Device and method for protection against a fault in an electric motor

Abstract

A protection system (1) against an electrical fault in a stator (90) of a motor comprises a first group (81) of turns (815) at a first longitudinal end (91) of the stator (90) and a second group (82) of turns (825) at a second longitudinal end (92) of the stator (90). The system (1) comprises at least one optical fiber (10, 20) without an opaque sheath, positioned near the turns (815, 825) of one of the groups (81, 82), a first deflector (31) (respectively a second deflector (32)) connected to a first end (11, 21) (respectively a second end (12, 22)) of the optical fiber (10, 20), a sensor (40) connected to the deflectors (31, 32), and a control unit (50) connected to the sensor (40) and capable of cutting off the power supply to the motor when the optical fiber (10, 20) detects light from one of the groups (81, 82). Figure 1

Description

Title of the invention: Device and method for protection against a fault in an electric motor

[0001] In certain applications, for example in electrically or hybrid electric-thermal powered aircraft, permanent magnet electric motors are used which operate at high direct current voltages, for example above 400 Volts.

[0002] It is necessary to detect short circuits or electrical arcs resulting from a fault in such a motor. This electrical fault may be an arc fault between two windings (loop-turn fault) of the same phase in the motor stator. Such a fault is difficult to detect electrically because it is located between two turns of the same phase.

[0003] The present invention relates to a system for protection against an electrical fault in a stator of a motor which extends along a longitudinal axis X with a first longitudinal end and a second longitudinal end and which comprises a first group of loop turns at the first longitudinal end and a second group of loop turns at the second longitudinal end.

[0004] For reliable and rapid detection of a fault in the stator of a motor, it is necessary to use a monitoring device with remote electronics that is substantial in terms of complex calculations and algorithms (such as, for example, spectral analysis, frequency analysis, Park vector analysis of voltages, fluxes, and currents), which is not practical. There are other, simpler devices for detecting winding faults, such as the detection of multiple heating generated by this fault, or the detection of a current jump between two star windings in the case of a motor with two three-phase star windings, both acting on the rotor's rotation (indeed, the two star windings then consume the same power, and a fault on one branch of one of the star windings will necessarily create a current imbalance between the two).However, these devices have the disadvantage that overheating or a current surge is only detectable after significant degradation of the windings, i.e., significant degradation of the motor, which is undesirable. Description of the invention

[0005] The present invention aims to remedy these drawbacks.

[0006] The invention aims to provide a protection system against an electrical fault in stator windings in an electric motor, this system being intended to allow for a rapid and reliable detection of this fault and the interruption of the motor.

[0007] This goal is achieved thanks to the fact that the system includes at least one optical fiber which is without an opaque sheath and which is positioned near all the turns of one of the groups of turns, a first deflector which is connected to a first end of the optical fiber, a second deflector which is connected to a second end of the optical fiber, a sensor which is connected to the deflectors and a control unit which is connected to the sensor and which is capable of cutting off the power supply to the motor when the optical fiber receives light from one of the groups.

[0008] Thanks to these features, and given that a fault in a group of turns immediately generates a flash of light, the detection system is able to shut down the motor as soon as the fault appears, before significant damage to the motor occurs. Furthermore, the transmission of information, namely light, via optical fiber contributes to the reliability of the system.

[0009] Advantageously, the system comprises a first optical fiber which is positioned near all the turns of the first group and a second optical fiber which is positioned near all the turns of the second group.

[0010] Advantageously, at least one optical fiber is located opposite the longitudinal end of the group of turns.

[0011] Advantageously, at least one optical fiber extends along the radially external periphery of the group of turns.

[0012] Advantageously, at least one optical fiber extends along the radially internal periphery of the group of turns.

[0013] Advantageously, at least one optical fiber is provided with a transparent sheath.

[0014] The invention also relates to a method of protection against an electrical fault in a motor stator which extends along a longitudinal axis X with a first longitudinal end and a second longitudinal end and which includes a first group of loop turns at the first longitudinal end and a second group of loop turns at the second longitudinal end.

[0015] According to the invention, the method comprises the following steps (a) an optical fibre is positioned near all the turns of one of the groups of turns, the optical fibre being devoid of opaque sheath; (b) a first deflector is connected to a first end of the optical fiber and a second deflector is connected to a second end of the optical fiber; (c) a sensor is connected to the deflectors and to a control unit; (d) the motor's power supply is cut off by means of the control unit when an optical fiber receives light from one of the groups.

[0016] Advantageously, in step (a) a first optical fiber is positioned near all the turns of the first group and a second optical fiber is positioned near all the turns of the second group.

[0017] The invention will be better understood and its advantages will become more apparent upon reading the following detailed description of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings in which:

[0018] [Fig-1] The [Fig. 1] is a perspective view of a stator of an electric motor and of a system for detecting an electrical fault in this motor according to the invention.

[0019] [Fig.2] Fig.2 is a longitudinal view of another embodiment of a detection system according to the invention.

[0020] [Fig.3] Fig.3 is a perspective view of an alternative embodiment of a detection system according to the invention.

[0021] [Fig.4] Fig.4 is a perspective view of another embodiment of a detection system according to the invention. Detailed description of the invention

[0022] By way of example, the invention is described in the case of an electrical network in an aircraft. An electric motor in such an electrical network comprises a stator 90 extending longitudinally along a longitudinal axis X, which is its axis of rotation. For example, the motor is air-cooled or liquid-cooled. In the description below, the terms "internal" and "inner" refer to an element oriented toward the longitudinal axis X or located closer to this axis. The terms "external" and "outer" refer to an element oriented in the opposite direction to the longitudinal axis X or located further from this axis. The term "radial" refers to a position or direction in a transverse plane perpendicular to the longitudinal axis X.

[0023] The stator 90 has an annular central element 93, a first longitudinal end 91, and a second longitudinal end 92 located longitudinally opposite the first longitudinal end 91. The first longitudinal end 91 comprises a first group 81 of loop turns 815 that form a ring extending longitudinally from the central element 93. The second longitudinal end 92 comprises a second group 82 of loop turns 825 that form a ring extending longitudinally from the central element 93. The loop turns (815, 825) are turns that exit a cavity in the central element 93 and each form a loop before entering another cavity in the central element 93.

[0024] The protection system 1 comprises at least one optical fiber (10, 20) which is positioned in close proximity to either all the turns 815 of the first group 81, or all the turns 825 of the second group 82. The term "in close proximity" means that the The optical fiber (10, 20) is in contact with the group (81, 82) or nearly in contact with the group (81, 82), for example, at a distance from the group (10, 20) that is on the order of the diameter of the optical fiber (10, 20). The optical fiber (10, 20) is unclad, opaque to visible light, so that its lateral surface is able to receive the light emitted by the occurrence of a fault between turns (815, 825), this fault being, for example, a short circuit or electric arc between turns (815, 825). Advantageously, the optical fiber (10, 20) is unclad, which simplifies the manufacture of the protection system 1. Alternatively, the optical fiber (10, 20) is equipped with a sheath transparent to visible light, which protects the optical fiber (10, 20) against mechanical (shocks) or thermal damage and / or amplifies light capture.

[0025] Figure 1 is a perspective view of the stator 90 of a motor where a first optical fiber 10 is positioned near the first group 81. The situation is similar when a second optical fiber 20 is positioned near the second group 82. The optical fiber (10, 20) forms a ring located opposite the longitudinal end of the group (81, 82) of turns at which it is positioned. In other words, the optical fiber (10, 20) lies in the longitudinal extension of this group (81, 82).

[0026] The ring formed by the optical fiber (10, 20) is split such that it has two opposing ends (11, 12, 21, 22). The protection system 1 includes a first deflector 31 which is connected to a first end 11 of the first optical fiber 10 (respectively to a first end 21 of the second optical fiber 20). The protection system 1 includes a second deflector 32 which is connected to a second end 12 of the first optical fiber 10 (respectively to a second end 22 of the second optical fiber 20). Advantageously, the second deflector 32 serves for an automatic transmission test. Thus, the system 1 can be tested at startup (PBIT "Power-on Built-in Test") or continuously during operation (CBIT "Continuing Built-in Test"). This makes it possible to verify that the system 1 is operational throughout the entire operating time of the engine.

[0027] In a first embodiment of the invention illustrated in [Fig. 1], the protection system 1 comprises either an optical fiber (10, 20) at one or the other of the groups (81, 82) of turns (815, 825). In a second embodiment, illustrated in [Fig. 2] in a longitudinal view, the protection system 1 comprises a first optical fiber 10 which is positioned at (i.e., near) the first group 81 and a second optical fiber 20 is positioned at the second group 82. Thus, fault detection is effective in all the turns (815, 825) of the stator, and damage to the motor is therefore more effectively prevented.

[0028] The protection system 1 includes a sensor 40 which is connected to the deflectors (31, 32). When there are two optical fibers (10, 20), each of the optical fibers (10, 20) is connected to the sensor 40 by a separate pair of deflectors (31, 32). The sensor 40 is capable of capturing light initially emitted by a defect in a group (81, 82) of turns (815, 825) and which travels in one of the optical fibers (10, 20) and then in the deflectors (31, 32).

[0029] The protection system 1 comprises a control unit 50 which is connected to the sensor 40. The connection between the sensor 40 and the control unit 50 is shown schematically in Figures 1 and 2. The control unit 50 is capable of cutting off the power supply to the motor when it receives a signal from the sensor 40, this signal being emitted when at least one of the optical fibers (10, 20) receives light from one of the groups (81, 82). Thus, system 1 makes it possible to stop the motor as soon as an inter-turn fault occurs in the stator, in the fastest and most efficient way.

[0030] The protection system 1 is reliable because the motor is located in a closed housing such that darkness reigns inside this housing (not shown). Thus, a flash of light emitted by either of the groups (81, 82) of turns (815, 825) is easily detectable.

[0031] Figure 3 is a perspective view of the first longitudinal end 91 of the stator 90, illustrating a variant of the protection system 1. The first optical fiber 10 is positioned around the first group 81, i.e., the first optical fiber 10 extends close to and along the radially external periphery of the first group 81 of turns 815. Similarly, in the second embodiment, the second optical fiber 20 is positioned around the second group 82, i.e., the second optical fiber 20 extends along the radially external periphery of the second group 82 of turns 825.

[0032] Figure 4 is a perspective view of the first longitudinal end 91 of the stator 90, illustrating another variant of the protection system 1. The first optical fiber 10 is positioned inside and against the first group 81, i.e., the first optical fiber 10 extends close to and along the radially internal periphery of the first group 81 of turns 815. Similarly, in the second embodiment, the second optical fiber 20 is positioned inside and against the second group 82, i.e., the second optical fiber 20 extends along the radially internal periphery of the second group 82 of turns 825. The region R of Figure 4 is shown in Figure 4.4] at the longitudinal end 91 is duplicated on the right with only the first optical fiber 10, the first deflector 31 and the second deflector 32 in order to show the connection between the first deflector 31 and the first end 11 of the first optical fiber 10, and the connection between the second deflector 32 and the second end 12 of the first optical fiber 10. .

[0033] The invention also relates to a method of protection against an electrical fault in a motor comprising a stator 90 as described above. In a step (a), an optical fiber (10, 20) is positioned near all the turns (815, 825) of one of the groups (81, 82) of turns (815, 825), the optical fiber being without an opaque sheath. In a step (b), a first deflector 31 is connected to a first end (11, 21) of the optical fiber (10, 20) and a second deflector 32 is connected to a second end (12, 22) of the optical fiber (10, 20). In a step (c) a sensor 40 is connected to the deflectors (31, 32) and to a control unit 50. In a step (d), the power supply to the motor is cut off by means of the control unit 50 when the optical fiber (10, 20) detects light from one of the groups (81, 82), this light is captured by the sensor 40 and a signal is then sent from the sensor 40 to the control unit 50.Steps (a), (b), and (c) can be in any order.

[0034] In the second embodiment, at step (a), a first optical fiber 10 is positioned near all the turns 815 of the first group 81 and a second optical fiber 20 is positioned near all the turns 825 of the second group 82.

Claims

Demands

1. A protection system (1) against an electrical fault in a stator (90) of a motor extending along an axis of rotation (X) with a first longitudinal end (91) and a second longitudinal end (92) and comprising a first group (81) of loop turns (815) at said first longitudinal end (91) and a second group (82) of loop turns (825) at said second longitudinal end (92), said system (1) being characterized in that it comprises at least one optical fiber (10, 20) which is unclad and which is positioned near all the turns (815, 825) of one of said groups (81, 82) of turns (815, 825), and a first deflector (31) which is connected to a first end (11, 21) of said optical fiber (10, 20), a second deflector (32) which is connected to a second end (12, 22) of said optical fiber (10, 20), a sensor (40) which is connected to said deflectors (31,32) and a control unit (50) which is connected to said sensor (40) and which is capable of cutting off the power supply to said motor when said at least one optical fiber (10, 20) receives light from one of said groups (81, 82).

2. Protection system (1) according to claim 1 such that it comprises a first optical fiber (10) which is positioned near all the turns (815) of said first group (81) and a second optical fiber (20) which is positioned near all the turns (825) of said second group (82).

3. Protection system (1) according to claim 1 or 2 such that at least one optical fiber (10, 20) is located opposite the longitudinal end of said group (81, 82) of turns (815, 825).

4. Protection system (1) according to claim 1 or 2 such that at least one optical fiber (10, 20) extends along the radially external periphery of said group (81, 82) of turns (815, 825).

5. Protection system (1) according to claim 1 or 2 such that at least one optical fiber (10, 20) extends along the radially internal periphery of said group (81, 82) of turns (815, 825).

6. Protection system (1) according to any one of claims 1 to 3 such that at least one optical fiber (10, 20) is provided with a transparent sheath.

7. A method of protection (1) against an electrical fault in a stator (90) of a motor extending along a longitudinal axis (X) with a first longitudinal end (91) and a second longitudinal end (92) and comprising a first group (81) of loop turns (815) at said first longitudinal end (91) and a second group (82) of loop turns (825) at said second longitudinal end (92), said method being characterized in that it comprises the following steps: (a) an optical fiber (10, 20) is positioned in close proximity to all the turns (815, 825) of one of said groups (81, 82) of turns (815, 825), said optical fiber being devoid of an opaque sheath; (b) a first deflector (31) is connected to a first end (11, 21) of said optical fiber (10, 20) and a second deflector (32) is connected to a second end (12, 22) of said optical fiber (10, 20);(c) a sensor (40) is connected to said deflectors (31, 32) and to a control unit (50); (d) the power supply to said motor is cut off by means of said control unit (50) when said at least one optical fiber (10, 20) receives light from one of said groups (81, 82).

8. Method according to claim 7 characterized in that, in step (a), a first optical fiber (10) is positioned near all the turns (815) of said first group (81) and a second optical fiber (20) is positioned near all the turns (825) of said second group (82).

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