Control of an asynchronous motor

Abstract

The invention relates to a device for controlling the torque output by an asynchronous motor, comprising: - a rotating slip ring current collection system adapted to be connected to the rotor of the asynchronous motor and configured to collect or supply power to at least one winding of the rotor of the asynchronous motor to change the impedance of the rotor and in turn the torque output by the asynchronous motor; - a variable resistor connected to the rotating slip ring current collection system to control the rotating slip ring current collection system; - a processing unit configured to calculate the value of the variable resistor as a function of the frequency of the supply voltage of the asynchronous motor, the torque required by the asynchronous motor and the corresponding rotor resistance, in turn controlling the supply voltage of the current collector so that the asynchronous motor outputs the required torque.

Description

Technical Field

[0001] This invention relates to the control of asynchronous motors, and more particularly to the control of asynchronous motors used in aircraft gas turbine engines. Background Technology

[0002] In addition to other components, gas turbine engines may include systems that contain asynchronous motors, such as variable-setting systems. These motors are typically powered by the aircraft's onboard network, which may have a variable frequency.

[0003] However, in gas turbine engines, in order to achieve a stable state for applications where the motor output has a fixed operating point, the motor's torque, speed, and power must be controlled.

[0004] To achieve the above objectives, a power electronic unit is provided between the airborne network and the motor to be powered, the power electronic unit including a rectifier and an inverter.

[0005] One problem with using the unit is the need for thermal management of its components. However, the unit's size, integration, and cost within the gas turbine engine raise further issues. This thermal management involves additional components that impact the size of the gas turbine engine. Summary of the Invention

[0006] Using this invention, it is possible to control the torque output by an asynchronous motor while avoiding the need for a power electronics unit.

[0007] Therefore, in a first aspect, the present invention provides an apparatus for controlling the torque output by an asynchronous motor, the apparatus comprising: - A rotating slip ring current collector system adapted to be connected to the rotor of an asynchronous motor and configured to collect or supply current to at least one winding of the rotor of the asynchronous motor to change the impedance of the rotor, thereby changing the torque output by the asynchronous motor; - A variable resistor connected to the rotating slip ring collector system to control the rotating slip ring collector system; - A processing unit configured to calculate the value of the variable resistor based on the frequency of the power supply voltage of the asynchronous motor, the torque required by the asynchronous motor, and the corresponding rotor resistance, and then control the power supply voltage of the current collector so that the asynchronous motor outputs the required torque.

[0008] The present invention is advantageously perfected by employing the following features alone or in any technically possible combination thereof: -The processing unit determines the rotor resistance using the following expression:

[0009] Required torque, in Newton-meters (Nm). Extreme logarithm The number of rotor phases, for an asynchronous motor, is equal to the number of rotor bars. Stator electrical pulsation, measured in radians per second (rad / s), corresponds to the supply voltage of the asynchronous motor. Rotor impedance, a function of slip, is measured in ohms. Rotor impedance modulus per square meter, expressed in ohms per square. Rotor resistance, in ohms Rotor inductance, measured in Henry. Slippage : The root mean square (RMS) value of electromotive force, measured in volts (Volts).

[0010] - The motor includes multiple poles, enabling it to achieve a torque range greater than that required by the components driving the gas turbine engine. - The device includes a voltage sensor or voltage measurement system configured to send a measured value of the supply voltage of the asynchronous motor to the processing unit, the processing unit being configured to perform a Fourier transform on the measured value to derive the frequency of the supply voltage therefrom; The motor is powered by 115 volts in a variable frequency range of 360 Hz to 800 Hz.

[0011] In a second aspect, the present invention provides a system for controlling components of an aircraft gas turbine engine, the system comprising: - An asynchronous motor, which is configured to output torque to components of a gas turbine engine; - An apparatus according to a first aspect of the invention.

[0012] In the system according to the second aspect, the component of the gas turbine engine is a pump for the variable pitch setting system of the propeller.

[0013] This invention provides control over the slip and torque of an asynchronous motor without the need for power electronic devices.

[0014] In particular, the present invention utilizes the relationship between the rotor impedance and slip of the motor to achieve torque control.

[0015] Therefore, even though the electrical frequency of the network is variable, torque and speed can still be controlled without power electronics. Attached Figure Description

[0016] Other features, objects, and advantages of the invention will become apparent from the following description, which is non-limiting and illustrative only, and should be read in conjunction with the single accompanying drawing illustrating a system for controlling elements of a gas turbine engine according to the invention. Detailed Implementation

[0017] Figure 1 A system S for controlling an element E of an aircraft gas turbine engine is shown, comprising an asynchronous motor 1 and a device D. The asynchronous motor 1 is configured to output torque to the element E of the gas turbine engine, and the device D controls the torque output by the motor 1. The motor 1 includes a rotor 21 and a stator 22, with the rotor 21 outputting torque to the element E.

[0018] Component E of a gas turbine engine is advantageously an electrically driven pump for a system with variable propeller pitch setting. More generally, component E is any type of pump integrated into a system that requires a fixed rate (i.e., a fixed operating point).

[0019] Motor 1 is preferably a wound-rotor asynchronous motor that uses three-phase electrical energy from an aircraft network that outputs an AC supply voltage V with a variable frequency. The supply voltage V is, for example, 115 volts in a variable frequency range of 360 Hz to 800 Hz.

[0020] Since the frequency of voltage V is variable, the output speed of motor 1 is also variable.

[0021] Therefore, in order to keep the speed of the asynchronous motor constant, and thus its torque constant, so that the element E is kept at its ideal operating point, the system S includes a device D for controlling the torque output of the motor 1.

[0022] The device D includes a rotating slip ring current collector 2 connected to the rotor 21 of the motor 1 to change the impedance of the rotor circuit, thereby changing the torque output by the motor.

[0023] The current collector 2 or slip ring consists of at least two conductive rings, which are mounted to the axis of the rotor 21 of the motor 1 via insulating spacers. Each ring is electrically connected to a stationary part via brushes. Preferably, the current collector 2 includes three rings and three brushes. The current collector 2 is powered by a variable voltage U, which provides control over the rotor impedance, thereby controlling the torque output of the asynchronous motor. Voltage V is the voltage of the network, supplying power to the stator, and voltage U supplies power to the rotor.

[0024] To change the voltage U, device D includes a variable resistor 3, the value of which is calculated by the processing unit 4 of device D.

[0025] Based on the frequency of the power supply voltage V of the asynchronous motor The torque required by the asynchronous motor The calculations performed with the corresponding rotor resistance Rr enable the calculation of the resistance value R of the variable resistor 3, thereby controlling the supply voltage U of the current collector 2 so that the motor 1 outputs the required torque. .

[0026] Torque has been confirmed as a factor of slip s and rotor resistance. The functions have the following relationship:

[0027] in: Electromagnetic torque, measured in Newton-meters. Extreme logarithm Number of rotor phases (for asynchronous motors, this is equal to the number of rotor bars) Stator electrical pulsation, measured in radians per second, corresponds to the supply voltage V. Rotor impedance, a function of slip, is measured in ohms. Rotor impedance modulus per square inch (in the denominator of the equation), in ohms per square inch. Rotor resistance, in ohms Rotor inductance, measured in Henry. Slippage : The root mean square value of electromotive force, in volts.

[0028] This equation shows that by controlling the rotor resistance Rr, the slip s is also controlled, thereby controlling the generated torque.

[0029] Advantageously, the number of poles of motor 1 allows it to achieve a torque range greater than that required by element E to drive the gas turbine engine; device D will then limit the excess torque to ensure normal operation, thereby keeping the machine at the correct speed and torque required for element E to operate.

[0030] To obtain the frequency of the supply voltage, the voltage measurement system 5 is connected to a phase and the voltage change is sent to the processing unit 4. The voltage change is then subjected to a fast Fourier transform to obtain the frequency.

Claims

1. A device (D) for controlling the torque output by an asynchronous motor (1), the device comprising: - A rotating slip ring current collector system (2), which is adapted to be connected to the rotor (21) of an asynchronous motor (1) and is configured to collect or supply current to at least one winding of the rotor (21) of the asynchronous motor (1) to change the impedance of the rotor and thereby change the torque output by the asynchronous motor (1), the rotating slip ring current collector system being powered by a supply voltage (U); - A variable resistor (3) is connected to the rotating slip ring collector system (2) to control the supply voltage (U) of the rotating slip ring collector system (2); - Processing unit (4), the processing unit (4) is configured to adjust the frequency (V) of the supply voltage (V) of the asynchronous motor (1) according to the frequency (V) of the supply voltage (V) of the asynchronous motor (1). The torque required by the asynchronous motor (2) ) and the corresponding rotor resistance (Rr), calculate the value (R) of the variable resistor (3), and then control the supply voltage (U) of the rotating slip ring collector system (2) to control the rotor resistance (Rr), so that the asynchronous motor outputs the required torque ( The rotor resistance (Rr) is obtained through the following expression: Required torque, in Newton-meters Extreme logarithm The number of rotor phases, for an asynchronous motor, is equal to the number of rotor bars. Stator electrical pulsation, measured in radians per second, corresponds to the supply voltage of the asynchronous motor. Rotor impedance, a function of slip, is measured in ohms. Rotor impedance modulus per square millimeter, in ohms per square millimeter. Rotor resistance, in ohms Rotor inductance, measured in Henry. Slippage : The root mean square value of electromotive force, in volts.

2. The apparatus according to claim 1, wherein, The motor (1) includes multiple poles, such that the motor (1) can achieve a torque range greater than that required by the element (E) driving the gas turbine engine.

3. The apparatus according to any one of the preceding claims includes a voltage sensor or voltage measurement system (5), the voltage sensor or voltage measurement system (5) being configured to send a measured value of the supply voltage of the asynchronous motor (1) to the processing unit (4), the processing unit (4) being configured to perform a Fourier transform on the measured value to derive the frequency of the supply voltage therefrom.

4. The apparatus according to any one of the preceding claims, wherein, The motor (1) is powered by 115 volts in a variable frequency range of 360 Hz to 800 Hz.

5. A system for controlling an element (E) of an aircraft gas turbine engine, the system comprising: - An asynchronous motor (1), which is configured to output torque to an element (E) of a gas turbine engine; - The apparatus (D) according to any one of the preceding claims.

6. The system according to the preceding claims, wherein, The element (E) of the gas turbine engine is a pump for a variable propeller pitch setting system.

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