JP6767414B2 - Motor cooling control system - Google Patents

Description

The present invention relates to a motor cooling control system, and more particularly to a motor cooling control system having a function of calculating a field winding temperature used for controlling the rotation speed of a fan driven by an inverter.

As a conventional motor cooling control system, there is a technique for realizing energy saving (see, for example, Patent Documents 1 and 2). The conventional motor cooling control system disclosed in Patent Document 1 calculates the stator winding temperature of the electric motor from the values of the main circuit current and the field current of the electric motor for rolling, and cools the electric motor for rolling. By properly controlling the air volume, the cooling fan is designed to save energy. Specifically, the winding temperature is calculated by managing the equivalent RMS to prevent the winding from being heated, and energy saving is achieved by controlling the air volume.

Further, the conventional field winding temperature calculation device disclosed in Patent Document 2 uses a VA method for calculating a winding resistance value by detecting a voltage value across a winding and a current value flowing through the winding. A method of applying and calculating the winding temperature is disclosed. This VA method
The field winding temperature is calculated based on the principle of field winding voltage ÷ field current = field winding resistance ∝ field winding temperature.

Japanese Unexamined Patent Publication No. 2004-180454 Japanese Unexamined Patent Publication No. 2004-180414

However, the prior art has the following problems.
Motor temperature control is one of the most important control indicators. Further, in determining the air volume of the cooling fan for realizing energy saving, it is important to control not only the stator winding temperature but also the field winding temperature. That is, the control of the stator winding temperature and the control of the field winding temperature play an important role in protecting the motor.

When the motor to be controlled is a large motor, a temperature sensor is incorporated in the stator winding. Therefore, the temperature of the stator winding can be controlled based on the detection result of this temperature sensor. However, it is structurally difficult to incorporate a temperature sensor into the field winding (rotor).

Therefore, in applications with large torque fluctuations such as rolling mills, that is, electric motors with large fluctuations in field current and field winding voltage, it is necessary to accurately obtain the field winding resistance, that is, the field winding temperature. Have difficulty. Therefore, the temperature control of the field winding for such an application is performed on the assumption that it is about the same as the temperature of the stator winding.

Here, it is conceivable to apply the VA method disclosed in Patent Document 2 as a method for calculating the field winding temperature without incorporating a temperature sensor. However, in the method of obtaining the winding temperature according to Patent Document 2, when the field winding voltage value and the field current value vary, the field winding temperature is determined by excluding the detected values outside the permissible range. It is calculated.

Here, for example, considering the temperature control of the electric motor in the rolling process of steel, there are the following problems. That is, in such a rolling process, the variation of the field winding voltage value and the field current value during rolling at a high temperature, that is, with a large load is large. Therefore, if such a detected value having a large variation is excluded, it is impossible to calculate the field winding temperature practically.

In other words, during idling with relatively small variation, that is, when the temperature is low and the load is small, the field winding temperature can be calculated with desired accuracy using the VA method. However, there is a problem that the field winding temperature cannot be calculated with a desired accuracy by using the VA method during load operation, that is, in a state where the load is large.

Therefore, when the VA method is applied, the field winding temperature can only be calculated intermittently in some states where the temperature is low during the load operation during the rolling process, and the rolling process is in progress. The field winding temperature of was not properly displayed.

The present invention has been made to solve the above-mentioned problems, and the field winding temperature is such that the drive control of the cooling fan with further improved energy saving efficiency as compared with the current system is possible. The purpose is to obtain a motor cooling control system having a function capable of calculating.

The motor cooling control system according to the present invention is a motor cooling control system that has a stator winding and a field winding and controls the cooling of a main engine motor that is continuously operated while sandwiching an idling state. A fan motor driven by an inverter, a fan driven by the fan motor that outputs cooling air to cool the stator windings and field windings of the main engine so that the temperatures are kept within the permissible range. Based on the measurement result of the field current and the field winding voltage related to the field winding, the first calculation unit that calculates the stator winding temperature based on the measurement result of the stator current related to the stator winding. , A second calculation unit that calculates the field winding temperature, and based on the stator winding temperature and the field winding temperature, to keep the temperature of the stator winding and the field winding within the permissible range. It is equipped with an arithmetic control unit that specifies the output frequency that controls the inverter so that the fan generates the required air volume, and the second arithmetic unit is measured in the idling state using the VA method in the idling state. The field winding temperature is calculated by calculating the resistance value from the field current and the field winding voltage, and the field winding temperature calculated in the idling state is used during the load operation performed after the idling state. As the initial value, the field winding temperature during the load operation is calculated by adding the correction amount stored in advance according to the load operation condition to the initial value.

According to the present invention, the field winding temperature can be calculated with high accuracy by switching the calculation method of the field winding temperature according to the load condition of the electric motor. As a result, it is possible to obtain a motor cooling control system having a function of calculating the field winding temperature so as to enable drive control of the cooling fan with further improved energy saving efficiency as compared with the current system.

It is a block diagram of the motor cooling control system in Embodiment 1 of this invention. It is a block diagram which summarized the structure which calculates the output frequency of the inverter by the energy saving calculation control unit and the rotor temperature calculation display unit in Embodiment 1 of this invention. It is explanatory drawing concerning the measurement of the field current and the field winding voltage in Embodiment 1 of this invention. It is explanatory drawing which showed the measurement result of the field current, the field winding voltage, and the calculated field winding temperature in Embodiment 1 of this invention.

Hereinafter, preferred embodiments of the motor cooling control system of the present invention will be described with reference to the drawings.
In this embodiment, a motor cooling control system for cooling a relatively large DC motor or AC motor such as rolling equipment used for iron making, paper making, etc. will be described. However, the present invention is not limited to such an application example, and can be applied to a synchronous machine that is operated with a period in which input / output torque fluctuations are small.

Embodiment 1.
FIG. 1 is a configuration diagram of a motor cooling control system according to the first embodiment of the present invention. The motor cooling control system shown in FIG. 1 includes a main motor motor 11, a fan 12, a fan motor 13, an inverter 14, an energy-saving calculation control unit 20, and a rotor temperature calculation display unit 30.

The main motor motor 11 is configured to include a stator having a stator winding and a rotor having a field winding. The fan 12 supplies cooling air to the main motor motor 11. Therefore, the main motor motor 11 receives the supply of the cooling air volume from the fan 12 and drives the stator winding and the field winding while cooling them. The fan motor 13 is a motor that gives rotational power to the fan 12. The inverter 14 is a power supply driving device for the fan motor 13.

The energy-saving calculation control unit 20 includes a stator winding temperature calculation unit 21 and an energy-saving control output unit 22. Further, the rotor temperature calculation display unit 30 includes a field winding temperature calculation unit 31, a temperature display unit 32, and a parameter storage unit 33.

The stator winding temperature calculation unit 21 obtains the stator winding current as the load current information of the main motor motor 11 and calculates the stator winding temperature. On the other hand, the field winding temperature calculation unit 31 obtains information on the field current and the field winding voltage of the main motor motor 11 and calculates the field winding temperature. Then, the energy-saving control output unit 22 is an inverter based on the stator winding temperature calculated by the stator winding temperature calculation unit 21 and the field winding temperature calculated by the field winding temperature calculation unit 31. The output frequency of 14 is calculated, and the frequency is instructed to the inverter 14.

The temperature display unit 32 displays the field winding temperature calculated by the field winding temperature calculation unit 31. The temperature display unit 32 can also display the stator winding temperature calculated by the stator winding temperature calculation unit 21, if necessary. The temperature display unit 32 may be omitted.

The parameter storage unit 33 stores in advance the relationship between the field current and the temperature correction amount ΔTf with the output frequency of the inverter 14 as a parameter.

Next, the stator winding temperature calculation unit 21 and the energy-saving control output unit 22 in the energy-saving calculation control unit 20 and the field winding temperature calculation unit 31 in the rotor temperature calculation display 30 are interlocked to finally complete the operation. The flow of determining the output frequency of the inverter 14 will be described in detail. FIG. 2 is a block diagram summarizing the configuration in which the output frequency of the inverter 14 is calculated by the energy-saving calculation control unit 20 and the rotor temperature calculation display unit 30 according to the first embodiment of the present invention.

In the block diagram shown in FIG. 2, the stator winding temperature calculation unit 21 calculates an equivalent RMS (Root Main Square) based on the stator winding current Ia, which is a load current, and the equivalent RMS that changes every moment. The stator winding temperature Ta is calculated by calculating the temperature rise value of the stator winding from the value of. A specific method for calculating the stator winding temperature Ta by the stator winding temperature calculation unit 21 is described in detail in Patent Document 1 which is a prior application by the applicant of the present application, and the description thereof will be omitted.

On the other hand, the field winding temperature calculation unit 31 acquires the field current If, the field winding voltage Vf', and idling information. Here, the "idling information" means information indicating a period during which the main motor motor 11 is not rolling, that is, a period during which the load operation is not in progress.

FIG. 3 is an explanatory diagram relating to the measurement of the field current If and the field winding voltage Vf'in the first embodiment of the present invention. The field current If is measured as a current value supplied to the field winding. Further, the field winding voltage Vf'is measured via a slip ring as a voltage value in consideration of the field winding resistance Rf, the brush resistors Rb1, Rb2, and the cable resistors Rc1 and Rc2.

FIG. 4 is an explanatory diagram showing the measurement results of the field current If, the field winding voltage Vf', and the calculated field winding temperature Tf in the first embodiment of the present invention. As shown in FIG. 4, the main motor motor 11 is repeatedly rolled, and as a result, there is a state of idling during the rolling process.

During the rolling process, the field current If and the field winding voltage Vf'contain noise and ripple components in the current and voltage, and the pulsation is very large. An insulating amplifier and a low-pass filter (LPF) are provided. The component needs to be removed (see Figure 3). Therefore, it is difficult to obtain accurate instantaneous values of the field current If and the field winding voltage Vf'. On the other hand, during idling, the field current If and the field winding voltage Vf'are stable as compared with those during the rolling process, and the desired accuracy is obtained even after passing through the insulating amplifier and the low-pass filter. You can get the instantaneous value with.

Therefore, the field winding temperature calculation unit 31 according to the first embodiment of the present embodiment uses a known VA method to obtain a field winding based on the field current If and the field winding voltage Vf'acquired during idling. The resistance value is calculated, and the field winding temperature Tf is calculated from the calculated resistance value. In other words, the present invention presents the field winding by the VA method when idling in a relatively stable region (that is, when not rolling = small change in field and stator current = small temperature change). It has a technical feature in that the temperature Tf is calculated.

The field winding temperature calculation unit 31 acquires, as an external signal, a signal indicating that the rolling process is completed from the system side that performs the rolling process as a "signal indicating that the rolling process is not performed". Can be done. Further, instead of receiving the external signal, the field winding temperature calculation unit 31 maintains a stable state in which the stator winding current Ia and the field current If are within the permissible range for a predetermined time. It can also be determined that the vehicle is idling.

Returning to the description of FIG. 2, the energy-saving control output unit 22 has the stator winding temperature Ta calculated by the stator winding temperature calculation unit 21 and the field winding calculated by the field winding temperature calculation unit 31. By acquiring the temperature Tf and performing steps 221 to 224, the output frequency of the inverter 14 for outputting the air volume that realizes the energy saving effect is calculated.

Specifically, in step 221 the energy-saving control output unit 22 has the stator winding temperature Ta calculated by the stator winding temperature calculation unit 21 and the field calculated by the field winding temperature calculation unit 31. Compare with winding temperature Tf. Then, when the field winding temperature Tf is equal to or higher than the stator winding temperature Ta, the energy-saving control output unit 22 proceeds to the process of step 222, and the field winding temperature Tf is less than the stator winding temperature Ta. In that case, the process proceeds to step 223. This is to always select the one with the higher temperature to determine the appropriate air volume.

It is the maximum temperature applied to the insulation that greatly affects the life of the main motor motor 11. Therefore, the energy-saving control output unit 22 calculates the output frequency of the inverter 14 based on the higher winding temperature by executing the determination process of the step 221.

When the process proceeds to step 222, the energy-saving control output unit 22 uses the field winding temperature Tf as the temperature of the main motor motor 11 and calculates the output frequency of the inverter 14. On the other hand, when the process proceeds to step 223, the energy-saving control output unit 22 uses the stator winding temperature Ta as the temperature of the main motor motor 11 and calculates the output frequency of the inverter 14. Finally, in step 224, the energy-saving control output unit 22 executes an output process for instructing the output frequency f to the inverter 14.

The energy-saving calculation control unit 20 can control the output frequency of the inverter 14 so that the necessary and sufficient air volume is obtained if the temperature rise allowable value is set in advance. As a result, the motor cooling control system according to the first embodiment can realize energy-saving control in which the amount of electric power is suppressed by realizing the necessary and sufficient air volume every moment in response to the changing load.

Here, in order to obtain the output frequency of the inverter 14, it is necessary to accurately calculate the temperature rise of the stator winding and the field winding. However, the temperature rise is greatly affected by the history of past temperature rises, and even if the current load is the same, the current temperature rise differs depending on whether the previous temperature rise is high or low. Therefore, it is necessary to take into account the influence of the history of such temperature rise.

Therefore, the stator winding temperature calculation unit 21 and the field winding temperature calculation unit 31 according to the first embodiment use the calculated value of the equivalent RMS described in Patent Document 1 to increase the temperature in the past. The temperature rise is calculated in consideration of the history, and the output frequency of the inverter 14 is calculated based on the calculation result.

Further, the energy-saving control output unit 22 according to the first embodiment calculates the output frequency of the inverter 14 by using the higher winding temperature of the field winding temperature Tf and the stator winding temperature Ta. As a result, more appropriate air volume control can be realized as compared with the case where the field winding temperature Tf is not taken into consideration. As a result, it is possible to obtain a motor cooling control system having a function of calculating the field winding current temperature so as to enable drive control of the cooling fan with further improved energy saving efficiency in consideration of the life of the electric motor. ..

According to the above-mentioned method, the calculated value of the field winding temperature Tf can be obtained during idling. However, as shown in FIG. 4, the rolling process corresponding to the load operation is repeatedly executed with the idling state in between. Therefore, it is conceivable that the field winding temperature will be higher than the value calculated in the previous idling period due to the rolling process executed after a certain idling period.

In such a case, in order to connect the idling state and the idling state, the field winding temperature calculated during idling is used as the initial value, and the correction amount ΔTf is sequentially set to the initial value according to the operating condition of the rolling process. It is conceivable to calculate the field winding temperature Tf during the rolling process by adding to.

As a method of correcting the field winding temperature during such a rolling process, the following method can be considered. As the first method, the field winding temperature calculation unit 31 calculates Ifrmseq as the root mean square value (RMS) of the field current If, which has a large fluctuation during the rolling process, and calculates the field. It is conceivable to calculate the magnetic winding temperature Tf. In addition, this first method can apply the technique detailed in Patent Document 1 which is the prior application by the applicant of the present application, and the description thereof will be omitted.

の関係があり、熱時定数は、熱伝達率、熱容量、および冷却風と接する部分の表面積により決まる値である。 Further, as a second method, the relationship between the field current and the temperature correction amount ΔTf when the output frequency of the inverter 14 is set to a certain fixed value is collected in advance with the output frequency as a parameter, and the parameter storage unit is used. It is conceivable to store it in 33 as a table.
That is, according to the technique detailed in Patent Document 1, ΔTf is obtained from Ifrmseq, and Ifrmseq is obtained as a function of If and the thermal time constant.

The thermal time constant is a value determined by the heat transfer coefficient, the heat capacity, and the surface area of the part in contact with the cooling air.

Here, the heat capacity and surface area of the object to be cooled are constant, but the heat transfer coefficient changes depending on the amount of cooling air. That is, Ifrmseq is a function of If and the cooling air volume. Therefore, ΔTf can be stored in advance in the storage unit as a numerical table with If and the cooling air volume as parameters. As described above, since the field current fluctuates greatly, the reliability of the cooling system can be improved by obtaining ΔTf using the maximum value of Ifrmseq during the rolling process.

In this case, the field winding temperature calculation unit 31 sets the correction amount ΔTf corresponding to the output frequency of the inverter 14 during the rolling process and the field current Ifrmseq calculated as the root mean square value (RMS) during the rolling process. , Extract from the table in the parameter storage unit 33.

Further, the field winding temperature calculation unit 31 adds a correction amount ΔTf to the field winding temperature calculated during idling immediately before the rolling process, so that the field winding temperature Tf during the rolling process is added. Is calculated.

As described above, according to the first embodiment, during idling, the field of the main motor is highly accurate by using the VA method based on the field current and the field winding voltage that can be measured with high accuracy. The winding temperature is calculated, and during load operation, the field current equivalent RMS is used to correct between idling and the field winding temperature of the main motor can be calculated with high accuracy. .. As a result, regarding the energy saving system of the main engine cooling fan, which is the current technology, the energy saving efficiency can be further improved by realizing the online control of the field winding temperature in consideration of the life of the electric motor.

In particular, during idling, the measured value with relatively little fluctuation can be used without using the processed value based on the root mean square value, and the energy saving control of the cooling fan can be realized with high accuracy. Further, the drive frequency of the cooling fan can be controlled in consideration of the field winding temperature during both idling and load operation. Therefore, it is possible to control the air volume that can realize a more excellent energy saving effect as compared with the case where only the stator winding temperature is considered.

In other words, the present invention has a configuration in which the stator winding temperature and the field winding temperature can be compared and a higher temperature can be selected to specify the cooling air volume. As a result, it is possible to realize air volume control that saves energy for the entire system while keeping all windings within the set allowable temperature rise value in response to the load that changes over time, resulting in accurate energy saving efficiency. Can be achieved.

Furthermore, during load operation where the field winding temperature cannot be measured with the desired accuracy by the VA method, the field winding temperature can be adjusted with high accuracy by correcting the gap between idling using the field current equivalent RMS. Calculations can be made. In addition, in the input section of the field winding, by adopting a low-pass filter of about 10 Hz as an example in order to remove noise, it is possible to further improve the calculation accuracy of the field winding temperature.

11 Main motor, 12 Fan, 13 Fan motor, 14 Inverter, 20 Energy saving calculation control unit, 21 Stator winding temperature calculation unit (1st calculation unit), 22 Energy saving control output unit (Calculation control unit), 30 Rotor Temperature calculation display unit, 31 field winding temperature calculation unit (second calculation unit), 32 temperature display unit, 33 parameter storage unit.

Claims (5)

A motor cooling control system that has a stator winding and a field winding and controls the cooling of the main motor that is continuously operated while sandwiching the idling state.
With an inverter
The fan motor driven by the inverter and
A fan driven by the fan motor to output cooling air to cool the stator winding and the field winding of the main motor so that the temperature is maintained within an allowable range.
A first calculation unit that calculates the stator winding temperature based on the measurement result of the stator current related to the stator winding, and
A second calculation unit that calculates the field winding temperature based on the measurement results of the field current and the field winding voltage related to the field winding, and
Based on the stator winding temperature and the field winding temperature, the fan generates an air volume required for the stator winding and the field winding to maintain a temperature within the allowable range. An arithmetic control unit that specifies the output frequency that controls the inverter,
With
The second arithmetic unit is
In the idling state, the field winding temperature is calculated by calculating the resistance value from the field current and the field winding voltage measured in the idling state by using the VA method.
During the load operation performed after the idling state, the field winding temperature calculated in the idling state is used as the initial value, and the correction amount stored in advance according to the load operation condition is added to the initial value. A motor cooling control system that calculates the field winding temperature during the load operation. The second calculation unit receives a signal indicating that the idling state has been reached as an external signal, or determines that the time-series data of the measurement result of the field current is within the permissible fluctuation amount. The motor cooling control system according to claim 1, wherein the idling state is determined. The second calculation unit calculates the field winding temperature using the current squared square root mean value calculated from the time-series data of the measurement result of the field current during the load operation. 2. The motor cooling control system according to 2. During the load operation, the second calculation unit uses at least one of the cooling air volume and the output frequency, and the current squared square root mean value calculated from the time series data of the measurement result of the field current. The motor cooling control system according to claim 1 or 2, wherein the field winding temperature is calculated. The arithmetic control unit
Comparing the stator winding temperature with the field winding temperature,
When the field winding temperature is higher than the stator winding temperature, the output frequency is specified based on the field winding temperature.
The motor cooling control system according to any one of claims 1 to 3, wherein when the field winding temperature is equal to or lower than the stator winding temperature, the output frequency is specified based on the stator winding temperature. ..

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