Control device and method for controlling a high-power electric motor

Abstract

Control device (10) and corresponding method for controlling a high-power (P) electric motor (12), preferably of the order of megawatts (MW), preferably of a crushing device (11) or associated with said crushing device (11), preferably for crushing very large and heavy objects and provided with rotating crushing means (13) connected to the rotor of said electric motor (12). The control circuit (20) is configured to control the electric motor (12) so that it can be selectively operated in different operating modes.

Description

Technical Field

[0001] This invention relates to a control device and method for controlling a high-power electric motor, preferably in the megawatt (MW) range, and preferably, but not limited to, motors of crushing or pulverizing equipment or those capable of being associated with such equipment. For example, the motor can be associated with a crushing device used for, for example, crushing very large and heavy objects, such as vehicle bodies (which may have already been compacted), electric motors, mechanical components, household appliances, or others, thus requiring very high crushing forces to obtain waste, such as metals, ferrous and non-ferrous materials, suitable for then being recycled or recovered, for example, to be fed into a melting furnace. The invention can also be applied to managing electric motors associated with other equipment or apparatus, for example, for crushing and pulverizing other materials in different processes, such as, for example, paper, plastics, inert materials, wood, minerals, or others. Background Technology

[0002] In particular (but not only) in the steel industry, there is a continuous increase in the availability of raw materials for the production of new products and a related need to recycle as much material as possible from objects that are no longer in use, such as ferrous materials from discarded objects, for example, for the production of steel through a melting furnace. It is known that crushing equipment equipped with crushing or pulverizing devices, also known as crushers, is used to crush or pulverize even large and very heavy ferrous objects, such as, for example, vehicle bodies, household appliances, mechanical components, electric motors, etc., which may have been reduced in volume by pressing them in special presses.

[0003] The primary function of crushing equipment is to pulverize and reduce the volume of waste materials into smaller pieces, and then separate various waste materials from the waste materials in the process, especially by separating metal waste (both ferrous and non-ferrous) from other waste materials so that it can be specified for new uses.

[0004] The material to be processed typically first undergoes volume reduction, and then enters the crushing chamber of the crushing unit directly via a suitable conveyor belt.

[0005] The most common crushing devices typically include a rotating component called a grinder, which is basically composed of a rotating drum. Multiple crushing components (called hammers) are associated with the rotating drum and configured to violently impact the object to be crushed.

[0006] Typically, the rotation of the drum is advantageously commanded by a single electric motor with a high nominal power (P), such as up to 10 MW or more (approximately 13,400 hp). The motor is configured to rotate at different speeds (ω) depending on the torque (T) required to crush different objects, based on the well-known formula P = T·ω. The operating temperature of the motor (t) also has a direct, proportional effect on the transmitted torque.

[0007] Furthermore, since the productivity of the crusher is proportional to the rotational speed (ω) of the motor connected to the rotary drum, it is clear that in order to obtain high productivity, there is a tendency to make the rotary drum, and therefore the motor, operate at the highest feasible rotational speed.

[0008] The rotating drum has a large mass, so that once it is turned by the electric motor, it rotates by inertia due to the flywheel effect, and then the electric motor itself only supplies power input to it, which is necessary to maintain the rotational speed necessary to generate the kinetic energy required to crush the object or material to be crushed by impact.

[0009] The pulverized material discharged from the crushing unit is collected on a second conveyor belt, where lighter components are separated, for example, by an airflow. The material then enters a section equipped with magnetic devices to separate ferrous metals from non-ferrous materials and from inert and / or sterile materials. Each component is then collected in a specific container for further processing or storage.

[0010] The power supply to electric motors is usually managed automatically by control circuits to optimize equipment productivity.

[0011] However, the management is quite complex, especially considering the considerable forces involved, which are highly variable during the crushing process because the type of material being processed can vary considerably, as can its density. This necessitates different hardness and size of the supplied object, which creates varying resistance to the crushing hammer, thus generating variable loads or rotational resistance on the motor, resulting in fluctuations in the power required for processing.

[0012] The variability of the load is related to the variability of the supplied material, making the crushing unit essentially unpredictable from the perspective of the working cycle. Therefore, the electrical power required for the process is unpredictable and may even exceed the nominal performance of the motor itself.

[0013] Therefore, during these high-power transients, motors draw current peaks from public or private power grids, causing significant or even considerable interference or damage to the network itself.

[0014] Figure 1 This schematically illustrates how the operating power transmitted from the electric motor to the rotating drum can be increased to a value represented by Pmax, which corresponds to a fixed finite value related to the characteristics of the electric motor; exceeding this finite value will damage the motor. Figure 1 It can be noted that the rotational speed ω of the motor associated with the rotating drum can increase (ω+) or decrease (ω-) relative to the intermediate nominal value.

[0015] When the shredder strikes larger materials, the rotational speed of the drum decreases as they encounter greater resistance.

[0016] If the torque is not increased, the available power decreases. This is disadvantageous because the crushing hammer may not have the energy required to crush the material, leading to a reduction in the productivity of the crushing unit.

[0017] Therefore, in order to avoid a decrease in productivity, when the crusher encounters harder or larger materials, it also attempts to increase the transmitted torque, thereby causing a current absorption peak from the common network as described above during transients.

[0018] However, in an attempt to transmit the maximum power supplied by the electric motor to maintain high productivity, both the electric motor itself and the motion transmission mechanism are under great stress, forcing installers to make these components too large, resulting in increased costs.

[0019] In an attempt to limit these effects, known types of crusher devices employ protection systems; however, these protection systems do not provide entirely satisfactory results.

[0020] One known solution involves using an oil connector to transmit power between the electric motor and the grinding machine. The oil connector is manufactured in a way that protects the drive from overload and damped torsional vibration.

[0021] Another solution is known to attempt to reduce damage due to uncontrolled overload, which provides a liquid rheostat driver of the type called LRS (Liquid Resistance Starter), which consists of a power supply system for the motor, in which the motor rotor is surrounded by a salt solution and thus conductive, with electrodes disposed therein; the immersion level of the electrodes in the liquid can be selectively adjusted to increase or decrease the conductivity between the stator and rotor, thereby enabling the grinding mill to change the power required from the motor. Adjustment is feasible by using a current transformer that detects the need for greater absorption, thus allowing for variations in the height of the electrodes within the conductive salt solution.

[0022] This known system allows for partial attenuation of uncontrolled absorption peaks, thus protecting the motor (which loses 8%-9% of its power in heat). However, from the perspective of response speed over time (2-3 seconds), this intervention capability is limited and does not prevent energy waste under any circumstances, which causes power dissipation in the "liquid starter".

[0023] In any case, the phenomenon of power peaks is not completely eliminated by this known solution, so it is still necessary to make the motor oversized: for example, in order to work properly without the excessive risk of being ruined by high power peaks, a motor with a nominal power of 3,700kW (about 5,000hp) is forced to not exceed 65%-70% of the aforementioned nominal power, so that the motor can operate at an average of about 2,500kW (about 3,350hp).

[0024] This solution is not very effective because it is impossible to fully utilize the engine's power, and therefore impossible to transfer all available energy to the hammer to crush the material, thus greatly limiting the equipment's performance and overall productivity.

[0025] US10476421B1 describes a control system for a switched reluctance motor capable of selecting between multiple operating modes to control the current supplied to the motor by an inverter based on motor speed, transient speed, and motor power. These operating modes include a current regulation mode, a single-pulse mode, and a continuous conduction mode. Specifically, the solution described in US10476421B1 provides a method for comparing the motor speed with a first threshold to determine whether to control the motor using a current regulation operating mode or a single-pulse operating mode. If the motor speed exceeds the nominal threshold, power stability is maintained by operating the motor in a flux-reducing region (i.e., by reducing the motor flux). This operating mode allows for significantly increased speeds but requires increased current to compensate for the reduced flux, leading to undesirable power spikes. This solution does not allow for maximizing motor utilization and efficiency.

[0026] The known solutions also have the drawback of being strictly dependent on the available network and current, so in regions or countries with limited current, it is necessary to reduce the nominal power of the motor. Summary of the Invention

[0027] The object of the present invention is to provide a control device and associated method for controlling a high-power electric motor, preferably in the megawatt (MW) range, preferably but not limited to a crushing or pulverizing device, or capable of being associated with a crushing or pulverizing device, wherein the control device and associated method are capable of allowing the electric motor to deliver the maximum available energy of the motor under any circumstances.

[0028] In particular, one objective is to provide a control device and method that allows an electric motor to be used at its nominal power without the risk of power spikes associated with load variations, which could lead to serious problems and / or damage to the network supplying current to the motor.

[0029] Another object of the present invention is to provide a control device and associated method for controlling a high-power electric motor, which allows for high rotational speeds of the motor rotor and thus the associated rotating components, providing high productivity of the crushing equipment in relation to the power transmitted and the torque applied to the rotating components themselves.

[0030] Another object of the present invention is to provide a control method and apparatus that allows for maximizing the applied torque.

[0031] Another objective is to provide a control method and apparatus that can be applied to existing crushing equipment to improve their performance and overall efficiency by fully utilizing the nominal power of the electric motors, and can also be applied to newly constructed equipment, thereby allowing the correct sizing of the electric motors themselves as required, and also relating to the available electrical energy.

[0032] The applicant has designed, tested, and implemented the present invention to overcome the disadvantages of the prior art and to obtain these and other objectives and advantages.

[0033] To achieve the above objectives, a control device for controlling a high-power electric motor, preferably in the megawatt range, preferably a motor of a crushing device or associated with the crushing device, preferably for crushing very large and heavy objects and equipped with a rotating crushing device connected to the rotor of the motor, the control device comprising: a power supply device associated with the motor to selectively supply it with voltage and current, enabling the motor to operate at a selected temperature, supply the power, rotate at an appropriate rotational speed, and apply a determined torque to the rotating crushing device required for crushing the object; and a control circuit connected to the power supply device and configured to control the motor to selectively operate at the aforementioned temperature, supply the aforementioned power, rotate at the aforementioned rotational speed, and apply the torque to the rotating crushing device.

[0034] According to the feature scheme of the present invention, the control circuit described above includes a selection device configured to select the supply of the voltage and current, such that the motor can selectively operate in any of the following three operating modes: a first operating mode with a stable rotational speed and power limited to a selected value; a second operating mode with stable power and torque limited to a selected value greater than or equal to the nominal torque value; and a third operating mode with stable torque and the temperature of the motor being limited to a selected value.

[0035] According to some embodiments, the control circuit is configured to select the supply of the aforementioned voltage and current in relation to the load type of the crushing equipment, so as to return the motor to operate in a second operating mode with stable power or maintain the motor operating in the second operating mode.

[0036] According to some embodiments, in the second operating mode, the motor operates at a nominal magnetic flux value that is substantially equal to its nominal magnetic flux value in the first operating mode. In other words, the magnetic flux of the motor remains near the nominal value and does not decrease with increasing speed.

[0037] According to some embodiments of the present invention, the selection device includes an inverting circuit or an inverter.

[0038] According to other embodiments of the present invention, the inverter may include a plurality of thyristors.

[0039] The ability to adapt the motor's operation to the selected components allows for adjustments to the current, enabling the hammer's speed and / or torque to be increased or decreased based on operational requirements, ensuring maximum available energy is transferred to the waste. In fact, thanks to the inverter device, a dynamic operating process is achieved, adapting in real time to the type / amount of the load to be crushed and to the requirements of the power grid.

[0040] According to some embodiments of the invention, the motor is electrically powered by a medium-voltage (MV) power supply device, with a power transformer inserted between the latter and the motor, the power transformer being configured to convert the voltage from medium voltage (MV) to medium-low voltage (LV) and to connect to the control circuit.

[0041] According to some embodiments, the electric motor is provided with one or more detection devices suitable for detecting one or more operating parameters, the operating parameters being selected from rotational speed, torque, absorbed current, and temperature.

[0042] According to other embodiments of the invention, the control circuit further includes a programmable electronic control unit configured to command the motor to be in one of the three operating modes, also based on feedback signals received from the detection device of the motor.

[0043] According to some embodiments of the present invention, in the first operating mode, the power absorbed by the motor reaches a set maximum power level, preferably between 105% and 115% of the nominal power of the motor, for example, 110%.

[0044] According to some embodiments of the present invention, in the third operating mode, the maximum torque corresponding to the maximum operating temperature of the motor is preferably set to a value between 140% and 160% of the nominal value, for example, 150%.

[0045] The present invention also relates to a control method for controlling a high-power electric motor via a control device, the electric motor preferably being in the megawatt (MW) range, preferably a motor of a crushing device or associated with said crushing device, said crushing device preferably being used to crush very large and heavy objects and having a rotating crushing device connected to the rotor of said motor, the control device comprising: a power supply device associated with said motor to selectively supply power to said motor with voltage and current, such that said motor can operate at a selected temperature, supply said power, rotate at said appropriate rotational speed, and apply said determined torque to said rotating crushing device for crushing said object; and a control circuit connected to said power supply device and configured to control said motor such that said motor selectively operates at said temperature, supplies said power, rotates at said rotational speed, and applies said torque to said rotating crushing device.

[0046] The method according to the invention includes at least a first step, wherein the control circuit controls the motor to operate in at least a first operating mode, wherein the motor has a stable rotational speed and the power is limited to a set maximum power value.

[0047] According to some embodiments, when the maximum power value is reached, the method provides to select the supply of the voltage and the current such that the motor can selectively operate in at least one of the following modes: a second operating mode, controlled for stable power and with torque limited to a selected value greater than or equal to the nominal torque value; or a third operating mode, controlled for stable torque and with the temperature of the motor limited to a selected value.

[0048] The three operating modes can be selected in each case based on the type and amount of waste to be shredded, and / or the limitations of the electrical energy available in the power supply network, so as to modify the motor's operating parameters in terms of power, speed and torque, so as to always deliver the maximum available energy to the waste.

[0049] In particular, by setting the motor to stable parameters so that it operates at or even above its nominal power most of the time, and by adjusting the speed and torque accordingly, the equipment efficiency is increased due to the fact that the full available power of the motor is utilized, and the transfer of maximum available energy is also achieved.

[0050] This solution allows for maximizing the energy delivered to the waste to be crushed at every moment, thereby effectively utilizing the potential of the electric motor at its thermal capacity limit without compromising its proper operation.

[0051] According to some embodiments of the present invention, the method provides that, in each operating mode, the motor operates substantially always at a stable magnetic field flux value substantially equal to the nominal flux value.

[0052] According to some embodiments, the method provides that, at least in a second operating mode and possibly in a third operating mode, the motor can be operated under variable load and stable power, but with torque overload, that is, the maximum torque value is set to be higher than the nominal torque value, preferably between 140% and 160% of the nominal value, for example 150%.

[0053] According to other embodiments, the method according to the invention provides that the voltage and current supply of the motor are adjusted such that the motor remains in the second operating mode or returns to the second operating mode.

[0054] The maximum torque value can be set based on the maximum temperature that the motor can reach.

[0055] The method according to the invention provides for continuously monitoring the temperature of the motor in order to appropriately adjust the voltage and current supplied to the motor. Furthermore, this solution allows operation even under overload conditions of the waste containment chamber, as it enables real-time control of the motor's operation, particularly torque and speed, and also utilizes energy transfer between the waste materials themselves.

[0056] When applied to existing equipment, the control devices and methods allow for a significant improvement in the overall efficiency of the equipment, while in the case of new equipment, they allow for the sizing of the motors based on actual needs, eliminating the need to compensate for any power peaks. Attached Figure Description

[0057] Referring to the accompanying drawings, these and other aspects, features, and advantages of the invention will become apparent from the following description of an embodiment given by way of example, which does not limit the field and scope of protection, in which:

[0058] Figure 1 A known graph schematically illustrates the relationship between the rotor rotational speed (ω) and the rotor power (P), torque (T), and temperature (t°) parameters of an electric motor, as previously seen;

[0059] Figure 2 This is a block diagram of a control circuit associated with crushing equipment according to the present invention;

[0060] Figure 3 It is a brief representation Figure 2 A graph showing the trend of the rotational speed (ω) of the rotor of the electric motor used in the crushing equipment relative to the corresponding power (P), torque (T) and temperature (t°) parameters of the rotor according to three modes A, B and C, which are used to control the electric motor according to the present invention with stable rotational speed (ω), stable power (P) and stable torque (T), respectively.

[0061] Figure 4 It is a brief representation used for control Figure 3 The following are examples of graphs showing the trends of the following three parameters over time (t) in three operating modes of the electric motor (first A, second B, and third C): rotational speed (ω) in revolutions per minute (rpm) (the dashed curve above); power (P) (the dashed curve below), as a percentage of the motor's nominal power; and torque (T) (the solid curve in the center), also as a percentage of the motor's nominal torque.

[0062] Figure 5 yes Figure 2 A schematic diagram of the control circuit;

[0063] Figure 6 It is a graph showing the trend of power (P) supplied by the motor controlled by the control circuit according to the present invention over time (t) compared with the power controlled according to the prior art (the gray curve above). Detailed Implementation

[0064] Reference will now be made in detail to the feasible embodiments of the invention illustrated in the accompanying drawings. These examples are provided to illustrate the invention and should not be construed as limiting the invention.

[0065] Before describing these embodiments, we must also clarify that this specification, in its application, is not limited to the details of the construction and arrangement of the components described below using the accompanying drawings. Other embodiments may be provided in this specification and may be obtained or implemented in different ways. We must also clarify that the wording and terminology used herein are for descriptive purposes only and should not be considered limiting.

[0066] refer to Figure 2 The control device 10 according to the invention is shown as being associated with a crushing device 11 of a known type, the crushing device 11 having a motor 12, the rotor of the motor 12 being connected, for example, by an extension to a rotating drum or grinder 13, the rotating drum or grinder being provided with a crushing hammer of a known type, not shown in the figures.

[0067] The rotating drum 13 is associated upstream with a device 14 for introducing the object or material to be crushed, and downstream with a device 15 for collecting the crushed pieces.

[0068] The crushing equipment 11 is connected to a power supply device 16 of a known type, which is, for example, a medium voltage (MV) grid capable of supplying voltages from 11 kV to 20 kV at a power (P) of up to about 10-15 MW.

[0069] An MV / LV power transformer 17 is inserted between the power supply device 16 and the motor 12. It is configured to convert the voltage from medium voltage (MV) to low voltage (LV), and in the example given here, it is indicated to be converted to a value between about 300V and 700V, with a power of about 3-3.5MW.

[0070] The control device 10 includes a control circuit 20 connected to the power transformer 17 and equipped with a selection device 21 controlled by a programmable electronic control unit 22 (e.g., a PLC), and also controlled based on appropriate feedback signals from the motor 12, indicating at least the torque T, power P, and rotational speed ω.

[0071] According to some embodiments, the programmable electronic control unit 22 can receive feedback signals detected and / or monitored in real time by one or more detection devices 25 associated with the motor 12. According to some embodiments, the detection device 25 may include sensors adapted to detect one or more of torque, rotational speed, absorbed current, or motor temperature.

[0072] The detection device 25 includes at least a temperature sensor adapted to detect the temperature of the motor 12 and send the detected value to the control circuit 20 and / or the programmable electronic control unit 22.

[0073] The selected device 21 includes, for example, an inverter circuit or inverter 23, which preferably includes a plurality of thyristors 24. Figure 2 and Figure 5 ).

[0074] The control circuit 20 is configured to actively manage the control parameters (power P, torque T, rotational speed ω) of the motor 12 via the inverter 23 and the programmable electronic control unit 22. All of these are done in a dynamic manner, fully utilizing the potential of the motor 12 in terms of the percentage of the maximum torque that can be supplied under permanent thermal conditions.

[0075] In particular, the control circuit 20 can disconnect the motor 12 from the power supply device 16 (i.e., from the power grid) so that the current at the output of the inverter 23 can be controlled and the motor 12 can be powered in a controlled manner, thereby preventing stress on the motion transmission mechanism and interference from the power grid itself.

[0076] In particular, the control device 10 allows operation in three different control operation modes.

[0077] The first operating mode A basically provides control at a stable rotational speed ω, but limits the power P.

[0078] In the first operating mode A, the rotational speed ω is a control parameter and remains stable. Therefore, its value is numerically fixed through automation and can be selectively set in an attempt to achieve maximum productivity, since the rotational speed ω is proportional to the productivity of the crushing equipment 11.

[0079] For a high rotational speed ω set based on the formula P=T·ω, the torque T and power P also increase until the set power limit Pmax is reached. The set power limit is a limit that cannot be exceeded in order not to damage the motor 12.

[0080] The power P absorbed by the motor 12 reaches a set maximum power level Pmax, which is preferably between 105% and 115% of the nominal power P of the motor 12, for example, 110%. This corresponds to Figure 3 Point A in the diagram. Exceeding this limit will damage the motor 12. In fact, as in the prior art, this limit may only be exceeded if the motor size is excessively large. However, the present invention does not provide for such excessive size, but instead provides for an automatic and programmed transition to a subsequent second operating mode B.

[0081] The second operating mode B basically provides control at a stable power P and limits the torque T.

[0082] In the second operating mode B, power P is the control parameter and remains stable, while torque T and rotational speed ω are variable. When torque T increases, rotational speed ω decreases to keep power P stable.

[0083] In particular, in the second operating mode B, the power P remains basically stable at the set maximum power value Pmax, or in any case, remains below this value.

[0084] The torque T is increased by increasing the current absorption. According to the formula I²t, a higher current leads to an increase in the specific energy passing through the motor 12, where "I" is the effective value of the short-circuit current (in amperes), "t" is the duration of the current, and the temperature t° of the motor 12 increases accordingly.

[0085] Therefore, advantageously, the temperature t° of the motor 12 is measured and its value is sent to the control circuit 20 so that the potential of the motor 12 can be fully utilized within its thermal capacity limit without compromising its proper operation.

[0086] Therefore, by keeping the power P below or at most equal to the set maximum value Pmax, the torque transmitted from the motor 12 to the rotating drum 13 can be increased to the maximum torque level T according to the temperature t° of the motor 12. The maximum torque level T is set to correspond to the maximum temperature t°max that the motor 12 can reach without damage, based on its built characteristics.

[0087] At stable power ( Figure 3 In this second operating mode B (of the central area), the following advantages are obtained:

[0088] - Productivity increases by 25%-30%;

[0089] - No current absorption peak was observed on the power supply device 16 side;

[0090] - Maximum energy is transferred to the side of the rotating drum 13;

[0091] - The electric motor 12 is not subject to thermal stress.

[0092] Furthermore, the on and off of the feed rollers, which feed the waste to the crushing equipment, and their speed can be controlled by the control circuit 20 and the inverter 23, so as to keep the engine power stable at a fixed value and transfer the maximum feasible energy to the waste.

[0093] According to some embodiments, the second operating mode B with a stable power limit allows for adaptive adjustment of the operation of the motor 12 based on available electrical energy. In fact, even if a limit equal to 120% of the nominal power cannot be set and must be limited to 80%, in the second operating mode B, the motor 12 can still operate at a torque T that varies between 100% and 150% of the nominal torque, regardless of the power.

[0094] The third operating mode C provides control at a basically stable torque T and limits the temperature t° of the motor 12.

[0095] When the maximum transmittable torque T corresponding to the maximum temperature t°max that the motor 12 can safely reach is reached, the torque T becomes a control parameter that remains stable, thereby allowing for (especially reducing) the possibility of variations in rotational speed ω and power P.

[0096] The amount of time that motor 12 can operate under these conditions depends on the percentage of torque T used relative to its nominal value, as well as the previous operating history of motor 12 itself, which affects its temperature conditions.

[0097] When the torque limit T is reached and control is executed according to the temperature t°, the control method then provides to limit the power supply to the motor 12.

[0098] According to some embodiments, it can be provided that after a certain time interval during the execution of the third operating mode, the supply current to the motor 12 decreases, causing the operating parameters of torque T, rotational speed ω, and power P to return to the values ​​provided in the second operating mode B (see...). Figure 3 (Charts in the text).

[0099] In particular, unlike what usually occurs in known solutions, the method according to the invention provides that it initially operates with speed control to increase the power to a maximum value Pmax, and then transitions to control at a stable power level by gradually increasing the torque T until a set limit is reached, which is set at the value Pmax.

[0100] According to some embodiments, the voltage and current supplied to the motor can be adjusted so that the motor 12 remains in a second operating mode.

[0101] Figure 4 The graph shows the actual records of three control parameters, namely power P, torque T and rotational speed ω, on the operating crushing equipment 11 under three operating modes A, B and C during the crushing process.

[0102] especially, Figure 4 The graph shows the trend of rotational speed ω in revolutions per minute (rpm) at the top (the dashed curve above), the torque T as a percentage in the central part with a solid line, and the power P as a percentage relative to the nominal power of motor 12 with a dashed line at the bottom.

[0103] The operation of the control device 10 described so far (which also corresponds to the control method according to the invention) provides a first step, wherein the control circuit 20 controls the motor 12 according to a first operating mode A, and thus the rotational speed ω is set to increase until the maximum power threshold is reached. Figure 3 (Pmax in the middle).

[0104] After reaching the threshold, the control circuit 20 switches to the second step of adopting the second operating mode B, so that the power P is kept at a fixed value, such as the maximum power value Pmax, preferably between 105% and 115% of the nominal power P, such as 110%.

[0105] The second operating mode B allows full utilization of the power of motor 12, such as... Figure 4 As can be seen, the dotted line below never exceeds 110% of this threshold and remains basically stable, significantly improving the average power used compared to known solutions until it almost reaches the nominal value.

[0106] As mentioned earlier, in the second operating mode B, as the transmitted torque T increases, the temperature t° of the motor 12 also increases until it reaches the maximum operating temperature of the same motor 12. Figure 3 The maximum torque T that can be transmitted under t°max.

[0107] According to some embodiments, in the second operating mode B, the motor 12 always operates at a stable magnetic flux value that is substantially equal to the nominal flux value.

[0108] When the maximum operating temperature is reached, the control circuit 20 enters the third step, in which the third operating mode C is adopted.

[0109] According to some embodiments, the torque value T in the second operating mode B and the third operating mode C is greater than or equal to the nominal torque value.

[0110] exist Figure 4 In the curve, the maximum torque T corresponding to the maximum operating temperature (t°max) of the motor 12 is set to a value preferably between 140% and 160% of the nominal value, for example, 150%.

[0111] When loaded into the rotating drum 13 via the introducing device 14 Figure 2 When the type of material to be crushed allows it to fall below the torque T limit set by the control circuit 20, it can return to the operating range of the second operating mode B. This is the ideal mode for the machine to operate, as it is the area where the motor 12 supplies maximum power P without exerting effort, yet still achieves the highest productivity. This operating mode varies between points A and C, where point A corresponds to the maximum rotational speed ω of the motor 12 and therefore the maximum rotational speed ω of the rotating drum 13 and a lower torque T, and point C corresponds to the maximum torque T and minimum rotational speed ω at the same power P.

[0112] To switch from the third operating mode C to the second operating mode B, inverter 23 can be activated to reduce the supplied current.

[0113] According to some embodiments, the method according to the invention provides that the motor 12 operates in each operating mode A, B, C with a stable magnetic field flux value that is substantially equal to the nominal flux value.

[0114] Figure 6 The graph represents the results of a comparative study between the trend of the power P supplied by the motor 12 controlled by the control circuit 20 over time (t) (the solid curve below) and the trend of the power P supplied by the motor according to the prior art over time (t) (the dashed curve above). In the former case, the power P is limited to a maximum of 4MW and there are no abnormal power peaks. In the latter case, two uncontrolled power peaks can be seen, the highest of which is 7.2MW.

[0115] from Figure 6 As can be seen from the graph, compared to the need for ultra-large-sized motors with a nominal power greater than 7.2MW under the existing technology, thanks to this invention, motors with a nominal power equal to or even less than 4MW can be used with the same performance, resulting in savings in production and consumption costs.

[0116] Furthermore, compared to the time of several seconds (2 to 3 seconds) in the prior art, for example using a known LRS, the control circuit 20 responds essentially instantly to load changes borne by the motor 12 using the control device 10 according to the invention, on the order of milliseconds.

[0117] Obviously, modifications and / or additions to the control device 10 and method as described above can be made without departing from the scope and range of the invention as defined by the claims.

[0118] It is also clear that although the invention has been described with reference to some specific examples, those skilled in the art will certainly be able to implement many other equivalent forms of the apparatus 10 and method for controlling a high-power electric motor, preferably in the megawatt (MW) range, preferably a motor of a crushing or pulverizing device, having the features described in the claims, and thus all within the scope of protection defined herein.

[0119] In claims, the sole purpose of reference marks in parentheses is for readability: they should not be regarded as limiting factors on the scope of protection claimed in a particular claim.

Claims

1. A control method for controlling a high-power (P) motor (12) via a control device (10), the motor being in the megawatt (MW) range, the motor being a motor of or associated with a crushing device (11) for crushing very large and heavy objects and having a rotating crushing device (13) connected to the rotor of the motor (12), the control device comprising: A power supply device (16), associated with the motor (12) to selectively supply it with voltage (V) and current (I), such that the motor (12) operates at a selected temperature (t°), supplies the power (P), rotates at a selected rotational speed (ω), and applies a determined torque (T) to the rotating crusher (13) required for crushing the object; and a control circuit (20), connected to the power supply device (16) and configured to control the motor (12) such that it selectively operates at the temperature (t°), supplies the power (P), rotates at the rotational speed (ω), and applies the torque (T) to the rotating crusher (13), characterized in that it includes at least a first step, wherein the control circuit (20) controls the motor (12) such that it operates at least in a first operating mode (A), the first operating mode (A) providing control at a stable rotational speed (ω), and limiting to a set maximum power value (Pm). a The power (P) of x), and the maximum power value (Pm) is reached. a After x), the control method provides the selection of the supply of the voltage (V) and the current (I) so that the motor (12) can selectively operate in at least one of the following modes: a second operating mode (B) which provides control at a stable power (P) and the torque (T) is limited to a selected value greater than or equal to the nominal torque value; or a third operating mode (C) which provides control at a stable torque (T) and the temperature (t°) of the motor (12) is limited to a selected value.

2. The control method according to claim 1, characterized in that, In the second operating mode (B), the torque (T) applied to the motor (12) is increased by increasing the current (I) absorbed by the motor (12).

3. The control method according to claim 1 or 2, characterized in that, After reaching the maximum power value (Pmax), it provides that the second operating mode (B) is selected and maintained until the torque (T) of the motor (12) reaches the maximum transmittable torque (T) value corresponding to the predetermined maximum achievable operating temperature (t°max), the maximum operating temperature (t°max) corresponding to the value of the selected temperature of the third operating mode (C), and after reaching the maximum operating temperature (t°max), it provides that the third operating mode (C) is adopted.

4. The control method according to claim 1 or 2, characterized in that, In the third operating mode (C), the torque (T) is kept stable, and the rotational speed (ω) and power (P) are reduced.

5. The control method according to claim 1 or 2, characterized in that, It provides that the motor (12) is controlled in the first operating mode (A) until the power (P) absorbed by the motor (12) reaches the maximum power value (Pm) set between 105% and 115% of the nominal power (P) of the motor (12). a x).

6. The control method according to claim 3, characterized in that, In the third operating mode (C), the maximum transmittable torque (T) corresponding to the maximum operating temperature (t°max) of the motor (12) is set to a value between 140% and 160% of the nominal value of the torque.

7. The control method according to claim 3, characterized in that, When the torque limit related to the selected temperature (t°) is reached in the third operating mode (C), or when the third operating mode (C) has been running for a predetermined period of time, it provides to reduce the current supplied to the motor (12) so that the motor (12) returns to operation in the second operating mode (B).

8. The control method according to claim 1 or 2, characterized in that, It provides that, in each of the aforementioned operating modes (A, B, C), the motor (12) operates with a stable magnetic field flux value that is substantially equal to the nominal flux value.

9. The control method according to claim 1 or 2, characterized in that, It provides that the temperature of the motor (12) is continuously detected, and the detected value is sent to the control circuit (20) each time so as to properly adjust the voltage and the current so as to fully utilize the potential of the motor (12) within the limits of its thermal capacity without impairing its proper operation.

10. A control device (10) configured to perform the control method of any one of the preceding claims for controlling a high-power (P) motor (12), the motor being in the megawatt (MW) range, being a motor of or associated with a crushing device (11) for crushing very large and heavy objects, and having a rotating crushing device (13) connected to the rotor of the motor (12), the control device comprising: A power supply device (16), associated with the motor (12) to selectively supply it with voltage (V) and current (I), such that the motor (12) operates at a selected temperature (t°), supplies the power (P), rotates at a selected rotational speed (ω), and applies a determined torque (T) to the rotating crusher (13) required for crushing the object; and a control circuit (20), connected to the power supply device (16), and configured to control the motor (12) such that it selectively operates at the selected temperature (t°), supplies the power (P), rotates at the selected rotational speed (ω), and applies the determined torque (T) to the rotating crusher (13) required for crushing the object. Torque (T), wherein the control circuit (20) includes a selection device (21) configured to select the supply of the voltage (V) and the current (I) such that the motor (12) can selectively operate in any of the following three operating modes: a first operating mode (A) which provides control at a stable rotational speed (ω) and power (P) limited to a selected value; a second operating mode (B) which provides control at a stable power (P) and torque (T) limited to a selected value greater than or equal to the nominal torque value; and a third operating mode (C) which provides control at a stable torque (T) and the temperature (t°) of the motor (12) is limited to a selected value.

11. The control device (10) according to claim 10, characterized in that, The selection device (21) includes an inverter circuit or an inverter (23).

12. The control device (10) according to claim 11, characterized in that, The inverter (23) includes a plurality of thyristors (24).

13. The control device (10) according to any one of claims 10 to 12, characterized in that, The motor (12) is electrically powered by a medium-voltage MV power supply device (16), and a power transformer (17) is inserted between the power supply device (16) and the motor (12), the power transformer (17) being configured to convert the voltage from medium-voltage MV to low-voltage LV and to be connected to the control circuit (20).

14. The control device (10) according to any one of claims 10 to 12, characterized in that, The control circuit (20) also includes a programmable electronic control unit (22) configured to command the motor (12) to be in one of the three operating modes, also based on feedback signals received from the motor (12).

15. The control device (10) according to claim 14, characterized in that, The programmable electronic control unit (22) is connected to a detection device (25) associated with the motor (12) and receives the feedback signal from the detection device (25), and includes a sensor suitable for detecting one or more of torque, rotational speed, absorbed current or motor temperature.

16. The control device (10) according to any one of claims 10 to 12, characterized in that, In the first operating mode (A), the set maximum power value (Pmax) of the power (P) absorbed by the motor (12) is between 105% and 115% of the nominal power (P) of the motor (12).

17. The control device (10) according to any one of claims 10 to 12, characterized in that, In the third operating mode (C), the maximum torque (T) corresponding to the maximum operating temperature (t°max) of the motor (12) is set to a value between 140% and 160% of the nominal value.

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