Power supply switching method and power supply switching device

Abstract

To provide a power supply switching method capable of preventing engine stall when a power supply of a single-phase load and that of a three-phase load are both switched to an engine-driven power generator that is a standby power supply.SOLUTION: In a power supply switching method, when a power supply connected to a load 40 is switched from a commercial power supply 20 to an engine-driven generator 30 that is a backup power supply, first switching processing is firstly executed that switches the power supply connected to a first load (for example, a three-phase load 42) that is one of a single-phase load 41 and the three-phase load 42 from the commercial power supply 20 to the backup power supply 30. Then, second switching processing is executed that switches the power supply connected to a second load (for example, the single-phase load 41) that is the other of the single-phase load 41 and the three-phase load 42 from the commercial power supply 20 to the backup power supply 30.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power supply switching method and a power supply switching device. More specifically, in the switching of a power supply connected to a load between a normal power supply such as a commercial power supply and an engine-driven generator as an emergency power supply, the present invention relates to a power supply switching method and a power supply switching device characterized by an operation when switching the power supply from the normal power supply to the emergency power supply.

Background Art

[0002] Even when a normal power supply such as a commercial power supply fails due to natural disasters such as earthquakes, typhoons, lightning strikes, heavy snow, floods, fires, troubles in power plants or transmission lines, or planned power outages due to power shortages, public facilities, hospitals, factory facilities, agricultural facilities (e.g., farms and livestock houses), communication facilities (e.g., radio towers and relay bases for mobile phones), etc. should be able to maintain their functions. Therefore, power outage countermeasures for deploying engine-driven generators as emergency power supplies in these facilities are becoming widespread.

[0003] When an engine-driven generator is provided as an emergency power supply in this way, it is necessary to switch the power supply connected to the load between the normal power supply and the emergency power supply. Therefore, when installing an engine-driven generator as an emergency power supply, a power supply switching device such as an ATS panel (ATS: Automatic Transfer Switch) that automatically performs the power supply switching operation is also installed.

[0004] As shown in FIG. 5, this ATS panel is connected to a normal power supply such as a commercial power supply, an engine-driven generator as an emergency power supply, and a load such as electrical equipment that operates by receiving power supply from these power supplies, respectively. When it is detected that power supply is being performed by the normal power supply, the load is connected to the normal power supply. When a power outage of the normal power supply is detected, a start command is output via a signal line to start the engine-driven generator as the emergency power supply, the connection between the load and the normal power supply is cut off, and the emergency power supply and the load are connected. When it is detected that the power failure of the normal power supply has been restored, the connection between the load and the standby power supply is cut off, the load is connected to the normal power supply, and a stop command is output via the signal line to automatically stop the engine-driven generator, respectively.

[0005] In addition, Fig. 5 shows a configuration in which an ATS board is provided separately from the engine-driven generator as a power switching device. Instead of this configuration, an emergency power supply device in which a power switching device that automatically switches the power supply is incorporated into the soundproof box of the engine-driven generator by using the dead space in the engine-driven generator has also been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Among engine-driven generators, there are those that output only one of single-phase three-wire and three-phase three-wire, and there are also those that can output both single-phase three-wire and three-phase three-wire simultaneously.

[0008] Therefore, when an engine-driven generator capable of simultaneous output of single-phase three-wire and three-phase three-wire is provided as a standby power supply, it is conceivable to connect both single-phase loads and three-phase loads to the power switching device so that both three-phase loads and single-phase loads can be connected to the engine-driven generator as the standby power supply in the event of a power failure of the normal power supply (commercial power supply).

[0009] Here, among the electrical equipment connected to the power supply switching device as a load, there are many whose power consumption at startup exceeds the rated power consumption. In particular, when the load is a device equipped with a single-phase or three-phase induction motor as a drive source, such as a pump or compressor driven by a motor, or a ventilation fan, etc., a starting current of 5 to 8 times the rated current is required as an example, so the power consumption at startup increases significantly compared to the rated operation.

[0010] Therefore, as shown in FIG. 6, even when an engine-driven generator having a rated output Pgr with a sufficient margin with respect to the sum Pcr of the rated power consumption of the single-phase load and the rated power consumption of the three-phase load is adopted as the standby power supply, when the single-phase load and the three-phase load are simultaneously connected to the engine-driven generator, the maximum value Pcmax of the total power consumption of the single-phase load and the three-phase load at startup may exceed the rated output Pgr of the engine-driven generator. In this case, as a result of an excessive load being applied to the engine of the engine-driven generator, the engine stalls and the engine-driven generator stops.

[0011] On the other hand, when an engine-driven generator that generates a rated output Pgr' with a necessary margin with respect to the maximum value Pcmax of the total power consumption of the single-phase load and the three-phase load at startup is adopted as the standby power supply, even when the single-phase load and the three-phase load are started simultaneously, it is possible to prevent the engine-driven generator from stopping due to engine stall. However, a relatively large-sized engine-driven generator is adopted as the standby power supply, which not only increases the introduction cost of the standby power supply, but also increases the running cost because the engine-driven generator becomes over-spec for the load in the rated operation state and the fuel consumption deteriorates.

[0012] Therefore, there is a demand to enable a smaller engine-driven generator to be adopted as a common standby power supply for single-phase loads and three-phase loads without causing engine stall or the like when the load starts up.

[0013] Therefore, the present invention has been made to solve the drawbacks in the above prior art, and even when a relatively small engine-driven generator is adopted as a common emergency power source for single-phase loads and three-phase loads, it is possible to make it difficult to cause the engine-driven generator to stop due to engine stalling at the start of the load. An object of the present invention is to provide a power supply switching method and a power supply switching device.

Means for Solving the Problems

[0014] Means for solving the problems will be described below together with the reference numerals used in the embodiments for carrying out the invention. This reference numeral is for clarifying the correspondence between the description of the claims and the description of the embodiments for carrying out the invention, and needless to say, it is not used restrictively for interpreting the technical scope of the present invention.

[0015] In order to achieve the above object, the power supply switching method of the present invention is In a power supply switching method for switching the power supply connected to the load 40 between the normal power supply 20 and the emergency power supply 30, An engine-driven generator capable of simultaneously performing single-phase output and three-phase output with one unit is provided as the emergency power supply 30, and a single-phase output unit 21, 31 and a three-phase output unit 22, 32 are provided in each of the normal power supply 20 and the emergency power supply 30. A single-phase load 41 and a three-phase load 42 are provided as the load 40. The single-phase load 41 is made connectable to either the normal power supply 20 or the emergency power supply 30 via the single-phase output unit 21 of the normal power supply 20 or the single-phase output unit 31 of the emergency power supply 30. The three-phase load 42 is made connectable to either the normal power supply 20 or the emergency power supply 30 via the three-phase output unit 22 of the normal power supply 20 or the three-phase output unit 32 of the emergency power supply 30. When switching the power supply connected to the load 40 from the normal power supply 20 to the emergency power supply 30, First, execute a first switching process of switching the power supply connected to the first load (the three-phase load 42 in the embodiment), which is either the single-phase load 41 or the three-phase load 42, from the normal power supply 20 to the standby power supply 30. Next, execute a second switching process of switching the power supply connected to the second load (the single-phase load 41 in the embodiment), which is the other of the single-phase load 41 or the three-phase load 42, from the normal power supply 20 to the standby power supply 30 (Claim 1).

[0016] The determination of the aforementioned first load and second load may be performed arbitrarily, but preferably, Based on the values of the rated currents I3r and I1r and the starting currents I3s and I1s of the three-phase load 42 and the single-phase load 41 respectively, which are defined in advance, or based on the values of the rated currents I3r and I1r of the three-phase load 42 and the single-phase load 41 respectively, which are defined in advance, and the values of the starting currents I3s and I1s of the three-phase load 42 and the single-phase load 41 respectively, which are calculated from the values of the rated currents I3r and I1r, compare the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 with the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41. When the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is greater than the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r > I3r + I1s), the three-phase load 42 is made the first load and the single-phase load 41 is made the second load. When the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is smaller than the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r < I3r + I1s), the single-phase load 41 is made the first load and the three-phase load 42 is made the second load (Claim 2).

[0017] In this case, a value obtained by subtracting the maximum value P2max of the power consumption at the start of the second load (single-phase load 41 in the embodiment) from the rated output Pgr of the engine-driven generator 30 is used as a determination reference power Ps. After the execution of the first switching process, when a predetermined start condition preset as a determination criterion for the power consumption of the first load (three-phase load 42 in the embodiment) being equal to or less than the determination reference power Ps is satisfied, it is preferable to execute the second switching process (Claim 3).

[0018] In this case, further, it is also possible to execute the second switching process with the passage of a predetermined switching standby time Ts after the execution of the first switching process as the start condition (Claim 4; see FIG. 2).

[0019] Alternatively, after the execution of the first switching process, it is also possible to execute the second switching process with the start condition that the power consumption of the first load (three-phase load 42 in the embodiment) has dropped below a predetermined threshold value Pth set within the range of being equal to or less than the determination reference power Ps (Claim 5; see FIG. 3).

[0020] Furthermore, it is also possible to execute the second switching process with the start condition that a predetermined switching standby time Ts has passed after the execution of the first switching process and the power consumption of the first load (three-phase load 42 in the embodiment) has dropped below a predetermined threshold value Pth set within the range of being equal to or less than the determination reference power Ps (Claim 6; see FIG. 4(A)).

[0021] Also, the power supply switching device 10 of the present invention In a power supply switching device 10 that switches the power supply connected to the load 40 between the commercial power supply 20 and the emergency power supply 30, A commercial power supply input unit 11 connected to the commercial power supply 20, an emergency power supply input unit 12 connected to the emergency power supply 30, and a load output unit 13 connected to the load 40 are provided. The input section 11 for the normal power supply and the input section 12 for the standby power supply are each provided with a single-phase input section 111, 121 and a three-phase input section 112, 122. The load output section 13 is provided with a single-phase output section 131 to which a single-phase load 41 is connected and a three-phase output section 132 to which a three-phase load 42 is connected. A single-phase power supply switching means 141 that connects the single-phase output section 131 of the load output section 13 to either the single-phase input section 111 or 121 of either the normal power supply input section 11 or the standby power supply input section 12. Three-phase power supply switching means 142 that connect the three-phase output section 132 of the load output section 13 to either the three-phase input section 112 or 122 of either the normal power supply input section 11 or the standby power supply input section 12 are provided respectively. An operation control means 15 for controlling the operations of the single-phase power supply switching means 141 and the three-phase power supply switching means 142 is further provided. When switching the power supply connected to the load 40 (41, 42) from the normal power supply 20 to the standby power supply 30, the operation control means 15 first executes a first switching process of switching the power supply connected to a first load (the three-phase load 42 in the embodiment), which is either the single-phase load 41 or the three-phase load 42, from the normal power supply 20 to the standby power supply 30. Then, a second switching process of switching the power supply connected to a second load (the single-phase load 41 in the embodiment), which is the other of the single-phase load 41 or the three-phase load 42, from the normal power supply 20 to the standby power supply 30 is executed (Claim 7).

[0022] In the power supply switching device 10 configured as described above, the operation control means 15 includes a storage means 151, and based on the values of the rated currents I3r and I1r and the starting currents I3s and I1s of the three-phase load 42 and the single-phase load 41 respectively stored in the storage means 151 in advance, or based on the values of the rated currents I3r and I1r of the three-phase load 42 and the single-phase load 41 respectively stored in the storage means 151 in advance and the values of the starting currents I3s and I1s of the three-phase load 42 and the single-phase load 41 respectively calculated from the values of the rated currents I3r and I1r, the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 and the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 are compared, and for the single-phase power supply switching means 141 and the three-phase power supply switching means 142, when the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is larger than the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r > I3r + I1s), the three-phase load 42 is made the first load and the single-phase load 41 is made the second load, and the first switching process and the second switching process are executed, when the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is smaller than the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r < I3r + I1s), it may be configured such that the single-phase load 41 is made the first load and the three-phase load 42 is made the second load, and the first switching process and the second switching process are executed (Claim 8).

[0023] In this case, a value obtained by subtracting the maximum value P2max of the power consumption at the start of the second load (the single-phase load 41 in the embodiment) from the rated output Pgr of the engine-driven generator 30 is used as the determination reference power Ps, After the operation control means 15 executes the first switching process, when a predetermined start condition set in advance as a determination criterion for the power consumption of the first load (in the embodiment, the three-phase load 42) being equal to or less than the determination reference power Ps is satisfied, the second switching process may be executed (Claim 9).

[0024] In this case, further, the storage means 151 stores a predetermined switching standby time Ts as the start condition, and when the switching standby time Ts has elapsed after the operation control means 15 executes the first switching process, the start condition is satisfied, and the single-phase power supply switching means 141 or the three-phase power supply switching means 142 may be made to execute the second switching process (Claim 10; see FIG. 2).

[0025] Alternatively, the storage means 151 stores a predetermined threshold value Pth set within the range equal to or less than the determination reference power Ps as the start condition, and when the power consumption of the first load (in the embodiment, the three-phase load) has decreased to be equal to or less than the threshold value Pth after the operation control means 15 executes the first switching process, the start condition is satisfied, and the single-phase power supply switching means 141 or the three-phase power supply switching means 142 may be made to execute the second switching process (Claim 11; see FIG. 3).

[0026] Furthermore, the storage means 151 stores both a predetermined switching standby time Ts and a predetermined threshold value Pth set within the range equal to or less than the determination reference power Ps as the start condition, and when the switching standby time Ts has elapsed and the power consumption of the first load (in the embodiment, the three-phase load 42) has decreased to be equal to or less than the threshold value Pth after the operation control means 15 executes the first switching process, the start condition is satisfied, and the single-phase power supply switching means 141 or the three-phase power supply switching means 142 may be made to execute the second switching process [Claim 12; see FIG. 4(A)].

Advantages of the Invention

[0027] With the configuration of the present invention described above, the power supply switching method and the power supply switching device 10 of the present invention can achieve the following remarkable effects.

[0028] By connecting a first load (the three-phase load 42 in the embodiment), which is either the single-phase load 41 or the three-phase load 42, to the engine-driven generator 30 serving as the standby power supply, and then connecting the other second load (the single-phase load 41 in the embodiment) to the engine-driven generator 30, when switching to the standby power supply 30, the start of the single-phase load 41 and the start of the three-phase load 42 are performed with a time difference, so that the start of a load whose power consumption may be larger than that at rated conditions is dispersed between the single-phase load 41 and the three-phase load 42. As a result, when starting the load 40 (41, 42) with the standby power supply 30, the load torque applied to the engine of the engine-driven generator 30 can be reduced.

[0029] As a result, even when a relatively small engine-driven generator is provided as the standby power supply 30, it is possible to switch the power supply from the commercial power supply 20 to the standby power supply 30 without causing the engine to stall or the like.

[0030] When the sum (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is greater than the sum (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r > I3r + I1s), the three-phase load 42 is made the first load and the single-phase load 41 is made the second load. When the sum (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is less than the sum (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r < I3r + I1s), in the configuration where the single-phase load 41 is made the first load and the three-phase load 42 is made the second load, among the single-phase load 41 or the three-phase load 42, the one with a larger increase in the starting current with respect to the rated current, and thus the one with a larger increase in the power consumption at startup with respect to the rated power consumption, is connected to the emergency power supply 30 first as the first load and started. By doing so, compared to the case of connecting in the reverse order, the load torque applied to the engine of the engine-driven generator 30 during the startup of the load can be further reduced. As a result, a smaller engine-driven generator 30 can be adopted as the emergency power supply.

[0031] In this case, a value obtained by subtracting the maximum value P2max of the power consumption at the start of the second load (the single-phase load 41 in the embodiment) from the rated output Pgr (the sum of the single-phase output and the three-phase output) of the engine-driven generator 30 is set as the determination reference power Ps. When a predetermined start condition set as the determination criterion that the power consumption of the first load (the three-phase load 42 in the embodiment) is equal to or less than the determination reference power Ps is satisfied after the execution of the first switching process, in the configuration where the second switching process is executed, it is possible to prevent the total power consumption of the load 40 from exceeding the rated output Pgr of the engine-driven generator 30 when switching to the emergency power supply 30.

[0032] In this case, in the configuration where the second switching process is executed with the elapse of a predetermined switching standby time Ts from the start of the execution of the first switching process as the start condition, the control of the timing for executing the second switching process is easy.

[0033] In addition, in a configuration where the second switching process is executed with the start condition that the power consumption of the first load (the three-phase load 42 in the embodiment) has dropped below a predetermined threshold value Pth, since the change in the power consumption of the first load (the three-phase load 42 in the embodiment) is actually monitored to start the second load (the single-phase load 41 in the embodiment), it is possible to more accurately determine that the power consumption of the first load is equal to or less than the reference power Ps.

[0034] Furthermore, in a configuration where the second switching process is performed assuming that the start condition is satisfied when a predetermined switching standby time Ts has elapsed and the power consumption of the first load (the three-phase load 42 in the embodiment) is equal to or less than a predetermined threshold value Pth, it is possible to more reliably prevent the total power consumption of the loads 40 (41, 42) at the start of the second load (the single-phase load 41 in the embodiment) from exceeding the rated output Pgr of the engine-driven generator 30 which is the emergency power source.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Best Mode for Carrying Out the Invention

[0036] Hereinafter, with reference to the accompanying drawings, the power supply switching device 10 of the present invention and the power supply switching method executed by the power supply switching device 10 will be described.

[0037] Reference numeral 10 in FIG. 1 is the power supply switching device of the present invention. In the illustrated embodiment, this power supply switching device 10 is provided separately from the engine-driven generator 30 which is a standby power supply. However, this power supply switching device 10 may be configured to be accommodated in the empty space within the engine-driven generator 30, similar to the invention described in the aforementioned Patent Document 1.

[0038] This power supply switching device 10 is provided with a normal power supply input section 11 connected to a normal power supply (commercial power supply) 20, a standby power supply input section 12 connected to an engine-driven generator 30 which is a standby power supply, and a load output section 13 to which a load 40 is connected.

[0039] The normal power supply input section 11 among these is provided with a single-phase input section 111 and a three-phase input section 112. By connecting a single-phase lead wire (single-phase output section) 21 and a three-phase lead wire (three-phase output section) 22 from the commercial power supply 20 which is the normal power supply to the single-phase input section 111 and the three-phase input section 112 provided in this normal power supply input section 11 respectively, the power supply switching device 10 can be connected to the commercial power supply 20 which is the normal power supply.

[0040] Also, an engine-driven generator capable of simultaneously performing single-phase three-wire output and three-phase three-wire output with one unit is connected as a standby power supply 30 to the standby power supply input section 12 of the power supply switching device 10. The single-phase input section 121 provided in the standby power supply input section 12 of the power supply switching device 10 and the single-phase output section 31 provided in the engine-driven generator 30 are connected via a cable 33, and the three-phase input section 122 of the standby power supply input section 12 and the three-phase output section 32 of the engine-driven generator 30 are connected via a cable 34, whereby the power supply switching device 10 is connected to the engine-driven generator 30 which is the standby power supply.

[0041] Furthermore, a single-phase output section 131 and a three-phase output section 132 are respectively provided in the load output section 13 of the power supply switching device 10. Among these, a single-phase load 41 is connected to the single-phase output section 131, and a three-phase load 42 is connected to the three-phase output section 132.

[0042] This power supply switching device 10 is further provided with a power supply switching section 14 that switches the power supply connected to the load 40 (41, 42) between the normal power supply 20 and the standby power supply 30.

[0043] This power supply switching section 14 is provided with two switches 141 and 142 constituted by electromagnetic contactors or the like. One of them serves as single-phase power supply switching means 141 for switching the power supply for the single-phase load 41, and the other serves as three-phase power supply switching means 142 for switching the power supply for the three-phase load 42. The single-phase power supply switching means 141 selectively connects the single-phase output section 131 provided in the load output section 13 to either the single-phase input section 111 provided in the normal power supply input section 11 or the single-phase input section 121 provided in the standby power supply input section 12, thereby switching the power supply connected to the single-phase load 41 between the normal power supply (commercial power supply) 20 and the standby power supply (engine-driven work machine) 30.

[0044] Also, the three-phase power supply switching means 142 selectively connects the three-phase output section 132 provided in the load output section 13 to either the three-phase input section 112 provided in the normal power supply input section 11 or the three-phase input section 122 provided in the standby power supply input section 12, thereby switching the power supply connected to the three-phase load 42 between the normal power supply (commercial power supply) 20 and the standby power supply (engine-driven work machine) 30.

[0045] In this way, the power supply switching device 10 of the present invention is configured to be able to independently perform switching of the power supply for the single-phase load 41 and switching of the power supply for the three-phase load 42 by providing the single-phase power supply switching means 141 and the three-phase power supply switching means 142 respectively.

[0046] The power supply switching device 10 is further provided with an operation control means 15 for controlling the operations of the single-phase power supply switching means 141 and the three-phase power supply switching means 142 provided in the power supply switching section 14.

[0047] This operation control means 15 is realized by an electronic control device such as a microcontroller. It receives the detection signal of the power failure detection means 113 provided in the normal power supply input section 11, monitors the power supply state from the normal power supply 20, and performs the following processes.

[0048] When power is being supplied from the normal power supply 20, a control signal for connecting the load output section 13 to the normal power supply input section is output to the power supply switching section 14, and the load 40 is connected to the normal power supply 20.

[0049] When a power failure (zero current or zero voltage) of the normal power supply 20 is detected, a control signal for starting the engine-driven generator 30, which is the standby power supply, is output to start the engine-driven generator 30. At the same time, a control signal for switching the connection of the load output section 13 from the normal power supply input section 11 to the standby power supply input section 12 is output to the power supply switching section 14, and the power supply connection to the load 40 is switched from the normal power supply 20 to the standby power supply 30.

[0050] When the restoration of the power failure of the normal power supply 20 is detected, a control signal for switching the connection to the load output section 13 from the standby power supply input section 12 to the normal power supply input section 11 is output to the power supply switching section 14, and the power supply connected to the load 40 is switched back from the standby power supply 30 to the normal power supply 20. At the same time, a control signal for stopping the engine-driven generator 30 is output to stop the engine-driven generator 30.

[0051] Among the power supply switching processes performed by the operation control means 15 in this way, when performing the process of switching the power supply connected to the load 40 from the normal power supply 20 to the standby power supply 30, the above-described operation control means 15 first executes the first switching process of switching the power supply of the first load (the three-phase load 42 in this embodiment), which is either the single-phase load 41 or the three-phase load 42, from the normal power supply 20 to the standby power supply 30, and then controls the operations of the single-phase power supply switching means 141 and the three-phase power supply switching means 142 of the above-described power supply switching unit 14 so as to execute the second switching process of switching the power supply of the second load (the single-phase load 41 in this embodiment), which is the other of the single-phase load 41 or the three-phase load 42, from the normal power supply 20 to the standby power supply 30.

[0052] Here, although it may be arbitrarily determined which of the single-phase load 41 and the three-phase load 42 is the first load, when either the single-phase load 41 or the three-phase load 42 is constituted by an electrical device provided with a drive source in which the starting current significantly increases with respect to the rated current, such as an induction motor, it is preferable to determine the first load and the second load according to the following criteria.

[0053] When the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is larger than the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r > I3r + I1s), the three-phase load 42 is taken as the first load and the single-phase load 41 is taken as the second load.

[0054] When the sum value (I3s + I1r) of the starting current I3s of the three-phase load 42 and the rated current I1r of the single-phase load 41 is smaller than the sum value (I3r + I1s) of the rated current I3r of the three-phase load 42 and the starting current I1s of the single-phase load 41 (I3s + I1r < I3r + I1s), the single-phase load 41 is taken as the first load and the three-phase load 42 is taken as the second load.

[0055] By determining the first load and the second load by the above method, the side where a device equipped with an induction motor or the like, which has a large increase rate of starting current with respect to the rated current, is connected as a load is set as the first load.

[0056] In this case, in advance, the values of the rated currents I1r and I3r and the starting currents I1s and I3s of the single-phase load 41 and the three-phase load 42 are stored in the storage means 151 provided in the operation control means 15, and the first load and the second load are determined based on the values of the rated currents I1r and I3r and the starting currents I1s and I3s stored in this storage means 151. It may be.

[0057] Alternatively, in advance, the values of the rated currents I1r and I3r of the single-phase load 41 and the three-phase load 42, the types of the single-phase load 41 and the three-phase load 42 (for example, motor load, inverter load, other loads), and the starting conditions of the motor load (for example, direct starting, Y-Δ starting, etc.) are stored in the storage means 151 provided in the operation control means 15, respectively. The first load and the second load may be determined based on the rated currents I1r and I3r stored in this storage means 151 and the starting currents I1s and I3s of the single-phase load 41 and the three-phase load calculated by the operation control means 15 based on the rated currents I1r and I3r and the types and starting conditions of the loads.

[0058] Thus, when the operation control means 15 is made to calculate the starting currents I1s and I3s based on the rated currents I1r and I3r, the storage means 151 further stores, for each type of load and starting condition of the motor load, the calculation coefficient of the starting current with respect to the rated currents I1r and I3r. For example, when starting directly in a motor load, the calculation coefficient is "5", when starting with Y-Δ in a motor load, the calculation coefficient is "4", when it is an inverter load, the calculation coefficient is "3", and when it is other loads, the calculation coefficient is "1.2". It may be calculated by multiplying the values of the rated currents I1r and I3r of the single-phase load 41 and the three-phase load 42 stored in the storage means 151 by the calculation coefficient specified based on the types and starting conditions of the loads stored in the storage means 151 to calculate the values of the starting currents I1s and I3s of the single-phase load 41 and the three-phase load 42.

[0059] Note that, in this embodiment, a case where the three-phase load 42 is the first load and the single-phase load 41 is the second load will be described as an example. However, depending on the type and combination of loads connected to the power supply switching device 10, conversely, there may be a case where the single-phase load 41 is the first load and the three-phase load 42 is the second load.

[0060] In this way, as a method of connecting to the standby power supply 30 in the order of the first load (three-phase load) 42 and the second load (single-phase load) 41, the operating sequences of the two switches 141 and 142 provided in the power supply switching unit 14 are determined in advance. To the output terminal 132 of the load output unit 13 connected to the switch 142 that operates first among these, the three-phase load 42, which is the first load in this embodiment, is connected. At the same time, the three-phase output unit 22 of the commercial power supply 20 and the three-phase output unit 32 of the standby power supply 30 are connected to the input terminal 112 of the commercial power supply input unit 11 and the input terminal 122 of the standby power supply input unit 12 connected to this switch 142. Thus, this switch is made into the three-phase power supply switching means 142. To the output terminal 131 of the load output unit 13 connected to the switch 141 that operates later, the single-phase load 41, which is the second load in this embodiment, is connected. At the same time, the single-phase output unit 21 of the commercial power supply 20 and the single-phase output unit 31 of the standby power supply 30 are connected to the input terminal 111 of the commercial power supply input unit 11 and the input terminal 121 of the standby power supply input unit 12 connected to this switch 141. It is also possible to make this switch into the single-phase power supply switching means 141.

[0061] Alternatively, which of the single-phase load 41 and the three-phase load 42 is the first load and the second load may be stored in advance in the storage means 151 provided in the operation control means 15. According to the correspondence relationship stored in the storage means by the operation control means, among the single-phase power supply switching means 141 and the three-phase power supply switching means 142, the power supply switching by the three-phase power supply switching means 142 to which the three-phase load 42, which is the first load, is connected is performed first, and then, the power supply switching by the single-phase power supply switching means 141 to which the single-phase load 41, which is the second load, is connected is performed. It may be configured in this way.

[0062] Here, even when attempting to adopt as small an engine-driven generator 30 as possible as the backup power source, in order to start the second load (single-phase load) after starting the first load (three-phase load) without stalling the engine, the rated output Pgr must be larger than the maximum value P1max of the power consumption at the start of the first load (three-phase load) 42, and also larger than the sum of the maximum value P2max of the power consumption at the start of the second load (single-phase load) 41 and the rated power consumption P1r of the first load (three-phase load) 42. And it is necessary to execute the second switching process, that is, start the second load (single-phase load) 41, at the timing when the sum of the maximum value P2max of the power consumption of the second load (single-phase load) 41 and the power consumption of the first load (three-phase load) at the time of occurrence of this maximum value P2max is less than or equal to the rated output Pgr of the engine-driven generator.

[0063] Therefore, taking the value obtained by subtracting the maximum value P2max of the power consumption at the start of the second load (single-phase load) 41 from the rated output Pgr of the engine-driven generator 30 as the determination reference power Ps, if the second load is started when the power consumption of the first load (three-phase load) 42 is less than or equal to this determination reference power, even when adopting as small an engine-driven generator 30 as possible as the backup power source, the first load (three-phase load) 42 and the second load (single-phase load) 41 can be started without stalling the engine.

[0064] From the above perspective, in this embodiment, after the operation control means 15 starts the first load (three-phase load) 42 by connecting it to the engine-driven generator 30 by executing the first switching process, when a predetermined start condition preset as a determination criterion for the power consumption of the first load (three-phase load) 42 being less than the determination reference power Ps is satisfied, the second switching process is executed to connect the second load (single-phase load) 41 to the engine-driven generator 30 and start it. Thus, the operation of the single-phase power source switching means 141 or the three-phase power source switching means 142 (in this embodiment where the single-phase load is the second load, the operation of the single-phase power source switching means 141) is controlled.

[0065] As such starting conditions, any of the conditions shown in the following Examples 1 to 3 can be adopted.

[0066] [Example 1] ·Elapse of the switching standby time (see Fig. 2) In this example (Example 1), after starting the start of the first load (three-phase load) 42 by executing the first switching process, the second switching process is executed using the elapse of a predetermined switching standby time Ts as the above-described starting condition to start the second load (single-phase load) 41.

[0067] In this example, the time required until the power consumption of the first load (three-phase load) 42 drops below the above-described determination reference power Ps is set as the "switching standby time Ts", and after the first switching process, the second switching process is executed using the fact that this switching standby time Ts has elapsed as the above-described starting condition, so that the sum of the maximum value P2max of the power consumption of the second load (single-phase load) and the power consumption of the first load (three-phase load) 42 at this time does not exceed the rated output Pgr of the engine-driven generator 30.

[0068] Here, since the time required for the direct starting of a general three-phase induction motor (the time required to increase to the rated rotational speed) is about 5 to 10 seconds and about 10 seconds for the star-delta starting, for example, if a time of about 10 seconds is secured as the above-described switching standby time Ts, it can be predicted that even if the first load is equipped with an induction motor or the like, the power consumption has dropped to near the rated power consumption, which is below the determination reference power Ps, and such a time may be set as the switching standby time Ts.

[0069] However, as long as this switching standby time Ts can be set as a time longer than the time required until the power consumption of the first load (three-phase load) 42 becomes below the above-described determination reference power Ps after starting, a time obtained in advance by experiments, calculations, etc. may be adopted, and it is not limited to the above example.

[0070] By executing the second switching process assuming that the start condition is satisfied as the switching standby time Ts elapses in this way, the second load (single-phase load) 41 can be started without exceeding the rated output Pgr of the engine-driven generator 30.

[0071] 〔Embodiment 2〕 · Decrease in power consumption of the first load to below the threshold value (see Fig. 3) In this embodiment (Embodiment 2), a threshold value Pth is set in advance within the range of not more than the above-described determination reference power Ps. After the execution of the first switching process, the change in the power consumption of the first load (three-phase load) 42 (see the broken-line graph in Fig. 3) is monitored. When the power consumption of the first load (three-phase load) 42 once exceeds the above-described threshold value Pth and then decreases again to below the threshold value Pth, the second switching process is executed using the above-described start condition.

[0072] In the above-described Embodiment 1, it is determined that the power consumption of the first load (three-phase load) 42 has decreased below the above-described determination reference power Ps as the predetermined switching standby time Ts elapses, and the second switching process is executed without measuring the actual change in the power consumption of the first load (three-phase load) 42.

[0073] Therefore, if for some reason the power consumption of the first load (three-phase load) 42 has not decreased below the determination reference power Ps even as the switching standby time Ts elapses, and the second load (single-phase load) 41 is started by executing the second switching process as the switching standby time Ts elapses, the total power consumption of the second load (single-phase load) 41 and the first load (three-phase load) 42 may exceed the rated output Pgr of the engine-driven generator 30, and there is a possibility of stalling the engine.

[0074] In contrast, in the configuration of this embodiment (Embodiment 2), the change in the power consumption of the first load (three-phase load) 42 is monitored in real time, and when the power consumption of the first load (three-phase load) 42 drops below a predetermined threshold value Pth set within the range of the determination reference power Ps or less, the second switching process is executed, thereby reliably preventing the second switching process from being executed when the power consumption of the first load (three-phase load) 42 is in a state higher than the determination reference power Ps.

[0075] 〔Embodiment 3〕 ·Elapse of the switching standby time and decrease of the power consumption of the first load to the threshold value (see Fig. 4) In this embodiment (Embodiment 3), the second switching process is executed using, as the above-described start condition, the satisfaction of both conditions: the elapse of the above-described switching standby time Ts and the power consumption of the first load (three-phase load) 42 being below the above-described threshold value Pth.

[0076] In the configuration of Embodiment 2 in which the second switching process is executed using only the fact that the power consumption of the first load (three-phase load) 42 has dropped below the above-described threshold value Pth as the start condition, for example, as shown in Fig. 4, when the power consumption of the first load (three-phase load) 42 shows a special change such that after once dropping below the threshold value Pth at the position of arrow B and then rising again above the threshold value Pth to the determination reference power Ps or more, the second switching process is started at the timing when it first drops below the threshold value Pth (the position of arrow B in Fig. 4(A)). In this case, as shown in Fig. 4(B), the subsequent increase in the power consumption of the first load (three-phase load) 42 and the increase in the power consumption at the start of the second load (single-phase load) 41 overlap, so that the total power consumption of the first load (three-phase load) 42 and the second load (single-phase load) 41 may exceed the rated output Pgr of the engine-driven generator 30 and stall the engine.

[0077] On the other hand, in the configuration of this embodiment (Embodiment 3), even if the power consumption of the first load (three-phase load) 42 drops below the threshold value Pth before the switching standby time Ts elapses, the second load (single-phase load) 41 is not started by the second switching process. Therefore, at the timing when the power consumption of the first load (three-phase load) 42 first drops below the threshold value Pth (arrow B in FIG. 4(A)), the second load (single-phase load) 41 is not started. Thus, it is possible to prevent the engine from stalling by starting the second load at this timing (arrow B position).

[0078] On the other hand, when the second switching process is executed with only the elapse of the switching standby time Ts as the start condition, if the power consumption of the first load (three-phase load) 42 that has risen again still exceeds the reference power Ps even when the switching standby time Ts has elapsed, and the second switching process is executed at this timing (arrow C in FIG. 4(A)) to start the second load (single-phase load) 41, as shown in FIG. 4(C), the total power consumption of the first load (three-phase load) 42 and the second load (single-phase load) 41 may exceed the rated output Pgr of the engine-driven generator 30.

[0079] On the other hand, in the configuration of this embodiment (Embodiment 3), even if the switching standby time Ts has elapsed, if the power consumption of the first load (three-phase load) 42 at this time has not dropped below the predetermined threshold value Pth, the second switching process is not executed. The second switching process is performed at the timing when the power consumption of the first load drops below the threshold value for the second time (arrow A in FIG. 4(A)). Therefore, it is also possible to prevent the engine from stalling that may occur when the second switching process is executed with only the elapse of the switching standby time Ts as the start condition.

Explanation of Signs

[0080] 10 Power switching device 11 Input section for normal power supply 111 Single-phase input section 112 Three-phase input section 113 Power failure detection means 12 Input section for emergency power supply 121 Single-phase input section 122 Three-phase input section 13 Output section for load 131 Single-phase output section 132 Three-phase output section 14 Power supply switching section 141 Single-phase power supply switching means (switch) 142 Three-phase power supply switching means (switch) 15 Operation control means 151 Memory means 20 Normal power supply (commercial power supply) 21 Single-phase lead-in wire (single-phase output section) 22 Three-phase lead-in wire (three-phase output section) 30 Emergency power supply (engine-driven generator) 31 Single-phase output section 32 Three-phase output section 33, 34 Cable 40 Load 41 Single-phase load 42 Three-phase load I1s Starting current of single-phase load I3s Starting current of three-phase load I1r Rated current of single-phase load I3r Rated current of three-phase load Pgr, Pgr’ Rated output of engine-driven generator (single-phase + three-phase) Ps Judgment reference power Pth Threshold value Pcr Total of rated power consumption of single-phase load and rated power consumption of three-phase load Pcmax Maximum value of total power consumption of single-phase load and three-phase load P1max Maximum value of power consumption of first load P2max Maximum value of power consumption of second load P1r Rated power consumption of first load Ts Switching standby time

Claims

1. In a power supply switching method for switching a power supply connected to a load between a normal power supply and a standby power supply, an engine-driven generator capable of simultaneously performing single-phase output and three-phase output with a single unit is provided as the standby power supply, and a single-phase output section and a three-phase output section are provided for each of the normal power supply and the standby power supply, and a single-phase load and a three-phase load are provided as the load, either the normal power supply or the standby power supply can be connected to the single-phase load via the single-phase output section of the normal power supply or the single-phase output section of the standby power supply, either the normal power supply or the standby power supply can be connected to the three-phase load via the three-phase output section of the normal power supply or the three-phase output section of the standby power supply, when switching the power supply connected to the load from the normal power supply to the standby power supply, first, a first switching process of switching the power supply connected to a first load, which is either the single-phase load or the three-phase load, from the normal power supply to the standby power supply is executed, then, a second switching process of switching the power supply connected to a second load, which is the other of the single-phase load or the three-phase load, from the normal power supply to the standby power supply is executed. A power supply switching method characterized by this.

2. Based on the rated current and starting current values of the three-phase load and the single-phase load respectively specified in advance, or based on the rated current values of the three-phase load and the single-phase load respectively specified in advance and the starting current values of the three-phase load and the single-phase load calculated from the rated current values, the sum of the starting current of the three-phase load and the rated current of the single-phase load and the sum of the rated current of the three-phase load and the starting current of the single-phase load are compared, when the sum of the starting current of the three-phase load and the rated current of the single-phase load is greater than the sum of the rated current of the three-phase load and the starting current of the single-phase load, the three-phase load is made the first load and the single-phase load is made the second load, when the sum of the starting current of the three-phase load and the rated current of the single-phase load is smaller than the sum of the rated current of the three-phase load and the starting current of the single-phase load, the single-phase load is made the first load and the three-phase load is made the second load. The power supply switching method according to Claim 1, characterized by this.

3. A value obtained by subtracting the maximum value of the power consumption at the start of the second load from the rated output of the engine-driven generator is used as a determination reference power. When a predetermined start condition set in advance as a criterion for determining that the power consumption of the first load is equal to or less than the determination reference power after the execution of the first switching process is satisfied, the second switching process is executed. The power supply switching method according to claim 2, characterized in that.

4. The power supply switching method according to claim 3, characterized in that the second switching process is executed using, as the start condition, that a predetermined switching standby time has elapsed since the execution of the first switching process.

5. The power supply switching method according to claim 3, characterized in that the second switching process is executed using, as the start condition, that after the execution of the first switching process, the power consumption of the first load has dropped below a predetermined threshold set within a range where the power consumption is equal to or less than the determination reference power.

6. The power supply switching method according to claim 3, characterized in that the second switching process is executed using, as the start condition, that a predetermined switching standby time has elapsed since the execution of the first switching process and that after the execution of the first switching process, the power consumption of the first load has dropped below a predetermined threshold set within a range where the power consumption is equal to or less than the determination reference power.

7. In a power supply switching device that switches the power supply connected to a load between a main power supply and a backup power supply, a main power supply input unit connected to the main power supply, a backup power supply input unit connected to the backup power supply, and a load output unit connected to the load are provided. A single-phase input unit and a three-phase input unit are provided in each of the main power supply input unit and the backup power supply input unit, and a single-phase output unit to which a single-phase load is connected and a three-phase output unit to which a three-phase load is connected are provided in the load output unit. Single-phase power supply switching means for connecting the single-phase output unit of the load output unit to one of the single-phase input units of the main power supply input unit or the backup power supply input unit. Three-phase power supply switching means for connecting the three-phase output unit of the load output unit to one of the three-phase input units of the main power supply input unit or the backup power supply input unit are provided respectively. An operation control means for controlling the operations of the single-phase power supply switching means and the three-phase power supply switching means is further provided. When switching the power supply connected to the load from the main power supply to the backup power supply, the operation control means first executes a first switching process of switching the power supply connected to a first load, which is either the single-phase load or the three-phase load, from the main power supply to the backup power supply. Next, a second switching process is executed to switch the power supply connected to the second load, which is the other of the single-phase load or the three-phase load, from the normal power supply to the standby power supply. A power supply switching device characterized by this.

8. The operation control means includes a storage means, and based on the rated current and starting current values of the three-phase load and the single-phase load respectively stored in the storage means in advance, or based on the rated current values of the three-phase load and the single-phase load respectively stored in the storage means in advance and the starting current values of the three-phase load and the single-phase load respectively calculated from the rated current values, the sum of the starting current of the three-phase load and the rated current of the single-phase load, and the sum of the rated current of the three-phase load and the starting current of the single-phase load are compared, and for the single-phase power supply switching means and the three-phase power supply switching means, When the sum of the starting current of the three-phase load and the rated current of the single-phase load is greater than the sum of the rated current of the three-phase load and the starting current of the single-phase load, the three-phase load is made the first load, and the single-phase load is made the second load, and the first switching process and the second switching process are executed. When the sum of the starting current of the three-phase load and the rated current of the single-phase load is smaller than the sum of the rated current of the three-phase load and the starting current of the single-phase load, the single-phase load is made the first load and the three-phase load is made the second load, and the first switching process and the second switching process are executed. The power supply switching device according to claim 7, characterized by this.

9. A value obtained by subtracting the maximum value of the power consumption at the start of the second load from the rated output of the engine-driven generator is used as the determination reference power. When a predetermined start condition set in advance as a determination criterion for the power consumption of the first load being equal to or less than the determination reference power after the execution of the first switching process is satisfied, the operation control means executes the second switching process. The power supply switching device according to claim 8, characterized by this.

10. The storage means stores a predetermined switching standby time as the start condition, and when the switching standby time has elapsed after the execution of the first switching process, the operation control means causes the single-phase power supply switching means or the three-phase power supply switching means to execute the second switching process on the assumption that the start condition is satisfied. The power supply switching device according to claim 9, characterized by this.

11. The memory means stores a predetermined threshold value set within a range equal to or lower than the determination reference power as the start condition, and the operation control means causes the single-phase power supply switching means or the three-phase power supply switching means to execute the second switching process on the assumption that the start condition is satisfied when the power consumption of the first load drops below the threshold value after the execution of the first switching process. The power supply switching device according to claim 9, characterized in that.

12. The memory means stores both a predetermined switching standby time and a predetermined threshold value set within a range equal to or lower than the determination reference power as the start condition, and the operation control means causes the single-phase power supply switching means or the three-phase power supply switching means to execute the second switching process on the assumption that the start condition is satisfied when the switching standby time has elapsed and the power consumption of the first load has dropped below the threshold value after the execution of the first switching process. The power supply switching device according to claim 9, characterized in that.

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