Method for Monitoring and Controlling the Coolant Temperature of a Separator Drive Device

Abstract

A method for controlling the coolant temperature of an electric motor of a drive device (8) of a rotor of a centrifuge, preferably a separator (1) having a vertical axis of rotation, in particular a method during centrifugation of a suspension into at least two different product phases, the rotor having at least one rotatable drum (2), the drive device having an electric motor (8) for directly or indirectly rotating the rotor, the drive device further having a device (100) for supplying coolant to the electric motor, the device having a control device, the method comprising: a) providing a drive device to the centrifuge; b) driving the rotor by means of the electric motor, in particular during centrifuging the suspension into at least two different product phases; and c) cooling the electric motor in a controlled state in a cooling cycle interrupted by breaks, at least during step b).

Description

Technical Field

[0001] The present invention relates to a method for controlling the coolant temperature of an electric motor of a drive device of a rotor of a centrifuge as described in the preamble of claim 1.

Background Art

[0002] To achieve a compact configuration of this general type of centrifuge separator, the drive devices of these separators are equipped with an integral water-cooled electric motor for directly driving the rotor together with the separator drum.

[0003] It is known to supply a coolant in a required amount and within an allowable temperature range in order to cool the electric motor according to the specifications of the electric motor manufacturer. In this way, the maximum allowable motor temperature can be maintained. The required supply amount is restricted, for example, by a corresponding orifice or needle valve.

[0004] An additional open valve opens the coolant supply while the electric motor is operating and closes the coolant supply immediately when the switch of the electric motor is turned off. The open valve for the coolant is permanently open during the operation of the drive motor, and the coolant flows through the drive motor at a flow rate specified by the electric motor manufacturer.

[0005] In this approach, the coolant consumption is always the same regardless of the load of the drive motor (product processing capacity, discharge frequency, and size) and the actual temperature of the incoming coolant. Therefore, in order to solve this problem, prior art solutions have been developed.

[0006] German Patent No. 38 09 149 describes a method of stepwise changing the cross-sectional area of a coolant discharge line according to the coolant discharge temperature of a drive unit (engine). German Utility Model No. 20 2007 004 983 describes the use of a water cooling system as a circuit configuration for cooling the drive device of a centrifuge, resulting in the need for a circulation pump and a heat exchanger. European Patent Publication No. 00 16 584 describes the use of water cooling supplied to a heat exchanger for cooling the drive device of a centrifuge.

[0007] Concepts for cooling the electric motor of a separator according to the prior art have been actually demonstrated. The drawback of these concepts is that the consumption of the coolant is still quite high. Summary of the Invention Problems to be Solved by the Invention

[0008] The object of the present invention is to solve this problem. Means for Solving the Problems

[0009] The present invention achieves this object by the method of claim 1. A method for controlling the coolant temperature of an electric motor of a drive device of a rotor of a centrifuge, particularly in a separator having a vertical axis of rotation, particularly during centrifuging a suspension into at least two different product phases, wherein the rotor of the centrifuge has at least one rotatable drum, the drive device has an electric motor for directly or indirectly rotating the rotor, the drive device further has a device for supplying a coolant to the electric motor, and includes a control device, at least a) providing a drive device to the centrifuge; b) driving the rotor with the electric motor particularly during centrifuging the suspension into at least two different product phases; and c) cooling the electric motor in a controlled state during limited cooling stages in a cycle interrupted by a break, at least during step b).

[0010] The length of the cooling phase of each cycle is calculated by the control device taking into account one or more measured values, and it is also preferred that at least one measured value or several measured values can be the measured temperature values. Cooling in a cycle usually significantly reduces the coolant consumption compared to continuous cooling. In a cooling system set up as a circuit, it is possible to operate by reducing the amount of coolant per cycle or by reducing the coolant moving within the circuit.

[0011] According to a particularly advantageous variant, the cycle of step c) includes the following sub-steps. c1) Opening the open valve of the coolant supply system to generate a flow of coolant through the cooling fluid system of the electric motor, which has at least one coolant supply line and one coolant discharge line as well as a motor coolant passage; c2) In the coolant discharge line, after a predetermined time tmeas has elapsed, instantaneously measuring the temperature Tinst of the coolant by a temperature measuring device and transmitting the measured value of that temperature Tinst to the control device, where the predetermined time tmeas is determined as a function of the length of the coolant discharge line between the electric motor and the temperature measuring device; c3) Comparing the measured value of the temperature Tinst with the upper limit value of the coolant temperature Tlimit; c4) Calculating, by the control device, the time tcool as a function of the temperature Tinst, during which time the open valve remains open; c5) After the times tmeas and tcool have elapsed, closing the open valve during the cycle stop time tpause, where the sub-steps c1) to c5) are substantially infinitely re-executed in a program loop manner after the time tpause has elapsed until the drive motor of the centrifuge stops operating. Thereby, the total cycle time of time tcycle = time tmeas + time tcool + time tpause is obtained.

[0012] Thereby, a method for monitoring and controlling the coolant temperature of a centrifuge is generated, in which the instantaneous coolant temperature can be kept as constant as possible at a defined upper limit of the coolant temperature. In this way, the electric motor of the separator operates at the maximum allowable temperature and with the lowest possible coolant consumption, regardless of its load, ambient temperature, and the temperature of the incoming coolant.

[0013] A further advantage of the method according to the invention or of a separator equipped correspondingly with a control device is that, basically, only a temperature measuring device on the coolant discharge line needs to be added on the hardware side, so that it can be easily retrofitted to existing coolant-cooled electric motors. A temperature sensor inside the electric motor is not necessary, but it may be provided. Furthermore, only a simple valve having two switching positions ("open" and "closed") as an open valve is required. Therefore, a control valve or a controllable throttle diaphragm, as in the solutions of the prior art, is not required, nor are several valves and lines.

[0014] A computer program product is stored and executed on a control device or on another memory connected to or connectable to the control device, the computer program product including instructions for causing steps of a method for cooling an electric motor within a cycle, in particular steps of the method according to any one of claims 1 to 14, to be executed on a separator for cooling a drive device.

[0015] According to a variant of a particularly preferred embodiment of the invention, if the instantaneous temperature Tinst of the coolant falls below the upper limit value of the coolant temperature Tlimit, the open valve is closed immediately after a time tmeas. Thereby, the coolant can absorb thermal energy up to the defined upper temperature for the coolant, whereby the required volume flow rate of the coolant can be advantageously reduced.

[0016] According to a variant of an even more particularly preferred embodiment of the present invention, when the instantaneous temperature Tinst of the coolant is equal to or higher than the upper limit value of the coolant temperature Tlimit, the release valve remains open for an additional time tcool. As a result, the increase in the coolant temperature is reduced to the upper limit temperature defined for the coolant, while at the same time advantageously minimizing the volumetric flow rate of the coolant required for this.

[0017] Furthermore, a correlation table of the measured values of the temperature Tinst and the time tcool is experimentally determined, so that a characteristic curve specific to the centrifuge or the coolant supply system representing the relationship between the temperature Tinst and the time tcool is obtained, and the temperature control of the coolant is configured as a control of a kind of characteristic curve. This advantageously provides a simple operating principle for coolant control that can be adapted individually to each separator.

[0018] Alternatively, according to a variant of another particularly preferred embodiment of the present invention, in step c), one or more measured values of the instantaneous temperature Tinst of the coolant, and preferably further one or more measured values of the ambient temperature and one or more instantaneous motor load characteristic values are supplied to a control device, in particular a higher-level control device of the separator, and the control device may be provided with determining the cooling time tcool according to an algorithm using these measured values. If the coolant temperature does not change in the desired direction after several subsequent cooling cycles, the algorithm is adapted by the control device, preferably by a higher-level control device, until the coolant temperature is set to the value Tlimit. The adaptability of this algorithm means that the control system can adapt particularly well to changing operating conditions.

[0019] Alternatively, according to a variant of another particularly preferred embodiment of the present invention, a PID controller can be used as the control device. Thereby, the coolant temperature can be monitored and controlled in a particularly flexible manner. The present invention can be constructively used in various variants of cooling systems.

[0020] Similarly, according to a variant of another particularly preferred embodiment of the present invention, it can be provided that the coolant supply system is configured according to the principle of a closed coolant circuit. According to a variant of an even more particularly preferred embodiment of the present invention, it is provided that the coolant is pumped into the circuit with the aid of a pump, cooled in a heat exchanger, and the required cooling capacity is supplied to the heat exchanger via a refrigeration circuit.

[0021] Furthermore, according to a variant of another particularly preferred embodiment, the coolant may be taken out of the storage tank, passed through an electric motor to absorb heat, and then pumped back into the storage tank. This forms an open circuit through which the coolant can be added or removed as required. This is advantageous, for example, for short peak loads. In this variant, the consumption of the coolant is also effectively minimized.

[0022] In this context, according to a variant of a further preferred embodiment, it may be provided that the heat absorbed by the coolant is released so as to be returned to the surroundings of the storage tank by convection through the wall of the storage tank. This effectively minimizes the possible amount of coolant replenishment and thereby advantageously conserves the coolant.

[0023] It is particularly advantageous if the wall of the storage tank is provided with suitable means for improving convective heat dissipation. This further effectively minimizes any possible amount of coolant replenishment and thereby conserves the coolant.

[0024] The present invention also provides a separator comprising a control device and other means adapted to perform the steps of one of the methods of claims 1 to 14. The present invention also provides a computer program product including commands or instructions for causing the separator according to claim 15 to perform the steps of the method according to any one of claims 1 to 14. A computer-readable medium is also generated, on which a computer program is stored.

[0025] Further advantageous configurations of the present invention can be found in the other dependent claims.

Brief Description of the Drawings

[0026] In the following, the present invention will be described in more detail with reference to the drawings by way of exemplary embodiments. The present invention is not limited to these exemplary embodiments and can also be realized in other ways according to the language or in other equivalent ways.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0027] Some exemplary embodiments are described in the following description of the drawings. The individual features of these exemplary embodiments can also be combined with exemplary embodiments not shown and are suitable in each case as advantageous configurations of the object described in one or more of the main claims and dependent claims.

[0028] Figure 1 shows a centrifuge that can be configured as a separator 1. The centrifuge - in this case, the separator - has a rotor. This rotor comprises, in this case, a rotatable drum 2 with a vertical axis of rotation D. This drum 2 may be surrounded by a hood device 3. Terms such as "upper" and "lower" below refer to the exemplary vertical arrangement of the drum 2. The drum 2 is attached to a drive spindle 4. The drive spindle is rotatably mounted by a bearing device within a bearing housing 7, which here comprises an upper bearing 5 and a lower bearing 6. This bearing arrangement has, by way of example, two roller bearings. Other configurations are also conceivable (not shown here).

[0029] The drive device of the separator has an electric motor 8 for rotating the rotor together with the drum 2. This electric motor 8 has an electric motor housing 9 with a stator 10 or stator winding and a motor rotor or rotor 11.

[0030] The electric motor 8 preferably does not have its own bearings, enabling a more cost - efficient configuration. Instead, the bearing device is, here by way of example, arranged between the electric motor 8 and the drum 2. However, the bearing device can also be realized in other ways.

[0031] Also, the drive spindle 4 can be connected directly - i.e., preferably without an intermediate element such as a coupling - to the rotor 11. The electric motor housing 9 with the stator 10, on the one hand, can be firmly and without springs arranged on the machine frame 12 of the separator 1 or supported on the machine frame 12.

[0032] Thus, the drum 2 with the drive spindle 4, the rotor 11, and the bearing housing 7 are elastically supported on the machine frame 12, forming a vibration unit not belonging to the stator 10, so that relative movement occurs between the rotor 11 and the stator 10.

[0033] The drive spindle 4 is arranged by means of bearings 5 and 6 within the hole-shaped opening 13 of a bearing housing 7 of single or multiple parts. The bearing housing 7 has an upper flange 14 and a lower sleeve-shaped part 15 and extends through an opening 16 of the machine frame 12.

[0034] The upper flange 14 is supported on the machine frame 12 via elastically damping elements 17 distributed in the circumferential direction, which are distributed between the lower side of the flange 14 and the upper side of the machine frame 12, and ring-shaped steps 18, 19 are provided in the region of the elastically damping elements 17 on the flange 14 and the machine frame 12.

[0035] Furthermore, a lubricant supply unit 20 is provided which can supply lubricant to the bearings 5, 6.

[0036] In this regard, this specification relates to advantageous exemplary embodiments but is not limited to this configuration. Rather, the coolant supply system and related methods described below can be used with the separator described above, but can also be used with separators of different configurations.

[0037] A centrifuge according to the invention configured like the separator of FIG. 1, for example, has a coolant supply system 100 which supplies coolant to a drive device, or in this case its electric motor 8. The coolant is a fluid, in particular water. Other suitable fluids can also be used as the coolant. The coolant supply system 100 has at least one coolant supply line 101, also known as a coolant supply line, and one coolant discharge line 102, also known as a coolant return line. The motor coolant passage 113 is arranged between the coolant supply line and the coolant discharge line, and this can be routed through and / or past components of the electric motor. This is where the actual cooling of the electric motor takes place, and in particular, the stator which heats the coolant in this section is cooled. The coolant supply system 100 can have further components such as one or more controllable valves.

[0038] Figure 2 particularly shows the components of an exemplary coolant supply system 100 for a separator - for example, the separator of FIG. 1. Here too, the coolant supply system 100 has a coolant supply line 101, a motor coolant passage 113, and a coolant discharge line 102, each of which is connected to an electric motor. A controllable open valve 103 can be provided in the coolant supply line 101. The open valve 103 is configured to be controllable. The open valve can preferably be opened and closed by an electric actuator or an electromagnetic actuator controlled by a control device 105. Alternatively, the open valve 103 can also be actuated by other means.

[0039] Next, the coolant discharge line 102 of the exemplary embodiment of FIG. 2 has a temperature measuring device 104. The temperature measuring device 104 can be configured, for example, as a resistance temperature sensor. The temperature measuring device 104 can also be configured in another way. The coolant supply system 100 further includes a control device 105. The control device 105 can be configured as an independent control device that only controls the coolant. Alternatively, it can be integrated into a higher - level control device of the separator. The control device is configured to receive measurement values from the temperature measuring device 104. The temperature measuring device 104 is connected to the control device 105 so that it can process the recorded measurement values. The control device 105 is also configured to control actuators such as the valve 103, particularly directly or in a control - device - like manner via intermediate control means.

[0040] The control device 105 can have a microprocessor and an interface, as well as further intermediate control means such as a gateway, and components connected downstream thereof, with the help of which it can be connected to at least controllable actuators such as the open valve 103 and one or more sensors such as the temperature measuring device 104. This connection can be made via a wired or wireless data transmission path.

[0041] The method described below has been proposed for monitoring and controlling the coolant temperature of the separator drive 1. This is used to actively control the metering of the coolant flow through the electric motor 8 of the separator drive.

[0042] For this purpose, it can advantageously and simply be provided that the control device 105 pulses the opening valve 103 during the operation of the separator or during the operation of a drive having the electric motor 8 as a drive, where the duration of the opening pulse depends on the measured temperature Tinst of the coolant in the coolant discharge line 102 of the electric motor, measured by the temperature measuring device 104. In this procedure, the coolant consumption is very low. In this way, it is often possible to achieve a reduction in the amount of coolant used compared to the specifications of the electric motor manufacturer, for example, a reduction in water usage in the long term.

[0043] First, a centrifuge is provided (together with its drive), the rotor is rotated together with the electric motor 8, and centrifugation is started (Figure 5 - steps a, b). During the rotation of the rotor (from the start), cooling also starts in parallel in the cycle (Figure 5 - step c), and the sub - steps of this step c can then be repeated during centrifugation (see Figure 6).

[0044] Particularly at the start of each cooling cycle of the electric motor 8, which operates during centrifugation and rotates the drive spindle 4 of the separator 1, the open valve 103 for supplying coolant to the drive motor is opened for a defined time tmeas (Figure 6 - step c1), whereby the heated coolant is pushed from the motor coolant passage 113 (e.g., the cooling jacket of the electric motor 8) into the coolant discharge line 102, in which a temperature measuring device 104 is also arranged. The temperature measuring device measures the instantaneous temperature Tinst of the coolant after the elapse of time tmeas and transmits this measured value to the control device 105. To ensure that the temperature of the coolant is accurately recorded, the time tmeas can be appropriately selected as a function of the length of the coolant discharge line 102 between the electric motor and the temperature measuring device 104, according to empirical values from previous cycles or other measured values from comparable centrifuges. Depending on the temperature Tinst, the control device 105 calculates an additional time tcool for which the open valve 103 remains open.

[0045] If the measured value of the temperature Tinst is below the upper limit value (e.g., 40 °C) of the coolant temperature Tlimit, the open valve 103 is closed again immediately after the time tmeas. If the measured value of the temperature Tinst exceeds the upper limit value of the coolant temperature Tlimit, the open valve 103 is opened further for the time tcool.

[0046] The values or assignment table of the measured values of the temperature Tinst and the time tcool can be determined experimentally. This results in a characteristic curve specific to the centrifuge or coolant supply system that represents the relationship between the temperature Tinst and the time tcool, and thus the temperature control of the coolant is configured as a kind of characteristic curve control.

[0047] Alternatively, the control device (105) can also be supplied with the measured value of the instantaneous coolant temperature, optionally the measured value of the ambient temperature, and optionally the measured value of the engine load. The control device supplies these measured values to an appropriate algorithm for determining the cooling time tcool. If the temperature of the coolant does not change in the desired direction after several subsequent coolings, the algorithm is adjusted by the control device until the temperature of the coolant is set to Tlimit. Due to the intelligent adaptability of this algorithm, the control system can adjust itself in a particularly advantageous way to changing operating conditions.

[0048] Alternatively, a PID controller can also be used, in which the control of the limit value is realized using a parameter - adjustable controller, whereby the time tcool is configured to be calculated individually depending on the temperature Tinst. After the time tmeas and the time tcool have elapsed, the open valve 103 remains closed during the cycle stop time tpause. Then, the cooling cycle resumes. Thus, the total cycle time tcycle is the sum of the time tmeas, the time tcool, and the time tpause.

[0049] Thus, each cycle is simplified as follows and includes the following sub - steps. c1) A sub - step of opening the open valve 103 of the coolant supply system 100 to generate a flow of coolant through the cooling fluid system of the electric motor 8; c2) After a predetermined time tmeas has elapsed, measuring the instantaneous temperature Tinst of the coolant by the temperature measuring device 104 in the coolant discharge line 102 and transmitting the measured value of the instantaneous temperature Tinst to the control device 105, where the predetermined time tmeas is determined as a function of the length of the coolant discharge line 102 between the electric motor (8) and the temperature measuring device 104; c3) A sub - step of comparing the measured value of the temperature Tinst with the upper limit value of the coolant temperature Tlimit; c4) A sub-step in which the control device 105 calculates the time tcool as a function of the temperature Tinst, and the release valve 103 remains open; c5) After the times tmeas and tcool have elapsed, including a sub-step of closing the release valve 103 during the cycle stop time tpause; Here, the sub-steps c1) to c5) of the method are "substantially infinitely" executed again in a program loop manner after the time tpause has elapsed until the drive motor of the centrifuge stops operating.

[0050] Therefore, the sub-steps c1) to c5) of the method are repeatedly executed using the control device 105, or preferably looped until the operation of the drive motor ends. Thereafter, the program is terminated. The purpose of the coolant temperature control according to the present invention is to keep the instantaneous coolant temperature Tinst as constant as possible at Tlimit (manufacturer's specification). In this way, the electric motor 8 is operated at the maximum allowable temperature and with the lowest possible coolant consumption regardless of its load and the temperature of the incoming coolant.

[0051] The manufacturer's specification regarding the flow rate of the incoming coolant is generally a static specification for the rated load of the electric motor 8. For example, in the case of a maximum coolant temperature of 40 °C and a rated load of 37 kW, a flow rate of 3 l / min is specified.

[0052] In practice, such an operating point hardly occurs without coolant temperature control. Either the electric motor 8 is operated at a partial load and / or the supply temperature of the coolant is lower than the maximum allowable temperature. As a result, generally, the electric motor 8 is supplied with more coolant per unit time than is required for the operating conditions of the electric motor 8. The present invention eliminates this drawback in a simple way.

[0053] A further advantage of this measuring and control device is that it can be easily retrofitted to existing coolant-cooled electric motors, since only the temperature measuring device 104 needs to be added to the coolant discharge line 102. A temperature sensor inside the electric motor 8 (for example, in the coolant chamber) is not required. In addition, only a simple valve having two switching positions ("open" and "closed") is required as the open valve 103. Therefore, a control valve or a controllable throttle diaphragm, as in the prior art solutions, is not required, nor are several valves and lines.

[0054] In FIG. 3, the coolant supply system 100 is configured according to the principle of a closed coolant circuit. This enables a further reduction in coolant usage. For this purpose, the coolant is pumped through the circuit with the aid of the pump 106 and cooled in the heat exchanger 107. The required cooling capacity is supplied to the heat exchanger 107 via the cooling circuit 108.

[0055] In a variant of a further embodiment of the coolant supply system 100 according to FIG. 4, the coolant is taken in from the storage tank 109, flows through the electric motor, and after the heat has been absorbed, is pumped back to the storage tank 109. The heat absorbed by the coolant is mainly released back to the surroundings of the storage tank 109 via the wall 110 of the storage tank 109 by convection. The wall 110 of the storage tank 109 can be provided with suitable means for improving convective heat dissipation, such as cooling fins. If the heat capacity of the coolant in the storage tank 109 and the heat dissipation via convection are not sufficient, the coolant that is too hot can be discharged via the first line 111, and the cooler coolant can be supplied via the second line 112.

[0056] In the following application example of the method according to the invention for monitoring and controlling the coolant temperature of the separator 1, it is shown that a significant amount of coolant can be saved, for example, in a drive motor cooled by coolant (configured here as a three-phase motor) with the following performance data. Pab = 37 kW Pauf = 40 kW Coolant flow rate: 3 l / min (manufacturer's specification) Maximum cooling water temperature: 40 °C (manufacturer's specification)

[0057] The parameters for coolant control were as follows. tmeas: 2 s tcool: 2 s tpause: 6 s tcycle: 10 s Experiment 1: (Measurement after thermally stable operation) Load 35.9 kW Coolant inlet temperature: 23.1 °C Coolant outlet temperature: 40.8 °C Coolant flow rate: 1.85 l / min Temperature rise: 17.7 K

[0058] Experiment 2: (Measurement after thermally stable operation) Load 26.3 kW Coolant inlet temperature: 23.5 °C Coolant outlet temperature: 40.9 °C Coolant flow rate: 1.73 l / min Temperature rise: 17.4 K Advantageously, it has been shown that the required amount of coolant can be minimized.

Description of symbols

[0059] List of symbols 1 Separator 2 Drum 3 Hood device 4 Drive spindle 5 Upper bearing 6 Lower bearing 7 Bearing housing 8 Electric motor 9 Motor housing 10 Stator 11 Rotor 12 Machine frame 13 Opening 14 Flange 15 Section 16 Opening 17 attenuation element 18 stages 19 stages 20 lubricant supply section 100 coolant supply device 101 coolant supply line 102 coolant discharge line 103 open valve 104 temperature measuring device 105 control device 106 pump 107 heat exchanger 108 refrigeration circuit 109 storage tank 110 wall 111 first line 112 second line 113 motor coolant passage D rotating shaft

Claims

1. A method for controlling the coolant temperature of an electric motor of a rotor drive unit (8) of a centrifuge, preferably a separator (1) having a vertical axis of rotation, and particularly a method during centrifugation of a suspension into at least two different product phases, The rotor has at least one rotatable drum (2), the drive unit has an electric motor (8) that rotates the rotor directly or indirectly, the drive unit further has a device (100) for supplying a coolant to the electric motor, and the device (100) has a control device (105), a) The step of installing a drive device in the centrifugal separator, b) The step of driving a rotor with an electric motor while centrifugating the suspension into at least two different product phases, c) A method comprising the step of controlling the cooling of an electric motor during a limited cooling phase of a cooling cycle that is interrupted by a rest for at least the duration of step b).

2. The method according to claim 1, wherein the length of each cooling stage is determined by a control device (105) taking into account one or more measured values.

3. The method according to claim 2, characterized in that the length of each cooling stage is determined by a control device (105) taking into account one or more measured temperature values.

4. The cooling cycle in step c) c1) A substep in which an open valve (103) of a coolant supply system (100) is opened to generate a flow of coolant through a cooling fluid system for an electric motor (8), wherein the cooling fluid system comprises at least a coolant supply line (101) and a coolant discharge line (102) and a motor coolant passage (113), c2) In the coolant discharge line (102), after a predetermined time tmeas has elapsed, the instantaneous temperature Tinst of the coolant is measured by a temperature measuring device (104), and the measured value of the instantaneous temperature Tinst of the coolant is transmitted to the control device (105), and the predetermined time tmeas is determined as a function of the length of the coolant discharge line (102) between the electric motor (8) and the temperature measuring device (104), in a substep, c3) A substep of comparing the measured instantaneous temperature Tinst of the coolant with the upper limit of the coolant temperature Tlimit, c4) A substep in which the control device (105) calculates time tcool as a function of the instantaneous temperature Tinst of the coolant, wherein the release valve (103) remains open during time tcool, c5) After a specified time tmeas and time tcool have elapsed, the substep includes closing the open valve (103) during a cycle pause time, The method according to claim 1, wherein substeps c1) to c5) are executed again in the manner of a program loop after a cycle pause time has elapsed until the electric motor stops operating.

5. The method according to claim 4, wherein in substep c5), if the instantaneous temperature Tinst of the coolant falls below a predetermined upper limit of the coolant temperature Tlimit, the opening valve (103) is closed immediately after the time tmeas.

6. The method according to claim 4, wherein the opening valve (103) remains open for a further time tcool when the instantaneous temperature Tinst of the coolant exceeds a predetermined upper limit Tlimit of the coolant temperature.

7. The method according to any one of claims 4 to 6, wherein a correlation table of measured values ​​of temperature Tinst and time tcool is experimentally determined, and as a result a characteristic curve specific to the centrifuge or coolant supply system that represents the relationship between temperature Tinst and time tcool is obtained, and the temperature control of the coolant is configured as control of the characteristic curve.

8. The method according to any one of claims 1 to 6, wherein a PID controller is used as the control device (105).

9. In step c), the control device (105) is supplied with one or more measured values ​​of the instantaneous temperature Tinst of the coolant, and preferably, further supplied with one or more measured values ​​of the ambient temperature and one or more instantaneous motor load characteristic values. The method according to any one of claims 1 to 6, wherein the control device (105) uses these measurements to determine a cooling time tcool according to an algorithm, and if the coolant temperature does not change in the desired direction after several subsequent cooling cycles, the algorithm is adapted by the control device until the coolant temperature is adjusted to the value Tlimit.

10. The method according to any one of claims 1 to 6, wherein the coolant supply system (100) is configured according to the principle of a closed coolant circuit.

11. The method according to claim 10, wherein the coolant is pumped into the circuit with the help of a pump (106), cooled in a heat exchanger (107), and the required cooling capacity is supplied to the heat exchanger (107) via a refrigeration circuit (108).

12. The method according to any one of claims 1 to 6, wherein the coolant is taken out from the storage tank (109), flows through the electric motor (8) to absorb heat, and then pumped back into the storage tank (109).

13. The method according to claim 12, wherein the heat absorbed by the coolant is released back into the vicinity of the storage tank (109) by convection through the wall (110) of the storage tank (109).

14. The method according to claim 12, wherein coolant that is too hot is discharged from the storage tank (109) via a first line (111), and coolant that is too cold is supplied to the storage tank (109) via a second line (112).

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