color different from the first color when the temperature of the cap becomes lower than the first temperature. 
     A cap of a load test device according to the present invention is an insulating cap that is attached to a portion of a terminal of a resistor that protrudes from a wall in the load test device including a resistor unit that includes a plurality of the resistors that receive supplied power and the wall that holds opposite ends of each of the plurality of resistors. 
     The cap is composed of a material that is deformed by heat. 
     When a temperature of the terminal becomes equal to or higher than a first temperature, the cap is deformed by the heat and detached from the terminal. 
     Advantageous Effects of Invention 
     As described above, according to the present invention, it is possible to provide the load test device and the like capable of finding a failure at an early stage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a front view of a load test device according to the present embodiment. 
         FIG.  2    is a side view of the load test device according to the present embodiment. 
         FIG.  3    is a schematic diagram illustrating a configuration of the load test device according to the present embodiment. 
         FIG.  4    is a view illustrating one side surface of a resistor unit. 
         FIG.  5    is a view illustrating the other side surface of the resistor unit. 
         FIG.  6    is a perspective view illustrating the periphery of terminals of resistors before caps are attached. 
         FIG.  7    is a perspective view illustrating the periphery of the terminals of the resistors after the caps are attached. 
         FIG.  8    is a perspective view illustrating the periphery of the terminals of the resistors at the moment when one of the caps is deformed and detached from the terminal. 
         FIG.  9    is a cross-sectional configuration diagram illustrating a positional relationship among the resistors, a holding frame, a cover, and a first detection unit before the cover and the caps are attached. 
         FIG.  10    is a cross-sectional configuration diagram illustrating a positional relationship among the resistors, the holding frame, the cover, and the first detection unit after the cover and the caps are attached. 
         FIG.  11    is a cross-sectional configuration diagram illustrating a positional relationship among the resistors, the holding frame, the cover, and the first detection unit after one of the caps is deformed and detached from the terminal after the cover and the caps are attached. 
         FIG.  12    is a perspective view illustrating the periphery of the terminals of the resistors at the moment when one of caps without a lid portion is deformed and detached from the terminal. 
         FIG.  13    is a cross-sectional configuration diagram illustrating a positional relationship among the resistors, the holding frame, the cover, and the first detection unit (a first device and a second device) after one of the caps without the lid portion is deformed and detached from the terminal after the cover and the caps without the lid portion are attached. 
         FIG.  14    is a diagram illustrating a configuration of the first detection unit including an ultrasonic sensor. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present embodiment will be described with reference to the drawings. 
     Note that the embodiment is not limited to the following embodiment. In addition, the contents described in one embodiment are similarly applied to other embodiments in principle. Further, each embodiment and each modification can be appropriately combined. 
     (Load Test Device  1 ) 
     A dry load test device  1  according to the present embodiment includes a frame  10 , a resistor unit  20 , a relay unit  25 , a cooling unit  30 , an insulator  35 , a connection switching unit  40 , a circuit breaker  80 , a first detection unit  91 , a second detection unit  92 , and a communication unit  95  ( FIGS.  1  to  11   ). 
     Note that, in describing directions, a horizontal direction in which the connection switching unit  40  and the frame  10  are arranged will be described as an x direction, a horizontal direction perpendicular to the x direction will be described as a y direction, and a vertical direction perpendicular to the x direction and the y direction will be described as a z direction. 
     (Frame  10 ) 
     The frame  10  has an upper portion accommodating the resistor unit  20  and a lower portion accommodating the cooling unit  30 . In addition, the connection switching unit  40  is provided on a side portion of the frame  10 , and casters are provided therebelow. 
     Terminals  63 , a cable connected to the terminals  63 , a short-circuit bar SB connected to the terminal  63 , a cover  11  for protecting a holding frame  21  for holding resistors R, and the like are provided on a side surface of the frame  10  (a surface on which the terminals  63  of the resistors R constituting a resistor unit  20  can be seen) (see  FIG.  2   ). 
     The cover  11  is composed of a transparent material or a translucent material, such as polycarbonate. 
     The cover  11  is composed of an insulating resin material. 
     Here, the term “transparent” refers to a property of a substance through light is transmitted, and refers to a state in which transmittance is extremely high, and the other side of the substance can be seen through said substance. 
     Therefore, in a case where the cover  11  is composed of a transparent material, members provided inside the load test device  1  such as a cap  70  can be clearly seen from the outside of the cover  11  through the cover  11  as illustrated in  FIG.  2   . 
     In addition, the term “translucent” refers to a property of transmitting light similarly to the term “transparent”, but a shape or the like on the other side cannot be clearly recognized through said translucent material unlike the “transparent” material because transmitted light is diffused or transmittance is low. 
     Therefore, in a case where the cover  11  is composed of a translucent material, members provided inside the load test device  1  such as the cap  70  can be seen through the cover  11  from the outside of the cover  11  although not as clear as illustrated in  FIG.  2   . 
     (Resistor Unit  20 ) 
     The resistor unit  20  is formed by arranging a plurality of resistor rows in which a plurality of rod-shaped resistors R parallel to the y direction are arranged at predetermined intervals in the x direction in a plurality of stages in the z direction, and is used to perform a load test for a test target power supply such as a generator or a battery connected via a terminal connection unit  43 . The resistor R receives power supplied from the test target power supply. 
     The resistor unit  20  may be used to perform a load test for an air conditioning facility that cools a computer server or the like. 
     In the present embodiment, nine resistor rows of the resistors R arranged in the x direction are arranged in 13 stages in the z direction. However, the number of resistors R arranged in each resistor row, the number of stages in which the resistor rows are layered, and the like are not limited thereto. 
     It is desirable that the resistors R in at least one resistor row (the uppermost resistor row in the example illustrated in  FIGS.  4  and  5   ) are used as spares for replacement in a case where another resistor R fails, and the resistors R constituting the resistor rows in other stages are used as the resistors R constituting first to twelfth resistor groups G 1  to G 12 . 
     In the resistors R constituting the resistor unit  20 , six or twelve resistors R adjacent to each other are set as one resistor group, and the load test is performed while changing the number of resistor groups to which a voltage is to be applied from the test target power supply. 
     Further, connection in the resistor group (a connection state of the resistors R in the resistor group) may be changed according to the type of the load test target power supply. 
     The resistor unit  20  includes the first to twelfth resistor groups G 1  to G 12 . The present embodiment shows an example in which the first resistor group G 1  including six resistors R (rated capacity: 1 kW) in which each said resistor R has a rated voltage of 400 V and a rated capacity of 1.67 kW, the second resistor group G 2  including six resistors R (rated capacity: 2 kW, and the same applies to the third resistor group G 3 ) in which each said resistor R has a rated voltage of 116 V and a rated capacity of 334 W, the fourth resistor group G 4  including six resistors R (rated capacity: 5 kW) in which each said resistor R has a rated voltage of 116 V and a rated capacity of 834 W, the fifth resistor group G 5  including six resistors R (rated capacity: 10 kW, and the same applies to the sixth resistor group G 6 ) in which each said resistor R has a rated voltage of 116 V and a rated capacity of 1.67 kW, and the seventh resistor group G 7  including 12 resistors R (rated capacity: 20 kW, and the same applies to the eighth to twelfth resistor groups G 8  to G 12 ) in which each said resistor R has a rated voltage of 116 V and a rated capacity of 1.67 kW are provided. However, the number of resistor groups G, the rated voltage and rated capacity of each resistor R, and the like are not limited to the above-described configuration. 
     (Resistor R) 
     The resistor R includes a resistance wire  61 , the terminal  63 , a nut  66 , and a cylindrical portion  67  (see  FIGS.  6  to  11   ). 
     The terminals  63  are electrically connected to the resistance wire  61  and are provided at opposite ends of the resistance wire  61 . 
     The nut  66  is screwed to the terminal  63  in such a way as to sandwich a first insulating member  65   a.    
     The cylindrical portion  67  holds the terminal  63  via the first insulating member  65   a , and covers side surfaces of the resistance wire  61  and a portion of the terminal  63  (a portion not exposed to the outside from a wall constituting the holding frame  21 ). 
     A heat radiation fin  69  is provided on a side surface of the cylindrical portion  67 . 
     The terminal  63  of the resistor R is connected to the terminal  63  of another resistor R by the short-circuit bar SB, or connected to the terminal connection unit  43  or the relay via a cable. 
     The side surface of the resistor R is covered with the holding frame  21  constituted by four walls. However, a part of an end portion of the resistor R such as the terminal  63  protrudes outward (in the y direction) from a region surrounded by the holding frame  21 . 
     In such a positional relationship that a distal end of the terminal  63  attached to the holding frame  21  and the cover  11  attached to the frame  10  are separated by a first distance d 1 , a portion of the resistor R that is not electrically connected to the terminal  63  (for example, a portion near opposite ends of the cylindrical portion  67  holding the terminal  63  via the first insulating member  65   a ) is held by the wall constituting said holding frame  21  via a second insulating member  65   b.    
       FIGS.  6  to  8    illustrate end portions of four resistors R held by the holding frame  21 , in which the terminals  63  of two resistors R are connected to each other via the short-circuit bar SB. 
     A length of the first distance d 1  is determined in such a way that a space, in which when the cap  70  to be described later is deformed by heat, the deformed cap  70  can fall downward, is formed between the terminal  63  and the cover  11 . 
     For example, the dimensions of the respective portions are determined in such a way that the first distance d 1  is larger than the height of the cap  70  (the sum of the dimensions of a tubular portion  71  and a lid portion  73  in the y direction). 
     Further, the holding frame  21  has an upper surface and a lower surface opened to allow cool air from the cooling unit  30  provided therebelow to flow upward. 
     (Cap  70 ) 
     The cap (protective cover)  70  is put on an exposed portion of the terminal  63  of the resistor R that protrudes from the wall constituting the holding frame  21 . 
     Since the cap  70  covers the terminal  63 , it is possible to prevent dust or the like from adhering to the terminal  63 . 
     The cap  70  includes the tubular portion  71  and the lid portion  73 . 
     The tubular portion  71  covers a side surface of the portion of the terminal  63  that protrudes from the wall constituting the holding frame  21 . 
     The lid portion  73  is provided at one end portion of the tubular portion  71 , and faces the distal end of the terminal  63 . 
     The height (second distance d 2 ) of an inner wall of the tubular portion  71  is equal to the length of the portion of the terminal  63  that is exposed through the wall constituting the holding frame  21 . 
     The cap  70  is composed of an insulating member. 
     The cap  70  is composed of a resin that is deformed by heat, such as polyvinyl chloride. 
     Specifically, the cap  70  is composed of a material that becomes soft and be deformed when a temperature Tt of a region of the terminal  63  that is in contact with the inner wall of the tubular portion  71  becomes equal to or higher than a first temperature T 1  (for example, T 1 =65° C.), and the cap  70  falls from the terminal  63  due to said deformation. 
     The first temperature T 1  is a temperature of the terminal  63  that is not likely to be reached when the resistor R is operating normally, but is likely to be reached when the resistor R is not operating normally. 
     It is desirable that the cap  70  is composed of a material whose color changes depending on the temperature. 
     For example, the cap  70  becomes a first color (red) when a temperature Tc of the cap  70  becomes the first temperature T 1 , and becomes a second color (white) when the temperature Tc is lower than the first temperature T 1 . 
     (Arrangement of Resistors R) 
     In order to efficiently perform cooling by the cooling unit  30 , the resistors R of each resistor row are arranged in such a way that a resistor R of a resistor row is arranged at a position corresponding to a middle between resistors R adjacent to each other in the x direction in another resistor row adjacent to the resistor row in the z direction. 
     (Relay Unit  25 ) 
     The relay unit  25  is used to control power supply from the test target power supply to any one of the resistor groups. 
     A relay of the relay unit  25  is provided for each resistor group in the resistor unit  20 . 
     The relay unit  25  includes first to twelfth relays  25   a  to  251 . 
     The first relay  25   a  is used for on/off control of the first resistor group G 1 . 
     The second relay  25   b  is used for on/off control of the second resistor group G 2 . 
     The third relay  25   c  is used for on/off control of the third resistor group G 3 . 
     The fourth relay  25   d  is used for on/off control of the fourth resistor group G 4 . 
     The fifth relay  25   e  is used for on/off control of the fifth resistor group G 5 . 
     The sixth relay  25   f  is used for on/off control of the sixth resistor group G 6 . 
     The seventh relay  25   g  is used for on/off control of the seventh resistor group G 7 . 
     The eighth relay  25   h  is used for on/off control of the eighth resistor group G 8 . 
     The ninth relay  25   i  is used for on/off control of the ninth resistor group G 9 . 
     The tenth relay  25   j  is used for on/off control of the tenth resistor group G 10 . 
     The eleventh relay  25   k  is used for on/off control of the eleventh resistor group G 11 . 
     The twelfth relay  251  is used for on/off control of the twelfth resistor group G 12 . 
     (Cooling Unit  30 ) 
     The cooling unit  30  including a cooling fan is provided below the resistor unit  20  (the lower portion of the frame  10 ). 
     The cooling unit  30  and the relay unit  25  are driven based on a power supply (a power supply for driving the load test device) different from the test target power supply (see  FIG.  3   ). 
     In a case of performing a load test for an air conditioning facility that cools a computer server or the like, the resistors R of the first to twelfth resistor groups G 1  to G 12  of the resistor unit  20  receive power supplied from the power supply for driving the load test device via the circuit breaker  80 . Even in a case of performing the load test for the test target power supply, the cooling unit  30  and the relay unit  25  may be driven based on the test target power supply. 
     (Insulator  35 ) 
     The insulator  35  is provided at a position where insulation due to separation is necessary, such as a position between the frame  10  and the resistor unit  20  or a position between the resistor unit  20  and the cooling unit  30 . 
     (Connection Switching Unit  40 ) 
     The connection switching unit  40  includes an operation unit  41  and the terminal connection unit  43  (see  FIGS.  2  and  3   ). The terminal connection unit  43  may be disposed at a position away from the operation unit  41  (for example, a back surface of the operation unit  41  and the like). 
     The operation unit  41  includes a mode switch  41   a  and resistor switches  41   b.    
     The mode switch  41   a  is a rotary operation switch, and is used to turn on/off the load test device  1  and to select the type of the test target power supply (mode switching). 
     The resistor switches  41   b  are slide-type (or toggle-type or push-button-type) operation switches, and are switches for performing on/off control on the relays of the first to twelfth resistor groups G 1  to G 12 . The resistor switches  41   b  include first to twelfth operation switches S 1  to S 12 . 
     When the first operation switch S 1  is turned on, the relay (first relay  25   a ) of the first resistor group G 1  is turned on (conductive state), so that it becomes in a state in which a current from the test target power supply connected to the load test device  1  can flow to the first resistor group G 1  via the terminal connection unit  43 . 
     Similarly, when the second to twelfth operation switches S 2  to S 12  are turned on, the relays of the corresponding resistor groups are turned on (conductive state), and it becomes in a state in which a current from the test target power supply connected to the load test device  1  can flow to the resistor groups via the terminal connection unit  43 . 
     When a rotational position of the mode switch  41   a  is adjusted to a rotational position (operation mode) corresponding to the type of the test target power supply, the cooling fan of the cooling unit  30  is driven, and on/off control is performed on the relays (the first to twelfth relays  25   a  to  251 ) of the first to twelfth resistor groups G 1  to G 12  based on the operation state of the resistor switches  41   b.    
     Note that a main power switch may be provided, and when the main power switch is turned on and the rotational position of the mode switch  41   a  is adjusted to the rotational position (operation mode) corresponding to the type of test target power supply, the cooling fan may be driven, and on/off control may be performed on the relays (the first to twelfth relays  25   a  to  251 ) of the first to twelfth resistor groups G 1  to G 12 . 
     The terminal connection unit  43  is a terminal for connecting the test target power supply. 
     The test target power supply and the first to twelfth resistor groups G 1  to G 12  are brought into a connectable state via the terminal connection unit  43  and the circuit breaker  80 . 
     (Circuit Breaker  80 ) 
     The circuit breaker  80  is implemented by a vacuum circuit breaker (VCB) or the like, and is provided between the resistor unit  20  and the terminal connection unit  43 . When the circuit breaker  80  is in an on state, power from the test target power supply is supplied to the resistor unit  20 . When the circuit breaker  80  is in an off state, supply of power from the test target power supply to the resistor unit  20  is stopped. 
     The on/off control of the circuit breaker  80  is performed based on the operation state of the mode switch  41   a.    
     When the rotational position of the mode switch  41   a  is adjusted to the rotational position (operation mode) corresponding to the type of the test target power supply and the load test device  1  is turned on, the circuit breaker  80  is turned on. 
     While the load test device  1  is operating normally, the on state of the circuit breaker  80  is maintained. 
     In a case where it is determined that there is an abnormality in the load test device  1  based on information from the first detection unit  91 , the circuit breaker  80  is turned off. 
     When the rotational position of the mode switch  41   a  is adjusted to a rotational position (stop mode) corresponding to turning off and the load test device  1  is turned off, the circuit breaker  80  is turned off. 
     (First Detection Unit  91 ) 
     The first detection unit  91  acquires information regarding a temperature, a humidity, a sound, a vibration, an impact, a discharge voltage, a smell, and the like, of periphery. 
     The first detection unit  91  is electrically connected to another device (the circuit breaker  80  or the communication unit  95 ) included in the load test device  1 . 
     The first detection unit  91  is driven based on a power supply (the power supply for driving the load test device) different from the test target power supply or a built-in battery. 
     The first detection unit  91  is provided, for example, in a region where the terminal  63  and the cap  70  are located inside the frame  10 . 
     In this case, the first detection unit  91  acquires, inside the frame  10 , information regarding at least one of a temperature, a humidity, a sound, an impact, a discharge voltage, or a smell in the region where the terminal  63  and the cap  70  are located. 
     In a case where the first detection unit  91  is implemented by a sensor that acquires information regarding a discharge voltage, and the cover  11  is composed of a radio wave transmissive material, the first detection unit  91  may be provided outside the load test device  1 . 
     In a case where the first detection unit  91  is implemented by a sensor that acquires information regarding a vibration of the cover  11  based on electromagnetic waves generated from the resistor R, the first detection unit  91  may be provided outside the load test device  1 . 
     The vibration of the cover  11  based on the electromagnetic waves generated from the resistor R is different between a case where the resistor R is normally operating and a case where the resistor R is not normally operating. Therefore, the first detection unit  91  or the like records at least one of a vibration pattern in a case where the resistor R is operating normally or a vibration pattern in a case where the resistor R is not operating normally, and off control to be described later can be performed based on comparison with the vibration acquired by the first detection unit  91 . 
     On/off control of the circuit breaker  80  is performed based on the information acquired by the first detection unit  91 . 
     The information acquired by the first detection unit  91  is transmitted to an external device  100  through the communication unit  95 . 
     That is, the information acquired by the first detection unit  91  is used for operation of other devices of the load test device  1 . 
     (Example of Off Control) 
     For example, in a case where a temperature T detected by the first detection unit  91  is equal to or higher than a first temperature threshold Tth 1 , a control device of the first detection unit  91  (or another control device) determines that there is an abnormality in the load test device  1  and turns off the circuit breaker  80 . 
     In a case where a humidity H detected by the first detection unit  91  is equal to or higher than a first humidity threshold Hth 1 , the control device of the first detection unit  91  (or another control device) determines that there is an abnormality in the load test device  1  and turns off the circuit breaker  80 . 
     In a case where the first detection unit  91  detects at least one of a sound or an impact caused by falling of the cap  70 , the control device of the first detection unit  91  (or another control device) determines that there is an abnormality in the load test device  1  and turns off the circuit breaker  80 . 
     Specifically, in at least one of a case where a difference between a waveform of a sound caused by falling of the cap  70  recorded in advance in the first detection unit  91  or the like and a waveform of a sound detected by the first detection unit  91  is small or a case where a difference between a waveform of a vibration caused by falling of the cap  70  recorded in advance in the first detection unit  91  or the like and a waveform of a vibration detected by the first detection unit  91  is small, it is determined that at least one of the sound or the impact caused by the falling of the cap  70  has been detected. 
     In a case where a discharge voltage V detected by the first detection unit  91  is equal to or higher than a first voltage threshold Vth 1 , the control device of the first detection unit  91  (or another control device) determines that there is an abnormality in the load test device  1 , and turns off the circuit breaker  80 . 
     In a case where the first detection unit  91  detects a burnt smell or the like, the control device of the first detection unit  91  (or another control device) determines that there is an abnormality in the load test device  1 , and turns off the circuit breaker  80 . 
     (Display Unit  91   a ) 
     It is desirable that the first detection unit  91  includes a display unit  91   a  that outputs information detected by the first detection unit  91  by light. 
     For example, in a case where the information detected by the first detection unit  91  does not include information at the time of abnormality (first state), the display unit  91   a  emits light of a third color (green). 
     In a case where the information detected by the first detection unit  91  includes information close to that at the time of abnormality (second state), the display unit  91   a  preferentially emits light of a fourth color (yellow) rather than light of the third color. 
     Specifically, in at least one of a case where the temperature T detected by the first detection unit  91  is equal to or higher than a second temperature threshold Tth 2  (Tth 2 &lt;Tth 1 ) and lower than the first temperature threshold Tth 1 , a case where the humidity H detected by the first detection unit  91  is equal to or higher than a second humidity threshold Hth 2  (Hth 2 &lt;Hth 1 ) and lower than the first humidity threshold Hth 1 , or a case where the discharge voltage V detected by the first detection unit  91  is equal to or higher than a second voltage threshold Vth 2  (Vth 2 &lt;Vth 1 ) and lower than the first voltage threshold Vth 1 , the display unit  91   a  emits light of the fourth color (yellow). 
     In a case where the information detected by the first detection unit  91  includes information at the time of abnormality, the display unit  91   a  emits light of a fifth color (red) preferentially over the light of the third color and the light of the fourth color. 
     Specifically, in at least one of a case where the temperature T detected by the first detection unit  91  is equal to or higher than the first temperature threshold Tth 1 , a case where the humidity H detected by the first detection unit  91  is equal to or higher than the first humidity threshold Hth 1 , or a case where the discharge voltage V detected by the first detection unit  91  is equal to or higher than the first voltage threshold Vth 1 , the display unit  91   a  emits light of the fifth color (red). 
     (Second Detection Unit  92 ) 
     The second detection unit  92  is composed of a member whose color changes according to a state (whether the temperature is high or not) of the attached portion. 
     In a state of not communicating with the external device  100  and not electrically connected to other devices included in the load test device  1 , the second detection unit  92  is provided at a portion (specific portion) of the load test device  1  at which an abnormality may occur during the load test and which is visible from the outside through the cover  11 . 
     For example, the second detection unit  92  is attached to the short-circuit bar SB. 
     In this case, the second detection unit  92  becomes the first color (red) when a temperature Ts of the short-circuit bar SB becomes equal to or higher than a predetermined second temperature T 2  (for example, T 2 =50° C.), and becomes the second color (white) when said temperature Ts is lower than second temperature T 2 . 
     The second temperature T 2  is a temperature of the short-circuit bar SB that is not likely to be reached when the resistor R is operating normally, but is likely to be reached when the resistor R is not operating normally. 
     (Communication Unit  95 ) 
     The communication unit  95  wirelessly communicates with a device (external device  100 ) provided outside the load test device  1 . 
     The information obtained by first detection unit  91  is transmitted to the external device  100  via the communication unit  95 . 
     The information transmitted from the external device  100  is received by the communication unit  95 . 
     A signal from the external device  100  may be received, and the on/off control of the circuit breaker  80  may be performed based on said signal. 
     For example, the external device  100  displays detection information from the first detection unit  91 , and a user of the external device  100  performs an instruction signal transmission operation related to the off control of the circuit breaker  80 . 
     The external device  100  transmits an instruction signal related to the off control to the communication unit  95 , and once the communication unit  95  receives the instruction signal related to said off control, the control device of the first detection unit  91  (or another control device) turns off the circuit breaker  80 . 
     (Effect Obtained by Providing Cap  70  Deformed by Heat and Detached) 
     In a case where the nut  66  is loose, the resistor R may generate more heat than in a normal state as compared with a case where the nut  66  is sufficiently fastened. 
     In a case where the resistor R generates more heat than in a normal state, the cap  70  is deformed by the heat and detached from the terminal  63 . For this reason, for example, when the resistor R generates more heat than in a normal state, it is possible to easily visually recognize a situation in which the resistor R generates heat from the outside due to deformation of the cap  70  and detachment of the cap  70  from the terminal  63 . 
     That is, it is possible to detect a failure of the load test device  1  at an early stage. 
     (Effect Obtained by Providing Transparent Cover  11 ) 
     By providing the cover  11 , it is possible to prevent dust or the like from entering from the outside and adhering to the terminal  63  or the like. 
     As the cover  11  is composed of a transparent material, it becomes possible to visually recognize a region where the terminal  63  is located inside the load test device  1  from the outside. 
     In addition, the cover  11  vibrates based on electromagnetic waves generated from the resistor R or the like, and functions as a speaker that generates a sound based on said electromagnetic waves. The vibration of the cover  11  based on the electromagnetic waves generated from the resistor R or the like is different between a case where the resistor R is normally operating and a case where the resistor R is not normally operating. Therefore, a worker or the like around the load test device  1  can listen to the sound based on the vibration of the cover  11  and determine whether said sound is a sound when the resistor R or the like is operating normally or a sound when the resistor R or the like is not operating normally. 
     (Effect Obtained by Increasing Distance Between Terminal  63  and Cover  11 ) 
     The distance between the terminal  63  and the cover  11  is larger than a dimension of the cap  70  in the height direction (the sum of the dimensions of the tubular portion  71  and the lid portion  73  in the height direction). Therefore, a space where the cap  70  deformed by heat falls downward is sufficiently secured. 
     By comparing the terminal  63  from which the cap  70  is detached with the terminal  63  covered with the cap  70 , it becomes possible to easily determine a resistor R in which a failure has occurred. 
     (Effect Obtained by Changing Color of Cap  70 ) 
     Since the color of the cap  70  changes by heat, it is possible to visually recognize, for example, a situation in which the resistor R generates more heat than in a normal state from the outside by the color change when the resistor R generates more heat than in a normal state. 
     (Effect Obtained by Providing First Detection Unit  91 ) 
     The first detection unit  91  detects a temperature, a humidity, a sound, an impact, a discharge voltage, a smell, or the like, and thus, in a case where there is an abnormality in the load test device  1 , it becomes possible to stop (perform off control) application of a voltage to the resistor R or notify the external device  100  based on these pieces of information. 
     In particular, in a case where the nut  66  is loose, the discharge voltage V may increase as compared with a case where the nut  66  is sufficiently fastened. 
     However, in the present embodiment, since the first detection unit  91  performs the off control based on the discharge voltage V or the like, it becomes possible to find a failure of the load test device  1  at an early stage. 
     (Effect Obtained by Providing Display Unit  91   a ) 
     The display unit  91   a  emits light based on the information acquired by the first detection unit  91 , so that the information regarding whether or not an abnormality has occurred in the load test device  1  can easily be visually recognized from the outside. 
     (Effect Obtained by Providing Second Detection Unit  92 ) 
     Similarly to the first detection unit  91 , the second detection unit  92  acquires information such as a temperature. 
     The second detection unit  92  is not electrically connected to and does not communicate with another device. 
     Therefore, the second detection unit  92  can be more easily arranged in a complicated load test device  1  having many wirings as compared with a detection member that is electrically connected to or communicates with another device, such as the first detection unit  91 . 
     (Modification of Cap  70 ) 
     In the present embodiment, the cap  70  includes the tubular portion  71  and the lid portion  73 , and one of openings of the tubular portion  71  is closed by the lid portion  73 . 
     However, the cap  70  does not have to include the lid portion  73 , and the opposite ends of the tubular portion  71  may be opened (see  FIGS.  12  and  13   ). 
     In this case, the terminal  63  is inserted into one end portion of the tubular portion  71  of the cap  70  in a state where the other end portion of the tubular portion  71  is opened. 
     (Modification 1 of First Detection Unit  91 ) 
     In the present embodiment, an example has been described in which the first detection unit  91  is composed of a sensor that acquires information regarding a temperature, a humidity, a sound, a vibration, an impact, a discharge voltage, a smell, and the like, of periphery. 
     However, instead of or in addition to said sensor, the first detection unit  91  may be composed of a communication device that transmits radio waves and receives the radio waves may be included (see  FIG.  13   ). 
     In this case, the first detection unit  91  includes a first device  911  and a second device  912 . 
     The first device  911  includes the display unit  91   a , a first communication unit  91   b   1 , and a first reflection unit  91   c   1 . 
     The second device  912  includes a second communication unit  91   b   2  and a second reflection unit  91   c   2 . 
     The first device  911  and the second device  912  are provided in a region where the terminal  63  and the cap  70  are located inside the frame  10 , and are arranged in a positional relationship in which the region where the terminal  63  and the cap  70  are located is sandwiched. 
     For example, the first device  911  is arranged below the region where the terminal  63  and the cap  70  are located inside the frame  10 , and the second device  912  is disposed above the region where the terminal and the cap  70  are located inside the frame  10 . 
     The first communication unit  91   b   1  transmits a first signal to the second communication unit  91   b   2  and receives a second signal from the second communication unit  91   b   2 . 
     The first reflection unit  91   c   1  reflects the first signal from the first communication unit  91   b   1  toward the direction (upper side) where the second communication unit  91   b   2  is located, and reflects the second signal from the second communication unit  91   b   2  toward the direction (lower side) where the first communication unit  91   b   1  is located. 
     The second communication unit  91   b   2  transmits the second signal toward the first communication unit  91   b   1  and receives the first signal from the first communication unit  91   b   1 . 
     The second reflection unit  91   c   2  reflects the second signal from the second communication unit  91   b   2  toward the direction (lower side) where the first communication unit  91   b   1  is located, and reflects the first signal from the first communication unit  91   b   1  toward the direction (upper side) where the second communication unit  91   b   2  is located. 
     The control device of the first detection unit  91  (or another control device) performs the off control of the circuit breaker  80  based on information regarding the radio waves such as a radio wave intensity and the waveform of each of the second signal received by the first communication unit  91   b   1  and the first signal received by the second communication unit  91   b   2 . 
     Furthermore, the information regarding the radio waves may be transmitted to the external device  100  via the communication unit  95 . 
     Since there is a difference in electromagnetic waves generated from the resistor R and the like between a case where the resistor R or the like is operating normally and a case where the resistor R or the like is not operating normally, a difference occurs in the radio wave intensity and the waveform of the second signal received by the first communication unit  91   b   1  from the second communication unit  91   b   2  and in the radio wave intensity and the waveform of the first signal received by the second communication unit  91   b   2  from the first communication unit  91   b   1 . 
     A difference occurs in the radio wave intensity and the waveform of the second signal received by the first communication unit  91   b   1  from the second communication unit  91   b   2  and the radio wave intensity and the waveform of the first signal received by the second communication unit  91   b   2  from the first communication unit  91   b   1  between a state in which the cap  70  is attached and a state in which the cap  70  is detached. 
     A difference occurs in the radio wave intensity and the waveform of the second signal received by the first communication unit  91   b   1  from the second communication unit  91   b   2  and the radio wave intensity and the waveform of the first signal received by the second communication unit  91   b   2  from the first communication unit  91   b   1  between a state in which the color of the cap  70  is not changed by heat and a state in which the cap  70  has been changed by heat. 
     Therefore, the first detection unit  91  or the like records the radio wave intensity, the waveform, and the like when the resistor R or the like is operating normally, and it is possible to perform the OFF control of the circuit breaker  80  based on at least one of the radio wave intensity or the waveform. 
     Examples of communication means of the wireless communication performed by the first communication unit  91   b   1  and the second communication unit  91   b   2  include communication means that transmits its own identification information to the outside while the wireless communication means is turned on, such as IEEE 802.15.1 (Bluetooth (registered trademark), 2.4 GHz), or IEEE 802.11 (wireless LAN, 2.4 GHz or 5 GHz) in addition to a communication method such as a telephone line and an RF tag. 
     By providing the first reflection unit  91   c   1  and the second reflection unit  91   c   2 , the reception sensitivity of the first communication unit  91   b   1  and the second communication unit  91   b   2  can be enhanced. 
     One of the first communication unit  91   b   1  and the second communication unit  91   b   2  may perform only signal transmission, and the other of the first communication unit  91   b   1  and the second communication unit  91   b   2  may perform only signal reception. 
     An example in which one first communication unit  91   b   1  and one second communication unit  91   b   2  are provided in the load test device  1  has been described. However, a plurality of sets of the first communication unit  91   b   1  and the second communication unit  91   b   2  may be provided in a positional relationship in which one or more terminals  63  and one or more caps  70  are sandwiched. In this case, it becomes easy to identify the resistor R in which a failure has occurred. 
     In addition, a plurality of sets of the first communication unit  91   b   1  and the second communication unit  91   b   2  may be provided in a positional relationship in which a relay such as the first relay  25   a  is sandwiched. In this case, it becomes easy to specify a relay in which a failure has occurred. 
     (Modification 2 of First Detection Unit  91 ) Furthermore, in the present embodiment, an example has been described in which the first detection unit  91  is composed of a sensor that acquires information regarding a temperature, a humidity, a sound, a vibration, an impact, a discharge voltage, a smell, and the like, of periphery. 
     However, instead of or in addition to said sensor, the first detection unit  91  may detect ultrasonic waves and perform off control or the like based on the ultrasonic waves. 
     In this case, the first detection unit  91  includes an ultrasonic sensor  91   d   1 , a conversion unit  91   d   2 , an output unit  91   d   3 , and a sound collection unit  91   d   4  (see  FIG.  14   ). 
     The ultrasonic sensor  91   d   1  is a sensor (or a microphone) that detects a signal having a higher frequency than a predetermined frequency band, that is, ultrasonic waves (for example, a sound of 20,000 Hz or more). 
     The conversion unit  91   d   2  converts the frequency of the signal detected by the ultrasonic sensor  91   d   1  into a frequency in an audible range (for example, 1,000 Hz). 
     The output unit  91   d   3  outputs the signal obtained by conversion performed by the conversion unit  91   d   2  as sound. 
     The sound collection unit  91   d   4  collects the sound output by the output unit  91   d   3 . 
     For example, in a case where the sound corresponding to the ultrasonic waves is collected by the sound collection unit  91   d   4 , the control device of the first detection unit  91  (or another control device) determines that there is an abnormality in the load test device  1  and turns off the circuit breaker  80 . Furthermore, information regarding the sound collected by the sound collection unit  91   d   4  is transmitted to the external device  100  via the communication unit  95 . In a case where the sound corresponding to the ultrasonic waves is collected by the sound collection unit  91   d   4 , the display unit  91   a  emits light of the fifth color (red) or the like. 
     In a case where deterioration such as carbonization of the inside of the relay of a relay unit  25 , contamination of an insulator  35 , generation of a leakage current, a failure of the resistor R, or the like has occurred, ultrasonic waves may be emitted from a portion where a failure has occurred. Therefore, by detecting the ultrasonic waves and making the ultrasonic wave be audible or visible, it becomes possible to find a failure of the load test device  1  at an early stage. 
     Here, a mode has been described in which ultrasonic waves acquired by the ultrasonic sensor  91   d   1  are converted into an audible range sound and output to determine whether or not ultrasonic waves have been generated. 
     However, whether or not ultrasonic waves have been generated may be determined by another method such as reading a waveform in information regarding ultrasonic waves acquired by the ultrasonic sensor  91   d   1 . 
     Although some embodiments of the present invention have been described, these embodiments have been presented as examples, and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. The accompanying claims and their equivalents are intended to cover these embodiments and modifications thereof as would fall within the scope and gist of the invention. 
     REFERENCE SIGNS LIST 
     
         
           1  Load test device 
           10  Frame 
           11  Cover 
           20  Resistor unit 
           21  Holding frame 
           25  Relay unit 
           25   a  to  251  First to twelfth relays 
           30  Cooling unit 
           35  Insulator 
           40  Connection switching unit 
           41  Operation unit 
           41   a  Mode switch 
           41   b  Resistor switch 
           43  Terminal connection unit 
           61  Resistance wire 
           63  Terminal 
           65   a  First insulating member 
           65   b  Second insulating member 
           66  Nut 
           67  Cylindrical portion 
           69  Heat radiation fin 
           70  Cap 
           71  Tubular portion 
           73  Lid portion 
           80  Circuit breaker  80   
           91  First detection unit 
           911  First device 
           912  Second device 
           91   a  Display unit 
           91   b   1  First communication unit 
           91   b   2  Second communication unit 
           91   c   1  First reflection unit 
           91   c   2  Second reflection unit 
           91   d   1  Ultrasonic sensor 
           91   d   2  Conversion unit 
           91   d   3  Output unit 
           91   d   4  Sound collection unit 
           92  Second detection unit 
           95  Communication unit 
           100  External device 
         d 1  First distance 
         d 2  Second distance 
         G 1  to G 12  First to twelfth resistor groups 
         H Humidity detected by first detection unit 
         Hth 1  First humidity threshold 
         Hth 2  Second humidity threshold 
         R Resistor 
         S 1  to S 12  First to twelfth operation switches 
         SB Short-circuit bar 
         T Temperature detected by first detection unit 
         T 1  First temperature (temperature at which cap is deformed) 
         T 2  Second temperature (temperature at which color of second detection unit changes) 
         Tc Temperature of cap 
         Ts Temperature of short-circuit bar 
         Tt Temperature of terminal 
         Tth 1  First temperature threshold 
         Tth 2  Second temperature threshold 
         V Discharge voltage detected by first detection unit 
         Vth 1  First voltage threshold 
         Vth 2  Second voltage threshold