Electric system with pre-heating function for protecting its motor against condensation

Abstract

An electric system (1) includes a motorized unit (2) equipped with a motor (20) and a frequency converter (21) powered by a power source (3), the motor having a rotor and stator assembly including multiple coils, the frequency converter (21) being controlled by a monitoring / control unit (5) for turning on the motor (20) in a variable speed operating mode or for turning off the motor; and includes a measuring system (6) suitable for measuring at least one condensation parameter (T; P; H), the condensation parameter representing condensate contained in ambient air, and the monitoring / control unit being designed to control the frequency converter according to the condensation parameter during motor shutdown, such that a preheating current flows through the coils to enable preheating of the motor when the motor is off.

Description

Technical Field

[0001] This invention relates to an electric system and a method for preventing condensation in the electric system.

[0002] More specifically, the present invention relates to an electric system comprising a motor having a rotor and stator assembly including a plurality of coils, wherein the motor is driven at a rotational speed by a frequency converter powered by a power source to supply the coils with a variable frequency current, the frequency converter being controlled by a monitoring / control unit for turning the motor on in a variable speed operating mode or for turning the motor off. Background Technology

[0003] This invention finds its most popular non-limiting application in the electric systems used in cranes.

[0004] In cranes, the electric motors used for operation (lifting, orientation, distribution, etc.) are located externally and are therefore exposed to the effects of climate change, including sunlight, humidity, rain, condensation, wind, snow, frost, etc. Furthermore, electric motors typically have covers or housings that provide some degree of protection against the effects of climate.

[0005] However, it is difficult to resist the moisture from condensation in the ambient air, and this moisture affects the mechanical parts of the motor (housing, bearings, magnetic metal sheets, etc.) through oxidation or corrosion, and also affects the electrical parts (coils, etc.) through reduced insulation.

[0006] Therefore, in order to extend the service life of these motors, it is necessary to remove moisture present in the motor by condensing water vapor contained in the air onto the surface. Heating the motor when it is off is known for this purpose, and thus these solutions are known.

[0007] The first solution involves adding a specific heating resistor to the motor's coils, while the second solution involves powering the motor's coils with additional equipment (such as a transformer) besides a frequency converter.

[0008] Therefore, these solutions require additional components (e.g., inside or outside the motor, at the electrical cabinet), which means an increase in the price of the electric system, a decrease in its reliability, and an increase in space requirements due to the added components. Summary of the Invention

[0009] The present invention proposes a solution to overcome the above-mentioned drawbacks by allowing the motor to be heated when it is off without adding any additional components to avoid condensation in the motor.

[0010] Another object of the present invention is to provide a preheating function that allows the motor to be preheated with the right current when it is necessary to avoid any condensation.

[0011] Another objective of this invention is to increase the service life of the motor while maintaining the quality of the insulator.

[0012] Another objective of the present invention is to perform preheating by limiting the temperature rise to just the required level so as not to damage components and to consume minimal energy during the service life of the motor.

[0013] Therefore, the present invention proposes an electric system comprising a motorized unit equipped with a motor and a frequency converter powered by a power source. The motor is provided with a rotor and stator assembly including multiple coils. The motor is driven at a rotational speed by the frequency converter, which powers its coils with a variable frequency current. The frequency converter is controlled by a monitoring / control unit for starting the motor in a variable speed operating mode or for turning the motor off. The significant feature of this electric system is that:

[0014] It further includes a measuring system adapted to measure at least one condensation parameter, which represents the condensate contained in ambient air, and

[0015] - A monitoring / control unit, which is connected to the measuring system, is designed to control the frequency converter according to the condensation parameters during motor shutdown, so that preheating current flows through the coil to enable motor preheating when the motor is off.

[0016] Therefore, using the present invention, the preheating function is implemented without the use of additional components. The preheating function is performed by a monitoring / control unit and a frequency converter, and this is performed by providing a preheating mode in the monitoring / control unit, which is triggered when the motor is turned off and depends on the condensation parameters used to optimize the triggering.

[0017] The measurement system can be placed in an environment that is more or less close to the motor, such as in a place that is protected from solar radiation and harsh weather (such as rain and snow).

[0018] It should also be understood that, in the sense of the present invention, the preheating mode activated by the monitoring / control unit when the motor is off will certainly result in the coil being powered by current, in this case, a preheating current, without having to rotate the motor which is kept off.

[0019] In a first embodiment, the motorization unit includes a motor brake that can be configured between an open configuration and a closed configuration, the open configuration enabling the motor to rotate during motor operation and the closed configuration preventing the motor from rotating when the motor is off, regardless of whether preheating is enabled.

[0020] Therefore, in a candidate for a preheating function under certain conditions, the motor includes a motor brake that is opened when the motor movement is controlled in the on mode. In the preheating mode, the motor brake is not controlled and therefore remains closed, thereby preventing any rotational movement of the motor, even in the presence of preheating current.

[0021] It is conceivable that a monitoring / control unit is connected to the motor brake to control the motor brake to be in an open configuration during motor operation and to control the motor brake to be in a closed configuration when the motor is off, regardless of whether preheating is enabled.

[0022] In the second embodiment, the motorized unit does not have a motor brake.

[0023] This second embodiment is advantageous for hydroelectric power generation devices that include hydraulic pumps driven by motors of motorized units.

[0024] According to one characteristic, the preheating current has a lower value compared to the variable frequency current during motor start-up.

[0025] In one possibility, the measurement system includes a temperature measuring device suitable for measuring the temperature of ambient air, which thus constitutes a condensation parameter, and the monitoring / control unit is designed to preheat the motor when the temperature is less than or equal to the dew point temperature.

[0026] The dew point temperature is a temperature below which dew naturally deposits. In other words, water (or water vapor) present in the ambient air condenses (liquefies) at this temperature to form water droplets that deposit on the motor components. Therefore, when the ambient temperature reaches or falls below this dew point temperature, the monitoring / control unit automatically triggers preheating, which helps heat the inside of the motor and thus prevents condensation.

[0027] According to another possibility, the measurement system includes a pressure measuring device suitable for measuring the pressure of ambient air, which thus constitutes a condensation parameter, and the monitoring / control unit is designed to preheat the motor when the pressure is greater than or equal to the saturated vapor pressure.

[0028] Saturated vapor pressure is a pressure above which water (or water vapor) present in the ambient air condenses and forms water droplets deposited on the motor components. Therefore, when the ambient pressure reaches or exceeds this saturated vapor pressure, the monitoring / control unit automatically triggers preheating, which helps heat the inside of the motor and thus prevents condensation.

[0029] According to another possibility, the measurement system includes a humidity measuring device suitable for measuring the moisture content in ambient air, which thus constitutes a condensation parameter, and the monitoring / control unit is designed to preheat the motor when the moisture content is greater than or equal to a predetermined threshold.

[0030] In a particular embodiment, the monitoring / control unit is designed to stop the motor's preheating during the motor's operation.

[0031] Therefore, once the motor is turned on, preheating automatically stops in order to perform operations (such as crane operation) because current flows through the coil to make the motor rotate, thus necessarily heating is obtained inside the motor.

[0032] Advantageously, the monitoring / control unit calculates the value of the preheating current based on the condensation parameters and the characteristic parameters of the coil.

[0033] In other words, based on the coil (size, material, quantity), the monitoring / control unit determines the value of the preheating current, which will be suitable for sufficient preheating to avoid condensation.

[0034] The present invention also relates to a crane comprising at least one electric system according to the invention, wherein the motorization unit of the electric system is connected to at least one movable component of the crane to actuate the displacement of at least one movable component and ensure crane operation when the motor is turned on.

[0035] In a particular embodiment, the crane includes a plurality of motorized units connected to corresponding movable components of the crane to actuate their respective displacements and ensure corresponding crane operation, and a monitoring / control unit is shared by all motorized units.

[0036] Therefore, the monitoring / control unit may include a monitoring / control system that is shared by all these mechanical units, and is also designed to control all operations of the crane.

[0037] The present invention also relates to a method for protecting a motor in an electric system from condensation, wherein the electric system includes a motorized unit equipped with a motor and a frequency converter powered by a power supply, the motor having a rotor and stator assembly including multiple coils, the motor being driven at a rotational speed by the frequency converter, the frequency converter supplying its coils with a variable frequency current, the frequency converter being controlled by a monitoring / control unit for starting the motor in a variable speed operating mode or for turning off the motor, and the protection method implementing the following steps:

[0038] - Measure at least one condensation parameter, which represents the condensate contained in ambient air;

[0039] - During motor shutdown, the frequency converter is controlled by the monitoring / control unit according to the condensation parameters, so that preheating current flows through the coil to preheat the motor when it is turned off;

[0040] In advantageous applications, this protection method is implemented for the electric system of a crane, which is connected to at least one movable component of the crane to actuate its displacement and ensure crane operation when the motor is turned on. Attached Figure Description

[0041] Other features and advantages of the invention will become apparent from the following detailed description of non-limiting examples of implementations, taken with reference to the accompanying drawings, in which:

[0042] Figure 1 This is a schematic diagram of the electric system according to the present invention;

[0043] Figure 2 This is a schematic diagram of a crane according to the present invention. Detailed Implementation

[0044] Reference Figure 1 The electric system 1 according to the invention includes a motorization unit 2, which is equipped with:

[0045] - A rotary electric motor type motor 20, which is provided with a rotor and stator assembly including several coils;

[0046] - Frequency converter 21, which is powered by power supply 3 to power the coil with variable frequency current CE, thereby driving motor 20 at rotational speed.

[0047] The motor 20 is connected to the movable member 4 at its output end to ensure the displacement of the movable member; the function of the motor 20 is to make the movable member 4 move at a variable speed.

[0048] It should be noted that power source 3 can be the main power source or a backup power source, such as a generator or battery.

[0049] The electric system 1 further includes a monitoring / control unit 5, which controls the frequency converter 21 for:

[0050] -Activate motor 20 in variable speed operation mode to allow movable member 4 to move at a variable speed, or

[0051] - Turn off motor 20 to stop the movement of movable component 4.

[0052] The motorization unit 2 further includes a motor brake 8, which can be configured between:

[0053] - An opening mechanism that allows the motor 20 to rotate when it is turned on, and

[0054] -A shut-off mechanism that prevents motor 20 from rotating when the motor is turned off.

[0055] In a variant not shown, the motorized unit 2 does not have this motor brake 8. This variant has found its most popular non-limiting application in hydroelectric power plants that include a hydraulic pump driven by the motor 20 of the motorized unit 2.

[0056] According to the present invention, the electric system 1 includes a measuring system 6 adapted to measure at least one condensation parameter T, P, H, which represents condensate contained in ambient air.

[0057] The measurement system 6 may include at least one of the following measurement devices:

[0058] - A temperature measuring device suitable for measuring the temperature T of ambient air, which thus constitutes a condensation parameter;

[0059] - A pressure measuring device suitable for measuring the pressure P of ambient air, which thus constitutes a condensation parameter;

[0060] – A humidity measuring device suitable for measuring the moisture content H in ambient air, which thus constitutes a condensation parameter.

[0061] As long as the measurement value of the measuring device represents the air surrounding the motor 20, all or part of the measuring device can be separated from the motor 20 by a greater or shorter distance. In other words, the measuring system 6 can be installed outside the motor 20. Alternatively, all or part of the measuring device can be placed inside the motor 20, particularly below the housing of the motor 20.

[0062] In addition, in order to achieve the preheating function when the motor 20 is off to protect the motor 20 from condensation, the monitoring / control unit 5 is connected to the measuring system 6 and is designed to control the frequency converter 21 according to the condensation parameters T, P, H during the motor 20 being off, so that the preheating current CEP flows through the coil for preheating the motor 20 when the motor is off.

[0063] The preheating current CEP has a lower value compared to the variable frequency current CE, which flows through the coil when the motor 20 is turned on or during the motor 20's operation. Of course, during preheating in the motor 20's off mode, the motor brake 8 is always in a closed configuration, preventing the motor 20 from rotating and thus preventing the movable member 4 from shifting, even though the preheating current CEP flows through the coil.

[0064] Therefore, when the temperature T is a condensation parameter, the monitoring / control unit 5 is designed to preheat the motor 20 when the temperature T is less than or equal to the dew point temperature.

[0065] In the case where pressure P is a condensation parameter, the monitoring / control unit 5 is designed to preheat the motor 20 when pressure P is greater than or equal to the saturated vapor pressure.

[0066] In the case where the moisture content H is a condensation parameter, the monitoring / control unit 5 is designed to preheat the motor 20 when the moisture content H is greater than or equal to a predetermined threshold.

[0067] Furthermore, during the operation of motor 20, in other words, when motor 20 is turned on to move movable component 4 at a variable speed, monitoring / control unit 5 is designed to automatically stop the preheating of motor 20.

[0068] This invention is in Figure 2 The most popular and non-limiting application is found in the crane 7 schematically shown, which includes a distributor boom 70 mounted on a tower 71 (also called a mast); it should be noted that the invention can be applied to other types of cranes, such as self-erecting cranes, deployable cranes, luffing boom cranes or mobile cranes.

[0069] The boom 70 can be rotatably mounted on the tower 3 along a vertical axis, and the crane 7 can include a motorizing unit 2R that actuates the boom 70 in a rotatable manner along the vertical axis and thus ensures the directional manipulation of the boom 70, as schematically shown by arrow OR.

[0070] The crane 7 further includes a lifting device 72 for distributing loads (not shown) along the boom 70. The lifting device 72 includes a distribution trolley 73 that rolls along the boom 70 and supports a lifting member 74 for hooking loads, and may be in the form of a hook.

[0071] Therefore, the crane 7 may include a 2D motorized unit that actuates the lifting device 72 (specifically the distribution trolley 73) along the boom 70, thereby ensuring the distribution manipulation of the load, schematically indicated by arrow DI. The motorized system 2D may have its motor driving a distribution winch 75, which is equipped with a distribution drum connected to a distribution cable 76 having strands fixed to either side of the distribution trolley 73.

[0072] The crane 7 may also include a motorization unit 2L that actuates the lifting member 74 to move up and down, thus ensuring the lifting operation of the load schematically indicated by arrow LE. The motorization system 2L may have its motor driving a lifting winch 77, which is equipped with a lifting drum connected to a lifting cable 78, on which the lifting member 74 is suspended.

[0073] In applications not shown, the crane may include a hydroelectric power generation device comprising a hydraulic pump driven by a motor of the motorized unit according to the invention, for example, to actuate a hydraulic cylinder.

[0074] The motorized units 2R, 2D, and 2L are all equipped with motors and frequency converters, as previously referenced. Figure 1 As described above, in this crane 7, the monitoring / control unit 5 is shared by all the motorized units 2R, 2L, and 2D equipped with the crane 7.

[0075] Similarly, as Figure 2 As shown, the measurement system 6 can be shared by all the mechanized units 2R, 2L, and 2D equipped with the crane 7. The measurement system 6 can be located, for example, at the bottom of the tower 71, and, for example, below the electrical control cabinet (not shown), to protect it from solar radiation and rain.

[0076] Therefore, the monitoring / control unit 5 is connected to the frequency converter of the motorization units 2R, 2D, 2L to trigger all or part of the preheating in the motorization units 2R, 2D, 2L according to the condensation parameters T, P, H.

[0077] If all motorization units 2R, 2D, and 2L are turned off, the monitoring / control unit 5 triggers preheating in all motorization units 2R, 2D, and 2L. If at least one motorization unit is turned off while at least one other motorization unit is turned on, the monitoring / control unit 5 triggers preheating only in the motorization unit that is turned off.

Claims

1. An electric drive system (1) comprising a motorized unit (2) equipped with a motor (20) provided with a rotor and stator assembly comprising a plurality of coils and a frequency converter (21) powered by an electric power source (3), said motor (20) being driven by the frequency converter (21) at a rotational speed, said frequency converter powering its coils with a variable frequency current, said frequency converter (21) being controlled by a monitoring / control unit (5) for starting the motor (20) in a variable speed operation mode or for stopping the motor (20), characterized in that, The electric system further includes a measuring system (6) adapted to measure at least one condensation parameter (T; P; H), the condensation parameter representing condensate contained in ambient air and being the temperature, pressure, or humidity content of the ambient air, and wherein the monitoring / control unit (5) is connected to the measuring system (6) and is designed to calculate the value of the preheating current based on the condensation parameter (T; P; H) and based on characteristic parameters of the coil, and to control the frequency converter (21) during the shutdown of the motor (20) such that the preheating current (CEP) flows through the coil to enable preheating of the motor when the motor (20) is shut off, and wherein the motorizing unit (2) includes a motor brake (8) configurable between an open configuration and a closed configuration, the open configuration enabling the motor to rotate during the startup of the motor (20), and the closed configuration preventing the rotation of the motor (20) when the motor (20) is shut off, regardless of whether preheating is enabled.

2. The electric system (1) according to claim 1, wherein, During the start-up of the motor (20), the preheating current (CEP) has a lower value compared to the variable frequency current (CE).

3. The electric system (1) according to any one of claims 1 and 2, wherein, The measurement system (6) includes a temperature measuring device suitable for measuring the temperature (T) of ambient air, which thus constitutes a condensation parameter, and the monitoring / control unit (5) is designed to preheat the motor (20) when the temperature (T) is less than or equal to the dew point temperature.

4. The electric system (1) according to any one of claims 1 to 3, wherein, The measurement system (6) includes a pressure measuring device suitable for measuring the pressure (P) of ambient air, which thus constitutes a condensation parameter, and the monitoring / control unit (5) is designed to preheat the motor (20) when the pressure (P) is greater than or equal to the saturated vapor pressure.

5. The electric system (1) according to any one of claims 1 to 4, wherein, The measurement system (6) includes a humidity measuring device suitable for measuring the moisture content (H) in ambient air, which thus constitutes a condensation parameter, and the monitoring / control unit (5) is designed to preheat the motor (20) when the moisture content (H) is greater than or equal to a predetermined threshold.

6. The electric system (1) according to any one of claims 1 to 5, wherein, The monitoring / control unit (5) is designed to stop preheating of the motor (20) during the start-up of the motor (20).

7. The electric system (1) according to any one of claims 1 to 6, wherein, The characteristic parameters of the coil are its size, material, and quantity.

8. A crane (7) comprising at least one electric system according to any one of claims 1 to 7, wherein a motorization unit (2R; 2D; 2L) of the electric system is connected to at least one movable member (70; 73; 74) of the crane (7) to actuate displacement of the movable member and ensure crane operation (OR; DI; LE) when the motor (20) is turned on.

9. The crane (7) according to claim 8, comprising a plurality of motorized units (2R; 2D; 2L) connected to corresponding movable components (70; 73; 74) of the crane (7) to actuate their respective displacements and ensure corresponding crane operation (OR; DI; LE), and wherein, The monitoring / control unit (5) is shared by all motorized units (2R; 2D; 2L).

10. A method for protecting the motor (20) of an electric system (1) from condensation, wherein, The electric system (1) includes a motorized unit (2) equipped with a motor (20) and a frequency converter (21) powered by a power source (3). The motor is provided with a rotor and stator assembly including multiple coils. The motor (20) is driven at a rotational speed by the frequency converter (21), which powers its coils with a variable frequency current. The frequency converter is controlled by a monitoring / control unit (5) to turn the motor (20) on in a variable speed operating mode or to turn the motor (20) off. The motorized unit (2) includes a motor brake (8) connected to the monitoring / control unit (5) and configurable between an open configuration and a closed configuration. The open configuration allows the motor (20) to rotate during operation, and the closed configuration prevents the motor (20) from rotating when it is turned off. The protection method implements the following steps: - Measure at least one condensation parameter (T; P; H), which represents the condensate contained in ambient air and is the temperature, pressure, or humidity content of the ambient air; - Calculate the value of the preheating current based on the condensation parameters (T; P; H) and the characteristic parameters of the coil; - During the shutdown of the motor (20), the frequency converter (21) is controlled by the monitoring / control unit (5) to cause a preheating current (CEP) to flow through the coil for preheating the motor when the motor (20) is shut off; - The monitoring / control unit (5) controls the motor brake (8) to be in an open configuration during the start-up of the motor (20) and in a closed configuration when the motor (20) is turned off, regardless of whether preheating is enabled.

11. The protection method according to claim 10, wherein, The protection method is implemented for the electric system (1) of the crane (7), which is connected to at least one movable component of the crane (7) to actuate the displacement of at least one movable component when the motor (20) is turned on and to ensure crane operation.

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