JPH0731189A - Motor protector - Google Patents

Abstract

PURPOSE:To allow highly efficient driving of a motor. CONSTITUTION:When a reference current value deciding the magnitude of motor current value is set in a decision current value setting means 3, a motor current designating means 7 designates a motor current value and a motor current detecting means 2 detects the current value of a motor 1, a motor current difference operating means 4 determines the difference between the decision current value and the detected motor motor current value and a motor current difference accumulating means 5 accumulates the difference multiplied by a predetermined coefficient determined based on the absolute rated current value of the motor 1. A maximum current determining means 6 determines a maximum current limit value depending on the accumulated value from the accumulating means 5, a motor current comparing/determining means 8 determines a motor current supply value based on the maximum current limit value and the motor current designated value, and a motor drive means 9 feeds the motor 1 with a motor current based on the motor current supply value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor protection device for driving an electric motor by limiting a current flowing through the electric motor.

[0002]

2. Description of the Related Art Conventionally, as a motor protection device, for example, as disclosed in Japanese Patent Laid-Open No. 1-186468, a maximum current supplied to the motor is limited according to an average value of the motor current supplied to the motor. What you have done is known.
This is to limit the maximum current according to the magnitude of the average value of the motor current when the current continuously flows through the electric motor for a predetermined time. Specifically, the motor current is, for example, once /
It is detected periodically in a period of -100 msec, and the average value of the motor current is calculated every predetermined time of 30 sec-3 min, for example. When the calculated average value is large, for example, 60 to 80% or more of the maximum motor current instruction value supplied to the electric motor, the maximum motor current instruction value supplied to the electric motor is reduced by a predetermined value such as 5 to 10%, If the average value of the motor current calculated in the next cycle continues to be large, the control to reduce the maximum motor current instruction value by a predetermined value is repeated, and even if the motor current is continuously supplied to the motor, the motor output of the motor or control device For example, the motor current value of 50% or less of the motor maximum command current is held so that the power element in the circuit does not cause thermal destruction. On the contrary, when the average value of the calculated motor currents is small, for example, 40% or less of the maximum motor current instruction value, the maximum motor current instruction value is increased by the predetermined value,
If the average value of the motor current calculated in the next cycle is also small, the control for further increasing the maximum motor current instruction value by a predetermined value is repeated to increase and hold the first maximum motor current instruction value. Then, when the calculated average value of the motor current is medium, the control is such that the maximum motor current instruction set from the average value of the motor current in the immediately preceding cycle is maintained.

In addition to the above, the temperature of the electric motor is proportional to the product of the value obtained by squaring the motor current and the motor resistance value. Therefore, the temperature of the electric motor is estimated from the motor current value and the motor resistance value. A motor protection device is also known in which the maximum motor current instruction value is controlled according to the estimated temperature.

[0004]

The former electric motor protection device which limits the maximum motor current instruction value by the average value of the motor current in the above-mentioned conventional method, as shown in FIGS. 9 and 10, changes the maximum motor current instruction value. As the motor current is within the range to decrease the increase / decrease of the maximum motor current indication value, the maximum motor current indication value increases / decreases by a predetermined value regardless of the motor current value, and the average value of the motor current Although the motor drive time differs depending on, the speed at which the maximum motor current instruction value is decreased is uniform, and the motor cannot be driven efficiently.

Further, in the latter electric motor protection device which limits the maximum motor current instruction value by the estimated temperature of the conventional electric motor, the maximum motor current instruction value is limited according to the value obtained by squaring the motor current value. As the motor current value increases, the speed at which the maximum motor current instruction value is limited changes abruptly.Therefore, when this is used for something that performs control related to feeling, such as an electric power steering system, the maximum motor current There is an inherent problem in that the speed at which the instruction value is limited becomes too fast, and the operation feels uncomfortable.

The present invention has been made to solve the above problems, and an object thereof is to obtain an electric motor protection device for efficiently driving an electric motor.

[0007]

[Means for Solving the Problem] A first aspect described in claim 1.
According to another aspect of the present invention, there is provided an electric motor protection device, an electric motor, a motor current instructing means for instructing a motor current supplied to the electric motor, a motor current detecting means for detecting a motor current flowing in the electric motor, and a judgment current for setting a judgment current value. Value setting means, motor current deviation calculating means connected to the output side of the judgment current value setting means and output side of the motor current detecting means, and motor current deviation integrating means connected to the motor current deviation calculating means, The maximum current determination means connected to the output side of the motor current deviation integration means, the motor current comparison determination means connected to the output side of the maximum current determination means and the output side of the motor current instruction means, and the motor current comparison Motor driving means connected to the output side of the determining means and supplying a current for driving the electric motor.

According to a second aspect of the present invention, there is provided an electric motor protection device comprising: an electric motor; a motor current instruction means for instructing a motor current supplied to the electric motor; and a judgment current value setting means for setting a judgment current value. A motor current deviation calculation means connected to the output side of the judgment current value setting means and an output side of the motor current instruction means, and a motor current deviation integration means connected to the output side of the motor current deviation integration means,
The maximum current determination means connected to the output side of the motor current deviation integration means, the motor current comparison determination means connected to the output side of the maximum current determination means and the output side of the motor current instruction means, and the motor current comparison Motor driving means connected to the output side of the determining means and supplying a current for driving the electric motor.

According to a third aspect of the present invention, there is provided a motor protection device in which a judgment current value set in the judgment current value setting means is provided with hysteresis.

[0010]

In the motor protection device according to the first aspect of the present invention, the judgment current value serving as a reference for judging the magnitude of the motor current supplied to the motor is set in the judgment current value setting means, and the motor current instruction means supplies the motor. When the current value is indicated and the motor current detection means detects the motor current value flowing in the electric motor, the motor current deviation calculation means obtains the deviation between the judgment current value and the motor current detection value, and the motor current deviation integration means determines the motor current deviation. A value obtained by multiplying the deviation obtained by the calculating means by a predetermined coefficient determined based on the absolute rated current value of the electric motor is integrated, and the maximum current determining means calculates the electric current according to the integrated value obtained by the motor current deviation integrating means. The maximum current limit value to be supplied to the motor drive means, and the motor current comparison determination means determines the motor current supply value based on the maximum current limit value and the motor current instruction value. The motor current based on the motor current supply value supplied to the electric motor.

In the motor protection device according to the second aspect of the present invention, the judgment current value serving as a reference for judging the magnitude of the motor current value supplied to the electric motor is set in the judgment current value setting means, and the motor current instruction means supplies the motor. If you specify the current value,
The motor current deviation calculation means obtains the deviation between the judgment current value and the motor current instruction value, and the motor current deviation integration means determines the deviation obtained by the motor current deviation calculation means based on the absolute rated current value of the electric motor. The value multiplied by the coefficient is integrated, the maximum current determination means determines the maximum current limit value to be supplied to the electric motor according to the integrated value obtained by the motor current deviation integration means, and the motor current comparison determination means determines the maximum current limit value. And the motor current instruction value, determine the motor current supply value,
The motor drive means supplies a motor current based on the motor current supply value to the electric motor.

In the motor protection device according to the third aspect of the present invention, when the motor current deviation calculation means obtains the deviation between the judgment current value and the motor current instruction value, the motor current deviation calculation means uses the first judgment current value while the change in the motor current is increasing. However, the second determination value is used while the change in the motor current is decreasing.

[0013]

Embodiments of the present invention will be described with reference to FIGS.

Example 1. (Corresponding to Claim 1) FIG. 1 is a configuration diagram showing an electric motor protection device according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes an electric motor to be controlled, which is, for example, a current servomotor or the like which constitutes a drive source of an electric power steering device of an automobile. Reference numeral 2 denotes a motor current detecting means, which detects a motor current value Im flowing through the electric motor 1. Reference numeral 3 is a judgment current value setting means, which sets a judgment current value Ih determined by the absolute rated value of the electric motor 1. Reference numeral 4 denotes a motor current deviation calculation means, which receives a motor current detection value Im as an output of the motor current detection means 2 and a determination current value Ih as an output of the determination current value setting means 3 and receives the motor current detection value. The deviation between Im and the judgment current value Ih is obtained, and the deviation is weighted by multiplying the deviation by a predetermined constant K determined from the absolute rated value of the electric motor 1 (hereinafter, in order to distinguish from the above deviation, a weighted deviation Is called). This constant K is set to K1 when the motor current detection value Im is equal to or larger than the judgment current value Ih, and is set to K2 when the motor current detection value Im is smaller than the judgment current value Ih, so that the maximum current limit value Imx ( The increase / decrease pattern of n) can be set according to the characteristics of the electric motor 1 or the driving method of the electric motor 1. Reference numeral 5 is a motor current deviation integrating means, which receives and integrates the weighted deviation as the output of the current deviation computing means 4. 6 is a maximum current determining means,
This receives the integrated value of the weighted deviation as the output of the motor current deviation integration means 5, and determines the maximum current limit value Imx (n) according to the integrated value of the weighted deviation. Reference numeral 7 denotes a motor current instruction means for instructing a motor current instruction value Iobj determined according to the steering torque as a motor current instruction value Iobj to be passed through the electric motor 1 in an electric power steering device of an automobile, for example. Reference numeral 8 denotes a motor current comparison and determination means, which is a maximum current determination means 6
Current limit value Imx (n) as the output of the motor current and the motor current instruction value Iobj as the output of the motor current instruction means 7.
Is received, the motor current instruction value Iobj is compared with the maximum current limit value Imx (n), and the motor current instruction value Io is compared.
If bj is smaller than the maximum current limit value Imx (n),
The motor current value supplied to the electric motor 1 is set to the motor current instruction value I
obj, and if the motor current instruction value Iobj is larger than the maximum current limit value Imx (n), the electric motor 1
The motor current value to be supplied to the maximum current limit value Imx (n)
To decide. Reference numeral 9 denotes a motor driving means, which receives a motor current value as an output of the motor current comparison and determination means 8 and supplies a current according to the motor current value to the electric motor 1 to drive the electric motor 1.

On the other hand, the motor current deviation calculation means 4, the motor current deviation integration means 5, the maximum current determination means 6, the motor current instruction means 7 and the motor current comparison determination means 8 are shown in FIG.
And a judgment current value setting means 3 is constituted by storing a judgment current value Ih determined by an absolute rated value of the electric motor 1 in a memory, and the motor driving means 9 is configured as described above. A motor drive circuit connected to the output port of the input / output interface connected to the microprocessor and the input end of the electric motor 1, and the motor current detection means 2 is configured to supply the electric power system supplied from the motor drive circuit to the electric motor 1. The current sensor is configured to detect a flowing current, and the output end of the current sensor is connected to the input port of the input / output interface.

Next, the operation of the motor protection device of the first embodiment will be described with reference to the flow charts of FIGS. 2 and 3. When the maximum current limit control shown in FIG. 2 starts, the motor current detection value Im is read in step 101, the motor current detection value Im and the determination current value Ih are compared in step 102, and whether the motor current detection value Im is large or Step 1 when equal
03, the process proceeds to step 104 when the detected motor current value Im is small. In step 103, the difference between the motor current detection value Im and the determination current value Ih is obtained, and the difference is calculated as
The result obtained by multiplying a predetermined coefficient K1 determined from the absolute rated value of is subtracted from the previous maximum current limit value Imx (n-1) (Imx (n) = Imx (n-1)-(Im-Ih) ×
K1). In step 104, the difference between the detected motor current value Im and the determined current value Ih is obtained, and the difference is multiplied by a predetermined coefficient K2 determined from the absolute rated value of the electric motor 1 to obtain the result of the previous maximum current limit value Imx ( n-1) (Im
x (n) = Imx (n−1) − (Im−Ih) × K
2). However, the motor current detection value Im and the judgment current value Ih
In comparison, since the determination current value Ih is larger, the difference (Im-Ih) is a negative number. That is, the above equation is Im
It is replaced with x (n) = Imx (n-1) + (Ih-Im) * K2. The maximum current limit value Imx (n) is stored in the memory and is updated each time the process shown in FIG. 2 is repeated. Therefore, the maximum current limit value Imx (n) obtained in the (n-1) th process is the maximum. Current limit value Imx (n-
It becomes 1).

In step 105, the maximum current limit value Imx calculated in step 103 or step 104
In order to limit the upper limit of (n), the maximum current limit value Imx
(N) is compared with the upper limit value IHLIM, and when the maximum current limit value Imx (n) is greater than or equal to the upper limit value IHLIM, in step 106 the maximum current limit value Imx.
(N) is rewritten to the upper limit value IHLIM and step 107
Proceed to. In step 107, in order to limit the lower limit of the maximum current limit value Imx (n) calculated in step 104, the maximum current limit value Imx (n) calculated in step 103 or step 105 or the maximum current limit rewritten in step 106. Value Imx (n) = upper limit value IHLIM
Is compared with the lower limit value ILLIM, and the maximum current limit value Imx
When (n) is smaller than or equal to ILLIM, the lower limit value IL is set to the current value limit data LIMT in step 108.
Set LIM and set the maximum current limit value Imx (n) to IL
When it is larger than LIM, the current limit data LI is set at 109.
The current limit value Imx (n) is set in MT. The upper limit value IHLIM is for obtaining the maximum current energizable time from the absolute rating of the electric motor 1, for example, and setting it so that 30% of the maximum current energizable time can be energized.
When the motor current detection value Im is fixed to the maximum current in the calculation formula of step 103, Im, Ih, and K become fixed values, respectively, and the reduction rate of the maximum current limit value Imx (n) becomes constant. Therefore, the maximum current limit value Imx (n)
The upper limit value IHLIM is set such that the time until the motor control current maximum value MAX becomes equal to or less than (maximum current can be conducted) is, for example, 30% of the maximum energizable time. Further, the lower limit value ILLIM is set to a continuous energizing current of the electric motor 1.

In short, the maximum current limit value Imx (n) obtained in either step 103 or 104 is increased by performing the processing in steps 105 to 109.
If it exists between HLIM and the lower limit value ILLIM, the maximum current limit value Imx (n) obtained in either step 103 or 104 is stored in the memory as current limit value data LIMT. Unlike this, the maximum current limit value I found in either step 103 or 104
When mx (n) is equal to or higher than the upper limit value IHLIM, the upper limit value IHLIM is stored in the memory as the current limit value data LIMT. On the contrary, when the maximum current limit value Imx (n) obtained in either step 103 or 104 is less than or equal to the lower limit value ILLIM, the lower limit value ILLIM is stored in the memory as the current limit value data LIMT. As a result, the maximum current energizable time can be limited by the processing of steps 105 and 106, and steps 107 to
By the process of 109, the current that can be continuously supplied to the electric motor 1 is limited to the lower limit of the maximum current limit value Imx (n), and the electric current motor 1 can be efficiently controlled.

Next, when the output current limiting control shown in FIG. 3 starts, the motor current instruction value Iobj is read in step 201, and the motor current instruction value Iobj is set as the upper limit of the motor current instruction value Iobj. It is determined in step 202 whether the value is MAX or more. If the motor current instruction value Iobj is equal to or more than the motor control current maximum value MAX, the motor current instruction value Iobj is changed to the motor control current maximum value MA.
Proceed to step 203 of limiting with X. Further, in step 204, it is determined whether the motor current instruction value Iobj is equal to or more than the current limit data LIMT, and when the motor current instruction value Iobj is equal to or more than the current limitation data LIMT, the motor current instruction value I is determined.
Step 2 of limiting obj with current limit data LIMT
Go to 05.

Here, when the output shaft of the electric motor 1 is fixed so as not to rotate and the electric motor 1 is constantly energized with a maximum current, when the energization and de-energization of the maximum current are alternately repeated, the current is a sine wave. In this case, the heat generation state (temperature change) of the electric motor 1 was measured. The measurement results are shown in FIGS. 4 and 5.

FIG. 4 shows current limit data when the motor 1 is constantly supplied with the maximum current Ia and when the motor 1 is supplied with the current Ib which is fixed to a value which is equal to or larger than the judgment current value Ih and smaller than the maximum current value. It is a drawing of LIMT, and it can be seen that when the maximum current limit value Imx (n) is set to the upper limit value IHLIM, it is gradually reduced to the lower limit value ILLIM and held.

FIG. 5 shows the electric currents Ic, Id (I) fixed to the motor 1 at a value equal to or lower than the judgment current value Ih and equal to or higher than the lower limit value ILLIM.
Current limit data LI when c <Id) is energized
In the drawing, MT is a graph in which a motor current flows for a predetermined time or longer, and when a maximum current limit value Imx (n) is set to a lower limit value ILLIM value, the MT value is gradually increased to an upper limit value IHLIM and held. I understand.

Considering FIG. 4 and FIG. 5, the time until the maximum motor current instruction value Iobj is limited to a predetermined value becomes shorter as a large current flows through the electric motor 1.
That is, the time until the maximum motor current instruction value Iobj is limited to the predetermined value changes according to the motor current value. Therefore, in the case of the electric power steering device, by operating the coefficient K, the change in the motor current due to the limitation of the maximum motor current instruction value Iobj can be smoothed, and the change in the steering assist torque due to the change in the motor current can be changed. It is smooth, and you can suppress the feeling of strangeness in the operation feeling.

Example 2. (Corresponding to Claim 2) FIG. 6 is a configuration diagram showing an electric motor protection device as a second embodiment of the present invention. In the figure, the motor current detecting means is deleted from the first embodiment, and the motor current instruction value Iobj of the motor current instructing means 7 is output to the motor current deviation calculating means 4 and the motor current comparing and determining means 8 to output the motor current deviation. The calculation means 4 causes the motor current instruction value Iobj and the judgment current value Ih.
The structure is simplified by adopting a configuration for calculating the difference between and. In the process of the second embodiment, the motor current detection value Im shown in FIG.
It is the same as obj.

Example 3. (Corresponding to Claim 3) FIG. 7 is a block diagram showing an electric motor protection device as a third embodiment of the present invention. In the figure, in order to provide the judgment current value of the first embodiment with hysteresis, instead of the judgment current value setting means 3 of the first embodiment, a first judgment current value setting means 10 for setting a first judgment current value Ih1. And the first determination current value I
A second judgment current value setting means 11 for setting a second judgment current value Ih2 as a value higher than h1 is provided, and instead of the motor current deviation calculation means 4 of the first embodiment, a first motor current deviation calculation means 13 is provided. And a second motor deviation calculation means 14
The first motor current calculation means 13 receives the first determination current value Ih1 from the first determination current value setting means 10 and the motor current detection value Im from the motor current detection means 2, and receives the motor current detection value Im and the determination current value. The deviation from Ih1 is obtained, this deviation is multiplied by a predetermined constant K determined from the absolute rated value of the electric motor 1 to calculate a weighted deviation, and this weighted deviation is output to the motor current deviation integrating means 5. , The second motor current calculation means 14 is the second determination current value setting means 1
The second determination current value Ih2 from 1 and the motor current detection means 2
From the motor current detection value Im, the deviation between the motor current detection value Im and the second judgment current value Ih2 is obtained, and the deviation is weighted by multiplying the deviation by a predetermined constant K determined from the absolute rated value of the electric motor 1. The weighted deviation thus calculated is calculated, and the weighted deviation is output to the motor current deviation integrating means 5.

Therefore, the maximum current limit control of the third embodiment will be described with reference to the flowchart shown in FIG.
The motor current detection value Im is read in step 301, the motor current detection value Im and the first determination current value Ih1 are compared in step 302, and when the motor current detection value Im is large or equal, the process proceeds to step 304 to detect the motor current. When the value Im is small, the process proceeds to step 303. Step 3
In 03, the motor current detection value Im is set to the second determination current value Ih2.
When the detected motor current value Im is small, the routine proceeds to step 305, and when the detected motor current value Im is large, the routine proceeds to step 306. That is, steps 302 and 3
According to the determination of No. 03, the second determination current value Ih2 is used while the change of the motor current detection value Im is increasing, and the change of the motor current detection value Im after the motor current detection value Im exceeds the second determination current value Ih2. Is decreasing, the first judgment current value Ih
Use 1. In step 304, the difference between the motor current detection value Im and the first determination current value Ih1 is calculated, and the difference is calculated as the electric motor 1
The result obtained by multiplying a predetermined coefficient K1 determined from the absolute rated value of is subtracted from the previous maximum current limit value Imx (n-1) (Imx (n) = Imx (n-1)-(Im-Ih1).
× K1). In step 305, the motor current detection value Im
And the second determination current value Ih2 are obtained, and the difference is multiplied by a predetermined coefficient K2 determined from the absolute rated value of the motor 1 to subtract the result from the previous maximum current limit value Imx (n-1) ( Imx (n) = Imx (n-1)-(Im-Ih
2) x K2). However, when the motor current detection value Im and the second determination current value Ih are compared, the second determination current value Ih2 is larger, so the difference (Im-Ih2) is a negative number. That is, the above equation is Imx (n) = Imx (n-1) + (I
h2-Im) × K2. Step 306
Then, the maximum current limit value Imx (n) is replaced with the previous maximum current limit value Imx (n-1). The maximum current limit value Imx (n) is stored in the memory and is updated each time the process shown in FIG. 2 is repeated, so that the maximum current limit value Imx (n) obtained in the (n-1) th process is the maximum. It becomes the current limit value Imx (n-1).

In step 307, steps 304 to 30 are executed.
In order to limit the upper limit of the maximum current limit value Imx (n) calculated in 6, the maximum current limit value Imx (n) and the upper limit value IH
When the maximum current limit value Imx (n) is larger than or equal to the upper limit value IHLIM, the maximum current limit value Imx (n) is compared with the upper limit value IHLI in step 308.
Rewrite to M and proceed to step 309. Step 309
Then, in order to limit the lower limit of the maximum current limit value Imx (n) calculated in steps 304 to 306, step 30
Maximum current limit value Imx (n) calculated in 4 to 306 or maximum current limit value Imx replaced in step 308
(N) = Upper limit value IHLIM is compared with the lower limit value ILLIM, and when the maximum current limit value Imx (n) is smaller than or equal to ILLIM, the lower limit value ILLIM is set in the current value limit data LIMT in step 310, and the maximum current value is set. When the limit value Imx (n) is larger than ILLIM, at step 311, the current limit value I is added to the current limit data LIMT.
Set mx (n). Therefore, it is possible to suppress hunting of the maximum current limit value Imx (n) when the motor current flowing through the electric motor 1 is near the determination current value in the first embodiment.

In the third embodiment as well, the second embodiment is used.
Similarly, the motor current detection value Im is set to the motor current instruction value Io.
The motor current detecting means 2 can be omitted by replacing it with bj.

[0029]

As described above, according to the first aspect of the present invention,
The maximum current is limited according to the value of the current flowing in the electric motor, so the time to limit the maximum current can be changed so that the motor can be driven efficiently and thermal damage to the motor and power elements in the motor output circuit of the control device can be prevented. This is possible, and moreover, there is an effect that the maximum current is smoothly limited by operating a predetermined coefficient determined based on the absolute rated current value of the electric motor. In particular, when performing control related to feeling, such as an electric power steering device, it is possible to suppress the feeling of strangeness when limiting the maximum current.

According to the second aspect of the invention, the difference between the motor current instruction value and the judgment current value is used to change the maximum current limit time according to the current value flowing in the motor. Although it has a simple structure in which the detecting means is omitted, it has an effect of exhibiting stable performance that is not easily affected by noise such as disturbance. In particular, when performing control related to feeling, such as an electric power steering device, it is possible to suppress the feeling of strangeness when limiting the maximum current.

According to the third invention, since the judgment current value is provided with hysteresis, there is an effect that the hunting of the motor current can be suppressed when the current flowing through the electric motor is near the judgment current value. In particular, when performing control related to feeling, such as an electric power steering device, it is possible to suppress the feeling of strangeness when limiting the maximum current.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an electric motor protection device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing maximum current limit control according to the first embodiment.

FIG. 3 is a flowchart showing output current limiting control according to the first embodiment.

FIG. 4 is a limiting current characteristic diagram showing a decrease in maximum instruction current when the motor current of Example 1 is fixed to be equal to or higher than a determination current value.

FIG. 5 is a limiting current characteristic diagram showing an increase in the maximum command current when the motor current of Example 1 is fixed to be equal to or lower than the determination current value.

FIG. 6 is a configuration diagram showing an electric motor protection device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing an electric motor protection device of a third embodiment according to the present invention.

FIG. 8 is a flowchart showing maximum current limit control according to the third embodiment.

FIG. 9 is a diagram illustrating a conventional operation.

FIG. 10 is a diagram illustrating a conventional operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 motor 2 motor current detection means 3 judgment current value setting means 4 motor current deviation calculation means 5 motor current deviation integration means 6 maximum current determination means 7 motor current instruction means 8 motor current comparison determination means 9 motor drive means

Claims (3)

[Claims] 1. An electric motor, a motor current instructing means for instructing a motor current value supplied to the electric motor, and a motor current detecting means for detecting a motor current value flowing in the electric motor.
Judgment current value setting means for setting a judgment current value serving as a reference for judging the magnitude of the motor current value supplied to the electric motor, the judgment current value set in the judgment current value setting means and the motor current detection means. The motor current deviation calculating means for obtaining the deviation from the detected motor current value, and the deviation obtained by the motor current deviation calculating means are multiplied by a predetermined coefficient determined based on the absolute rated current value of the electric motor to be integrated. Motor current deviation integrating means, maximum current determining means for determining the maximum current limit value to be supplied to the electric motor according to the integrated value obtained by the motor current deviation integrating means, and maximum current determined by the maximum current determining means A motor current comparison and determination unit that determines a motor current supply value based on the limit value and the motor current instruction value instructed by the motor current instruction unit, and the motor current comparison and determination unit. Motor protection apparatus the motor current based on the motor current supply value determined by means, characterized in that a motor drive means for supplying to the electric motor. 2. An electric motor, a motor current instruction means for instructing a motor current value supplied to the electric motor, and a judgment current value setting for setting a judgment current value serving as a reference for judging the magnitude of the motor current value supplied to the electric motor. Means, a motor current deviation calculation means for obtaining a deviation between the judgment current value set in the judgment current value setting means and the motor current instruction value indicated by the motor current instruction means, and the motor current deviation calculation means And a motor current deviation accumulating means for accumulating a value obtained by multiplying the deviation by a predetermined coefficient determined based on the absolute rated current value of the electric motor, and supplying to the electric motor according to the integrated value obtained by the motor current deviation accumulating means. Maximum current determining means for determining the maximum current limiting value, the maximum current limiting value determined by the maximum current determining means, and the motor current designated by the motor current indicating means A motor current comparison and determination means for determining a motor current supply value based on the instruction value; and a motor drive means for supplying a motor current based on the motor current supply value determined by the motor current comparison and determination means to the electric motor. An electric motor protection device. 3. The motor protection device according to claim 1, wherein the judgment current value is provided with hysteresis.