JP7482088B2 - Motor winding deterioration status inspection system - Google Patents

Description

An embodiment of the present invention relates to a system for investigating the deterioration state of electric motor windings.

Industrial motors for steel mills and the like can experience large load fluctuations and severe operating temperature conditions. The windings of the motor are insulated before use, and motors with such windings are prone to sudden failures due to deterioration of the insulating material caused by temperature, and deterioration associated with mechanical stress on the coil ends caused by expansion and contraction due to heat cycles.

To prevent breakdowns due to insulation deterioration, when considering motor specifications, the load pattern during the rolling cycle is assumed, and a method for estimating and calculating the temperature fluctuation of the windings is used to estimate the change in temperature, resulting in a design that allows for sufficient margin for deterioration. For example, JEC-2140:2016 explains a method for calculating the temperature fluctuation of windings from the current flowing through the windings for variable-speed AC motors used in rolling mills.

On the other hand, sudden failures of industrial electric motors, such as those used in steel mills, can have a significant impact on production schedules. In addition, while it is possible to take into account load fluctuation patterns when estimating winding temperatures, the load pattern assumed when considering specifications may not continue, and the operating method itself may change. In other words, it is difficult to accurately estimate the deterioration state of a motor at the specification consideration stage. Therefore, in order to prevent sudden motor failures, it is necessary to inspect the deterioration state of the motor on a regular or irregular basis.

Japanese Patent Application Laid-Open No. 3-235069

When inspecting a motor, the motor is disassembled and the deterioration of the internal windings is checked visually and by other inspection methods. For this reason, inspections cannot be carried out during operation, and carrying out an inspection requires a great deal of time and cost.

The control of electric motors in a plant is performed under a control system that uses a programmable logic controller (PLC) or the like. In such a control system, for example, the PLC can collect various control data, including motor speed data, at the control period of the control system. The control data may include temperature data of the windings, and even if it does not include temperature data, it is possible to collect data for estimating the temperature of the windings.

However, sudden failures due to insulation deterioration usually only become evident after the motor has been in use for a long period of time, such as 10 years or more, and it is therefore not realistic to accumulate control data for such a long period of time.

The embodiment of the present invention has been made to solve the above problems, and aims to provide a motor winding deterioration state investigation system that makes it possible to collect data showing the deterioration state of a motor winding over a long period of time.

An embodiment of the present invention includes a controller that generates and collects control data including a speed command for an electric motor and data representing the operating state of the electric motor at a predetermined control period, and a drive device that drives the electric motor based on the speed command. The controller sequentially collects data on the winding temperature of the electric motor from the drive device for each control period, and calculates a deterioration score representing the degree of insulation deterioration of the electric motor based on the winding temperature data and the results of an accelerated test for the electric motor each time the winding temperature data is collected, and includes a calculation means that calculates a first accumulated value by integrating the deterioration score for each predetermined first period including a plurality of the control periods, and sequentially associates the first accumulated value with first identification data that identifies each time series of the first period, and a first storage means that stores the first identification data and the first accumulated value. After calculating the first accumulated value, the controller discards the data of the deterioration score.

In this embodiment, a motor winding deterioration status investigation system is realized that enables the collection of data representing the deterioration status of a motor winding over a long period of time.

1 is a schematic block diagram illustrating a motor winding deterioration state investigation system according to an embodiment; 1 is a schematic block diagram for explaining the operation of a motor winding deterioration state investigation system according to an embodiment; 5 is a schematic graph illustrating an example of an operation of the motor winding deterioration state investigation system according to the embodiment. 4A to 4D are examples of graphs for explaining the operation of the motor winding deterioration state investigation system according to the embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing.
In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed description thereof will be omitted as appropriate.

FIG. 1 is a schematic block diagram illustrating a motor winding deterioration state investigation system according to an embodiment.
As shown in Fig. 1, motor winding deterioration state investigation system 100 is connected to motor 30. Motor 30 is provided with a temperature sensor near its internal windings, and motor winding deterioration state investigation system 100 collects temperature data of the windings of motor 30. Motor winding deterioration state investigation system 100 calculates a deterioration score representing the state of insulation deterioration of the windings based on the temperature data of the windings of motor 30, calculates an integrated value of the calculated deterioration scores, and stores the integrated value.

The motor winding deterioration state investigation system 100 is communicatively connected to the host computer 50 via a communication network 102. The motor winding deterioration state investigation system 100 transmits data on the accumulated value of the deterioration score to the host computer 50, for example, based on a request from the host computer 50. The host computer 50 determines the deterioration status of the windings of the motor 30, for example, based on the acquired data on the accumulated value of the deterioration score.

The deterioration score is a function of the winding temperature of a motor that is determined for each series that has the same structure as the motor, and the formula for calculating the deterioration score outputs a higher value for the deterioration score as the winding temperature increases. The formula for calculating the deterioration score is determined in accordance with the Arrhenius equation, which is derived from accelerated testing performed for each series of motors. In other words, in the formula for calculating the deterioration score, the degree of insulation deterioration progresses exponentially with temperature, and for example, the insulation performance of the windings of a motor used at a temperature 100°C higher than the reference temperature is considered to deteriorate 10 times faster than at the reference temperature.

The configuration of the motor winding deterioration state investigation system 100 will be described.
The motor winding deterioration state investigation system 100 includes a controller 10 and a drive device 20. The controller 10 includes a calculation unit (calculation means) 12 and a storage unit (first storage means) 14. The controller 10 is, for example, a programmable logic controller. The controller 10 is connected to the drive device 20 via a communication network 40. The drive device 20 is connected to an electric motor 30.

The controller 10 generates a speed command for driving the electric motor 30 based on a preset program and set values, and supplies it to the drive unit 20 via the communication network 40. The drive unit 20 drives the electric motor 30 based on the received speed command. The drive unit 20 transmits data representing the actual speed of the electric motor 30 to the controller 10, and the controller 10 generates a new speed command based on the speed data received from the electric motor, etc.

The controller 10 collects data on the winding temperature of the electric motor 30 via the drive device 20. The controller 10 calculates a degradation score based on the winding temperature data. The winding temperature data is collected sequentially by the controller 10 in a control cycle in which data on the speed and output current of the electric motor 30, as well as various control data required by the controller 10 to control the electric motor 30, are generated and collected. The control cycle for these control data is a fixed cycle, for example, of several ms to several tens of ms.

The controller 10 calculates a deterioration score for each collected winding temperature using the calculation unit 12. The controller 10 accumulates the deterioration scores for each preset period, and stores the accumulated deterioration scores in chronological order in the memory unit 14. The accumulation period for the deterioration scores can be set to any appropriate period, and can be, for example, on a daily basis. The accumulation period is not limited to a single period, and can be multiple stages. For example, the accumulated value for each day can be stored, the accumulated value for each day can be accumulated for one week, and the accumulated value for each week can be accumulated for one month, etc.

The controller 10 discards the winding temperature data collected in the control cycle and the degradation score calculated using the winding temperature after calculating the integrated value of the degradation score. This makes it possible to avoid occupying the PLC memory with the huge amount of winding temperature data that may be collected in the memory unit 14 of the controller 10.

The drive device 20 can include a drive circuit 22 that drives the electric motor 30, as well as a memory unit (second memory means) 24. The controller 10 transmits the accumulated value of the deterioration score to the drive device 20 via the communication network 40, and the drive device 20 can store the received accumulated value of the deterioration score in the memory unit 24. Storing the accumulated value of the deterioration score in the memory unit 24 of the drive device 20 can be used as a backup of the data held by the controller 10.

The data stored in the memory unit 24 of the drive device 20 may have an accumulation period set according to the storage capacity of the memory unit 24. For example, when the accumulated values of the deterioration scores for each day and week are stored in the memory unit 14 of the controller 10, the memory unit 24 of the drive device 20 may be configured to store only the accumulated value of the deterioration score for each week (second accumulated value). The storage capacity of the memory unit 24 of the drive device 20 is often not sufficient compared to that of the controller 10, but even in such cases, it becomes possible to store more compressed data of the accumulated value of the deterioration score.

In this way, the motor winding deterioration state investigation system 100 of the embodiment accumulates and stores the deterioration scores for the winding temperature of the motor 30 collected during the control cycle for a specified period, and discards the data for each control cycle, so that the accumulated values of the deterioration scores over a long period of time can be stored with a small storage capacity.

The operation of the motor winding deterioration state investigation system 100 will be described.
FIG. 2 is a schematic block diagram for explaining the operation of the motor winding deterioration state investigation system of the embodiment.
2, in the motor winding deterioration state investigation system 100 of the embodiment, the controller 10 acquires data on the winding temperature of the motor 30 via the drive device 20. If it is not possible to provide a temperature sensor capable of measuring the winding temperature of the motor, the controller 10 may collect data on the current value that drives the motor 30 from the drive device 20 and calculate the winding temperature based on the collected current value. A well-known formula may be used as the formula for calculating the winding temperature from the winding current.

The controller 10 is preset with an arithmetic formula for inputting winding temperature data and calculating a deterioration score. The controller 10 uses the preset arithmetic formula via the calculation unit 12 to calculate a deterioration score each time winding temperature data is acquired, and stores the calculated deterioration score in the memory unit 14.

When the deterioration score data is accumulated for a predetermined period, the controller 10 calculates the accumulated value of the deterioration score for the predetermined period, and stores the calculation results in the memory unit 14 in sequential association with the data (first identification data) representing that period. For example, if the accumulation period is set to one day, the accumulated value of the deterioration score may be calculated at the end of operation for one day, or the accumulated value may be calculated for each unit time set in advance, regardless of whether operation has ended or not. If the accumulated value of the deterioration score is stored for a period of multiple stages, when the accumulation for the first stage period reaches the second stage period, the accumulated value is calculated, and the accumulated value is sequentially associated with the data (second identification data) representing the second stage period and stored in the memory unit 14.

Based on a request from the host computer 50, the controller 10 retrieves from the memory unit 14 the accumulated value of the deterioration score associated with the data representing the period and transmits it to the host computer 50.

The host computer 50 performs a deterioration judgment of the electric motor 30 based on the accumulated value of the received deterioration score.

The controller 10 transmits the accumulated value of the degradation score stored in the memory unit 14 to the drive device 20 and stores the data in the memory unit 24.

FIG. 3 is a schematic graph showing an example of the operation of the motor winding deterioration state investigation system according to the embodiment.
3 shows a graph related to the derivation of an arithmetic expression for calculating the deterioration score. This graph is for deriving the Arrhenius equation. The horizontal axis is the winding temperature T [° C.] of the motor 30, and the vertical axis is the life t. The life t has a dimension of time. As shown in FIG. 3, this graph is lnt=(ΔE/R)·(1/T)+A, and is derived by performing a predetermined accelerated test such as a high-temperature operation test on the target motor.

The graph in Figure 3 also shows the relationship between the lifespan t and the deterioration score according to the Arrhenius equation, with the deterioration score S on the vertical axis. The deterioration score S is formulated by taking the lifespan t at the design temperature value Tnom of the motor 30 as 1 and the lifespan at the maximum temperature Tmax of the motor 30 as 10 in the derived Arrhenius equation.

To explain using the example in Figure 3, the lifespan when the design value Tnom of the ambient temperature of the motor 30 is 40°C is set to a degradation score of 1. The lifespan when the maximum temperature Tmax of the motor 30 is 155°C is set to a degradation score of 10. Then, a degradation score equation is derived in which a constant corresponding to the constant A in the Arrhenius equation is determined, making it possible to find the degradation score Sx at any temperature Tx between Tnom and Tmax. Note that in this example, the winding temperature is assumed to be approximately equal to the ambient temperature.

The standard degradation score value is not limited to 1, but can be any appropriate value.

4A to 4D are examples of graphs for explaining the operation of the motor winding deterioration state investigation system according to the embodiment.
4A, the winding temperature Tw of the electric motor 30 varies over time. The controller 10 collects data on the winding temperature Tw at each control cycle. Therefore, although not shown, the collected data on the winding temperature Tw is discrete data for each control cycle.

The controller 10 calculates a degradation score each time data on the winding temperature Tw is collected. When the calculated degradation score S data is arranged in chronological order, it becomes as shown in FIG. 4(b).

In this example, the data of the deterioration score S calculated for each control cycle is accumulated for each operation day. The accumulated deterioration score is associated with the operation day and stored in the memory unit 14. The data of the deterioration score S calculated for each control cycle is discarded.

The accumulated value of the deterioration score associated with the operation date is read out as appropriate in response to a request from the host computer, and for example, as shown in Figures 4(c) and 4(d), the host computer 50 calculates the accumulated value of the deterioration score up to a specified date and compares the calculated accumulated value of the deterioration score with a specified threshold value to use it to make a deterioration judgment.

The effects of the motor winding deterioration state investigation system 100 according to the embodiment will be described.
In the electric motor winding deterioration state investigation system 100 of the embodiment, an arithmetic expression for calculating a deterioration score representing the degree of deterioration with respect to the winding temperature according to the electric motor is set in advance in the controller 10. The controller 10 collects data on the winding temperature of the electric motor 30 in the control period of the electric motor 30, calculates a deterioration score for the winding temperature each time data is collected, calculates an integrated value of the deterioration score in a predetermined integration period, and stores the integrated value in the storage unit 14. Therefore, a large amount of collected winding temperature data can be compressed into an integrated value of the deterioration score and stored in the storage unit 14, so that data representing the deterioration state of the electric motor 30 can be stored over a long period of time with a small storage capacity.

For example, if the controller 10 collects control data every 10 ms and the daily operating time is 8 hours, the number of collected winding temperature data points will be 8 [h] x 3600 [s]/10 [ms] ≒ 3M [items]. Therefore, by accumulating the degradation score each day and keeping only the accumulated value, the data will be compressed to about 1/3 million.

In the motor winding deterioration state investigation system 100 of the embodiment, the accumulated value of the deterioration score can also be stored in the memory unit 24 of the drive device 20. Since the memory unit 24 of the drive device 20 can be used as a backup, data can be managed more safely. In addition, by suppressing the amount of data stored in the memory unit 24 of the drive device 20, there is also the advantage that data can be easily moved and inherited when, for example, the drive device is replaced with a different model.

The embodiment described above makes it possible to realize a motor winding deterioration state investigation system that enables the collection of data representing the deterioration status of a motor winding.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are included within the scope and gist of the invention, as well as within the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments can be implemented in combination with each other.

10 Controller, 20 Drive device, 30 Motor, 40, 102 Communication network, 50 Host computer, 100 Motor winding deterioration status investigation system

Claims (3)

A controller that generates and collects control data including a speed command for an electric motor and data representing an operating state of the electric motor at a predetermined control period;
a drive device that drives the electric motor based on the speed command;
Equipped with
The controller:
a calculation means for sequentially collecting data on a winding temperature of the motor from the drive device for each of the control periods, calculating a deterioration score representing a degree of insulation deterioration of the motor based on the winding temperature data and a result of an accelerated test on the motor each time the winding temperature data is collected, integrating the deterioration score for each predetermined first period including a plurality of the control periods to calculate a first integrated value, and sequentially associating the first integrated value with first identification data that identifies each time series of the first period;
a first storage means for storing the first identification data and the first integrated value;
Including,
The motor winding deterioration state investigation system, wherein the controller discards the deterioration score data after calculating the first integrated value. the calculation means calculates a second integrated value by integrating the first integrated value for each predetermined second period that includes a plurality of the first periods , and sequentially associates the second integrated value with second identification data that identifies each time series of the second periods;
2. The motor winding deterioration state investigation system according to claim 1, wherein said first storage means stores said second identification data and said second integrated value.
The motor winding deterioration state inspection system according to claim 2, wherein the drive device includes a second storage means for receiving the second identification data and the second integrated value from the controller and storing the received second identification data and the second integrated value.

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