Protection system and protection device

Abstract

A protection system according to one embodiment of the present invention comprises: a generator connected to a rotating shaft of an engine; a converter that converts AC power output from the generator into DC power; a sensor that monitors the state of the generator; and a protection device configured so as to be able to generate, on the rotating shaft, a braking torque for suppressing the rotation speed of the rotating shaft to a predetermined rotation speed on the basis of the output of the sensor. The protection device comprises a resistance unit, a switch, and a control unit. The switch switches the connection state between the generator and the resistance unit. The control unit determines whether or not there is an abnormality in the generator on the basis of the output of the sensor, and when it is determined that there is an abnormality in the generator, outputs an opening / closing signal for generating the braking torque to the switch.

Description

Protection Systems and Devices

[0001] The present invention relates to a protection system and a protection device that can be applied to a generator connected to a rotating shaft of an engine installed in an aircraft.

[0002] A motor drive device that generates braking force by using a resistor in a DC section when using a synchronous motor as a generator is known. For example, Patent Document 1 discloses a motor drive device that controls a motor used to drive an electric vehicle, and that includes a connection configuration switching circuit that can switch between a drive connection configuration in which the three-phase motor is driven by battery power and a regenerative connection configuration in which the motor's generated power is charged to the battery during regenerative braking. The connection configuration switching circuit is an inverter with a total of six drive elements, each of which is a semiconductor switching element, connected in series, two on the positive voltage side and two on the negative voltage side for each phase. The connection configuration switching circuit is configured to be switchable to a short-circuit connection configuration in which the motor coil is short-circuited to generate braking force, and is equipped with a short-circuit current control means that controls the short-circuit current flowing in this short-circuit connection configuration.

[0003] Patent No. 5808923

[0004] Electrical equipment powered by a generator connected to the rotating shaft of an aircraft engine is typically equipped with a protective device that cuts off the power supply in the event of a malfunction. When the power supply is cut off by the protective device, the power required by the generator decreases, and the shaft torque also decreases, causing a temporary increase in generator rotation speed, i.e., engine rotation speed. If the power of the malfunctioning electrical equipment is small, the increase in the rotating shaft speed is also small, and can be ignored from the perspective of stable engine operation.

[0005] However, when the electrical equipment supplies large amounts of power, such as a motor driving a propeller or fan, the power can be several tens of percent of the engine's shaft power, resulting in a significant increase in rotational speed. This can lead to mechanical malfunctions in the engine. Specifically, this can include engine compressor surging and excessive turbine centrifugal force. These malfunctions can impair not only the generator but also the engine's stable operation and ultimately safe flight, so it is necessary to prevent malfunctions in the electrical equipment. To prevent such problems, for example, a Full Authority Digital Engine Controller (FADEC) can adjust the fuel flow rate to return the engine to its original rotational speed. However, this system has a long time constant, requiring time for stabilization, leading to reduced control responsiveness. Furthermore, in a system with a braking resistor in the DC section between the generator and converter, even if the generator is functioning normally, a converter failure can disable braking, reducing system reliability.

[0006] In view of the above circumstances, an object of the present invention is to provide a protection system that can improve the reliability of the system without reducing control responsiveness by converging the rotation speed to the original speed faster than the time constant required when the rotation speed is suppressed using only the FADEC and by generating a braking torque regardless of whether or not there is a converter failure.

[0007] To achieve the above object, one aspect of the present invention provides a protection system including a generator connected to a rotating shaft of an engine, a converter that converts AC power output from the generator into DC power, a sensor that monitors the state of the generator, and a protection device configured to generate a braking torque on the rotating shaft to limit the rotation speed of the rotating shaft to a predetermined rotation speed based on the output of the sensor. The protection device includes a resistor, a switch, and a control unit. The switch switches the connection state between the generator and the resistor. The control unit determines whether or not there is an abnormality in the generator based on the output of the sensor, and if it determines that there is an abnormality in the generator, outputs an opening / closing signal to the switch to generate the braking torque.

[0008] The power generation system described above can obtain braking torque using only the resistance connected to the generator, thereby reducing the torque that contributes to an increase in engine speed, thereby making it possible to suppress the increase in speed itself.

[0009] The sensor may be configured to monitor at least one of the rotational speed of the rotating shaft and the current generated by the generator, thereby improving system reliability without compromising control responsiveness.

[0010] In this case, the control unit may be configured to determine that an abnormality has occurred when the difference between the current rotation speed of the rotating shaft and a predetermined rotation speed during steady operation of the generator is equal to or greater than a predetermined value.

[0011] Alternatively, the control unit may be configured to determine that an abnormality has occurred when a difference between the current current and a predetermined current during steady operation of the generator is equal to or greater than a predetermined value.

[0012] Alternatively, the control unit may be configured to determine that an abnormality has occurred when oscillations different from oscillations in the current during steady-state operation of the generator are occurring in the current.

[0013] The control unit may be configured to output the opening / closing signal in accordance with a torque pattern based on a time constant of the engine.

[0014] In this case, the torque pattern may be configured to include gradually decaying the braking torque.

[0015] The protection system may further include an engine control unit that controls the amount of fuel introduced into the engine to control the rotation speed so that it becomes a rotation speed command value, and the control unit may be configured to output the opening / closing signal based on the rotation speed command value to the engine output from the engine control unit.

[0016] The predetermined rotation speed may be the rotation speed command value output from the engine control unit, and the control unit may be configured to determine the braking torque so as to maintain the rotation speed command value, and to output an opening / closing signal to the switch to generate the determined braking torque.

[0017] The resistor may be connected between a line of the generator and the converter and configured to consume the power generated by the generator.

[0018] The generator may have a stator wound with a three-phase electromagnetic coil, the lines may connect each of the three phases between the generator and the converter, and the resistor unit may be connected in parallel with the converter and between the lines of at least two of the three phases.

[0019] The switch may be configured to be provided between the line and the resistor portion.

[0020] The opening / closing signal may be a PWM signal, and the control unit may be configured to output the PWM signal based on the rotation speed command value.

[0021] The engine may be used in an aircraft, the predetermined rotational speed may be the rotational speed of the engine when the aircraft is cruising, and the control unit may be configured to generate the braking torque so that the rotational speed of the rotating shaft becomes the rotational speed of the engine.

[0022] A protection device according to one aspect of the present invention is a protection device for a protection system having a generator connected to a rotating shaft of an engine and a converter that converts AC power output from the generator into DC power, and includes a resistor, a switch, and a control unit. The resistor is connected between a line between the generator and the converter and consumes power generated by the generator. The switch shorts or opens the generator and the resistor. The control unit determines whether or not there is an abnormality in the generator based on the output of a sensor that monitors the state of the generator, and if it determines that there is an abnormality in the generator, outputs an open / close signal to the switch to generate the braking torque.

[0023] As described above, according to the present invention, the reliability of the system can be improved without causing a decrease in control responsiveness.

[0024] Fig. 1 is a schematic configuration diagram of a power generation system according to the present invention. Fig. 2 is a block diagram showing the configuration of a protection system. Fig. 3 is a graph showing the relationship between engine rotation speed, generator torque, and engine command torque. Fig. 4 is a flowchart showing control of the protection system. Fig. 5 is a diagram showing an example of generation of an opening / closing signal by a control unit. Fig. 6 is a diagram showing another example of generation of an opening / closing signal by a control unit.

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0026] 1 is a schematic diagram of a power generation system 100 according to the present invention. The power generation system 100 according to this embodiment is an engine with a generator mounted on an aircraft, and includes an engine 10, a generator 20, a FADEC 30, and a protection device 40.

[0027] Aircraft equipped with the power generation system 100 include, for example, aircraft equipped with the engine 10 as a propulsion device, as well as electric aircraft that use electricity from the generator 20 to drive propulsion systems such as fans and propellers.

[0028] The engine 10 is a jet engine and includes a compressor 11 , a combustor 12 , and a turbine 13 .

[0029] The compressor 11 has a rotary shaft 110 as an engine shaft, and a low-pressure compression section 11a and a high-pressure compression section 11b connected to the rotary shaft 110. The compressor 11 introduces air adiabatically compressed in the low-pressure compression section (LPC) 11a and the high-pressure compression section (HPC) 11b into a combustor 12 at a downstream stage.

[0030] The low-pressure compression section 11a and the high-pressure compression section 11b each have a plurality of rotor blades and a plurality of stator vanes. The rotor blades rotate together with the rotary shaft 110 and compress air between the rotor blades and the stator vanes. Although not shown, a fan that introduces air into the low-pressure compression section 11a may be installed upstream of the compressor 11. The fan is connected to the rotary shaft 110 and rotates integrally with the compressor 11.

[0031] The combustor 12 has a mixing chamber that mixes the air compressed by the compressor 11 with the fuel injected from the fuel injector 121, and a combustion chamber that burns the mixture, and discharges high-pressure combustion gas toward the downstream turbine 13. The flow rate of fuel introduced from the fuel injector 121 to the combustor 12 is controlled by the FADEC 30. Normally, the flow rate of fuel is adjusted based on the rotation speed of the rotating shaft 110 detected by the rotation speed sensor 111.

[0032] The turbine 13 has a high-pressure turbine section (HPT) 13a and a low-pressure turbine section (LPT) 13b connected to a rotary shaft 110, and is rotated by receiving combustion gas discharged from the combustor 12. The rotation of the high-pressure turbine section 13a and the low-pressure turbine section 13b is transmitted to the compressor 11 via the rotary shaft 110, and is used as driving force for continuously drawing in and compressing air.

[0033] The generator 20 has a drive shaft 21 directly connected to the rotating shaft 110. In this embodiment, the generator 20 is equipped with electromagnetic coils of three phases: U-phase, V-phase, and W-phase. Typically, the generator 20 is an AC generator that includes a rotor having a permanent magnet attached to the drive shaft 21 and a stator around which multi-phase electromagnetic coils are wound, and that converts the rotational force of the rotating shaft 110 into electrical energy.

[0034] The drive shaft 21 may be formed as a part of the rotating shaft 110. The generator 20 is not particularly limited to a multi-phase electromagnetic coil, as long as it is an electromagnetic coil through which two or more alternating currents of different phases flow. The generator 20 is not limited to being connected to the rear stage of the engine 10 (the turbine 13 side), but may be connected to the front stage of the engine 10 (the compressor 11 side).

[0035] The FADEC 30 controls the engine 10. For example, as described above, the FADEC 30 adjusts the flow rate of fuel introduced from the fuel injector 121 to the combustor 12 based on the output of the rotation speed sensor 111. In this embodiment, the FADEC 30 controls the rotation speed of the engine 10 (rotating shaft 110), which has increased due to torque loss, by adjusting the fuel flow rate so that the rotation speed of the engine 10 becomes equal to a rotation speed command value. For example, the rotation speed command value is the rotation speed of the engine 10 during steady operation. In other words, the rotation speed of the engine 10 when the aircraft is cruising without any problems (hereinafter referred to as a stable rotation speed) may be stored, and the rotation speed command value may be determined based on the stable rotation speed. In this embodiment, the FADEC 30 also outputs the rotation speed command value to the protection system 40.

[0036] The sensors used to control the FADEC 30 are not limited, and various sensors capable of measuring torque, pressure, temperature, etc. may be used to measure operational disturbances of the engine 10 .

[0037] The power generation system 100 further includes an ammeter 35. The ammeter 35 is connected between the generator 20 and a converter (transformer) 51. The ammeter 35 detects the magnitude of the current generated by the generator 20 and outputs the detection signal to the FADEC 30 and the protection device 40.

[0038] The protection device 40 is configured to be able to generate a braking torque on the rotating shaft 110 to suppress the rotation speed of the rotating shaft 110 to a predetermined rotation speed based on the outputs of the sensors (the ammeter 35 and the rotation speed sensor 111). For example, when an abnormality occurs, the protection device 40 controls the rotation speed of the engine 10 to a rotation speed command value output from the FADEC 30.

[0039] Here, the abnormal situation includes a situation where the load 61 described later is lost due to some kind of trouble, which causes the load on the engine 10 to disappear and the rotation speed of the engine 10 to suddenly increase, that is, a so-called torque loss.

[0040] That is, in this embodiment, the protection device 40 functions to return the rotation speed of the rotating shaft 110, which has increased due to the torque drop, to the rotation speed command value (for example, the rotation speed during steady operation). In addition, in this embodiment, the detection signals output from the ammeter 35 and the rotation speed sensor 111 are used to determine whether an abnormality has occurred.

[0041] For example, based on the detection signal, the protection device 40 determines that an abnormal situation has occurred from behavior such as a sudden decrease in the current generated by the generator 20, the generation of a current with vibrations different from those during steady operation, or the difference in the rotation speed of the rotating shaft 110 exceeding the acceleration / deceleration rate during steady operation.

[0042] How the protection device 40 restores the rotation speed of the engine 10 to normal will be explained later with reference to FIGS. 2 and 3.

[0043] In this embodiment, the protection device 40 operates on an independent power supply system that is different from the power generation system 100 (aircraft, etc.). This allows the protection system to operate even if the power supply system of the aircraft, etc., is lost. In other words, it is possible to constantly generate braking torque, and the operation of restoring the rotation speed to normal is performed stably.

[0044] The generated power obtained by utilizing the rotational force of the engine 10 is supplied to a power distribution line 60 connected to a load 61, a battery 62, etc. via a converter 51 that converts AC to DC. The converter 51 is a power conversion device that converts the power generated by the generator 20 into a predetermined power and supplies it to the power distribution line 60.

[0045] The power distribution line 60 may be provided with a protective device such as a circuit breaker that cuts off the power supply to the load 61 in the event of a malfunction such as a short circuit or a ground fault in the load 61. An auxiliary generator 70 driven by a power source other than the engine 10 may also be connected to the power distribution line 60. An example of the other power source is a propeller or other such drive mechanism. In this case, the auxiliary generator 70 generates power by the rotation of the propeller. The power generated by the auxiliary generator 70 is supplied to the power distribution line 60 via a power converter such as the converter 52.

[0046] The load 61 is, for example, a hydraulic pump that drives various hydraulic devices in the aircraft, an air conditioner, and other electronic devices, and in the case of an electric aircraft, includes a motor that drives a propeller or other thruster.

[0047] The battery 62 is a rechargeable secondary battery used as an auxiliary power source, and includes the battery itself and a charge / discharge circuit that controls the charging and discharging of the battery.

[0048] Fig. 2 is a block diagram showing the configuration of the protection device 40. For simplification, Fig. 2 only shows a portion of the engine 10, converter 51, etc. Also, the FADEC 30, ammeter 35, rotation speed sensor 111, auxiliary generator 70, etc. are omitted from the illustration.

[0049] As shown in FIG. 2 , the protection device 40 includes a resistor unit 41 , a switch 42 , and a control unit 43 .

[0050] The resistance unit 41 is disposed between the AC line between the generator 20 and the converter 51, and consumes the power generated by the generator 20. In this embodiment, the resistance unit 41 has resistors of the same value disposed in parallel for each of the three phases, U phase, V phase, and W phase. Also in this embodiment, the resistance unit 41 is disposed in parallel with the converter 51. Note that the resistance value and number of the resistance unit 41 are not limited, and resistors of different values ​​may be disposed, or the resistance unit 41 may be provided so as to be connected to at least two of the three phases.

[0051] The switches 42 switch between an open and closed connection state based on an opening / closing signal output from the control unit 43. In this embodiment, the switches 42 are semiconductor switches, and are arranged between each AC line and each resistor unit 41.

[0052] The control unit 43 controls the switch 42 when an abnormality occurs. In this embodiment, the control unit 43 determines whether an abnormality has occurred based on the rotation speed of the rotating shaft 110 detected by the rotation speed sensor 111 and the current of the generator 20 detected by the ammeter 35. In this embodiment, the control unit 43 also outputs an opening / closing signal to control the switch 42 based on the rotation speed command value output from the FADEC 30 so that the rotation speed of the rotating shaft 110, which has increased due to the abnormality, returns to an appropriate rotation speed.

[0053] In this embodiment, the switching signal is a PWM signal. The switch 42 starts a switching operation based on the switching signal. For example, when the switch 42 is short-circuited and the generator 20 is connected to the resistor 41, a braking torque is generated. In other words, the lost load torque seen from the engine 10 side is compensated for, and the torque that contributes to an increase in the rotation speed of the engine 10 is reduced, thereby suppressing the increase in the rotation speed.

[0054] In this embodiment, the control unit 43 controls the switch 42 so that the current rotation speed, which has increased due to torque loss, returns to a predetermined rotation speed. Here, the predetermined rotation speed is a rotation speed command value output from the FADEC 30. That is, the control unit 43 determines the value of the braking torque using a speed control system that maintains the rotation speed, using the rotation speed command value of the engine 10 during steady operation, and reflects this value in the switching operation of the switch 42.

[0055] The specified rotation speed is not limited to the rotation speed during steady-state operation, and an upper limit may be set based on the rotation speed (rotational speed) allowable by the engine 10, or a lower limit may be set based on the rotation speed at which aircraft, etc., cannot fly.

[0056] Here, the difference between the case where the rotation speed of the engine 10 is reduced using only the FADEC 30 and the case where the rotation speed of the engine 10 is reduced using the FADEC 30 and the protection device 40 will be described with reference to FIG.

[0057] 3A and 3B are graphs showing the relationship between the rotation speed of the engine 10, the generator torque, and the engine command torque. Fig. 3A shows the relationship when only the FADEC 30 is used. Fig. 3B shows the relationship when the FADEC 30 and the protection device 40 are used. In Fig. 3, the horizontal axis represents time, the left vertical axis represents torque, and the right vertical axis represents rotation speed.

[0058] As shown in FIG. 3A, when torque loss occurs due to loss of load 61 (see dashed line 80), the generator torque (line 81), which had been a negative value, becomes zero, and the rotation speed of engine 10 (line 82) increases.

[0059] Furthermore, in order to reduce the rotation speed 82 of the engine 10, the engine command torque 83 output to the engine 10 is reduced. In this embodiment, this is achieved by adjusting the flow rate of fuel introduced from the fuel injector 121 to the combustor 12 by the FADEC 30.

[0060] However, the time constant for fuel adjustment by the FADEC 30 is long, and it takes time for the rotation speed of the engine 10 to return to the rotation speed during steady operation. In other words, the FADEC 30, which throttles the flow rate of fuel in response to an increase in rotation speed, cannot completely suppress the increase in rotation speed of the engine 10.

[0061] The time constant refers to the time it takes for the engine speed to settle (reach a predetermined target value) after fuel control is started. Typically, the time constant is a specific value depending on the type of engine, etc.

[0062] As shown in FIG. 3B, when torque loss occurs (see dashed line 80), in order to reduce the rotation speed of the engine 10, the engine command torque 85 is reduced and an opening / closing signal is output to the switch 42.

[0063] The switch 42 performs a switching operation in accordance with a switching signal based on a rotation speed command value output from the FADEC 30. Note that in FIG. 3B, a time lag occurs between an operating period 84 during which the switching operation is performed and the timing 80 at which torque loss occurs. This occurs because fluctuations in rotation speed and current are detected when detecting torque loss. However, this operating period 84 is negligible from the engine's perspective and can therefore be ignored.

[0064] The operation period 84 may be set based on the time constant of the engine 10, or the switching operation may be continued until the rotation speed of the engine 10 falls within a predetermined range.

[0065] The control unit 43 also controls the braking torque (generator torque 86) in synchronization with the fuel adjustment (engine command torque 85) by the FADEC 30, and transitions to a steady operation state in which there is no output from the generator 20. At this time, the switch 42 returns to the open state. That is, the control unit 43 controls the generator torque by outputting an open / close signal to the switch 42, and controls the rotation speed of the engine 10 to a predetermined rotation speed that is a target value.

[0066] FIG. 4 is a flowchart showing the control of the protection device 40.

[0067] As shown in FIG. 4, the rotational speed of the rotating shaft 110 is detected by the rotational speed sensor 111, and the current of the generator 20 is detected by the ammeter 35 (step 101).

[0068] The control unit 43 determines whether an abnormal situation has occurred (step 102). In this embodiment, it is determined that an abnormal situation has occurred when at least one of the following cases is detected: a sudden decrease in the current of the generator 20, generation of a current with vibration different from that during steady operation, or a difference in the rotation speed of the rotating shaft 110 (for example, the difference between the current rotation speed and the rotation speed one frame before) exceeds the acceleration / deceleration rate during steady operation of the equipment.

[0069] If no abnormality has occurred (NO in step 102), the process returns to step 101. The timing at which the detection signal is output or the timing at which the protection device 40 requests a detection signal is not limited. For example, the detection signal may be output constantly, or the detection signal may be requested at predetermined time intervals. Furthermore, for example, the detection signal may be requested based on the timing at which the FADEC 30 performs fuel adjustment.

[0070] If an abnormal situation occurs (YES in step 102), the control unit 43 controls the switch 42 (step 103).

[0071] FIG. 5 is a diagram showing an example of generation of an opening / closing signal by the control unit 43. In FIG.

[0072] 5, in this embodiment, PI control is performed based on the rotation speed command value output from the FADEC 30 and the current shaft rotation speed of the generator 20. A switching signal (open / close signal) is obtained by comparing the duty ratio in the PWM control of the resistor unit 41 obtained by the PI control with a triangular wave.

[0073] Furthermore, based on the opening and closing signal, the current when the resistor unit 41 is on or off is calculated, and the current is calculated taking into account the time constant of the generator 20. The time constant of the generator 20 in this embodiment is the electrical time constant of the generator 20, and takes into account the response delay time from when the pulse-like voltage after switching obtained by the triangular wave comparison is applied to the generator 20 until it appears as a current value flowing through the generator 20.

[0074] When performing the calculation, the AC generator is treated as a DC generator and the calculation is performed using values ​​equivalent to DC current, so the shape of the current is sawtooth, similar to the torque waveform. The calculated current is converted to torque. Furthermore, the converted torque is controlled by the PWM controlled switching of the resistor unit 41 as described above and is obtained from the sawtooth current, so it becomes torque that changes over time in a sawtooth pattern. Note that the sawtooth shape refers to a shape like the generator torque 86 during the operating period 84 shown in Figure 3B.

[0075] This opening / closing signal is given to the switch 42. For example, the rotation speed of the engine 10 is constant in a stable state (for example, a state in which the aircraft is flying at a constant speed), and the braking torque is controlled in accordance with the current shaft rotation speed of the generator 20 using that rotation speed as a rotation speed command value.

[0076] In this embodiment, the control unit 43 controls the switch 42 to perform a switching operation so that the braking torque gradually decreases in synchronization with the fuel adjustment (engine command torque) by the FADEC 30 .

[0077] It is determined whether the rotation speed of the rotating shaft 110 has reached a predetermined rotation speed through the switching operation of the switch 42 by the control unit 43 and the fuel adjustment by the FADEC 30 (step 104). Note that the rotation speed of the rotating shaft 110 reaching the predetermined rotation speed does not only mean that the rotation speed matches the predetermined rotation speed, but also means that the rotation speed of the rotating shaft 110 has converged (stabilized) within a certain range of the predetermined rotation speed for a predetermined period of time. In other words, the rotation speed does not need to match the rotation speed command value output from the FADEC 30 without error, and some error is acceptable.

[0078] If the rotation speed falls within the predetermined range (YES in step 104), the control unit 43 opens the switch 42.

[0079] As described above, according to this embodiment, even if the load on the generator 20, such as the load 61, is lost, the load on the engine 10 is eliminated and the rotation speed of the rotating shaft 110 increases, the rotation speed of the engine 10 can be returned to the stable rotation speed when the vehicle was cruising safely before reaching the danger zone.

[0080] In particular, according to this embodiment, a resistance unit 41, which is a three-phase resistor for absorbing power, and a switch 42 having a mechanism for continuously switching the resistance unit 41 are provided in the AC section between the generator 20 and the converter 51, which is the controller for the generator 20. Therefore, the resistance unit 41 is connected via the switch 42, and when torque loss occurs, a braking torque of any magnitude can be generated from the generator 20 as a regenerative brake in coordination with fuel adjustment by the FADEC 30.

[0081] <Modifications> For example, in the above embodiment, the switch 42 is controlled by an opening / closing signal that feeds back the rotation speed of the rotating shaft 110 in response to a rotation speed command value, and the value of the braking torque is determined using a speed control system, but this is not limited to this. For example, according to the present invention, since the time constant of the FADEC 30 that adjusts the engine 10 is specific to each individual engine, the way in which the braking torque is reduced may be determined in advance using a fixed torque pattern that corresponds to the time constant.

[0082] 6A and 6B are diagrams showing other examples of generation of an opening / closing signal by the control unit 43. Fig. 6A is a diagram showing an example in which the opening / closing signal is controlled by a fixed torque pattern. Fig. 6B is a diagram showing an example of the fixed torque pattern.

[0083] As shown in Fig. 6A, for example, the rotation speed command value output from the FADEC 30 is treated as a duty ratio in the PWM control of the resistor unit 41, and a switching signal (open / close signal) is obtained by comparing the duty ratio with a triangular wave. For example, in the graph of Fig. 6B, the vertical axis represents the braking force (duty) and the horizontal axis represents the time from braking. In this case, the fixed torque pattern may include a ramp decay section (a section in which the torque decreases linearly) between a duty ratio of 1 (constant braking) and a duty ratio of 0 (brake release). In other words, a torque pattern may be set that gradually weakens the braking torque value.

[0084] Based on the switching signal, the current when the resistor unit 41 is on or off is calculated, and the current is calculated taking into account the time constant of the engine 10. When making the calculation, the AC generator is treated as a DC generator and the calculation is performed using values ​​equivalent to DC current, so the shape of the current is sawtooth, similar to the torque waveform. The calculated current is converted into torque. Furthermore, since the converted torque is controlled by the PWM controlled switching of the resistor unit 41 as described above and is obtained from the sawtooth current, the torque changes in a sawtooth pattern over time.

[0085] In this case, the speed control system only determines the maximum value of the braking torque, so that coordination with fuel adjustment by the FADEC 30 can be simplified, and the system configuration can be simplified and made highly reliable.

[0086] REFERENCE SIGNS LIST 10 engine 11 compressor 12 combustor 13 turbine 20 generator 21 drive shaft 30 FADEC 35 ammeter 40 protection device 41 resistor 42 switch 43 control unit 51, 52 converter 61 load 62 battery 70 auxiliary generator 100 power generation system 111 rotation speed sensor 121 fuel injector

Claims

1. A protection system comprising: a generator connected to a rotating shaft of an engine; a converter that converts AC power output from the generator into DC power; a sensor that monitors the state of the generator; and a protection device configured to be able to generate a braking torque on the rotating shaft to limit the rotation speed of the rotating shaft to a predetermined rotation speed based on the output of the sensor, wherein the protection device comprises a resistance unit, a switch, and a control unit, the switch switches a connection state between the generator and the resistance unit, and the control unit determines whether or not there is an abnormality in the generator based on the output of the sensor, and if it is determined that there is an abnormality in the generator, outputs an opening / closing signal to the switch to generate the braking torque.

2. A protection system according to claim 1, wherein the sensor monitors at least one of the number of revolutions of the rotating shaft or the current generated by the generator.

3. A protection system as claimed in claim 2, wherein the control unit judges that an abnormality has occurred when the difference between the current rotation speed of the rotating shaft and a predetermined rotation speed during steady operation of the generator is equal to or greater than a predetermined value.

4. A protection system as claimed in claim 2, wherein said control unit judges that an abnormality has occurred when the difference between the present current and a predetermined current during steady operation of said generator is equal to or greater than a predetermined value.

5. A protection system according to claim 2, wherein the control unit judges that an abnormality has occurred when oscillations different from oscillations of the current during steady-state operation of the generator are occurring in the current.

6. A protection system as claimed in claim 1, wherein said control unit outputs said opening / closing signal in accordance with a torque pattern based on a time constant of said engine.

7. A protection system according to claim 6, wherein said torque pattern includes gradually decaying said braking torque.

8. A protection system as claimed in claim 1, further comprising an engine control unit which controls the amount of fuel introduced into the engine to control the engine speed to a command value, and the control unit outputs the opening / closing signal based on the command value for the engine speed output from the engine control unit.

9. A protection system as claimed in claim 8, wherein the predetermined rotation speed is the rotation speed command value output from the engine control unit, and the control unit determines the braking torque so as to maintain the rotation speed command value, and outputs an opening / closing signal to the switch to generate the determined braking torque.

10. A protection system according to claim 1, wherein the resistor section is connected between the line of the generator and the line of the converter and consumes the power generated by the generator.

11. A protection system according to claim 1, wherein the generator has a stator wound with a three-phase electromagnetic coil, the lines connect the generator and the converter for each of the three phases, and the resistive section is connected in parallel with the converter and between the lines for at least two of the three phases.

12. A protection system according to claim 1, wherein the switch is provided between the line and the resistor portion.

13. A protection system according to claim 8, wherein the opening / closing signal is a PWM signal, and the control unit outputs the PWM signal based on the rotation speed command value.

14. A protection system as claimed in claim 1, wherein the engine is used in an aircraft, the predetermined rotation speed is the rotation speed of the engine when the aircraft is cruising, and the control unit generates the braking torque so that the rotation speed of the rotating shaft becomes the rotation speed of the engine.

15. A protection device for a protection system having a generator connected to a rotating shaft of an engine and a converter that converts AC power output from the generator into DC power, comprising: a resistor connected between a line between the generator and the converter and consuming power generated by the generator; a switch that switches the connection state between the generator and the resistor; and a control unit that determines whether or not there is an abnormality in the generator based on the output of a sensor that monitors the state of the generator, and if it is determined that there is an abnormality in the generator, outputs an opening / closing signal to the switch that generates the braking torque to limit the rotation speed of the rotating shaft to a predetermined rotation speed.

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