Method And Apparatus To Monitor The Condition Of An Apparatus

A method and apparatus to monitor the condition of an apparatus (e.g a variable speed drive), the apparatus comprising: a processor, a plurality of devices and a plurality of temperature sensors, each sensor associated with a device, the processor being arranged in use to: determine, for each of a plurality of sensors, the temperature of the associated device based on the temperature sensed by the sensor and the mode of operation of the device; compare the determined temperatures for each device with stored data relating to the mode of operation of the apparatus; and based on the comparison determine whether the apparatus is operating as expected in the mode of operation.

SUMMARY

A method and apparatus for monitoring the condition of an apparatus is described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the technique may be practised without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention.

In one aspect, a method for monitoring the condition of an apparatus is described. In other aspects, the proposed technique encompasses apparatus and a computer-readable medium configured to carry out the foregoing actions, as well as a data carrier carrying thereon or therein data indicative of instructions executable by processing means to cause those means to carry out the foregoing actions. Examples are CD-ROMs, memory sticks, dongles, transmitted signals, downloaded files etc. In particular, the method may be implemented in an apparatus for which temperature is a concern.

DETAILED DESCRIPTION

FIG. 1shows an example of an apparatus in which the proposed technique may be implemented. The apparatus100comprises a plurality of devices102, a plurality of temperature sensors104, a microprocessor106to control devices102and to receive inputs from temperature sensors104and one or more components108to cool the devices102within the apparatus100.

Clearly the apparatus may comprise more devices, temperature sensors etc than those shown. The apparatus shown is simplified for the understanding of the proposed technique and an apparatus as implemented is likely to include many more components. Devices102may be electronic devices such as discrete semi-conductor devices (for instance diodes, transistors etc.) or integrated circuits (ICs) or individual units (e.g. power supply etc) or other devices such as mechanical devices, electrical devices or physical parts (e.g. PCB temperature or enclosure temperature). Temperature sensors may comprise thermistors or the like. Cooling components108may be a fan or ventilation openings controlled by one or more flaps or other cooling components to cool the devices102within the apparatus100.

In operation the microprocessor controls the devices102according to an operating mode of the apparatus. For example, the operating mode could, for instance, be a cooling component108(e.g. a fan) operating when a device is working at full power, this being a subset of the devices of the apparatus, or an operating mode in which the cooling component108is operating and all devices are in a sleep mode or an operating mode in which a cooling component108is operating and the devices are not operating or any other operating mode.

The microprocessor stores data relating to expected temperatures when devices are operating in a given operating mode of the apparatus. This data may be in the form of temperature profiles for instance as shown inFIG. 2.

FIG. 2shows a stored profile with expected determined temperatures DTnat the relevant device102nfor a given operating mode of apparatus100. The actual determined temperature DTnof the device102nis determined from the actual temperature Tnsensed by the associated sensor104n(indicated inFIG. 2as Sn) and the current mode of operation of the associated device102nin the current operating mode of the apparatus.

For instance:

Where Tnis the actual temperature sensed by the sensor104n

mnis the operating performance of the associated device102ne.g. 0% to 100%

d is the distance of sensor104nfrom the associated device102n

Or alternatively:

Where Tnis the actual temperature sensed by the sensor104n

m is the operating performance of the associated device102ne.g. 0% to 100%

d is the distance of sensor104nfrom the associated device102n

k is a coefficient determined during testing,

accI is the accumulated current through the switching device

Thus the determined temperature DTnis not simply the temperature sensed remotely by the sensor102but it is intended to be a more accurate estimation of the actual temperature of the device in the specified operating mode. Where the device102is a discrete semiconductor device (e.g. a transistor, a diode or the like) the determined temperature DTngives an estimation of the actual junction temperature of the device.

Other temperature profiles may be stored for other operating modes of the device for example: one or more fans on or off, one or more devices on or off, or ratios (0 to 100%) of device off and on, and the current passing through the devices etc.

The profile may be differential profiles i.e. profiles that indicate the differences between the temperature determined from one sensor and the temperature determined from another sensor. For instance, as shown inFIG. 3, the temperature profile may be related to the difference between the determined temperature of the device1021and the determined temperature of each other device of relevant to the profile.

The apparatus monitors for conditions such as an incorrectly installed fan, blocked inlet or outlet vents, a clogged fan, a worn out fan, an unstable fan operation or other operating conditions of the apparatus. This monitoring is based on the stored temperature profile data. The stored data may relate to an expected temperature profile for a given operating condition and may relate to a faulty operating condition. For instance, the stored data may include a temperature profile relating to the expected temperature profile for a fan installed the wrong way around. If the microprocessor determines that the temperature profile of the apparatus is similar to the stored temperature profile relating to the expected temperature profile for a fan installed the wrong way around, then an alert may be issued with this as the detected fault.

The operation of the system will now be described. During operation of the apparatus100the microprocessor106receives signals from and sends signals to other components of the apparatus e.g. electronic devices102, the sensors104and the fans108. At any point during operation of the apparatus, the microprocessor is aware of how components are operating. The microprocessor106receives input from the temperature sensors104situated around the apparatus100. When the temperature sensed via a sensor104is equal to or greater than a threshold value, this triggers the microprocessor to undertake a review of the temperatures within the apparatus100.

To this end, the microprocessor reads the temperature sensed by the sensors104and, for each sensor104nrelevant to the operating mode of the apparatus, determines the temperature DTnindicating a current temperature of the device102nassociated with the sensor104. The microprocessor then determines the differences ΔDT in the determined temperatures DTnand compares these determined differences ΔDTnagainst the stored profile for the relevant sensors for the current operating mode of the apparatus.

For exampleFIG. 4shows a simplified apparatus100comprising two devices1021and1022, two sensors1041and1042, a microprocessor106and a fan108. Fan108, when operating correctly, causes air to flow in the direction of arrow110. Thus cool air from outside the apparatus100is drawn into the apparatus to cool device1022and then device1021and then exits the apparatus e.g. via a grill112.

The microprocessor stores temperature profiles relating to the sensors1041and1042for various operating modes of the device.FIGS. 5,6and7show an example of three temperature profiles stored for the apparatus shown inFIG. 4.FIG. 5shows an example temperature profile for the determined temperature differential ΔDT with respect to the determined temperature of device1021for the following conditions:

1. Fan on

For this profile the difference in temperature between the temperature determined from the reading of sensor1041and the determined temperature of sensor1042is indicated as a value of x. This is the expected difference in determined temperature ΔDT when the above operating conditions are in effect.

FIG. 6shows an example temperature profile for the determined temperature differential ΔDT with respect to the determined temperature of device1021for the following conditions:

1. Fan on

In this case the determined temperature differential ΔDT i.e. the difference between the determined temperature based on the reading from1041and the determined temperature based on sensor1042is given as y. This is the expected difference in determined temperature ΔDT when the above operating conditions are in effect.

FIG. 7shows an example temperature profile for the determined temperature differential ΔDT with respect to the determined temperature of device1021for the following conditions:

1. Fan on

In this case the determined temperature differential ΔDT i.e. the difference between the determined temperature based on the reading from1041and the determined temperature based on sensor1042is given as z. This is the expected difference in determined temperature ΔDT when the above operating conditions are in effect.

The operation of the system shown inFIG. 4will now be described in relation toFIG. 8. During operation of the apparatus100the microprocessor106receives signals from and sends signals to the other components of the apparatus e.g. electronic devices102, the sensors104and the fan108. At any point during the operation of the apparatus, the microprocessor106is aware of how components are operating. The microprocessor106receives inputs from the temperature sensors104. When the temperature sensed by a sensor104is equal to or greater than a threshold value, this triggers the microprocessor to undertake a review of the temperatures within the apparatus100.

To this end the microprocessor receives (operation800) the temperature readings from the first temperature sensor1041and the second temperature sensor1042. The microprocessor then determines if any of the sensed temperatures are above a trigger threshold (operation802). If not, the microprocessor returns to receiving the temperature reading (operation800). If a sensed temperature is above a trigger threshold, for each relevant sensor, microprocessor (operation804) determines the temperature DTnof a device indicating a current temperature of the device102nassociated with the sensor104n. The microprocessor then (operation806) determines the difference ΔDT between the determined temperature of the first device and the determined temperature of the second device and then the microprocessor (operation808) compares this determined difference ΔDT against the stored profile for the relevant temperature sensors and the current operating mode of the apparatus. On the basis of this comparison, the microprocessor (operation810) may determine whether the apparatus is operating as expected for the current operating mode and that there is not an alarm condition (operation810answered in the negative) or may determine that the apparatus is not operating as expected for the current operating mode and that there is an alarm condition (operation810answered in the positive). When the microprocessor (operation810) determines that the apparatus is operating as expected for the current operating mode and that there is not an alarm condition, then the microprocessor returns to monitoring the sensed temperatures (operation800). When the microprocessor (operation810) determines that the apparatus is not operating as expected for the current operating mode and that there is an alarm condition (operation810answered in the positive), then the microprocessor may cause an alert to be issued (operation812). This may take the form of a visual alert to a user of the apparatus or a message sent to a remote destination or the like.

For example, for the operating mode related to the profile shown inFIG. 6, in which a fan is on and both devices1021and1022are fully on, the profile for the difference in temperature between the temperature determined from the reading of the sensor1021and the temperature determined from the reading from sensor1042shows that the temperature at the sensor1041should be around +y (i.e., the determined temperature of device1022should be around y less than the determined temperature from the reading given by sensor1021for the current operating mode of the apparatus). If however the fan108is not working the determined temperature differential may be less than y. In this case the microprocessor may determine that there is a fault and can provide an alert local to the apparatus or to a remote destination e.g. by wireless transmission. In a similar scenario, should the fan108be installed incorrectly so that the direction of blow of fan108is in the reverse direction to that indicated by arrow110, the temperature determined from the reading of sensor1041may be less than that of1042. From this the microprocessor may determine that the fan is incorrectly installed and also alert the user.

During manufacture, incorrect fan installation in the product may be detected by sensing the direction of the blown air or the direction of rotation of the blade. Detecting an incorrect mounting of a fan in the field is currently quite difficult without difficult checks or putting additional sensors into the product, incurring extra cost.

The proposed technique uses sensors already fitted to the apparatus to measure device temperatures within a product and compare the reading from these sensors to thermal profiles stored in the software to determine the blown air direction or even the absence or presence of blown air. The devices in the product are of varying distances and positions from the fan so the temperature profiles within the product will vary according to the blown air direction, speed, operating mode and other variables in the system. Early warnings can be presented accordingly.

The apparatus described may be provided in variable speed drives, for example as used in manufacturing. These now typically include an installer replaceable fan that is usually manufactured in such a way that the supporting structure of the fan is symmetrical in all three axes allowing the fan to be mounted in a number of ways. This in turn causes problems in ensuring the correct orientation of the fan when installed in the product. There are rarely any mechanical features preventing incorrect mounting. This can be a serious issue as it can result in a fan moving air in an incorrect direction if mounted the wrong way, dramatically altering cooling within the product. The proposed solution provides a way in which the apparatus itself may detect fault conditions (e.g. a fan mounted in the wrong way round when installed) thereby allowing a warning to be presented to the user. The reliability of the apparatus should therefore be improved through correctly mounted fans, reduction in customer's support calls and a reduced chance of damaged drives through thermal overload.