DE102018118065A1 - Method for operating a machine with a motor protection device - Google Patents

Abstract

In the method according to the invention for operating a machine with at least one motor, the machine operation is monitored for compliance with predetermined limit values by means of a motor protection device by means of at least one first sensor, non-compliance with the predetermined limit values being recognized as an error and countermeasures for compliance with the limit values in the event of an error or the machine is switched off. In the event of an error, a distinction is made between an error according to a first error type and an error according to a second error type, the error according to the first error type being an error which leads to destruction of the machine within less than 30 minutes and the fault according to the second type of fault is a fault which only reduces the remaining life of the machine by a maximum of 50% within 60 minutes. The motor protection device can also be switched between operation of the machine in normal operation and operation of the machine in exceptional operation, different limit values for an error according to the second type of error being used in normal operation and in exceptional operation, the limit values in exceptional operation being timed Initiate the countermeasures to comply with the limit values later or switch off the machine later than in normal operation.

Description

The invention relates to a method for operating a machine with at least one motor, wherein a motor protection device monitors the operation of the machine by means of at least one first sensor for compliance with predetermined limit values, non-compliance with the predetermined limit values being recognized as an error and countermeasures in the event of an error Compliance with the limit values or switching off the machine can be triggered.

In conventional systems, for example a refrigeration system, in addition to the compressor, a controller for determining the current demand and a compressor protection device for monitoring at least one parameter characterizing the operating state of the compressor are provided. If the controller determines an increased demand, the compressor is controlled by the controller in the sense of an increase in output. The operating state of the compressor is monitored via the at least one parameter, for example the winding temperature of the motor or the hot gas temperature, an overshoot or undershoot of a predetermined shutdown threshold leading to the shutdown of the compressor.

The triggering of the compressor protection therefore means an inevitable interruption of the refrigeration circuit and can therefore have considerable consequences. In addition, a restart (automatic or manual) is associated with the uncertainty about the cause of the trigger. In such a case, some manufacturers of compressors do not allow the compressor to continue operating until the cause has been clarified or rectified. In the known control algorithm, the compressor protection can therefore be triggered without an actual component defect or a malfunction in the system due to an increased demand, an incorrectly designed system, an insufficient amount of coolant or an incorrect application.

The DE 10 2005 052 042 B4 proposes a method and a system for controlling a compressor, whereby protection trips based on demand should be avoided. In the method proposed there for controlling the compressor in a control circuit, the performance of the compressor is controlled as a function of demand, at least one parameter characterizing the operating state of the compressor being monitored in order to switch off the compressor when a predetermined switch-off threshold is exceeded or undershot. The current operating state of the compressor is taken into account in the capacity control of the compressor. This can prevent a further increase in performance from being initiated, even though the compressor is already being operated shortly before the shutdown threshold.

According to a preferred embodiment of this method, the performance of the compressor is controlled as a function of demand until a predetermined critical operating state of the compressor is reached. If the compressor is in the critical operating state, this control algorithm is partially or completely disabled to prevent the shutdown threshold from being reached prematurely.

However, there are now situations in a wide variety of applications in which the operator consciously accepts excessive wear and possibly even the destruction of the machine, since switching off the machine can possibly lead to an even greater loss. For example, when freezing fruit and vegetables during harvest, maximum cooling capacity is required. In practice, an operator will manually bypass any protective functions and accept a reduced remaining service life of the compressors in order to avoid loss of the refrigerated goods or the harvest.

The invention is therefore based on the object of further developing the motor protection circuit so that the motor protection can be adapted to special operating situations.

According to the invention, this is solved by the features of claim 1.

In the method according to the invention for operating a machine with at least one motor, the operation of the machine is monitored for compliance with predetermined limit values by means of a motor protection device by means of at least one first sensor, non-compliance with the predetermined limit values being recognized as an error and countermeasures for compliance with the in the event of an error Limit values or a shutdown of the machine are triggered. In the event of an error, a distinction is made between an error according to a first error type and an error according to a second error type, the error according to the first error type being an error which leads to destruction of the machine within less than 30 minutes and the fault according to the second type of fault is a fault which only reduces the remaining life of the machine by a maximum of 50% within 60 minutes. The motor protection device can also be switched over between operating the machine in normal operation and operating the machine in exceptional operation, in normal operation and Different limit values for an error according to the second type of error are used in exceptional operation, the limit values in exceptional operation initiating a later triggering of the countermeasures to comply with the limit values or a later switch-off of the machine than in normal operation.

The motor protection circuit according to the invention thus enables the machine to be operated for a longer period of time in an extreme operating situation (exceptional operation), since other limit values are used. One consciously accepts a significantly greater reduction in the remaining service life of the machine. The limit values are set so that the damage caused by an earlier replacement of the machine is still less than the damage that would result from an earlier shutdown of the machine.

The time which leads to destruction of the machine in the event of a fault in accordance with the first fault type depends crucially on the monitored parameters of the machine and the machine itself. However, these are preferably errors which lead to the destruction of the machine in less than 10 minutes, preferably in less than 5 minutes and most preferably in less than 1 minute, if the machine is not switched off. It is also conceivable that these are errors that can destroy the machine within 30 seconds or 10 seconds or even within 5 seconds. This can be the case, for example, if there is a blocked rotor in a reciprocating piston compressor or solid objects such as stones or wood block the impeller of a centrifugal pump. The failure of two phases in the network can also represent an error according to the first type of error and lead to the destruction of the machine within a few seconds.

An error according to the second type of error is, for example, an error in which a high level of friction occurs in the mechanics of a pump, a compressor or a conveying device. An undervoltage in the network does not immediately destroy the machine in a very short time, but only reduces the service life of the machine. A fault in accordance with the second type of fault can also be caused, for example, by a broken blade on a fan wheel for external ventilation of the motor or by an excessively high ambient temperature of the motor. Such errors, however, only lead to a reduction in the remaining service life by a maximum of 50%, preferably by a maximum of 30% and most preferably by a maximum of 20% or even only by a maximum of 10% in a time of 60 minutes.

According to a preferred embodiment of the invention, when an error occurs according to the first type of error, the machine is switched off regardless of whether the machine is in normal operation or in exceptional operation.

The following explanations relate to various options for switching the motor protection circuit between normal operation and exceptional operation. According to a preferred exemplary embodiment, an external signal is provided for this purpose, which is generated, for example, by a spatially distant control center or by actuating a switch in close proximity to the motor protection circuit. This external signal then causes the motor protection circuit to switch between normal operation and exceptional operation.

Within the scope of the invention, however, it is also conceivable for the motor protection circuit to switch over between normal operation and exceptional operation autonomously by evaluating at least one sensor signal. For example, the machine can be a pump in a pumping station for waste water, the external signal being generated by a level sensor. The changeover then takes place as a function of the rate of rise of the level sensor, taking into account the current pump output or as a function of a measurement with the pumps switched off.

If the machine is, for example, a refrigeration or air conditioning system, with the sensor measuring the electrical output or the cooling output of the system, the switchover between normal operation and exceptional operation can be determined depending on a currently generated cooling output in relation to the maximum possible cooling output of the system become. Likewise, the request signal of the refrigeration controller can also be used and, from a very high demand of refrigeration capacity, preferably greater than 80% of the maximum possible refrigeration capacity, can be switched to exceptional operation, because this requirement indicates, for example, the freezing process of fruit or vegetables during the harvest season.

Ventilators are used for ventilation in animal houses, whereby a sensor measures the air quality (for example the carbon dioxide or metal content) or the temperature in the animal house. The switchover between normal operation and exceptional operation can then be determined, for example, as a function of the outside temperature, the inside temperature and / or as a function of the air quality in the house. In principle, the method according to the invention can be used in a wide variety of applications. So the machine can in particular be a pump, a fan, a compressor, a hoist or a conveyor.

According to a further embodiment of the invention, the motor protection circuit continuously calculates the remaining service life of the machine. This is preferably done on the basis of empirical values and the previous load on the machine. It is advantageous if a maintenance signal is output when the machine falls below a predetermined minimum remaining service life.

Based on the expected service life of the machine, the initial value is reduced by one hour every hour the machine runs in normal operation. If the machine is operated in exceptional operation, the remaining expected service life of the machine is halved, for example, if the winding temperature of the motor is 10 ° K above the limit of normal operation. As a result, the empirical values of the Arrhenius Law are applied to the insulation of electric motors.

• 1 ein Blockschaltbild einer Maschine mit Motor und Motorschutzeinrichtung gemäß eine Ausführungsbeispiel der Erfindung und
• 2 ein Zustandsdiagramm des erfindungsgemäßen Verfahrens.

Further refinements of the invention and advantages are explained in more detail with reference to the following description and the drawing. Show the drawing

• 1 a block diagram of a machine with a motor and motor protection device according to an embodiment of the invention and
• 2 a state diagram of the inventive method.

With the in the block diagram of the 1 shown machine 1 it is for example a pump, a fan, a compressor, a hoist or a conveyor. Among other things, it has an engine 2 and an engine protection device 3 on, with the engine guard 3 the operation of the machine 1 by means of at least one first sensor 4 compliance with predetermined limit values, for example a first limit value 5 or a second limit 6 supervised. With the first sensor 4 it is, for example, a temperature sensor in a winding of the motor 2 is arranged and the winding temperature of the motor 2 continuously measures. A sensor signal generated in the process 7 is connected to the motor protection device 3 headed where it depends on the condition of the motor protection device 3 either with the first limit 5 or the second limit 6 is compared. Failure to comply with the specified limit value is recognized as an error, with countermeasures to comply with the limit values or a shutdown of the machine in the event of an error 1 or the engine 2 to be triggered. The motor protection device stands for this 3 via a relay output 3a with the engine 2 in operative connection, with an output signal 8th the motor protection device, for example the performance of the motor 2 reduced or switches it off.

The peculiarity of the motor protection device 3 consists in distinguishing between an error according to a first error type and an error according to a second error type. An error according to the first type of error is an error that can destroy the machine within less than 30 minutes 2 leads. Such a fault can be, for example, a blocked rotor in the case of a reciprocating piston compressor or an impeller blocked by a foreign body in the case of a centrifugal pump. Furthermore, the failure of two phases in the network is considered an error according to the first type of error.

A distinction is made between errors according to the second type of error, in which there is only a reduction in the remaining service life of up to 50% within 60 minutes. The error according to the second type of error can be caused, for example, by excessive friction in the mechanics of the machine (for example the pump of a compressor or a conveyor).

In principle, the monitoring for an error according to the first error type or an error according to the second error type can be carried out with one and the same sensor, that is to say for example with the first sensor 4 are carried out, for example in the case of the temperature measurement the measured temperature itself or the rise time of the temperature within which a predetermined limit value is reached is used as a criterion as to whether it is an error according to the first or second error type. For example, a very abrupt and rapid rise in temperature is an indication of a blocked rotor and thus an error according to the first type of error, while a slow but steady rise in temperature indicates an error according to the second type of error. The correct evaluation of errors that occur, in particular the correct detection of the error type, is based on empirical values, which can sometimes be very different from machine to machine and must be set individually for each application.

In the context of the invention, however, it can also have at least one second sensor 10 a second sensor signal 14 generated and to the motor protection device 3 to get redirected. So the second sensor 10 For example, monitor the failure of one or more phases of the power grid or the outside temperature.

Furthermore, individual sensors can only monitor an error according to one of the two error types. Alternatively, it is also possible that a sensor can detect errors of both types of errors. Every fault to be monitored according to the first fault type is in the motor protection device 3 assigned its own limit. By contrast, each fault to be monitored in accordance with the second fault type is assigned a separate limit value for normal operation and a separate limit value for exceptional operation in the motor protection circuit. For example, the limit value for the winding temperature can be 140 ° C in normal operation and 160 ° C in exceptional operation.

Another special feature of the motor protection device 3 is also that it is between one operation of the machine 2 in normal operation and operation of the machine 2 is switchable in an exceptional operation. Is it the machine 1 for example, around a pump, exceptional operation could be provided in the event of a heavy rain event. Is it the machine 1 For a refrigeration system that is used to cool / freeze vegetables, exceptional operation can be provided when a new crop has to be stored and the refrigeration system has to run at full capacity. The motor protection device 3 this is done via an external signal 9 switched between normal operation and exceptional operation. This external signal 9 can, for example, by operating a switch in close proximity to the motor protection device 3 or can also be generated by a spatially distant control center, for example the municipal utility.

Another possibility is that the external signal 9 by at least one external sensor 15 is generated, which is designed to recognize whether the machine 1 is currently to be operated expediently in normal operation or in exceptional operation. For example, if the machine is a pump for pumping wastewater / rainwater, the external sensor could 15 be designed as a level sensor, the level 11 in a pumping station 12 supervised. The rise time of the level (level) can be measured with the pumps switched off and the inflow can be transmitted in this way. If the pump delivery rate is known, the rate of increase of the level could also be determined during operation. On the basis of empirical values, the rate of increase can then be used to determine whether there is currently normal rain or a heavy rain event. In the event of a heavy rain event, the pumps run at maximum capacity to prevent flooding. In the exemplary embodiment shown, however, this also means that the winding temperature, which is measured via the first sensor, increases.

This can cause the first limit 5 is exceeded, which is recognized as an error and would trigger a corresponding countermeasure to maintain the limit value or even switch off the machine. Switching off the motor or the pump would mean that the level would continue to rise and, depending on the situation, cause great damage.

Has the engine protection device 3 due to the external signal 9 but recognizes that an operation of the machine in an exceptional operation is required does not become the first limit 5 , but the second limit 6 when evaluating the first sensor signal 7 used, the second limit 6 which is used in exceptional operation, initiates a later triggering of the countermeasures to comply with the limit value or a later switch-off of the machine than in normal operation.

The consequence of this is that one deliberately accepts a faster wear of the machine or a faster reduction in the remaining service life of the machine in order to keep the machine running longer in exceptional operation in order to prevent even greater damage.

However, the procedure described above only makes sense in the case of an error according to the second error type. If an error is detected in accordance with the first type of error, after which the machine is destroyed within less than 30 minutes, the machine is switched off regardless of whether the machine is in normal operation or in exceptional operation.

The procedure described above is shown in the state diagram 2 seen. It can be seen in particular that in the case of a motor protection circuit in normal operation in the case of the second type of error, the motor is switched off when the first limit value is exceeded 5 and in exceptional operation only when the second limit value is exceeded 6 he follows. If an error occurs according to the first type of error, the motor is switched off regardless of whether the motor protection circuit is in normal operation or in exceptional operation.

The motor protection device 3 also continuously determines the remaining service life of the machine. This is done on the basis of stored empirical values and the previous operation / utilization of the machine. In particular, the time during which the machine was running in exceptional operation and thus in a range between the first and second is taken into account Limit was operated. Furthermore, there is then the possibility that the calculated remaining service life of the machine is compared with a specified minimum service life of the machine and, if the specified minimum service life is undershot, a maintenance signal 13 is issued.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102005052042 B4 [0004]

Claims (14)

Method for operating a machine (1) with at least one motor (2), a motor protection device (3) monitoring the operation of the machine (1) by means of at least one first sensor (4) for compliance with predetermined limit values (5, 6), wherein non-compliance with the specified limit values (5, 6) is recognized as an error and, in the event of an error, countermeasures to comply with the limit values (5, 6) or a shutdown of the machine (1) are triggered, characterized in that in the event of an error between a A distinction is made between errors according to a first error type and an error according to a second error type, the error according to the first error type being an error which leads to destruction of the machine (1) within less than 30 minutes and is the fault according to the second type of fault is a fault that only reduces the remaining service life of the machine (1) within 60 minutes leads to a maximum of 50%, the motor protection device (3) can be switched between operating the machine (1) in normal operation and operating the machine (1) in exceptional operation, with different limit values (5, 6) for one in normal operation and in exceptional operation Errors according to the second type of error are used, the limit values (6) in exceptional operation initiating a later triggering of the countermeasures for compliance with the limit values or a later switch-off of the machine (1) than in normal operation. Procedure according to Claim 1 , characterized in that the error according to the first type of error is an error which leads to destruction of the machine (1) within less than 1 minute. Procedure according to Claim 1 , characterized in that the error according to the second type of error is an error which within 60 minutes only leads to a reduction in the remaining service life of the machine (1) by a maximum of 20%. Procedure according to Claim 1 , characterized in that when an error occurs in accordance with the first type of error, the machine (1) is switched off regardless of whether the machine (1) is in normal operation or in exceptional operation. Procedure according to Claim 1 , characterized in that the motor protection circuit (3) is switched between normal operation and exceptional operation via at least one external signal (9). Procedure according to Claim 5 , characterized in that the external signal (9) is generated by a spatially distant control center. Procedure according to Claim 5 , characterized in that the external signal (9) is generated by actuating a switch in close proximity to the motor protection device. Procedure according to Claim 5 , characterized in that the external signal (9) is generated by at least one external sensor (15). Procedure according to Claim 5 , characterized in that the machine (1) is a pump in a pumping station for waste water and the external signal (9) is generated by a level sensor. Procedure according to Claim 1 , characterized in that the machine (1) is a refrigeration or air conditioning system and an external sensor (15) measures the electrical output or the refrigeration output of the system or the refrigeration output requested by a controller and the switchover between normal operation and exceptional operation as a function of a currently generated cooling capacity in relation to the maximum possible cooling capacity of the system or the switchover takes place from a specific cooling capacity requested by the controller. Procedure according to Claim 1 , characterized in that the machine (1) is a ventilator for the ventilation of animal houses and an external sensor (15) measures the air quality (for example the carbon dioxide or methane content) or the temperature in the animal house and the Switching between normal operation and exceptional operation depending on the outside temperature, the inside temperature and / or depending on parameters of the air quality in the house. Procedure according to Claim 1 , characterized in that the machine (1) is a pump, a fan, a compressor, a hoist or a conveyor. Procedure according to Claim 1 , characterized in that the motor protection device (3) continuously calculates the remaining service life of the machine (1). Procedure according to Claim 12 , characterized in that a maintenance signal is output when the specified minimum service life of the machine (1) is undershot.

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