Initial excitation circuit, method for diagnosing the initial excitation circuit

Abstract

This initial excitation circuit is electrically connected to the excitation coil of a power generator to excite the excitation coil during the start-up of the power generator and comprises: an input terminal connected to a power supply supplying a DC power; an output terminal connected to the excitation coil via a brush and a spring which are possessed by the power generator; a breaker connected between the input terminal and the output terminal; and a control circuit for controlling the breaker.

Description

Technical Field

[0001] The present invention relates to an initial excitation circuit for exciting an excitation coil of a generator when the generator is started, and a diagnosis method thereof.

Background Art

[0002] Conventionally, a vehicle electric drive system is known that drives a generator using an internal combustion engine such as a diesel engine as a power source, and obtains a driving force for running a work vehicle by driving a motor using the generated electric power obtained thereby (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For the generator mounted on the electric drive system described in Patent Document 1, for example, a three-phase AC generator with brushes can be used. In this case, the excitation coil can be excited using the electromotive force during power generation, and the generator can be maintained in a power generation state. On the other hand, when starting the generator from a stopped state, the excitation coil can be excited using the electromotive force generated by the residual magnetic flux, and the generator can be brought into a power generation state. However, since the amount of residual magnetic flux is unstable, there is a possibility that the excitation coil cannot be properly excited when the generator is started. Also, when a poor contact occurs between the brush and the slip ring, there is a possibility that the excitation coil cannot be properly excited. In such a case, there is a risk that the generator becomes inoperable and the running of the work vehicle cannot be started.

[0005] In view of the above problems, a main object of the present invention is to surely start the generator mounted on a work vehicle. [Means for solving the problem]

[0006] The initial excitation circuit according to the present invention is electrically connected to the excitation coil of a generator and excites the excitation coil when the generator is started, and comprises an input terminal connected to a power source that supplies DC power, an output terminal connected to the excitation coil via brushes and slip rings of the generator, a circuit breaker connected between the input terminal and the output terminal, and a control circuit for controlling the circuit breaker. The method for diagnosing an initial excitation circuit according to the present invention is a method for diagnosing an initial excitation circuit that is electrically connected to the excitation coil of a generator and excites the excitation coil when the generator is started, wherein the initial excitation circuit comprises a positive input terminal connected to the positive side of a power supply that supplies DC power, a negative input terminal connected to the negative side of the power supply, a positive output terminal connected to one end of the excitation coil via brushes and slip rings of the generator, a negative output terminal connected to the other end of the excitation coil via the brushes and slip rings, and the positive input terminal The system includes a first circuit breaker connected between the positive output terminals, a second circuit breaker connected between the negative input terminal and the negative output terminal, and a diode between the first circuit breaker and the positive output terminal, with the anode connected to the first circuit breaker side and the cathode connected to the positive output terminal side. The system acquires a first voltage value corresponding to the voltage between the first circuit breaker and the diode, and a second voltage value corresponding to the voltage between the second circuit breaker and the negative output terminal, and diagnoses the initial excitation circuit based on the acquired first and second voltage values. [Effects of the Invention]

[0007] According to the present invention, a generator mounted on a work vehicle can be reliably started. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing a work vehicle equipped with a power generation device according to one embodiment of the present invention. [Figure 2]Configuration diagram of a power generation device relating to one embodiment of the present invention. [Figure 3] Diagram illustrating the diagnostic operation of the initial excitation circuit. [Figure 4] A flowchart illustrating the diagnostic process performed in the initial excitation circuit. [Figure 5] A diagram showing a list of diagnostic findings. [Figure 6] A diagram showing the correspondence between diagnostic conditions and diagnostic results for each type of diagnosis. [Modes for carrying out the invention]

[0009] In the following, an embodiment of the power generation device of the present invention will be described using the case where the work vehicle on which the power generation device is installed is a mining dump truck as an example.

[0010] Figure 1 is a schematic diagram showing a work vehicle equipped with a power generation device according to one embodiment of the present invention. The work vehicle, a dump truck 100, is equipped with a power generation device 1, an internal combustion engine 2, a rectifier circuit 3, an inverter 4, and an AC motor 5 as its drive system. The dump truck 100 has tires driven by the AC motor 5 and is further equipped with a driver's cab, a cargo bed (vessel), a hoist for raising and lowering the cargo bed, etc. It is used, for example, in a mine to transport excavated materials and waste within the mine.

[0011] The power generator 1 is driven by an internal combustion engine 2 to generate electricity, producing alternating current (AC) power which is then output to a rectifier circuit 3. The internal combustion engine 2 is, for example, a diesel engine, which drives the power generator 1 by transmitting the driving force generated by burning fuel to the power generator 1. The rectifier circuit 3 rectifies the AC power input from the power generator 1, converts it into DC power, and outputs it to an inverter 4. The inverter 4 uses the DC power input from the rectifier circuit 3 to generate AC power of the desired voltage and frequency, and outputs it to an AC motor 5. The AC motor 5 is driven by the AC power input from the inverter 4, generating the driving force necessary to move the dump truck 100. This allows the dump truck 100 to move.

[0012] Alternatively, a secondary battery may be installed between the rectifier circuit 3 and the inverter 4, and DC power may be temporarily stored and used in this secondary battery.

[0013] Figure 2 is a diagram showing the configuration of a power generation device according to one embodiment of the present invention. As shown in Figure 2, the power generation device 1 comprises a generator 10, an excitation circuit 20, and an initial excitation circuit 30.

[0014] The generator 10 is a brushed three-phase AC generator and has a stator 11, an excitation coil 12, slip rings 13a, 13b, brushes 14a, 14b, a U-phase output line 15u, a V-phase output line 15v, and a W-phase output line 15w.

[0015] The excitation coil 12 is excited by the flow of DC power supplied from the excitation circuit 20 or the initial excitation circuit 30, generating magnetic flux. The excitation coil 12 is installed on a rotor (not shown), and when the internal combustion engine 2 rotates the rotor, the excitation coil 12 rotates along with it inside the stator 11. This changes the amount of magnetic flux linked to the stator coil (not shown) installed on the stator 11, generating an electromotive force in the stator coil, which in turn generates electricity in the generator 10.

[0016] The three-phase AC power generated by the generator 10 is output via the U-phase output line 15u, the V-phase output line 15v, and the W-phase output line 15w. The U-phase output line 15u, the V-phase output line 15v, and the W-phase output line 15w are connected to the rectifier circuit 3 shown in Figure 1, respectively. As a result, the three-phase AC power is output from the power generator 1 to the rectifier circuit 3, where it is converted into DC power.

[0017] Slip rings 13a and 13b are connected to both ends of the excitation coil 12. The slip rings 13a and 13b rotate about the same rotation axis as the rotor as the rotor is rotationally driven. The brushes 14a and 14b are electrically connected to the excitation circuit 20 and the initial excitation circuit 30, and are fixedly arranged in the generator 10 so as to slide with respect to the rotation of the slip rings 13a and 13b respectively. Thereby, even when the rotor is rotationally driven, DC power can be supplied from the excitation circuit 20 or the initial excitation circuit 30 to the excitation coil 12.

[0018] The excitation circuit 20 is a circuit that excites the excitation coil 12 when the generator 10 is in a power generation state. The excitation circuit 20 includes reactors 21u, 21v, 21w, an excitation control circuit 22, and rectifying diodes 23a, 23b, 23c, 23d, 23e, 23f.

[0019] The reactors 21u, 21v, 21w are respectively connected to the U-phase output line 15u, the V-phase output line 15v, and the W-phase output line 15w. A part of the AC power of each phase flowing through the U-phase output line 15u, the V-phase output line 15v, and the W-phase output line 15w is output to the rectifying diodes 23a - 23f via the reactors 21u, 21v, 21w.

[0020] The rectifying diodes 23a - 23f rectify the AC power input via the reactors 21u, 21v, 21w, convert it into DC power, and output it to the generator 10. In the generator 10, the DC power input from the rectifying diodes 23a - 23f is output to the excitation coil 12 via the brushes 14a, 14b and the slip rings 13a, 13b. Thereby, an excitation current flows through the excitation coil 12 in the generator 10, and the excitation coil 12 is excited.

[0021] The excitation control circuit 22 controls the amount of current flowing through the reactors 21u, 21v, 21w respectively. Thereby, the DC power output from the rectifying diodes 23a - 23f to the generator 10 is controlled, and the excitation current flowing through the excitation coil 12 is adjusted.

[0022] The initial excitation circuit 30 is a circuit that excites the excitation coil 12 when starting the generator 10 from a stopped state. The initial excitation circuit 30 has resistors 31, 32, relays 33, 34, diode 35, capacitor 36, discharge resistor 37, control circuit 40, interface circuits 41, 42, 43, 44, positive input terminal 45p, negative input terminal 45n, positive output terminal 46p, and negative output terminal 46n.

[0023] The positive input terminal 45p is connected to the positive side of the battery 52 via the power switch 53. The negative input terminal 45n is connected to the negative side of the battery 52. ​​The battery 52 is a power source that supplies DC power to the initial excitation circuit 30 and is configured using, for example, a lead-acid battery. The battery 52 is connected to the charger 51 and is charged as needed by the charger 51. The charger 51 is configured using, for example, an alternator that is driven by the internal combustion engine 2 to generate electricity.

[0024] The power switch 53 is a switch for switching the power supply from the battery 52 to the initial excitation circuit 30. The power switch 53 is switched in conjunction with a start switch (not shown) provided on the dump truck 100, for example. That is, when the start switch of the dump truck 100 is switched on and the dump truck 100 is started, the power switch 53 is switched on accordingly, and power supply from the battery 52 to the initial excitation circuit 30 begins. In the following description, the power switch 53 may be abbreviated as "SW0".

[0025] Relay 33 has one end connected to the positive input terminal 45p via resistor 31, and the other end connected to the positive output terminal 46p via diode 35. Relay 34 has one end connected to the negative input terminal 45n via resistor 32, and the other end connected to the negative output terminal 46n. Relays 33 and 34, which are circuit breakers, are connected to the control circuit 40, and the control circuit 40 switches them to either a conduction state or a disconnection state, thereby switching the electrical connection state between the battery 52, the capacitor 36, and the excitation coil 12. In the following description, relays 33 and 34 may be abbreviated as "RL1" and "RL2," respectively.

[0026] When relays 33 and 34 are switched from the off state to the conductive state, DC power supplied from the battery 52 is output to the excitation coil 12 via resistors 31 and 32, relays 33 and 34, and diode 35. As a result, even when the generator 10 is stopped, an excitation current flows to the excitation coil 12 in the generator 10, and the excitation coil 12 can be excited. Subsequently, when the generator 10 is started and enters the power generation state, and power is supplied from the excitation circuit 20 to the excitation coil 12, relays 33 and 34 are switched to the off state to prevent the high-voltage DC power output from the excitation circuit 20 from flowing into the battery 52.

[0027] Resistors 31 and 32 are provided to limit the charging current that flows when relays 33 and 34 are switched to a conductive state and capacitor 36 is charged, so that the charging current does not exceed the rated current of relays 33 and 34 or diode 35. Diode 35 is provided between relay 33 and the positive output terminal 46p, with the anode connected to relay 33 and the cathode connected to the positive output terminal 46p. This prevents current from flowing back from the initial excitation circuit 30 to the battery 52. ​​Discharge resistor 37 is provided to discharge the residual charge of capacitor 36 when the generator 10 is stopped to ensure safety.

[0028] The control circuit 40 is a circuit that controls the operation of the initial excitation circuit 30 and is configured using a processing unit such as a microcontroller. The control circuit 40 has input terminals AI1 and AI2 and output terminals DO1 and DO2. Input terminals AI1 and AI2 are connected to the positive output terminal 46p side of relay 33 and the negative output terminal 46n side of relay 34, respectively, via interface circuits 41 and 42. Interface circuits 41 and 42 detect the voltage between relay 33 and diode 35 and the voltage between relay 34 and negative output terminal 46n, respectively, and convert these detected voltage values ​​into voltage values ​​corresponding to the input voltage characteristics of the control circuit 40 and output them to input terminals AI1 and AI2, respectively. As a result, the control circuit 40 can acquire voltage values ​​corresponding to the voltage between relay 33 and diode 35 and voltage values ​​corresponding to the voltage between relay 34 and negative output terminal 46n at input terminals AI1 and AI2, respectively, and monitor these voltages.

[0029] The output terminals DO1 and DO2 of the control circuit 40 are connected to relays 33 and 34, respectively, via interface circuits 43 and 44. Output terminals DO1 and DO2 output relay switching signals to interface circuits 43 and 44, respectively, to switch relays 33 and 34 from an open state to an open state. Interface circuits 43 and 44 convert the relay switching signals input from output terminals DO1 and DO2 into signals suitable for the operation of relays 33 and 34, respectively, and output them to relays 33 and 34. As a result, the control circuit 40 can control the switching operation of relays 33 and 34 using the relay switching signals output from output terminals DO1 and DO2.

[0030] Generally, in a three-phase AC generator, rotating the rotor from a stationary state generates an electromotive force due to residual magnetic flux. This electromotive force from residual magnetic flux can be used to excite the excitation coils, thereby starting the generator. However, because the amount of residual magnetic flux is unstable, it is not always possible to properly excite the excitation coils when starting the generator. In addition, in brushed three-phase AC generators, accidental contact failures can occur due to the formation of an oxide film between the brushes and slip rings or the adhesion of foreign matter (contamination). In such cases, even if the rotor is rotated, the excitation coils may not be properly excited, and in the worst case, the generator may not be able to start.

[0031] Therefore, in the power generation device 1 of this embodiment, an initial excitation circuit 30 is connected to the generator 10, and when the generator 10 is started, the control circuit 40 switches relays 33 and 34 to a conductive state. This charges the capacitor 36 using DC power supplied from the battery 52, and the charge stored in the capacitor 36 reliably excites the excitation coil 12 via the brushes 14a and 14b and slip rings 13a and 13b.

[0032] However, if the diode 35 in the initial excitation circuit 30 shorts out and the relays 33 and 34 are stuck in the ON state and cannot be switched to the OFF state, after the generator 10 starts up, the generator potential of the generator 10 will be electrically coupled to the battery 52 via the excitation circuit 20 and the initial excitation circuit 30. As a result, there is a risk of damaging the battery 52 and other equipment connected to the battery 52. ​​To prevent this, in the power generator 1 of this embodiment, the initial excitation circuit 30 diagnoses itself when the generator 10 starts up, and if an abnormality is detected, it forcibly switches the relays 33 and 34 to the OFF state to protect the battery 52 and other equipment.

[0033] The diagnostic operation of the initial excitation circuit 30 will be described below with reference to Figure 3. Figure 3 is an explanatory diagram of the diagnostic operation of the initial excitation circuit 30.

[0034] When starting the dump truck 100 equipped with the generator 1, the power switch 53 (SW0) is switched from off to on (time t0) in order to activate the on-board system including the generator 1. This starts the supply of power from the battery 52 to the initial excitation circuit 30, applies a DC voltage between the positive input terminal 45p and the negative input terminal 45n, and activates the control circuit 40.

[0035] Once the control circuit 40 has finished starting up, it switches relays 33 and 34 (RL1 and RL2) from off to on (time t1). This starts charging the capacitor 36 from the battery 52, and the potential of the anode side of the diode 35 gradually rises. As a result, as shown in Figure 3, the voltage at the input terminal AI1 rises at a predetermined time constant after time t1. This time constant is determined by the resistance values ​​of resistors 31 and 32 and the capacitance value of capacitor 36.

[0036] When capacitor 36 is charged, a DC voltage corresponding to the amount of charge stored in capacitor 36 is applied between the positive output terminal 46p and the negative output terminal 46n. This DC voltage is output to the excitation coil 12 via brushes 14a, 14b and slip rings 13a, 13b, and the excitation coil 12 is excited.

[0037] When the voltage at input terminal AI1 rises sufficiently and exceeds a predetermined threshold Vth1, and RL1 is switched off while RL2 remains on (time t2), the connection between battery 52 and capacitor 36 is interrupted, and the voltage at input terminal AI1 becomes 0. Subsequently, when RL1 is switched on and RL2 is switched off respectively (time t3), the voltage at input terminal AI1 rises again in accordance with the voltage on the positive terminal side of battery 52, returning to the state before time t2, and the voltage at input terminal AI2 rises accordingly. After time t3, the voltage at input terminal AI2 gradually decreases to 0.

[0038] As explained above, in the initial excitation circuit 30, the voltages at input terminals AI1 and AI2 change according to the switching state of RL1 and RL2. The control circuit 40 can diagnose the initial excitation circuit 30 by monitoring the voltages at these input terminals AI1 and AI2.

[0039] Figure 4 is a flowchart showing the diagnostic process performed in the initial excitation circuit 30. The process shown in the flowchart of Figure 4 is carried out by the control circuit 40 of the initial excitation circuit 30, for example, by executing a predetermined program.

[0040] When the power switch 53 is switched on and the control circuit 40 has finished starting up, in step S10 the control circuit 40 sets the value of variable t to the processing start time t1. In the next steps S20 and S30, the control circuit 40 outputs relay switching signals from output terminals DO1 and DO2, respectively, to switch RL1 and RL2 on. As a result, if the initial excitation circuit 30 is functioning correctly, charging from the battery 52 to the capacitor 36 begins, as explained in Figure 3, and the potential of the anode side of the diode 35 gradually rises.

[0041] In step S40, the control circuit 40 adds a predetermined value x to the value of the variable t, which was set to t=t1 in step S10. This predetermined value x is a count-up value used to determine time t2 in Figure 3, and is set in advance according to the processing cycle when the control circuit 40 executes the process shown in the flowchart of Figure 4.

[0042] In step S50, the control circuit 40 determines whether the value of variable t has reached t2. Time t2 is the time when, assuming the initial excitation circuit 30 is functioning correctly, the voltage at input terminal AI1 exceeds the aforementioned threshold Vth1, relative to the processing start time t1. This time is predetermined according to a time constant based on the resistance values ​​of resistors 31 and 32 and the capacitance value of capacitor 36. If the result of the determination in step S50 is that the value of variable t has not reached t2, the process returns to step S20 and is repeated. When t=t2, the process proceeds to the next step S60.

[0043] In step S60, the control circuit 40 detects the voltage at input terminal AI1 and determines whether this voltage is equal to or greater than the threshold Vth1. The threshold Vth1 is preset according to the voltage at which the battery 52 charges the capacitor 36. Specifically, for example, the threshold Vth1 is set within a range that does not exceed the value obtained by subtracting the forward voltage of the diode 35 from the voltage values ​​obtained by dividing the output voltage of the battery 52 according to the voltage division ratio of resistors 31, 32 and discharge resistor 37. If the result of the determination in step S60 is that the voltage at input terminal AI1 is equal to or greater than the threshold Vth1, it is determined that the capacitor 36 is being charged normally, and the process proceeds to step S70. On the other hand, if the voltage at input terminal AI1 is less than the threshold Vth1, it is determined that the capacitor 36 is not being charged normally, and the process proceeds to step S65.

[0044] In step S65, the control circuit 40 obtains a diagnosis that a charging abnormality has occurred in the initial excitation circuit 30 due to a break in the wire or other cause, and therefore the capacitor 36 is not sufficiently charged. After completing step S65, the process proceeds to step S115.

[0045] In step S70, the control circuit 40 stops the output of the relay switching signal from output terminal DO1, which was started in step S20, and switches RL1 to OFF. As a result, if the initial excitation circuit 30 is functioning correctly, the connection between the battery 52 and the capacitor 36 is interrupted, as explained in Figure 3, causing the voltage at input terminal AI1 to drop to near zero.

[0046] In step S80, the control circuit 40 detects the voltage at input terminal AI1 and determines whether this voltage is less than or equal to the threshold Vth2. The threshold Vth2 is preset according to the voltage generated on the anode side of diode 35 when the connection between battery 52 and capacitor 36 is interrupted. As a result of the determination in step S80, if the voltage at input terminal AI1 is less than or equal to the threshold Vth2, it is determined that the connection between battery 52 and capacitor 36 has been properly interrupted, and the process proceeds to step S90. On the other hand, if the voltage at input terminal AI1 is greater than the threshold Vth2, it is determined that the connection between battery 52 and capacitor 36 has not been properly interrupted, and the process proceeds to step S85.

[0047] In step S85, the control circuit 40 obtains a diagnosis result indicating that a short circuit failure in diode 35 or an ON-fixation abnormality of RL1 has occurred in the initial excitation circuit 30, and therefore the voltage of battery 52 or capacitor 36 is detected on the anode side of diode 35. After completing step S85, the process proceeds to step S115.

[0048] In step S90, the control circuit 40 resumes outputting the relay switching signal from output terminal DO1, which was stopped in step S70, and switches RL1 to ON. It also stops outputting the relay switching signal from output terminal DO2, which was started in step S30, and switches RL2 to OFF. As a result, if the initial excitation circuit 30 is functioning correctly, the voltage at input terminal AI2 will rise, as explained at time t3 in Figure 3.

[0049] In step S100, the control circuit 40 detects the voltage at input terminal AI2 and determines whether this voltage is equal to or greater than a predetermined threshold Vth3. If the result of the determination in step S100 is that the voltage at input terminal AI2 is equal to or greater than the threshold Vth3, it is determined that the connection between the battery 52 and the capacitor 36 has been properly disconnected, and the process proceeds to step S110. On the other hand, if the voltage at input terminal AI2 is less than the threshold Vth3, it is determined that the connection between the battery 52 and the capacitor 36 has not been properly disconnected, and the process proceeds to step S105.

[0050] In step S105, the control circuit 40 obtains a diagnosis result indicating that an ON-fixation abnormality of RL2 has occurred in the initial excitation circuit 30. After completing step S105, the process proceeds to step S115.

[0051] In step S110, the control circuit 40 obtains a diagnosis result indicating that the initial excitation circuit 30 is functioning correctly. In this case, RL1 and RL2 are switched back on to start the initial excitation circuit 30, and when the generator 10 is started, DC power supplied from the battery 52 is output to the excitation coil 12, thereby exciting the excitation coil 12. Subsequently, when the generator 10 is started and power is supplied from the excitation circuit 20 to the excitation coil 12, RL1 and RL2 are switched off.

[0052] In step S115, the control circuit 40, depending on the abnormality diagnosis result in steps S65, S85, or S105, stops the output of relay switching signals from output terminals DO1 and DO2, respectively, and forcibly shuts off RL1 and RL2 in order to protect the battery 52 and other circuits. This ensures that even if one of the circuit breakers, RL1 or RL2, is diagnosed as being stuck in the ON position in step S85 or S105, the other circuit breaker is switched to the OFF state to reliably disconnect the electrical connection with the battery 52, preventing the generated potential of the generator 10 from being transmitted to the battery 52. ​​However, if at least RL1 and diode 35 are normal, the battery 52 can be protected by turning off RL1, so the process in step S115 may be omitted after step S105, and the operation of the initial excitation circuit 30 may be continued.

[0053] After the processing in step S110 or S115, in step S120, the control circuit 40 notifies an external party of the diagnostic result of the initial excitation circuit 30. Here, for example, the diagnostic result is transmitted to a display device (not shown) mounted on the dump truck 100, and the driver of the dump truck 100 is notified of the diagnostic result of the initial excitation circuit 30 by displaying the diagnostic result on this display device. Alternatively, for example, the diagnostic result may be output to a transmission device (not shown) mounted on the dump truck 100, and the diagnostic result may be transmitted from this transmission device to the management center of the dump truck 100, thereby notifying the administrator in the management center of the diagnostic result of the initial excitation circuit 30. In addition to the above, it is possible to notify any party of the diagnostic result of the initial excitation circuit 30 by any other method.

[0054] After completing the process in step S120, the control circuit 40 terminates the diagnostic process shown in the flowchart of Figure 4.

[0055] Figure 5 is a diagram showing a list of diagnostic procedures performed in the initial excitation circuit 30. As shown in the table in Figure 5, at time t2 after the capacitor 36 has been charged, a diagnosis is performed to determine whether RL1 and RL2 have been successfully switched to the ON state by the process in step S60 of Figure 4. Subsequently, between time t2 and time t3, a diagnosis is performed to determine whether RL1 has been successfully switched to the OFF state and whether diode 35 has short-circuited. At time t3, a diagnosis is performed to determine whether RL2 has been successfully switched to the OFF state by the process in step S100 of Figure 4.

[0056] Figure 6 is a diagram showing the correspondence between diagnostic conditions and diagnostic results for each diagnostic item. As shown in the table in Figure 6, in the ON diagnostic of RL1 and RL2 performed at time t2, RL1 and RL2 are switched to the ON state, and the voltage at input terminal AI1 is compared with the threshold Vth1. As a result, if the voltage at input terminal AI1 is greater than or equal to the threshold Vth1, the ON operation of RL1 and RL2 is diagnosed as normal; if it is less than the threshold Vth1, RL1 or RL2 is diagnosed as having an open fault. In addition, in the OFF diagnostic of RL1 and the diagnosis of diode 35 performed between time t2 and time t3, RL1 is switched to the OFF state and RL2 is switched to the ON state, and the voltage at input terminal AI1 is compared with the threshold Vth2. As a result, if the voltage at input terminal AI1 is less than or equal to the threshold Vth2, the OFF operation of RL1 and diode 35 are diagnosed as normal; if it is greater than the threshold Vth2, RL1 or diode 35 is diagnosed as having a short fault. During the RL2 off-diagnosis performed at time t3, RL1 is switched to the ON state and RL2 to the OFF state, and the voltage at input terminal AI2 is compared with the threshold Vth3. As a result, if the voltage at input terminal AI2 is equal to or greater than the threshold Vth3, the RL2 off operation is diagnosed as normal; if it is less than the threshold Vth3, RL2 is diagnosed as having a short-circuit fault.

[0057] According to the embodiment of the present invention described above, the following effects are achieved.

[0058] (1) The initial excitation circuit 30 is electrically connected to the excitation coil 12 of the generator 10 and excites the excitation coil 12 when the generator 10 is started. The initial excitation circuit 30 includes an input terminal (positive input terminal 45p and negative input terminal 45n) connected to a battery 52 that supplies DC power, an output terminal (positive output terminal 46p and negative output terminal 46n) connected to the excitation coil 12 via brushes 14a, 14b and slip rings 13a, 13b of the generator 10, a circuit breaker (relays 33, 34) connected between the input terminal and the output terminal, and a control circuit 40 that controls the circuit breaker. In this way, the generator 10 mounted on the dump truck 100, which is a work vehicle, can be reliably started.

[0059] (2) The input terminals of the initial excitation circuit 30 include a positive input terminal 45p connected to the positive side of the battery 52 and a negative input terminal 45n connected to the negative side of the battery 52. ​​The output terminals include a positive output terminal 46p connected to one end of the excitation coil 12 and a negative output terminal 4n connected to the other end of the excitation coil 12. The circuit breaker of the initial excitation circuit 30 includes a relay 33 connected between the positive input terminal 45p and the positive output terminal 46p, and a relay 34 connected between the negative input terminal 45n and the negative output terminal 46n. In this way, the DC current flowing through the excitation coil 12 can be reliably controlled in the initial excitation circuit 30 using the DC power supplied from the battery 52.

[0060] (3) The initial excitation circuit 30 further includes a diode 35 connected between the relay 33 and the positive output terminal 46p, the diode 35 having its anode connected to the relay 33 side and its cathode connected to the positive output terminal 46p side. This prevents current from flowing back from the initial excitation circuit 30 to the battery 52.

[0061] (4) The control circuit 40 obtains the voltage value of input terminal AI1 corresponding to the voltage between relay 33 and diode 35, and the voltage value of input terminal AI2 corresponding to the voltage between relay 34 and negative output terminal 46n, and diagnoses the initial excitation circuit 30 based on these obtained voltage values. Specifically, the control circuit 40 energizes the excitation coil 12 by turning on relays 33 and 34 (steps S20, S30), and then diagnoses the quality of the tripping operation by relay 33 and the diode 35 based on the voltage value of input terminal AI1 when relay 33 is turned off (steps S70~S85, S110). In addition, the control circuit 40 energizes the excitation coil 12 by turning on relays 33 and 34 (steps S20, S30), and then diagnoses the quality of the tripping operation by relay 34 based on the voltage value of input terminal AI2 when relay 34 is turned off (steps S90~S105, S110). In this way, it is possible to reliably diagnose whether the initial excitation circuit 30 is operating correctly and to safely start the generator 10 using the initial excitation circuit 30.

[0062] (5) In diagnosing the initial excitation circuit 30, the control circuit 40 diagnoses whether relay 33 and relay 34 are stuck in the ON position, and if it diagnoses that either relay 33 or relay 34 is stuck in the ON position (steps S85, S105), it switches the other circuit breaker to the OFF position (step S115). In this way, even if relay 33 or relay 34 is faulty, the electrical connection with the battery 52 is reliably interrupted, preventing the generated potential of the generator 10 from being transmitted to the battery 52.

[0063] (6) The control circuit 40 notifies the external system of the diagnostic results of the initial excitation circuit 30 (step S120). In this way, if an abnormality occurs in the initial excitation circuit 30, the driver or manager of the dump truck 100 can be quickly notified.

[0064] In the embodiments described above, the initial excitation circuit 30 of a power generator 1 mounted on a dump truck 100, which is a work vehicle, was used as an example, but the present invention is not limited to this. For example, the present invention may be applied to the initial excitation circuit of a power generator mounted on a work vehicle other than a dump truck, or to a power generator used for other purposes. Furthermore, although a brushed three-phase AC generator was described as an example of a generator 10 connected to the initial excitation circuit 30, other types of generators may also be used. The present invention can be applied to any initial excitation circuit that is connected to an excitation coil provided on a brushed generator and excites this excitation coil when the generator is started.

[0065] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. [Explanation of symbols]

[0066] 1: Generator, 10: Generator, 11: Stator, 12: Excitation coil, 13a, 13b: Slip ring, 14a, 14b: Brush, 15u: U-phase output line, 15v: V-phase output line, 15w: W-phase output line, 20: Excitation circuit, 21u, 21v, 21w: Reactor, 22: Excitation control circuit, 23a, 23b, 23c, 23d, 23e, 23f: Rectifier diode, 30: Initial excitation circuit, 31, 32: Resistor, 33, 34: Relay, 35: Diode, 36: Capacitor, 37: Discharge resistor, 40: Control circuit, 41, 42, 43, 44: Interface circuit, 45p: Positive input terminal, 45n: Negative input terminal, 46p: Positive output terminal, 46n: Negative output terminal, 51: Charger, 52: Battery, 53: Power switch

Claims

1. An initial excitation circuit that is electrically connected to the excitation coil of a generator and excites the excitation coil when the generator is started, An input terminal connected to a power supply that provides DC power, including a positive input terminal connected to the positive side of the power supply and a negative input terminal connected to the negative side of the power supply, The generator has an output terminal which is connected to the excitation coil via brushes and slip rings, and includes a positive output terminal connected to one end of the excitation coil and a negative output terminal connected to the other end of the excitation coil. A circuit breaker including a first circuit breaker connected between the positive input terminal and the positive output terminal, and a second circuit breaker connected between the negative input terminal and the negative output terminal, A first resistor connected between the first circuit breaker and the positive input terminal, A second resistor connected between the second circuit breaker and the negative input terminal, An initial excitation circuit comprising: a control circuit that, in diagnosing the initial excitation circuit, diagnoses whether the first circuit breaker and the second circuit breaker are stuck in the ON position, and if it is determined that either the first circuit breaker or the second circuit breaker is stuck in the ON position, switches the other circuit breaker to the OFF position.

2. (delete)

3. In the initial excitation circuit according to claim 1, The device further comprises a diode connected between the first circuit breaker and the positive output terminal, The diode is an initial excitation circuit in which the anode is connected to the first circuit breaker side and the cathode is connected to the positive output terminal side.

4. In the initial excitation circuit according to claim 3, The control circuit acquires a first voltage value corresponding to the voltage between the first circuit breaker and the diode, and a second voltage value corresponding to the voltage between the second circuit breaker and the negative output terminal, and performs an initial excitation circuit diagnosis based on the acquired first voltage value and second voltage value.

5. In the initial excitation circuit according to claim 4, The control circuit is an initial excitation circuit that, after energizing the excitation coil by conducting the first circuit breaker and the second circuit breaker, diagnoses the tripping operation by the first circuit breaker and the quality of the diode based on the first voltage value obtained when the first circuit breaker is tripped.

6. In the initial excitation circuit according to claim 4 or 5, The control circuit is an initial excitation circuit that energizes the excitation coil by turning on the first circuit breaker and the second circuit breaker, and then diagnoses the quality of the tripping operation by the second circuit breaker based on the second voltage value obtained when the second circuit breaker is tripped.

7. (delete)

8. In the initial excitation circuit according to claim 4 or 5, The control circuit is an initial excitation circuit that notifies the diagnostic results of the initial excitation circuit to an external source.

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