Method for cooling a device, such as an electric motor drive or a general current transformer, and device, such as an electric motor drive or a general current transformer, for carrying out the cooling method

Abstract

A method for cooling a device, the device comprising a heat sink (1), electronic components connected to the heat sink (1), a heat pipe (2) connected to or integrated with the heat sink (1), an inlet air temperature measuring device and a cooling fan (3), wherein - the device determines whether the inlet air temperature is below a first temperature threshold (T EinlassluftNiedrig1 ) is close to the freezing point temperature of the working fluid of the heat pipe, and - the device operates the cooling fan (3) with a low inlet air temperature speed regime when the inlet air temperature is below the first temperature threshold (T EinlassluftNiedrig1 ), characterized in that - the device determines whether the inlet air temperature is above a second temperature threshold (T EinlassluftNiedrig2) and operates the cooling fan (3) with a high inlet air temperature speed regime when the inlet air temperature is above the second temperature threshold (T EinlassluftNiedrig2 ) and the device has previously been operated with the low intake air temperature speed regime and that - the second temperature threshold (T EinlassluftNiedrig2 ) higher than the first temperature threshold (T EinlassluftNiedrig1 ) is.

Description

[0001] The present invention relates to a method for cooling a device, such as an electric motor drive or a general power converter, the device comprising a heat sink, electronic components connected to the heat sink, a heat pipe connected to or integrated with the heat sink, an inlet air temperature measuring device, and a cooling fan. According to the method, the drive determines whether the inlet air temperature is below a first temperature threshold and operates the cooling fan at a low inlet air temperature speed regime when the inlet air temperature is below the first temperature threshold. The invention is also directed to a device, such as an electric motor drive or a general power converter, for carrying out the cooling method.

[0002] Forced air cooling is common for preventing overheating of electronic devices. Heat-generating components of electronic devices, such as electric motor drives or general power converters, are typically connected to a heat sink, and a fan is used to force air past the heat sink. To increase the efficiency of such cooling systems, a heat sink can be equipped with a heat pipe. Because the thermal conductivity of a heat pipe is considerably better than that of typical heat sink materials, such as aluminum, heat can be dissipated more efficiently into the heat sink and to the surrounding air.

[0003] A heat pipe is a sealed container from which all air has been removed and in which a vacuum or partial vacuum has been created. The heat pipe is partially filled with a working fluid, which may be water. Water can be used because of its low cost and suitable heat transfer capacity. However, a disadvantage of water is that it freezes when the ambient temperature drops below zero degrees Celsius. Although heat pipe freezing is not a major problem in itself, as thermal energy dissipated by a heat source usually thaws the heat pipe, problems can arise when forced cooling fans are combined with a heat pipe at low ambient temperatures. Such cooling fans are usually controlled so that their fan speed is determined experimentally and is a compromise value.The fan speed must be high enough to keep components cool, yet low enough to prevent a heat pipe from freezing in cold ambient conditions. The fan speed, and in particular a predefined lower fan speed limit, may depend on the characteristics of the cooling system, i.e., the characteristics of the fan, the heat sink, the heat pipe, the cooling channels, and / or the loss-generating components of the device.

[0004] Under unfavorable conditions, forced cooling can accelerate the freezing of the heat pipe and counteract the thawing effect of the heat source. Once the fluid in the heat pipe freezes, the cooling efficiency of the heat sink is significantly reduced, and components cooled by the heat sink may overheat and / or cause overtemperature shutdowns. Consequently, the performance of the electric motor drive may deteriorate or the drive may be damaged.

[0005] From the publication US 2020 / 0 281 092 A1, a cooling device and a cooling method are known, wherein the cooling device comprises a heat pipe, a fan, and temperature sensors. If the measured temperature exceeds a reference value, the fan operates at normal speed. Otherwise, the fan stops or slows down to save energy and control cooling. This prevents the coolant from freezing in low-temperature environments.

[0006] JP 2013-138041 A discloses an electronic device comprising a fan control unit and a threshold control unit. The fan control unit switches the fan speed from low to high speed when the temperature in the housing exceeds a first threshold, and from high to low speed when the temperature falls below a second threshold. The threshold control unit changes the second threshold to precisely control the fan speed and prevent excessive power consumption.

[0007] The object of the present invention is to provide an improved method and an improved device, such as an electric motor drive or general power converter, that eliminates the problems outlined above. This object is achieved by a method according to claim 1 and a device according to claim 12.

[0008] The invention provides a method for cooling a device, such as an electric motor drive or a general power converter. The device comprises a heat sink, electronic components connected to the heat sink, a heat pipe connected to or integrated with the heat sink, an inlet air temperature measuring device, and a cooling fan. The electronic components may comprise hardware required to provide a functional electric motor drive or general power converter. The connection between the heat sink on one side and the electronic components and heat pipe on the other side may be direct or indirect contact between the components. The fan is provided for blowing ambient air from outside the drive, through an inlet opening, and to the heat pipe and an outlet opening.According to the method, the device determines whether the inlet air temperature is below a first temperature threshold close to the freezing point temperature of the heat pipe's working fluid. The device operates the cooling fan at a low inlet air temperature speed regime when the inlet air temperature is below the first temperature threshold. The drive may comprise a controller and / or software implementation for carrying out the required method steps. According to the invention, the device determines whether the inlet air temperature is above a second temperature threshold and operates the cooling fan at a high inlet air temperature speed regime when the inlet air temperature is above the second temperature threshold and the drive has previously been operated at the low inlet air temperature speed regime.According to the invention it is further provided that the second temperature threshold value is higher than the first temperature threshold value.

[0009] The invention enables detection of cold ambient temperatures and corresponding restriction of the fan speed, so that the energy loss from a cooled component can keep the fluid in the heat pipe in a liquid form, even under subzero ambient temperatures. Thus, the present invention enables the avoidance of disadvantageous situations in which the drive experiences an overtemperature fault at low ambient temperatures. The invention prevents the heat pipe from freezing to the heat sink when the drive is operated at low ambient temperatures.

[0010] In a preferred embodiment of the invention, the first temperature threshold is 0°C ± 5°C.

[0011] The high inlet air temperature speed regime may be characterized by higher fan operating speeds than the low inlet air temperature speed regime. The second temperature threshold may be a higher temperature than the first temperature threshold. According to this embodiment, the fan may be operated with the low inlet air temperature speed regime at ambient temperatures between the two temperature thresholds if the drive has previously been operated with the low inlet air temperature speed regime. This means that if the heat pipe has been exposed to low temperatures, the fan will operate at lower speeds, even if the ambient temperature has risen above the first temperature threshold.Thus, only a limited amount of energy is dissipated from the heat pipe to the environment in the temperature range between the two thresholds, further reducing the risk of heat pipe freezing. Two threshold temperatures are used for hysteresis to avoid a situation where the fan modes constantly switch from one to the other, thus generating an annoying audible noise from the fan.

[0012] In a further preferred embodiment of the invention, the second temperature threshold is 5°C higher than the first temperature threshold. Thus, according to this embodiment, in a temperature range between, for example, 0°C and 5°C, the fan can be operated with a low inlet air temperature speed regime to prevent the heat pipe from freezing. The actual temperature thresholds can deviate from the temperature thresholds mentioned here by ±2°C. This example may apply to a heat pipe filled with water as the working fluid. For a different working fluid filled into the heat pipe, the temperature values ​​may differ considerably from this example. The actual temperature thresholds depend on the freezing point temperature of the working fluid used.

[0013] In a further preferred embodiment of the invention, the fan is operated at a predefined low speed. The predefined low speed can correspond to a standstill of the fan or a low rotational speed of the fan.

[0014] In a further preferred embodiment of the invention, the fan is operated at the high inlet air temperature speed regime according to a request from at least one of the electronic components. The request from the electronic components may be a function of the temperature of the component, which may be measured by a controller of the drive. The request may result in a signal that controls the fan speed such that the required cooling of the electronic component is achieved.

[0015] In another preferred embodiment of the invention, the working fluid of the heat pipe comprises water, methanol, and / or acetone. Water is a cost-effective working fluid of the heat pipe, but other suitable fluids may be used as an alternative.

[0016] In a further preferred embodiment of the invention, the inlet air temperature measuring device is an outdoor or indoor thermometer.

[0017] In a further preferred embodiment of the invention, a plurality of cooling fans and a plurality of associated temperature measuring devices are provided, wherein the device operates all cooling fans with the low inlet air temperature speed regime when the inlet air temperature measured by one of the temperature measuring devices is below the first temperature threshold, and / or the drive operates all cooling fans with the high inlet air temperature speed regime when the inlet air temperature measured by one of the temperature measuring devices is above the second temperature threshold and when the device has previously been operated in the low inlet air temperature speed regime, and / or the fan speeds of the plurality of cooling fans are controlled independently of one another.A drive controller may be connected to the cooling fans and the temperature measuring devices so that it can evaluate the measurements from all temperature measuring devices. The controller may control all fans so that the first temperature measuring device that indicates that a threshold has been exceeded triggers a change in the speed regime of the fans.

[0018] In a further preferred embodiment of the invention, the heat pipe is partially filled with working fluid and air has been removed from the heat pipe, and / or the working fluid in the heat pipe may be at least partially frozen in a region near the fan.

[0019] The invention also relates to an apparatus comprising a heat sink, electronic components connected to the heat sink, a heat pipe connected to the heat sink, an inlet air temperature measuring device, and a cooling fan. The apparatus is designed to carry out the method described herein.

[0020] Further features, details, and advantages of the invention are set forth in the claims and in the following description of the figures. In the figures: Fig. 1: an operating model of a heat pipe for cooling an electric motor drive at ambient temperature above 0 °C and according to the state of the art; Fig. 2: the heat pipe operation model at ambient temperature below 0 °C, with the cooling fan running at full speed and according to the state of the art; Fig. 3: an operating model of a heat pipe for cooling an electric motor drive when operated according to the present invention; and Fig. 4: a simple block diagram of the process described here.

[0021] Fig. Figure 1 shows an operating model of a heat pipe 2 for cooling an electric motor drive at ambient temperatures above 0°C. A heat pipe 2 is a sealed container from which all air has been removed and in which a vacuum or partial vacuum has been created. The heat pipe 2 is partially filled with a working fluid, such as water. Water can be used due to its low cost and suitable heat transfer capacity. However, water can freeze if the ambient temperature drops below 0°C. Freezing of the heat pipe 2 is not a problem in itself, as energy losses dissipated by a heat source usually thaw the heat pipe 2 or keep it unfrozen. However, problems can arise when forced cooling, e.g., by fans 3, is used at low ambient temperatures. This forced cooling accelerates the freezing of the heat pipe 2 and counteracts the thawing effect of the heat pipe 2.

[0022] The heat pipe 2 can be part of an electrical application, such as a motor drive. The evaporator 21 side of the heat pipe 2 can be in thermal contact with a heat sink 1 or another type of heat energy-receiving base plate. At high ambient temperatures above 0°C, water can circulate freely in the heat pipe 2 between the evaporator 21 shown on the left side of the figure and the condenser 22 of the heat pipe 2 shown on the right side. The circulation is indicated by arrows inside the heat pipe 2. Arrows outside the heat pipe 2 indicate heat transfers to and from the heat pipe 2. A fan 3 can be used to generate forced convection on the condenser 22 side of the heat pipe 2, thus enhancing heat transport from the heat pipe 2 and into the surrounding ambient air.

[0023] Fig. Figure 2 shows the heat pipe 2 under temperature conditions below 0°C with the fan 3 operating at full speed. As indicated in the heat pipe 2, the working fluid of the heat pipe 2 freezes, limiting heat transfer between the evaporator 21 and the condenser 22. The limited heat transfer can lead to damage to overheating components requiring cooling. The problem is exacerbated by the high-speed fan 3 forcing cold ambient air toward the heat pipe 2, further cooling it.

[0024] Fig. Figure 3 shows an operating model of a heat pipe 2 for cooling an electric motor drive when operating under temperature conditions below 0°C and according to the present invention. The drive comprises the heat sink 1, electronic components connected to the heat sink 1, the heat pipe 2, which is also connected to the heat sink 1, an inlet air temperature measuring device, and a cooling fan 3. The drive may comprise a controller or computer configured to determine whether the inlet air temperature is below a first temperature threshold T EinlassluftNiedrig1 and for operating the cooling fan 3 with a low inlet air temperature speed regime when the inlet air temperature is below the first temperature threshold T EinlassluftNiedrig1 is used. The first temperature threshold T EinlassluftNiedrig1 may be 0 °C, especially when water is used as a working fluid of the heat pipe 2.

[0025] As indicated by the reduced number of arrows pointing from the fan 3 to the condenser 22, the speed of the fan 3 has been reduced by the drive. Accordingly, the effect of forced convection caused by the fan 3 and also the cooling of the heat pipe 2 is reduced.

[0026] The actuator can detect whether the inlet air temperature is above a second temperature threshold T EinlassluftNiedrig2 and operate the cooling fan 3 with a high intake air temperature speed regime when the intake air temperature is above the second temperature threshold T EinlassluftNiedrig2 and the engine has previously been operated with the low intake air temperature speed regime. The second temperature threshold T EinlassluftNiedrig2can be 5°C. Accordingly, in this embodiment, at temperatures down to 5°C, the drive can operate the fan at the low inlet air temperature speed regime when the inlet air temperatures have previously reached subzero values. This feature can ensure that no freezing of the heat pipe 2 occurs under conditions where the drive is operated near the freezing point temperature of the working fluid of the heat pipe 2.

[0027] In the low inlet air temperature speed regime, the fan 3 may be operated at a minimum speed which may correspond to a standstill of the fan 3 or a speed which is as low as possible at which the fan 3 can be controlled by the drive.

[0028] In contrast, in the high inlet air temperature speed regime, the fan 3 can be operated according to a request from at least one of the electronic components of the drive.

[0029] The inlet air temperature measuring device may be an external or internal thermometer. An internal thermometer may be any temperature measuring device provided on or in the actuator that can provide readings indicative of the ambient air temperature or the actuator's inlet air temperature. An external thermometer may refer to an external temperature measuring device that can be connected to the actuator and provide corresponding readings.

[0030] In an embodiment not shown in the figures, a plurality of cooling fans 3 and a plurality of associated temperature measuring devices may be provided. The drive may operate all cooling fans 3 at the low inlet air temperature speed regime when the inlet air temperature measured by one of the temperature measuring devices is below the first temperature threshold T EinlassluftNiedrig1 Additionally or alternatively, the drive may operate all cooling fans 3 at the high inlet air temperature speed regime if the inlet air temperature measured by one or all of the temperature measuring devices is above the second temperature threshold T EinlassluftNiedrig2 and if the drive has previously been operated with the low intake air temperature speed regime.

[0031] The invention also relates to an electric motor drive comprising a heat sink 1, electronic components connected to the heat sink 1, a heat pipe 2 connected to the heat sink 1, an inlet air temperature measuring device, and a cooling fan 3, wherein the drive is designed to carry out the method described herein. In particular, the drive may comprise additional hardware components and / or may be programmed such that the method steps described herein can be carried out by the drive.

[0032] Fig.Figure 4 shows a simple block diagram of the method described here. At the beginning of the method implementation, the drive may be set to operate the fan 3 in a normal mode, i.e., with the high inlet air temperature speed regime, as the default setting. The drive's operating mode is referred to as Variable Fan Control. In this mode, the fan speed can be controlled based on the temperatures and corresponding cooling requirements of insulated-gate bipolar transistors, rectifiers, and / or other drive components.

[0033] The drive can have an intake air temperature sensor T Einlassluftwhich is used as an inlet air temperature measuring device. Its resolution can be selected to be ≤1 °C and it can perform measurements in a range of -40 to 100 °C. If the inlet air temperature is found to be below the first temperature threshold T EinlassluftNiedrig1 For example, if the intake air temperature is below zero, the FanControl variable can be set to 0, and the fan is controlled by the drive to run at a predetermined low speed. The method can continuously and / or periodically check whether the intake air temperature remains below zero.

[0034] If it turns out that the inlet air temperature is no longer below 0 °C, the FanControl variable can remain at 0 until the inlet air temperature is above the second temperature threshold T EinlassluftNiedrig2 of, for example, 5 °C.

[0035] The present invention modifies the topology of the main fan (3) speed control of a drive according to the inlet air temperature of fan 3. In parallel power units where multiple inlet air measurements are performed for multiple inlets of fan 3, all power units can measure their own inlet air temperature. For example, fans 3 can be controlled according to the first measurements that reach the temperature thresholds of the fan 3 control.

[0036] All features and advantages described in the claims, the description and the drawings, including details of construction, spatial arrangements and method steps, may be useful for the invention both individually and in all possible combinations. Reference symbol 1 heat sink 2 heat pipes 3 fans 21 evaporators 22 Capacitor T EinlassluftIntake air temperature sensor T EinlassluftNiedrig1 first temperature threshold T EinlassluftNiedrig2 second temperature threshold

Claims

[1] A method for cooling a device, the device comprising a heat sink (1), electronic components connected to the heat sink (1), a heat pipe (2) connected to or integrated with the heat sink (1), an inlet air temperature measuring device and a cooling fan (3), wherein - the device determines whether the inlet air temperature is below a first temperature threshold (T EinlassluftNiedrig1 ) is close to the freezing point temperature of the working fluid of the heat pipe, and - the device operates the cooling fan (3) with a low inlet air temperature speed regime when the inlet air temperature is below the first temperature threshold (T EinlassluftNiedrig1 ) lies, characterized by , that - the device determines whether the inlet air temperature is above a second temperature threshold (T EinlassluftNiedrig2) and operates the cooling fan (3) with a high inlet air temperature speed regime when the inlet air temperature is above the second temperature threshold (T EinlassluftNiedrig2 ) and the device has previously been operated with the low intake air temperature speed regime and that - the second temperature threshold (T EinlassluftNiedrig2 ) higher than the first temperature threshold (T EinlassluftNiedrig1 ) is. [2] Method according to claim 1, characterized by that the first temperature threshold (T EinlassluftNiedrig1 ) is 0°C ± 5 °C. [3] Method according to one of the preceding claims, characterized by that the device is an electric motor drive or a general current transformer [4] Method according to claim 3, characterized by that the second temperature threshold (T EinlassluftNiedrig2 ) 5 °C higher than the first temperature threshold (T EinlassluftNiedrig1 ) is. [5] Method according to one of the preceding claims, characterized by that the fan (3) is operated at a predefined low speed in the low inlet air temperature speed regime. [6] Method according to one of the preceding claims, characterized by that the fan (3) is operated with the speed regime for high inlet air temperature according to a request from at least one of the electronic components. [7] Method according to one of the preceding claims, characterized by that the working fluid of the heat pipe (2) comprises water, methanol and / or acetone. [8] Method according to one of the preceding claims, characterized by that the inlet air temperature measuring device is an outdoor or indoor thermometer. [9] Method according to at least claims 1 and 3, characterized bythat a plurality of cooling fans (3) and a plurality of associated temperature measuring devices are provided, the device operating all cooling fans (3) at the low inlet air temperature speed regime when the inlet air temperature measured by one of the temperature measuring devices is below the first temperature threshold (T EinlassluftNiedrig1 ), and / or the device operates all cooling fans (3) with the speed regime for high inlet air temperature when the inlet air temperature measured by one of the temperature measuring devices is above the second temperature threshold (T EinlassluftNiedrig2 ) and if the device has previously been operated in the low inlet air temperature speed regime, and / or the fan speeds of the plurality of cooling fans are controlled independently of each other. [10] Method according to one of the preceding claims, characterized bythat the heat pipe (2) is partially filled with working fluid and air has been removed from the heat pipe (2). [11] Method according to one of the preceding claims, characterized by that the working fluid in the heat pipe (2) may be at least partially frozen in an area near the fan (3). [12] A device comprising a heat sink (1), electronic components connected to the heat sink (1), a heat pipe (2) connected to the heat sink (1), an inlet air temperature measuring device and a cooling fan (3), characterized by that the device for carrying out the method is constructed according to one of claims 1-11.

Images