Method for adjusting the power supply source for a magnetic bearing control system

Abstract

According to one embodiment, a DC / DC voltage converter (108, 112) is disclosed, the DC / DC voltage converter (108, 112) being configured as a power supply for a magnetic bearing control system (111) comprising a regulation unit configured to regulate the DC / DC voltage converter (108, 112) by limiting an output DC by a time-dependent limit value (502) based on a time-dependent critical temperature (500) indicative of a margin against an overheating limit of the DC / DC voltage converter (108, 112) based on a thermal model thereof.

Description

Technical Field

[0001] The present invention relates to a DC / DC voltage converter for supplying power to a magnetic axis control system, such a magnetic axis control system, and a method of adjusting such a DC / DC voltage converter and such a magnetic axis control system.

Background Art

[0002] A magnetic bearing is a bearing in which mechanical friction with a shaft is reduced or avoided by applying an electromagnetic field. In the case of a shaft to which a bearing is attached using a magnetic bearing, the shaft is, so to speak, floating on a magnetic field generated by a coil around the shaft. As a result, magnetic bearings do not require lubrication and do not use oil and grease.

[0003] With an active electromagnetic bearing, the shaft is levitated by a magnetic field and rotates substantially without friction.

[0004] In order to ensure proper operation, the sensor needs to measure the deviation of the shaft from the reference position. The shaft is guided and held at the desired position by a control device and power electronics. This control device and power electronics can consist of various components such as a DC / DC voltage converter and a magnetic axis control system.

[0005] The DC / DC voltage converter supplies a stable DC voltage supply to the magnetic axis control system. Next, the magnetic axis control system further supplies a bias current to the coil that generates the magnetic field. A possible deviation of the shaft from the desired position is absorbed by changing this bias current based on the measured values by the sensor and the adjustment and control algorithms.

[0006] The initial deviation may occur during the startup of a rotating machine, where the rotor is equipped with one or more magnetic bearings. During startup, the rotor will be accelerated from a stationary state to reach its nominal rotational speed. During this transient or transient phenomenon, further vibrations may occur that cause the shaft to deviate from the desired position. In this case, the magnetic bearing control system will bias the coils by adjustment and control algorithms to minimize this deviation and keep the shaft in the desired position.

[0007] Furthermore, deviations can occur during the operation of rotating machinery, for example, when the rotating machinery is coupled to other machinery, such as a compressor, to supply mechanical torque. If a compressor surge occurs due to aerodynamic instability, this will affect the drive machinery and therefore the magnetic bearings. Here again, the magnetic bearing control system will maintain the shaft in the desired position through adjustment.

[0008] Another type of deviation can occur if the drive mechanism and the machinery connected to it stop for almost the same reasons as when they started.

[0009] Due to these deviations, the magnitude of the biasing current in the coils that holds the magnetic bearing in the desired position also exhibits transient behavior. In other words, in stable operation, the shaft can be held in the reference position by a similarly stable biasing current, but its magnitude changes in anticipation of the deviations and then converges to a stable value once a steady state is reached.

[0010] To ensure the proper functioning of the magnetic bearing control system, under current technology, this system is electrically powered by a DC power supply. Due to the aforementioned deviations, adjusting this power supply consists of keeping the output DC voltage of the DC voltage source as constant as possible. Therefore, if the biasing current value is high, the value of the DC current drawn from the power supply may also be high. To avoid the possibility of failure due to this DC current being too high, the DC / DC voltage converter is over-dimensioned as a power source for the magnetic bearing control system. This is disadvantageous from an economic and technical standpoint, because the oversized dimensions lead to the use of more expensive materials, while there remains the possibility that the magnetic bearing control system does not technically require such oversized dimensions or that it is an extremely exceptional case. [Overview of the project] [Problems that the invention aims to solve]

[0011] Accordingly, an object of the present invention is to provide a method and apparatus for adjusting a DC / DC voltage converter configured as a power source for a magnetic bearing control system, which overcomes one or more of the drawbacks described in the prior art. Furthermore, an object is to provide a method and apparatus for adjusting a magnetic bearing control system powered by such a DC / DC voltage converter, and a motor control device comprising the DC / DC converter and the magnetic bearing control system. [Means for solving the problem]

[0012] According to the present invention, the above object is achieved in a first aspect of the present invention by providing a method for adjusting the DC / DC voltage converter described in claim 1, wherein the DC / DC voltage converter is configured as a power source for a magnetic bearing control system, and the method is The steps include converting the input DC voltage from a DC / DC voltage converter into an output DC voltage suitable for use as a power supply, The steps include supplying power to the magnetic bearing control system with an output DC voltage, thereby generating an output DC when active, and Steps include monitoring the DC output and This method includes, The steps include determining the time-dependent critical temperature, which represents the margin against the overheating limit of the DC / DC voltage converter, based on the thermal model of the DC / DC voltage converter, and A step of determining a time-dependent current saturation limit over a predetermined period based on a time-dependent critical temperature, wherein the current saturation limit represents the warm-up of the DC / DC voltage converter over the predetermined period, thereby obtaining a time-dependent limit for the output DC. Furthermore, if the output DC exceeds a time-dependent limit, this method A step to limit the output DC to this limit, It also includes.

[0013] A DC / DC voltage converter functions as a power source for a magnetic bearing control system by supplying a DC voltage. This DC voltage supply is called the output DC voltage and functions as the input voltage for the magnetic bearing control system. The output DC voltage is established by converting the input DC voltage from the DC / DC voltage converter, which is located on the DC voltage rail. This value is also suitable as the input voltage for the magnetic bearing control system.

[0014] The magnetic bearing control system is electrically powered when in operation, i.e., when active, and current flows from a DC / DC voltage converter to the magnetic bearing control system. This current is further referred to as the output DC from the perspective of the DC / DC voltage converter.

[0015] Furthermore, a time-dependent critical temperature is determined, which represents a margin against the overheating limit of the DC / DC voltage converter. The critical temperature is the temperature that the DC / DC voltage converter can reach without overheating, and therefore the limit below which overheating is avoided. Overheating, therefore, means that the temperature of the DC / DC voltage converter is too high, and its proper operation cannot be guaranteed. This is because if the temperature is too high, one or more components, such as electronic components within the DC / DC voltage converter, may exhibit unpredictable or unreliable behavior or even fail.

[0016] This time-dependent critical temperature is determined based on a thermal model. This thermal model preferably includes measured quantities such as output DC and ambient temperature, and optionally output DC voltage, input DC voltage, input DC, and one or more internal temperatures.

[0017] Furthermore, the thermal model includes a thermal loss parameter that indicates the thermal loss of the DC / DC voltage converter when it is active, i.e., when the output DC flows from the DC / DC voltage converter to the magnetic bearing control system. As is known to those skilled in the art, electrical devices always have losses in the form of unwanted heating. Thus, the thermal loss parameter is an expression of Joule loss, which is the electrical loss due to ohmic resistance in the conductors of the DC / DC voltage converter. Furthermore, this thermal loss parameter may also include other losses that may occur in the electronic components of the DC / DC voltage converter. As a result, the thermal loss parameter represents the electrical loss of the DC / DC voltage converter that is converted into unwanted heat and therefore causes the DC / DC voltage converter to heat up when active.

[0018] Optionally, the thermal model may include cooling capacity parameters indicating the active and / or passive cooling capabilities of the DC / DC voltage converter. These cooling capacity parameters represent the extent to which the DC / DC voltage converter is designed to cool during operation. For example, active cooling capacity might be a controllable fan, while passive cooling capacity might be, for example, a cooling plate attached to the DC / DC voltage converter.

[0019] Furthermore, the thermal model includes a value for the equilibrium current, which indicates the thermal equilibrium of the DC / DC voltage converter when the output DC is equal to this equilibrium current. The equilibrium current is the current at which the heat loss of the DC / DC voltage converter equals its active and / or passive cooling capacity. Therefore, when the output current is equal to this equilibrium current, the temperature of the DC / DC voltage converter will remain constant. However, it should be noted that this value cannot be determined speculatively and depends on various parameters, including the active and / or passive cooling capacity, as well as other environmental parameters such as the ambient temperature in which the DC / DC voltage converter is installed, and the presence or absence of external ventilation, heating, and / or cooling.

[0020] Therefore, the balanced current is precisely the current that does not cause further heating, and thus the DC / DC voltage converter can supply it for an unlimited period of time without overheating. Overload as understood in this invention is a situation in which the DC / DC voltage converter must supply an output current higher than the balanced current described above, and therefore begins to generate heat internally.

[0021] Such situations may occur due to deviations such as changes in speed during startup, sudden external loads on a motor to which the shaft is mounted by magnetic bearings, sudden loads on the machine driving the motor, or other factors that cause deviations of the shaft from the desired position, as is known to those skilled in the art.

[0022] Based on the thermal model as described above, the time-dependent critical temperature is determined. Then, based on this time-dependent critical temperature determined previously, the time-dependent current saturation limit is determined. This current saturation limit determined based on the same thermal model represents, next, what the maximum constant output DC is that the DC / DC voltage converter may be able to supply over a predetermined period without overheating. Therefore, limiting the output DC to a time-dependent limit value equal to this time-dependent current saturation limit is a sufficient condition to ensure that the overheating limit of the DC / DC voltage converter will not be exceeded during the entire preset period. Depending on the thermal state of the DC / DC voltage converter, warm-up is allowed, and since this depends on the time-dependent critical temperature, it should be noted that this value may be higher than the equilibrium current. In other words, when the critical temperature of the DC / DC voltage converter at a certain time is lower than the overheating limit, a current higher than the equilibrium current is allowed.

[0023] Finally, according to the novel and innovative aspect of the present invention, instead of simply adjusting the voltage, the output DC is also monitored and is limited to a time-dependent limit value. During a specific time interval, a current higher than the equilibrium current can be allowed, and avoidance of overheating is expected. Therefore, the advantage of this method is that the limitation on the output DC is not so strict, the output DC flowing voltage decreases more slowly, in the case of short-term overload, the magnetic axis controlled system continues to function correctly, or in the case of long-term overload, on the one hand, the time between turning off the motor by the magnetic axis controlled system and on the other hand, turning off the magnetic axis controlled system itself becomes longer, and the rotor drops onto the emergency bearing at a lower speed.

[0024] According to one embodiment, the method further includes the step of adjusting the output DC voltage.

[0025] According to one embodiment of the present invention, the method further includes the step of sending a control signal including an instruction to turn off the magnetic axis controlled system to the magnetic axis controlled system when the output DC voltage exceeds a preset lower limit value.

[0026] As an additional safety precaution, this method can also ensure that the magnetic bearing control system turns off before the DC / DC voltage converter by sending a command to the magnetic bearing control system. This command can be sent when the output DC voltage drops below a preset lower limit. In other words, the magnetic bearing control system's response to the control signal from the DC / DC voltage converter is not to turn itself off, but to signal the controlled motor drive to stop the motor. The magnetic bearing control system will then attempt to keep the rotor levitating for as long as possible. The response of the magnetic bearing control system can also be triggered by a control signal from the magnetic bearing control system itself, as the magnetic bearing control system also monitors its own supply voltage.

[0027] The advantage of this is that the machine, which is fitted with the bearing, can be stopped safely rather than abruptly. In this way, damage to the machine, specifically its shaft, is avoided.

[0028] A second aspect of the present invention discloses a method for adjusting a magnetic bearing control system comprising an input connection section connectable to a DC power supply, a capacitor bank, and an output connection section connectable to one or more magnetic bearings, wherein the method is The first aspect of the present invention involves supplying the output DC voltage obtained to the magnetic bearing control system via the input connection section, The first aspect of the present invention involves storing electrical energy in a capacitor bank using the DC output obtained by the present invention, The steps include: biasing one or more magnetic bearings with a biasing current via an output connection; Including, When the output DC is limited according to the steps of the method according to the first aspect of the present invention, Steps to capture biasing current using a capacitor bank, Includes.

[0029] The method includes supplying power to a magnetic bearing control system using a DC / DC voltage converter adjusted according to a method according to a first aspect of the present invention. This power supply provides a biasing current to one or more magnetic bearings. Furthermore, this power supply is used to charge the capacitor bank of the magnetic bearing control system. If the power supply of the DC / DC voltage converter is insufficient, for example, because its output DC is limited by one of the steps described above, the biasing current will be supplemented by the capacitor bank. That is, the biasing current consists partly of the converted output DC of the DC / DC voltage converter and partly of the current originating from the capacitor bank.

[0030] The advantage of this is that the DC output limit of the DC / DC voltage converter prevents sudden failures in the magnetic bearing control system due to insufficient power supply.

[0031] If the DC output limit of the DC / DC voltage converter is subsequently removed, the capacitor bank can be recharged to anticipate this new DC output limit.

[0032] A third aspect of the present invention is disclosed, which is configured as a power source for a magnetic bearing control system that includes a control unit configured to adjust the DC / DC voltage converter according to the first aspect of the present invention.

[0033] A magnetic bearing control system is disclosed, comprising a magnetic bearing control system configured to bias one or more magnetic bearings, and an adjustment unit configured to perform the method of the second aspect of the present invention.

[0034] According to a fifth aspect of the present invention, a motor control device for driving an electric motor is provided, and the motor control device is A rectifier that rectifies the input AC current, A DC voltage rail that conducts the rectified input DC, A frequency converter connected to a DC voltage rail, which rectifies the input AC current that is used as the power source for an electric motor, A DC / DC voltage converter according to a third aspect of the present invention, connected to a DC voltage rail, It is equipped with.

[0035] A motor control device according to a fifth embodiment may further comprise a magnetic bearing control system according to a fourth embodiment of the present invention, connected to a DC / DC voltage converter.

[0036] The present invention will be further described below with reference to the drawings. [Brief explanation of the drawing]

[0037] [Figure 1] This is a schematic diagram of a frequency converter for an electric motor, a magnetic bearing control system with a DC / DC voltage converter, and a motor equipped with a magnetic bearing. [Figure 2] This shows the voltage regulation loop of a DC / DC voltage converter. [Figure 3] This shows the voltage regulation loop of a DC / DC voltage converter with a limited current requirement. [Figure 4] This shows the voltage regulation loop of a DC / DC voltage converter with variable current limiting. [Figure 5A] Figure 5B shows the current saturation limit and the time-dependent critical temperature corresponding to the progression of the DC output. [Figure 5B] This shows the progression of the current saturation limit and the DC output. [Modes for carrying out the invention]

[0038] The present invention is described with reference to specific drawings in relation to particular embodiments, but is not limited thereto and is defined solely by the claims. The drawings provided are merely schematic and non-limiting. In the drawings, the size of certain elements may be exaggerated and may not be shown to scale for illustrative purposes only. Dimensions and relative dimensions do not necessarily correspond to actual embodiments of the present invention.

[0039] In addition, terms such as "first," "second," and "third" are used in this specification and in the claims to distinguish similar elements and are not necessarily used to describe a sequential or chronological order. These terms are interchangeable under appropriate circumstances, and embodiments of the present invention may be used in an order other than that described or illustrated herein.

[0040] In addition, terms such as upper, lower, above, and below are used for illustrative purposes only in this specification and claims and do not necessarily describe relative positions. These terms are interchangeable under appropriate circumstances, and embodiments of the invention described herein may be used in orientations other than those described or illustrated herein.

[0041] Furthermore, while various embodiments are referred to as “preferred embodiments,” they should not be interpreted as limiting the scope of the present invention, but rather as illustrating how the present invention may be carried out.

[0042] The term “comprising” as used in the claims should not be interpreted as limiting the means or steps described below, nor should it exclude other elements or steps. The term should be interpreted as identifying the presence of the mentioned feature, element, step, or component, but not as excluding the presence or addition of one or more other features, elements, steps, or components, or groups thereof. Therefore, the expression “apparatus comprising means A and B” should not be limited to an apparatus consisting solely of components A and B. This means that, with respect to the present invention, only components A and B of the apparatus are described, and the claims should be interpreted as further including equivalents of these components.

[0043] Figure 1 is a schematic diagram of a frequency converter 106 for an electric motor 107, the motor shaft of which is mounted using one or more magnetic bearings. Furthermore, Figure 1 shows a magnetic bearing control system 111 and a DC / DC voltage converter 112. In the schematic diagram of Figure 1, the DC / DC voltage converter 112 is an external device, but it should be further understood that it can also be integrated into the magnetic bearing control system 111, and thus can be an internal device such that 111 and 112 are a single unit. Accordingly, in Figure 1, reference numerals 108 and 112 refer to the DC / DC voltage converter, and if the DC / DC voltage converter is integrated into the magnetic bearing control system 111, reference numeral 108 can be interpreted as the internal device of reference numeral 111.

[0044] The frequency converter 106 for the electric motor 107 converts the fixed input AC voltage 105 to an adjustable frequency AC voltage by first rectifying the fixed input AC voltage in the rectifier bridge 100, and then converting the resulting DC voltage to an adjustable frequency AC voltage in the inverter 102. A capacitor bank 101 between the rectifier 100 and the inverter 102 reduces voltage ripple at the output of the rectifier bridge 100. The adjustable frequency AC voltage is supplied to the motor stator 103.

[0045] The DC / DC voltage converter 112 converts the input DC voltage from the capacitor bank 101 into an output DC voltage suitable as a voltage source for the magnetic bearing control system (MCS) 111. The MCS 111 also includes a capacitor bank 109 to reduce potential fluctuations in the output DC voltage of the DC / DC voltage converter 112. Next, one or more power amplifiers 110 convert the input DC voltage from the MCS 111 into an adjustable current that supplies to the motor's magnetic bearing system 104.

[0046] The DC / DC voltage converter 112 is designed to convert a wide range of input DC voltages to a fixed nominal output DC voltage V_{MCS,nom} suitable for the MCS111. However, if the input DC voltage drops below a certain lower limit V_{DCDC,min}, the DC / DC voltage converter 112 itself will turn off.

[0047] The power amplifier 110 of the MCS111 is designed to continue functioning normally even when the DC voltage applied to the MCS111 is lower than normal. However, the MCS111 has an internal voltage meter, which is intended to turn off the MCS111 if the input DC voltage to the MCS111 falls below a predetermined lower limit V_{MCS,min}.

[0048] When the input AC voltage 105 from the power system becomes abnormal, the kinetic energy of the motor 107 is converted into electrical energy and stored in the motor 107's capacitor bank 101, initially keeping the input voltage of the DC / DC voltage converter 112 high. As the motor 107 decelerates, the input voltage of the DC / DC voltage converter 112 decreases. As long as the input voltage of the DC / DC voltage converter 112 is higher than V_{DCDC,min}, the output voltage of the DC / DC voltage converter 112 is equal to the nominal voltage V_{MCS,nom}, and the MCS 111 continues to function normally. However, as soon as the input voltage drops below V_{DCDC,min}, the DC / DC voltage converter 112 turns off, and as the input voltage of the MCS 111 drops below V_{MCS,min}, the MCS 111 also turns off. Because there is a considerable amount of time between the power system failure and the arrival of V_{MBS,min}, the MCS111 will only turn off if the motor 107 has already decelerated significantly, thereby reducing the likelihood of damage to the motor 107 due to the turning off of the magnetic bearing control system 104.

[0049] Figure 2 shows the voltage regulation loop of a DC / DC voltage converter, such as the DC / DC voltage converter 112 in Figure 1. The purpose of the voltage regulation loop of the DC / DC voltage converter 112 is to regulate the DC current 204, IDCDC supplied by the DC / DC voltage converter 112, so that the output DC voltage VMCS of the DC / DC voltage converter 112 is regulated to a desired output DC voltage VMBC,nom200. This regulation is based on feedback of the measured output DC voltage VMCS204. Based on the regulation error, VMBC,nom-VMCS, the voltage regulator 201 determines what the desired current IDCDC,wt203 is that can eliminate the regulation error. Next, the internal current regulation loop 202 of the DC / DC voltage regulator 201 ensures that the current IDCDC204 actually realized is as close as possible to the desired value IDCDC,wt203.

[0050] When the DC / DC voltage converter 112 supplies a larger current IDCDC 204, its internal losses increase. If these losses exceed the internal cooling capacity, the temperature of the DC / DC voltage converter 112 rises. Conversely, if the internal losses fall below the internal cooling capacity, the temperature of the DC / DC voltage converter 112 decreases. The balanced current IDCDC,ev is the current at which the internal losses are exactly equal to the internal cooling capacity, and the temperature of the DC / DC voltage converter 112 remains constant. In other words, IDCDC,ev is the maximum current that the DC / DC voltage converter 112 can supply for an unlimited period of time without overheating.

[0051] Therefore, overload is defined as a situation in which the DC / DC voltage converter 112 needs to supply a current higher than the balanced current I{DCCDC,ev}, resulting in internal heat generation. This situation can occur due to deviations such as changes in speed during startup, sudden external loads on a motor whose shaft is mounted using magnetic bearings, sudden loads on the machine driving the motor, or other factors known to those skilled in the art that cause deviations of the shaft from the desired position as listed above.

[0052] The internal temperature \(T_{DCDC}\) of the DC / DC voltage converter 112 is generally

Number

Number

[0053] When implemented digitally, the thermal model can be recursively formulated as

Number

[0054] If the DC / DC voltage converter 112 needs to supply a current higher than IDCDC,ev to keep the output DC voltage equal to VMBC,nom, i.e., in the case of an overload, the DC / DC voltage converter 112 will generate heat, posing a risk of overheating. A known method in modern technology is to turn off the DC / DC voltage converter 112 instantaneously or with a predetermined delay in the event of an overload. While this method protects the DC / DC voltage converter 112, it has the detrimental effect of instantaneously turning off the MCS 111, which could cause the rotor to fall destructively at high speed into the emergency bearing if present in the magnetic bearing control system 104.

[0055] The method for adjusting the DC / DC voltage converter 112 according to the present invention aims to protect the DC / DC voltage converter 112 in the event of an overload so that the output DC voltage drops as slowly as possible. In the event of a short-term overload, the MCS 111 continues to function normally, but in the event of a long-term overload, there is a significant amount of time between the motor being turned off by the magnetic bearing control system and the magnetic bearing control system itself being turned off, allowing the rotor to drop into the emergency bearing at a very low speed.

[0056] In a simple embodiment, this method means that the supply current is always limited to I_{DCDC,ev} by inputting a current limiter 302 between zero and I_{DCDC,ev}, as shown in Figure 3. Furthermore, the reference numbers in Figure 3 correspond to the reference numbers in Figure 2, respectively, for the desired output DC voltage V_{MBC,nom}300, the voltage regulator 301 for determining the desired current I_{DCDC,wt}304 from which the adjustment error can be adjusted, the internal current adjustment loop 303, and the output DC voltage V_{MCS} and output DC current I_{DCDC}305. In this way, the DC / DC voltage converter 112 can continue to supply current, and the MCS 111 can remain energized initially.

[0057] By limiting the current to IDCDC,ev, the voltage regulation loop shown in Figure 3 can no longer maintain VMCS, resulting in a decrease in VMCS. If the overload condition persists for a sufficiently long time, VMCS will eventually drop below VMCS,min, after which MCS111 will turn off, reducing the current demand to zero and allowing the DC / DC voltage converter 112 to cool. If the overload condition does not persist for a long time, VMCS will eventually rise again, and the system can resume normal operation until another overload condition occurs.

[0058] The improvement shown in Figure 3 means that a current I_{DCDC,ev} higher than I_{DCDC,ev} is temporarily acceptable, albeit with the limitation that this high current does not lead to overheating of the DC / DC voltage converter 112. This improved method is further shown in Figure 4. Furthermore, the reference numbers in Figure 4 correspond to Figures 2 and 3, respectively, for the output DC voltage V_{MBC,nom} 400, the voltage regulator 401 for determining the desired current I_{DCDC,wt}, the internal current regulation loop 403, and the output DC voltage V_{MCS} and output DC current I_{DCDC} 405. Furthermore, Figure 4 includes a current delimiter 402 similar to that in Figure 3, but it is variable between zero and an upper limit as a function of I_{DCDC}. The advantage of this is that the restriction on I_{DCDC} is loosened, resulting in a slower decrease in voltage V_{MCS}, and thus a higher probability that the MCS 111 will continue to function normally.

[0059] The restriction to prevent higher currents from leading to overheating of the DC / DC voltage converter 112 is imposed based on the thermal model of the DC / DC voltage converter 112. This thermal limit is calculated using the recursive relation proposed above.

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number

number

[0060] Furthermore, in the adjustment methods shown in Figures 3 and 4, it should be noted that, for practical implementation reasons, it is desirable to provide an "anti-wind-up" function to the current adjustment loop to prevent the internal PI adjuster from deviating when the current limit I_{DCDC} becomes active.

[0061] Referring to Figures 5A and 5B, examples of output DC and current saturation limits in relation to critical temperature are presented, respectively. In the examples considered, the overheat limit T of the DC / DC voltage converter is shown. DCDC,max The temperature is equal to 90 degrees Celsius, the ambient temperature T_env is equal to 20 degrees Celsius, and the equilibrium current I_{DCDC,ev} is equal to 1A.

[0062] In Figure 5A, the horizontal axis shows time (seconds) and the vertical axis shows temperature (°C). Graph 500 shows the critical temperature of the DC / DC voltage converter 112 as a function of time.

[0063] In Figure 5B, the horizontal axis shows time (seconds) and the vertical axis shows current (A). Graph 501 shows the output DC drawn from the DC / DC voltage converter 112. Graph 502 shows the current saturation limit of the output DC.

[0064] Figures 5A and 5B consider an example where a DC / DC voltage converter requires a constant output DC of 4.5A to adjust the output DC voltage to an appropriate value. The critical temperature 500 starts at ambient temperature and begins to rise when the 4.5A output DC 501 exceeds the equilibrium current of 1A. The time-dependent current saturation limit 502 starts at a value of 26.5A, far above the equilibrium current, because a large thermal margin of 90-20=70°C still remains at the start. However, as the critical temperature rises and the thermal margin decreases, the time-dependent current saturation limit also decreases. After 3.5 seconds, the time-dependent saturation current limit decreases to 4.5A, and from this moment onward, the output DC is limited by a saturation current limit that decreases in a time-dependent manner. Theoretically, after an infinitely long time, or in reality after about 4.5 seconds, the critical temperature reaches the superheat limit of 90°C. From that point onward, the time-dependent saturation current limit and the output DC coincide at an equilibrium current of 1A, resulting in a constant critical temperature equal to 90°C. [Explanation of Symbols]

[0065] 100 rectifier 102 Inverter 105 Input AC Voltage 107 Electric motor 108, 112 DC / DC Voltage Converters 111 Magnetic bearing control system 500 time dependent critical temperature 501 DC Output 502 Time-dependent limit

Claims

1. A method for adjusting DC / DC voltage converters (108, 112) configured as a power source for a magnetic bearing control system (111), The steps include converting the input DC voltage from the DC / DC voltage converter (108, 112) into an output DC voltage suitable for the power supply source, The steps include supplying power to the magnetic bearing control system (111) with the output DC voltage, thereby generating an output DC when active, The steps include monitoring the output DC, The method includes, The steps include determining a time-dependent critical temperature (500) that represents a margin against the overheating limit of the DC / DC voltage converter (108, 112) based on the thermal model of the DC / DC voltage converter (108, 112), A step of determining a time-dependent current saturation limit value (502) over a predetermined period based on the time-dependent critical temperature (500), wherein the time-dependent current saturation limit value (502) represents the warm-up of the DC / DC voltage converters (108, 112) over the predetermined period, thereby obtaining a time-dependent current saturation limit value for the output DC, The method further includes, if the output DC exceeds the time-dependent current saturation limit, A step of limiting the output DC to the time-dependent current saturation limit value, Methods that further include this.

2. The method according to claim 1, wherein the thermal model includes one or more measured quantities from a group of the output DC, the output DC voltage, the input DC voltage, the input DC, one or more internal temperatures, and / or ambient temperatures.

3. The aforementioned thermal model, A thermal loss parameter indicating the thermal loss of the DC / DC voltage converter (108, 112) when it is active, The cooling capacity parameters indicating the active and / or passive cooling capacity of the DC / DC voltage converters (108, 112), When the aforementioned output DCs are equal, the equilibrium current that indicates thermal equilibrium of the DC / DC voltage converter (108, 112) is, The method according to claim 1 or 2, comprising one or more of the group.

4. The step of adjusting the output DC voltage, The method according to claim 1 or 2, further comprising:

5. If the output DC voltage exceeds a preset lower limit, A step of sending a control signal to the magnetic bearing control system (111) that includes a command to turn off the magnetic bearing control system (111), The method according to claim 4, including the method described in claim 4.

6. A method for adjusting a magnetic bearing control system (111) comprising an input connection section connectable to a DC power supply, a capacitor bank, and an output connection section connectable to one or more magnetic bearings, The steps include supplying the output DC voltage obtained by the method described in claim 1 to the magnetic bearing control system (111) via the input connection section, The steps of storing electrical energy in the capacitor bank by the output DC obtained by the method of claim 1, The steps include: biasing one or more magnetic bearings with a biasing current via the output connection section; Includes, When the output DC is limited in accordance with the steps of the method according to claim 1, A step of capturing the biasing current using the capacitor bank, Methods that include...

7. DC / DC voltage converters (108, 112) configured as a power source for a magnetic bearing control system (111), comprising an adjustment unit configured to adjust the DC / DC voltage converters (108, 112) according to the method described in claim 1 or 2.

8. A magnetic bearing control system (111) configured to bias one or more magnetic bearings, comprising an adjustment unit configured to perform the method of claim 6.

9. A motor control device for driving an electric motor (107), A rectifier (100) that rectifies the input AC voltage (105), A DC voltage rail that conducts the rectified input DC, A frequency converter (106) connected to the DC voltage rail rectifies the input AC current that has been rectified to serve as the power source for the electric motor (107), A DC / DC voltage converter (108, 112) according to claim 7, connected to the DC voltage rail, A motor control device equipped with the following features.

10. The motor control device according to claim 9, further comprising a magnetic bearing control system (111) according to claim 8, connected to the DC / DC voltage converters (108, 112).

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