DD210144A5 - PROCESS FOR SIMULATION PROTECTION OF ELECTRIC MOTORS - Google Patents

Abstract

The essence of the invention is that the engine to be protected is replaced with respect to its thermal behavior by its heat flow network model, that the heat capacities and the heat transfer resistance values of the heat flow network model are determined based on the known data of the engine for at least two discrete parts of the engine, and that the heat sources of the heat network model are determined by the current consumption of the motor is scanned continuously or stepwise, wherein the measured value of the loss heat flow value is determined in a known manner and identified with the heat source. Furthermore, the ambient temperature is measured continuously or stepwise, wherein by exploiting all measurement data and the known initial conditions, the equation system of the heat network model is solved and thereby the current values of the node temperatures are determined, after which they are compared with the permissible temperature values. When the permissible values are reached or exceeded, e.g. an alarm signal is triggered or the engine is switched off.

Description

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Method for simulation protection of electric motors

Field of application of the invention;

The invention relates to a method for simulation protection of electric motors.

Characteristic of the known technical solutions:

The frequent cause of destruction of electric motors can be seen in the damage to the insulation caused by negligible heat. In order to prevent the overheating of the insulation, various thermal protection units are known, which operate on different principles.

The most commonly used bimetal thermal protector essentially provides a current fuse. By means of a Heisstromes, which is proportional to the motor current, the bimetal is heated and deformed, wherein

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upon reaching the degree of deformation set during the calibration, the bimetal activates a mechanical switch-off device which disconnects the motor from ¥ eta. One advantage of this bimetallic heat protection lies in its simplicity and cheapness. "What is disadvantageous, however, is that its thermal characteristics are much steeper than the characteristics of the motors, which usually leads to an early shutdown of the engine. This property is mainly detrimental to variable load motors. The motor does not reach the dangerous temperature for the insulation at a very short overload, so that the motor could endure this overload without damage. However, the bimetal motor protection does not allow this because it causes the premature shutdown because of its too steep characteristic.

Due to the early shutdown, overdimensioning of the motors is required. "However, the oversized motors are significantly more expensive and their performance can not be sufficiently exploited to make their use uneconomical.

The detrimental properties of the motor protection devices with bimetal can be eliminated with protection solutions provided by a built-in thermocouple. »The built-in thermal sensor is usually a thermistor, in some cases a miniaturized birnetall switching element. These are used to sense the temperature at the point of use, and when the dangerous temperature is reached, they cause the motor to be shut down directly or by appropriate means. Your tail section is that the installation of the sensor in manufacturing technology terms requires an extra effort. It can not be determined with accuracy when choosing the Fühlungspunktes exactly where the hottest point lies. The temperature-

The speed of the built-in sensor and the perceived temperature vary depending on the thermal coupling that forms during installation. protective point to an unknown extent. Sin Another !! Finally, it lies in the fact that when a necessary repair of the sensor, the engine must be taken apart and possibly even rewrapped.

To avoid the disadvantages described above, it has developed the installation of sensors not requiring analog or hybrid-analog simulation engine protection devices whose electronic unit can be adjusted due to the parameters of the su protective motor such that the characteristic of the protection of the thermal Characteristic of the engine approaches to the desired extent. Sine known variant of the simulation motor protection devices is described in the HU-PS 168.490. In this solution, the simulator sinewave is a tunable quadrupole made up of electronic elements, which corresponds to the model d & e engine to be protected in the form of a hybrid-analog quadrupole.

The modular motor protection devices are currently the most advanced version of motor protection without a built-in sensor. The tunable motor protection simulator is sufficiently close to the hot-spot temperature / time function of the motor to be protected, with an input voltage proportional to the motor current consumption forms. The practical realization of the Abstmmmungswert e, however, are limited by the discrete value size of the passive Stromsehaltelemente limits, which, a compromise is required. In addition, each simulation engine guard can only serve to protect a single engine.

Object of the invention:

It is an object of the invention to provide an improved simulation protection method in which the above disadvantageous trade-off is not required and a device for protecting a plurality of motors can serve.

presentation; the essence of the invention;

The digital simulation engine protection method according to the invention enables the elimination of the two aforementioned disadvantages. The invention thus relates to a simulation heat protection method for electrical machines, in which the arrangement according to the invention is made such that the engine to be protected is replaced with respect to its thermal behavior by its heat flow-Fetzmodell, the heat capacity and the heat transfer resistance values, the heat flow are calculated Hetzmodells from the data of the protected motor by dividing the engine into discrete portions in a known manner, the heat sources, the current consumption of the motor are measured either continuously or stepwise, and from & en measured values are at predetermined time periods, e.g., "B , every 10 years, the measured values obtained are identified in a known manner. Furthermore, based on the continuously or stepwise measured ambient temperature, the equation of the heat flow hets model is solved, and the nodes _-- Te2iperaturwerte are calculated using the previously acquired Snotenptuikte Temperattirwerte- to Losging this equation as an initial coefficient. The sensed node temperatures, or some selected values thereof (always the highest value, z.3) are compared with the allowable temperature values, and if the sensed value (or one of these values) is greater than the allowed one. Value is given a command sum off the motor.

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In a modified embodiment of the method according to the invention, instead of the ambient temperature, the temperature of an outer surface point is measured, for example on the stator casing or on the housing, or the temperature of the surface is measured. In this case, for the corresponding point of the heat flow type model the calculation of the above-mentioned values is realized as a first order limit condition, the calculation being carried out in the manner already described. For the realization and implementation of the control, a digital computer, suitably a microprocessor is expediently used. This microprocessor solves the equation describing the heat flow rate model, wherein the microprocessor or microprocessors are progra mm for controlling the process, in such a way that they can simultaneously provide the protection of multiple motors. This is done so that the data of the motors to be protected are stored in memory of the microprocessor in a manner known per se, and the control of the individual motors in the control time intervals, for example every 10 seconds, is controlled so that the method is incremental , ie .jeje engine repeated, is performed, and that for each engine, the detected measured values are stored at the last control until the next control, including the measurement data for the current consumption of the individual motors, or calculated from these values "the ambient temperature of the individual motors and / or the erflächentemperatür for Oh the same values obtained in the last control are 7 / eiterhin stored" heat sources

In the last step, the microprocessor compares the detected temperature values with the allowable temperature values, and if a temperature value is higher than the calculated value, a control signal is sent to the controller to disable the motor.

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The method according to the invention has all the advantages of simulation protection. At the same time, the inventive solution to tuning is much more advantageous because there are no sinusoidalities. Perner, the new solution is more economical since a single device can be used to simultaneously protect multiple motors.

Claims (2)

-v- 248848 1 Inventory of origin:  1. A method for simulation protection of electric motors, characterized in that the motor to be protected is replaced with respect to its thermal behavior by a heat flow TTetzmodell of him, that the heat capacities and the heat transfer resistance values of the heat flow Ifetzmodells based on the known data of the engine, on any number, but at least to two discrete parts determined by him determined that the heat sources of the heat flow network model are determined such that the power consumption of the motor continuously or stepwise, eg It is scanned every 10 seconds that the loss heat flow value is determined from the measured value in a manner known per se and identified with the heat flow sources such that the ambient temperature is continuously or stepwise, e.g. every 10 seconds, it is measured that by using all measured data and the known initial conditions or "due to the last detected node temperatures. Gieichungssysten the heat flow iTetzmodells resolved? Rird and thereby the current values of the node-point temperatures are determined, whereupon these or expediently the highest values of these are compared with the allowable temperature values, and that when reaching or exceeding the permissible values / erte an alarm signal and / or a shutdown command signal for disconnecting the motor from Hetz is supplied. 2. The method according to item 1, characterized in that when approaching to an extent to the allowable temperature of the motor to be protected and / or upon reaching a predetermined extent, the temperature change issued a warning signal and / or a shutdown command is. Method according to item 1 or 2, characterized in that a digital computer, preferably a microprocessor, is used for the realization and control of the method, and that the method is carried out successively or simultaneously for several motors by the data and / or the numerical values of the Y / Härmmod- Hetzmodellelementes are stored in the memory of the computer, whereupon the process for each motor is repeatedly carried out until the detected temperature values inn ralled) of predetermined temperature values, for example between 15 ⁰ C and 85 ⁰ G, · wherein the periodically detected Temperature values to be stored until the next inspection *