JP2012137386A - Motor-preventive maintenance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor-preventive maintenance device enabling an objective determination of an abnormality of a motor independently of a worker's skill and ability, thereby contributing to preventing the motor from suddenly failing.SOLUTION: A motor-preventive maintenance device performs: obtaining an amount of operation (a load factor) of a motor from a motor drive device and a state amount of the motor (a coil temperature-rise value) that has correlation with the obtained amount of operation, from a sensor installed in the motor; collating a correlation evaluation model with evaluation-use data representing a relationship between a specific state amount and the amount of operation obtained during the operation of the motor to thereby determine a degree of coincidence between the evaluation-use data and correlation evaluation model; and monitoring an abnormality of the motor on the basis of the aforementioned degree of coincidence.

Description

  The present invention relates to a preventive maintenance apparatus for an electric motor, and more particularly to a preventive maintenance apparatus suitable for use in predictive diagnosis of a large electric motor such as an electric motor used in a steel plant rolling plant.

  One of the equipment that makes up the rolling mill of an ironworks is an electric motor. The electric motor is an important element in the rolling plant, and its failure affects the entire rolling plant. For this reason, in the operation of a rolling plant, it is necessary to prevent failure of the electric motor by monitoring whether the electric motor is abnormal. In other words, preventive maintenance of the electric motor is required.

  In conventional preventive maintenance of an electric motor, for example, as disclosed in JP-A-60-66647, the temperature and vibration of the electric motor are measured and the measured values are monitored. Specifically, as shown in FIGS. 7 and 8, the measurement values to be monitored such as vibration and temperature are read on the time axis, and it is monitored whether or not the measurement values exceed the threshold value. Then, as shown in FIG. 7, while the measured value of the monitoring target does not exceed the threshold, it is determined that the electric motor is kept normal, and the measured value of the monitoring target exceeds the threshold as shown in FIG. 8. When the point was detected, an alarm was given that the motor was abnormal. In addition, for each abnormal point where the measured value of the monitored object exceeds the threshold value, a light failure alarm and a serious failure alarm are classified according to the magnitude of the abnormality.

JP 60-66647 A

  However, in the conventional method, when an abnormality is detected in an electric motor and an alarm is issued, whether or not to perform maintenance of the electric motor is determined by humans, that is, on-site Was entrusted to the workers. For this reason, the judgment differs depending on the ability of the worker, and as a result of erroneous judgment, a serious failure may occur. As described above, the failure of the electric motor affects the entire plant, and if it is a serious failure, the operation of the plant may be stopped. In particular, when a sudden failure occurs in a remote plant, it takes time to repair and repair, and a lot of resources are used.

  The present invention has been made in view of the problems as described above, and can determine an abnormality of the motor objectively without being influenced by the skill level and ability of the operator, and consequently, a sudden failure of the motor. It is an object of the present invention to provide a preventive maintenance device for an electric motor that can prevent the occurrence of the problem.

  In order to achieve the above object, the preventive maintenance device for an electric motor according to the present invention acquires the operation amount of the motor from the electric motor drive device, and the state quantity (specific state quantity) of the motor correlated with the acquired operation quantity. Is acquired by a sensor installed in the electric motor. Then, the data (evaluation data) indicating the relationship between the manipulated variable and the specific state quantity acquired during operation of the motor is collated with the correlation evaluation model, and the degree of coincidence between the evaluation data and the correlation evaluation model is determined. The correlation evaluation model is obtained by modeling the correlation between the operation amount and the specific state amount when the motor is normal, and the prepared model is stored in the preventive maintenance device. The preventive maintenance device for an electric motor according to the present invention monitors the abnormality of the electric motor based on the degree of coincidence between the evaluation data and the correlation evaluation model.

  As a specific method for monitoring the abnormality of the electric motor, it is preferable to detect that the degree of coincidence between the evaluation data and the correlation evaluation model is lower than a predetermined abnormality determination value as an abnormality of the electric motor. In addition, counting the number of times the degree of coincidence falls below a predetermined abnormality determination value within a certain period is also a preferable abnormality monitoring method. In addition, counting the number of times the degree of coincidence falls below a predetermined abnormality determination value (abnormal number) for each predetermined period and recording the change over time in the abnormal number is also one of the preferable abnormality monitoring methods.

  In the present invention, when there is a correlation between the operation amount of the motor and the specific state quantity, a mismatch occurs between the normal state and the abnormal state of the motor, and the degree of coincidence decreases as the degree of abnormality increases. The focus is on doing. In the present invention, as described above, the operation amount and the specific state amount acquired at a certain timing are based on the correlation evaluation model that models the correlation between the operation amount and the specific state amount when the motor is normal. It is determined whether the relationship is a normal motor relationship. According to this, compared with the method of simply comparing the measured values of vibration and temperature with the threshold values as in the conventional method, the abnormality of the motor can be objectively and accurately determined regardless of the skill level and ability of the worker. Can be judged. Therefore, according to the present invention, it is possible to know in advance the signs of the failure of the motor and appropriately perform maintenance according to the symptom, and the sudden failure of the motor that affects the operation of the entire plant Can be prevented in advance.

It is a block diagram which shows the structure of the system with which the preventive maintenance apparatus of the electric motor of Embodiment 1-3 of this invention is applied. It is a graph which shows the correlation evaluation model by Embodiment 1 of this invention. It is a graph which shows the method of abnormality monitoring by Embodiment 1 of this invention. It is a graph which shows the method of abnormality monitoring by Embodiment 2 of this invention. It is a graph which shows the method of abnormality monitoring by Embodiment 3 of this invention. It is a figure which shows aged deterioration of the winding coil insulation layer. It is a graph which shows the abnormality monitoring method of the motor performed by the preventive maintenance of the conventional motor. It is a graph which shows the abnormality monitoring method of the motor performed by the preventive maintenance of the conventional motor.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.

  FIG. 1 is a block diagram showing a configuration of a system to which the preventive maintenance device for an electric motor according to the present embodiment is applied. In this system, the electric motor 1 and the electric motor driving device 2 are arranged at remote locations, and are connected to the network 5 via the remote IO boards 3 and 4, respectively. The operation signal output by the electric motor drive device 2 is output to the network 5 via the remote IO board 4 and is input from the network 5 to the electric motor 1 via the remote IO board 3. The rotation of the electric motor 1 is controlled by an operation signal transmitted from the electric motor driving device 2. The electric motor 1 is provided with two resistance temperature detectors 6 and 7 as sensors for measuring the state quantity. One of them is a resistance temperature detector 6 for measuring the winding temperature for measuring the winding temperature of the electric motor 1. The other is a temperature measuring resistor 7 for measuring the refrigerant temperature for measuring the temperature of the refrigerant cooling the electric motor 1.

  The motor preventive maintenance device 8 of the present embodiment is connected to the network 5. The operation signal output from the electric motor drive device 2 includes load factor data that is the operation amount of the electric motor 1. The motor preventive maintenance device 8 collects and stores the load factor data of the motor 1 from the remote IO board 4 via the network 5. Further, the motor preventive maintenance device 8 collects and stores each measurement data of the resistance temperature measuring resistor 6 and the temperature measuring resistor 7 for measuring the refrigerant temperature from the remote IO board 3 via the network 5. The loading timing of the load factor data by the motor preventive maintenance device 8 and the loading timing of each measurement data are synchronized.

  The motor preventive maintenance device 8 calculates the root mean square of the load factor from the load factor data, and calculates the motor 1 from each measurement data of the resistance temperature measuring resistor 6 and the temperature measuring resistor 7 for measuring the refrigerant temperature. Calculate the rise in winding temperature. There is a correlation as described below between the root mean square of the load factor and the winding temperature rise value.

  The loss of the electric motor 1 includes iron loss, copper loss, stray load loss, mechanical loss, and the like. Among them, copper loss accounts for most of the loss. Since the winding temperature rise value is proportional to the loss of the electric motor 1, the copper loss and the winding temperature rise value are in a proportional relationship. Here, copper loss refers to the amount of heat generated by the winding coil. If the heat generation amount of the winding coil is Q, the heat generation amount Q is expressed by the following equation 1. In Equation 1, i is the winding current, R is the winding resistance, and t is time.

  From Equation 1, it can be seen that the winding temperature rise value is proportional to the square of the current. The relationship is shown in Equation 2. In Equation 2, ΔT is the winding temperature rise value.

  On the other hand, the load factor of the electric motor 1 can be obtained from the winding current. The relationship is shown in Equation 3. In Equation 3, L is a load factor.

When the root mean square of the load factor is RMS, the root mean square RMS is expressed by the following Equation 4. In Expression 4, L _j is a load factor, T is a time for calculating RMS, t _j is a sampling time within a time for calculating RMS, and j = 1, 2,... N.

  From the equations 4 and 3, the following equation 5 is obtained.

  Furthermore, the relationship of the following equation 6 is obtained from the equations 2 and 5.

From Equation 6, it can be seen that there is a proportional relationship between the winding temperature rise value ΔT and the root mean square value RMS ² of the load factor. In the present embodiment, each of the above-described data is collected during a certain period during normal operation of the electric motor 1, and a plurality of data indicating the relationship between the winding temperature rise value ΔT and the root mean square RMS of the load factor are acquired. Then, an approximate expression indicating the relationship between ΔT and RMS is determined by the least square method using the acquired data. The following expression 7 is an approximate expression. In Equation 7, κ is a known coefficient, and c is a known constant. Expression 7 is represented by a graph as shown in FIG.

  In the motor preventive maintenance apparatus 8, a linear equation shown in Expression 7 is stored as a correlation evaluation model. The motor preventive maintenance device 8 monitors the abnormality of the motor 1 using this correlation evaluation model. Specifically, during the operation of the electric motor 1, the RMS value is calculated from the load factor data in a certain time zone, and the winding temperature rises from the measured data of the resistance temperature detectors 6 and 7 in the time zone. The value ΔT is calculated. Thereby, data (evaluation data) indicating the relationship between the RMS square value and the winding temperature rise value ΔT in the time period is obtained. Then, as shown in FIG. 3, the obtained evaluation data (indicated by a point m in FIG. 3) is collated with a correlation evaluation model (indicated by a solid straight line in FIG. 3). The more the point indicating the evaluation data is away from the straight line indicating the correlation evaluation model, the lower the degree of coincidence between them.

A dotted straight line shown in FIG. 3 is an abnormality determination line for determining the degree of coincidence between the evaluation data and the correlation evaluation model. Regarding the value of RMS ^{2, when} the value of the winding temperature increase value ΔT exceeds the abnormality determination line, it can be determined that the evaluation data is abnormal data. For this reason, the motor preventive maintenance device 8 detects that the winding temperature rise value ΔT exceeds the abnormality determination line as an abnormality of the electric motor 1. The abnormality determination line can be set from experience values. For example, a line obtained by sliding the correlation evaluation model line by a predetermined value in the plus direction of the ΔT axis can be set as the abnormality determination line. Further, a line obtained by enlarging the correlation evaluation model line in the direction of the ΔT axis (for example, 1.5 times) can be set as the abnormality determination line.

  As described above, in the present embodiment, the motor 1 is acquired in an arbitrary time zone with reference to the correlation evaluation model that models the correlation between the load factor and the winding temperature rise value when the motor 1 is normal. It is determined whether or not the relationship between the load factor and the winding temperature rise value is a normal relationship. According to this, it is possible to objectively and accurately determine the abnormality of the electric motor 1 as compared with the case where one piece of data is compared with a threshold value as in the prior art.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to FIG. However, the preventive maintenance apparatus for an electric motor according to the present embodiment is applied to the system having the configuration shown in FIG. 1 as in the first embodiment.

  In the present embodiment, the motor preventive maintenance device 8 acquires the evaluation data at a constant monitoring cycle and collates with the correlation evaluation model each time. Then, the time when the evaluation data exceeds the abnormality determination line as a threshold is recorded, and the number of times the evaluation data exceeds the abnormality determination line within a certain period is counted. The recorded time and number of times are notified to the worker by sound or image.

  In the conventional method, an alarm is issued each time the temperature or vibration data to be monitored exceeds the threshold value, so the threshold value has to be set to be somewhat larger than the normal value. However, if the number of times exceeding the threshold is counted and the number of times is recorded and notified as in the present embodiment, the threshold can be set to a value close to the normal value. Therefore, in the present embodiment, a line closer to the correlation evaluation model than in the case of the first embodiment can be set as the abnormality determination line. For example, in FIG. 4, the correlation evaluation model is indicated by a solid line, the abnormality determination line in the first embodiment is indicated by a dotted line, and the abnormality determination line in the present embodiment is indicated by a one-dot chain line.

  According to the present embodiment, an abnormality determination line that is a threshold value can be set closer to a correlation evaluation model line that is a normal value, so that there is an effect that an abnormality of the electric motor 1 can be quickly seen.

Embodiment 3 FIG.
The third embodiment of the present invention will be described below with reference to FIGS. However, the preventive maintenance apparatus for an electric motor according to the present embodiment is applied to the system having the configuration shown in FIG. 1 as in the first embodiment.

  In the present embodiment, the motor preventive maintenance device 8 acquires the evaluation data at a constant monitoring cycle and collates with the correlation evaluation model each time. Then, the time when the evaluation data exceeds the abnormality determination line, which is a threshold, is recorded, and the number of times the evaluation data exceeds the abnormality determination line (abnormal number) is counted for a certain period, and the change in the number of abnormality over time Record. That is, in the present embodiment, the motor preventive maintenance device 8 monitors the increase / decrease in the number of abnormalities over a long period of time, and predicts the deterioration of the motor 1 over time.

  If the number of abnormalities increases or decreases in one direction, it can be determined that the electric motor 1 has deteriorated. For example, as shown in FIG. 5, when the number of abnormalities increases in one direction with the measurement for each fixed period, it is possible to estimate the deterioration of the motor 1 over time. In addition, as shown in FIG. 6, the insulating layer surrounding the coil of the electric motor 1 is deteriorated such as withering due to operation for many years. In order to grasp these deterioration trends, the temperature rise value obtained from the measured value of the resistance thermometers 6 and 7 is compared with the threshold value, and the increase and decrease of the points exceeding the threshold value are monitored over a long period of time. Appropriate recovery measures can be taken before such a serious failure occurs.

  According to the present embodiment, since the increase / decrease in the number of abnormalities exceeding the abnormality determination line that is the threshold value of the evaluation data is monitored over a long period of time, there is an effect that it is possible to predict the deterioration of the electric motor 1 over time.

Others.
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the load factor of the motor is used as the operation amount and the winding temperature rise value is used as the state amount. However, if there is a correlation, other combinations of the operation amount and the state amount are used. You can also.

DESCRIPTION OF SYMBOLS 1 ... Electric motor 2 ... Electric motor drive device 3, 4 ... Remote IO board 5 ... Network 6 ... Resistance temperature detector 7 for winding temperature measurement ... Resistance temperature detector 8 for refrigerant temperature measurement ... Electric motor preventive maintenance device

Claims (5)

A preventive maintenance device for an electric motor whose rotation is controlled by an operation signal input from an electric motor drive device,
An operation amount obtaining means for obtaining an operation amount of the electric motor from the electric motor driving device;
A state quantity acquisition means for acquiring a state quantity of the motor correlated with the operation quantity by a sensor installed in the motor;
Correlation evaluation model storage means for storing a correlation evaluation model that models the correlation between the operation amount and the state amount when the electric motor is normal;
A degree of coincidence determination means for collating data indicating a relationship between the manipulated variable and the state quantity acquired during operation of the electric motor with the correlation evaluation model and determining a degree of coincidence between the data and the correlation evaluation model; ,
An abnormality monitoring means for monitoring an abnormality of the electric motor based on the degree of coincidence;
A preventive maintenance device for an electric motor comprising:   2. The preventive maintenance apparatus for an electric motor according to claim 1, wherein the abnormality monitoring unit detects that the degree of coincidence is lower than a predetermined abnormality determination value as an abnormality of the electric motor.   2. The preventive maintenance apparatus for an electric motor according to claim 1, wherein the abnormality monitoring means counts the number of times that the degree of coincidence falls below a predetermined abnormality determination value within a predetermined period.   2. The preventive maintenance of an electric motor according to claim 1, wherein the abnormality monitoring unit counts the number of times that the degree of coincidence falls below a predetermined abnormality determination value every predetermined period, and records a change with time of the number of times. apparatus. The operation amount acquisition means acquires a load factor of the electric motor as the operation amount,
The state quantity acquisition means acquires the winding temperature rise value of the electric motor as the state quantity,
5. The correlation evaluation model storage unit stores a linear equation established between the winding temperature rise value and a root mean square of the load factor as the correlation evaluation model. The preventive maintenance device for an electric motor according to Item.

Images