JP2010206967A - Motor overload detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional motor overload detection device, wherein since overloading is detected based on a value which is determined by integrating a current value command by using the thermal time constant for the coils of all the phases, the single-phase coil is burnt during the stall state. <P>SOLUTION: In the motor overload detecting device, an all-phase coil overheat detection unit 12 detects the overheating state of the coils of all phases of a motor 30 by utilizing a first thermal time constant τ1, which is the thermal time constant of the coils of all phases, and a single-phase coil overheat detecting unit 13 detects the overheating state of the single-phase coil of the motor 30, by utilizing a second thermal time constant τ2 which is the thermal time constant of the single-phase coil. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor overload detection device that detects an overload state of a motor, and in particular, a state in which all phases of a motor coil are overheated and a state in which a single phase coil of a motor is overheated are paralleled. It is related with the novel improvement which can protect a motor from overheating more reliably, maintaining the performance of a motor by comprising so that it can detect.

  As this type of motor overload detection device that has been conventionally used, the configuration described in Patent Document 1 below is exemplified. FIG. 6 is a block diagram showing a conventional motor overload detection device. In the figure, the motor driver 10 is connected to a motor 30 via a drive circuit 20 and is also connected to an alarm notification device 40. The motor driver 10 is provided with a drive control unit 11 and an all-phase coil overheat detection unit 12, and the drive control unit 11 inputs a current value command Icmd and a rotation speed command Rcmd to the drive circuit 20. Thus, the driving direction, driving force, and rotation speed of the motor 30 are controlled.

  The all-phase coil overheat detection unit 12 detects the current value command Icmd output from the drive control unit 11 and uses the thermal time constant of all-phase coils included in the motor 30 (the thermal time constant of the entire motor). Then, the current value command Icmd is integrated, and when this integrated value reaches a predetermined overload level, the state where the coils of all the phases of the motor 30 are overheated is detected and an overload alarm 12a is issued. The alarm notification device 40 notifies the overload state when the overload alarm 12a from the all-phase coil overheat detection unit 12 is detected.

JP 2008-48577 A

By the way, the driving state of the motor 30 includes a rotating state in which current flows uniformly through all the coils in order to rotate the driving shaft of the motor 30, and a one-phase coil in order to stop and hold the driving shaft of the motor 30. And a stalled state in which current (stall current) continues to flow in a concentrated manner. In the stalled state, the coils of all phases are not heated, but only a specific single-phase coil is heated. The temperature increase of the single-phase coil due to the stall current is more rapid than when all the phase coils are heated.
In the conventional motor overload detection device as described above, since the overheating state of the all-phase coil is detected using the thermal time constant of the all-phase coil, the single-phase coil becomes overheated in the stall state. There is a possibility that this single-phase coil may be burned out. The problem that the single-phase coil burns out is particularly noticeable in small-diameter motors with low heat dissipation efficiency.
In consideration of the stall condition, it is possible to use the thermal time constant of the single-phase coil instead of the thermal time constant of the coil of all phases, but the coil of all phases is not overheated. Nevertheless, the integral value reaches the overload level, and the operating area (wattage) of the motor 30 cannot be used effectively.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a motor overload detection device that can more reliably protect the motor from overheating while maintaining the performance of the motor. It is.

The motor overload detection device according to the present invention uses an all-phase coil current integrated value that is an integrated value of a current value command Icmd to the motor using a first thermal time constant that is a thermal time constant of coils of all phases of the motor. Y1 is obtained, and the all-phase coil current integrated value Y1 is an overload level O.I. In order to monitor the heat generation in the stall state of the motor, and the all-phase coil overheat detection unit that detects the state that the coils of all phases of the motor are overheated and outputs an overload alarm when L is reached. In addition, a single-phase coil current integrated value Y2 that is an integrated value of the current value command Icmd is obtained using a second thermal time constant τ2 that is a thermal time constant of the single-phase coil of the motor, and the single-phase coil current integrated The value Y2 is the overload level O.D. And a single-phase coil overheat detection unit that detects an overheated state of the single-phase coil of the motor and outputs an overload alarm when the motor reaches L.
The single-phase coil overheat detection unit detects a rotational speed command Rcmd to the motor, and when the rotational speed command Rcmd is equal to or less than a predetermined threshold Th, the current value I for integration is referred to as the current value command Icmd. In addition, when the rotational speed command Rcmd is larger than the threshold Th, the current value I for accumulation is set to 0, and Y2 = {1-e ^{(−t / τ2)} } × {I−Y2 _(n−1) } + Y2 _(n-1) (where t is the time, τ2 is the second thermal time constant, I is the current value for integration, Y2 _(n-1) is the single-phase coil current immediately before the current value for integration I changes ₎ The single-phase coil current integrated value Y2 is obtained from the integrated value).
In addition, the single-phase coil overheat detection unit determines whether the all-phase coil current integrated value Y1 obtained by the all-phase coil overheat detection unit is smaller than the single-phase coil current integrated value Y2, When the all-phase coil current integrated value Y1 is smaller than the single-phase coil current integrated value Y2, the obtained single-phase coil current integrated value Y2 is maintained, and the all-phase coil current integrated value Y1 is When the phase coil current integrated value Y2 is equal to or greater than the single phase coil current integrated value Y2, the single phase coil current integrated value Y2 is rewritten to the all phase coil current integrated value Y1, and the value is maintained. The single-phase coil current integrated value Y2 with the overload level O.I. It is determined whether or not L has been reached.

According to the motor overload detection device of the present invention, a state in which the coils of all phases of the motor are overheated is detected using the first thermal time constant τ1, which is the thermal time constant of the coils of all phases. A state in which the single-phase coil of the motor is overheated using the second thermal time constant τ2, which is the thermal time constant of the single-phase coil, and the rotational speed command Rcmd to the motor, as detected by the detection unit Since the single-phase coil overheat detection unit detects the motor, the motor can be more reliably protected from overheating while maintaining the performance of the motor as compared with the case where only one of the first and second thermal time constants is used. . Since a small-diameter motor with low heat dissipation efficiency has a high possibility of burning a single-phase coil, the present invention is particularly useful for such a small-diameter motor.
Further, the single-phase coil overheat detecting unit sets the current value I for integration to the current value command Icmd when the rotation speed command Rcmd is equal to or less than a predetermined threshold Th, and the rotation speed command Rcmd is less than the threshold Th. When the current value I is large, the current value I for accumulation is set to 0, and Y2 = {1-e ^{(−t / τ2)} } × {I−Y2 _(n−1) } + Y2 _(n−1). Since the value Y2 is obtained, it is possible to obtain an index for monitoring the heat generation in the motor stall state more reliably, and to improve the reliability of overheating detection of the single-phase coil.
Further, the single-phase coil overheat detection unit calculates the value of the single-phase coil current integration value Y2 as the all-phase coil current integration value when the all-phase coil current integration value Y1 is equal to or greater than the single-phase coil current integration value Y2. Since the value Y1 is rewritten, the thermal fluctuation of the single-phase coil can be continuously monitored more reliably, and the reliability of detection of overheating of the single-phase coil can be improved.

It is a block diagram which shows the motor overload detection apparatus by Embodiment 1 of this invention. It is a graph which shows the fluctuation | variation of the all-phase coil current integrated value Y1 and the single-phase coil current integrated value Y2 calculated | required by the all-phase coil overheat detection part of FIG. It is explanatory drawing which shows rewriting of the value of the single phase coil current integration value Y2 when the single phase coil current integration value Y2 fluctuates like FIG. It is a flowchart which shows the all-phase coil overheat detection operation | movement which the all-phase coil overheat detection part of FIG. 1 performs. It is a flowchart which shows the single phase coil overheat detection operation | movement which the single phase coil overheat detection part of FIG. 2 performs. It is a block diagram which shows the conventional motor overload detection apparatus.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a motor overload detection apparatus according to Embodiment 1 of the present invention. In the figure, a motor driver 10 as a motor overload detection device is connected to a motor 30 via a drive circuit 20 and is also connected to an alarm notification device 40. The motor driver 10 includes a drive control unit 11, an all-phase coil overheat detection unit 12, and a single-phase coil overheat detection unit 13, and the drive control unit 11 sends a current value command to the drive circuit 20. By inputting Icmd and the rotation speed command Rcmd, the drive direction, drive force, and rotation speed of the motor 30 are controlled.

  The all-phase coil overheat detection unit 12 detects the current value command Icmd output from the drive control unit 11 and uses the first thermal time constant τ1, which is the thermal time constant of all-phase coils included in the motor 30. The current value command Icmd is integrated to obtain an all-phase coil current integrated value Y1.

Specifically, the all-phase coil overheat detection unit 12
Y1 = {1-e ^{(−t / τ1)} } × {Icmd−Y1 _(n−1) } + Y1 _(n−1) (1)
Thus, an all-phase coil current integrated value Y1 is obtained. However, t is time, (tau) 1 is a 1st thermal time constant, Icmd is an electric current value command, Y1 _(n-1) is an all-phase coil current integrated value just before the electric current value command Icmd changes.

  Further, the all-phase coil overheat detection unit 12 is configured such that the all-phase coil current integrated value Y1 is a predetermined overload level O.D. L is reached, and the overload level O.D. When it is determined that L has been reached, a state in which the coils of all phases of the motor 30 are overheated is detected, and an overload alarm 12a is issued. When the alarm notification device 40 detects the overload alarm 12a from the all-phase coil overheat detection unit 12, the alarm notification device 40 notifies the overload state.

  The single-phase coil overheat detection unit 13 is included in the motor 30 in order to detect the current value command Icmd and the rotation speed command Rcmd output from the drive control unit 11 and to monitor the heat generation in the stall state of the motor 30. Using the second thermal time constant τ2 that is the thermal time constant of the single-phase coil and the rotational speed command Rcmd, the current value command Icmd is integrated to obtain the single-phase coil current integrated value Y2. Note that the stall state is a state in which a stall current continues to flow while concentrating on the one-phase coil in order to stop and hold the drive shaft of the motor 30.

Specifically, the single-phase coil overheat detection unit 13 sets the current value I for integration to the current value command Icmd when the rotation speed command Rcmd is equal to or less than a predetermined threshold such as 10 rpm, and the rotation speed command Rcmd is When larger than the threshold value, the current value I for accumulation is set to 0,
Y2 = {1-e ^{(−t / τ2)} } × {I−Y2 _(n−1) } + Y2 _(n−1) (2)
Thus, the single-phase coil current integrated value Y2 is obtained. However, t is time, (tau) 2 is the 2nd thermal time constant, I is an integration current value, Y2 _(n-1) is a single phase coil current integration value just before the integration current value I changes. Note that fluctuations in the integral values Y1 and Y2 will be described later with reference to the drawings.

  Here, the single-phase coil current integrated value Y2 is an index indicating the temperature fluctuation of the single-phase coil due to the stall current. The current value command Icmd is used as the current value command Icmd when the rotation speed command Rcmd is equal to or less than the threshold Th. When the rotation speed command Rcmd is extremely low, the stall current flows in a specific single-phase coil. This is because the single-phase coil is heated according to the current value command Icmd and the second thermal time constant τ2. On the other hand, when the rotational speed command Rcmd is larger than the threshold value Th, the current value for integration I is set to 0 because the stall current does not flow in a specific single-phase coil in a concentrated manner, according to the second thermal time constant τ2. This is because the single-phase coil is dissipated.

  Further, the single-phase coil overheat detection unit 13 calculates the value of the single-phase coil current integrated value Y2 based on the comparison result between the total-phase coil current integrated value Y1 and the single-phase coil current integrated value Y2. Rewrite the value Y1.

Specifically, the single-phase coil overheat detection unit 13 maintains the obtained single-phase coil current integrated value Y2 when the all-phase coil current integrated value Y1 is smaller than the single-phase coil current integrated value Y2, When the coil current integrated value Y1 is equal to or greater than the single-phase coil current integrated value Y2, the value of the single-phase coil current integrated value Y2 is rewritten to the value of the all-phase coil current integrated value Y1.
This is because, when the all-phase coil current integrated value Y1 is equal to or greater than the single-phase coil current integrated value Y2, the current value command Icmd and the first value are larger than the single-phase coil is radiated according to the second thermal time constant τ2. This is because it is more dominant that the coil is heated according to the thermal time constant τ1. Further, by configuring the single-phase coil current integrated value Y2 to be rewritten, it is possible to continuously monitor the fluctuation of the coil heat more reliably.

  Further, the single-phase coil overheat detection unit 13 uses the single-phase coil current integrated value Y2 rewritten to the maintained single-phase coil current integrated value Y2 or the all-phase coil current integrated value Y1, The integrated current value Y2 is overload level O.D. It is determined whether or not L has been reached. The single-phase coil overheat detection unit 13 indicates that the single-phase coil current integrated value Y2 is an overload level O.D. When it is determined that L has been reached, a state where the single-phase coil of the motor 30 is overheated is detected and an overload alarm 13a is issued. The alarm notification device 40 also notifies the overload state when the overload alarm 13a from the single-phase coil overheat detection unit 13 is detected.

Next, FIG. 2 is a graph showing the fluctuations of the all-phase coil current integrated value Y1 and the single-phase coil current integrated value Y2 obtained by the all-phase coil overheat detecting unit 12 and the single-phase coil overheat detecting unit 13 in FIG. .
In FIG. 2, since the second thermal time constant τ2 is smaller than the first thermal time constant τ1, the single-phase coil current integrated value Y2 rises more rapidly than the all-phase coil current integrated value Y1. Here, assuming that the current value command Icmd is switched to 0 in a stepped manner at the timing T1, each integrated value Y1, Y2 is exponentially decreased from that time. Again, since the second thermal time constant τ2 is smaller than the first thermal time constant τ1, the single-phase coil current integrated value Y2 is suddenly decreased from the all-phase coil current integrated value Y1.

FIG. 3 is an explanatory diagram showing rewriting of the single-phase coil current integrated value Y2 when the single-phase coil current integrated value Y2 varies as shown in FIG.
In FIG. 3, the rotational speed command Rcmd is set to be equal to or less than the threshold value Th until the timing T2, and the rotational speed command Rcmd is set to be larger than the threshold value Th from the timing T2. In FIG. 3, since the rotational speed command Rcmd is equal to or less than the threshold Th until the timing T2, I = Icmd is set in the above equation (2), and the single-phase coil current integrated value Y2 is increased. Next, since the rotational speed command Rcmd is greater than the threshold value Th from the timing T2, I = 0 is set in Expression (2), and the single-phase coil current integrated value Y2 is decreased. Here, since all-phase coil current integrated value Y1 is increased according to the first thermal time constant τ1 regardless of rotation speed command Rcmd, all-phase coil current integrated value Y1 becomes single-phase coil current integrated value Y2 at timing T3. Is bigger than. Therefore, from this timing T3, the value of the single-phase coil current integrated value Y2 is rewritten to the value of the all-phase coil current integrated value Y1.

Next, the operation of each of the overheat detection units 12 and 13 will be described.
FIG. 4 is a flowchart showing the all-phase coil overheat detection operation performed by the all-phase coil overheat detection unit 12 of FIG. In the figure, when the power of the motor driver 10 is turned on, the current value command Icmd output from the drive control unit 11 is detected (step S10), and the current value command Icmd is integrated by the above equation (1). Thus, an all-phase coil current integrated value Y1 is obtained (step S11). Next, the all-phase coil current integrated value Y1 becomes the overload level O.D. It is determined whether or not L has been reached (step S12). When it is determined that L has not been reached, the calculation operation of all-phase coil current integrated value Y1 (steps S10 and S11) is repeatedly performed.

  On the other hand, the all-phase coil current integrated value Y1 is an overload level O.D. If it is determined that L has been reached, a state in which the coils of all phases of the motor 30 are overheated is detected, an overload alarm is output (step S13), and this all-phase coil overheat detection operation is terminated. The Note that the all-phase coil overheat detection operation is started again, for example, when a return signal is input from the outside to the motor driver 10.

Next, FIG. 5 is a flowchart showing a single-phase coil overheat detection operation performed by the single-phase coil overheat detection unit 13 of FIG.
In the figure, when the power of the motor driver 10 is turned on, a rotation speed command Rcmd output from the drive control unit 11 is detected (step S20), and the rotation speed command Rcmd is equal to or less than a threshold value Th such as 10 rpm. Is determined (step S21). At this time, if it is determined that the rotation speed command Rcmd is equal to or less than the threshold value Th, the current value command Icmd from the drive control unit 11 is detected, and the current value I for integration is set as the current value command Icmd (step) S22), the single-phase coil current integrated value Y2 is obtained by the above equation (2) (step S23). On the other hand, if it is determined that the rotational speed command Rcmd is larger than the threshold value Th, the current value I for integration is set to 0 (step S24), and the single-phase coil current integrated value Y2 is obtained by the above equation (2) ( Step S23).

  When the single-phase coil current integrated value Y2 is obtained, it is determined whether or not the all-phase coil current integrated value Y1 obtained by the all-phase coil overheat detecting unit 12 is smaller than the single-phase coil current integrated value Y2 (step). S25). At this time, if it is determined that all-phase coil current integrated value Y1 is smaller than single-phase coil current integrated value Y2, the current value of single-phase coil current integrated value Y2 is maintained (step S26). On the other hand, if it is determined that the all-phase coil current integrated value Y1 is equal to or greater than the single-phase coil current integrated value Y2, the value of the single-phase coil current integrated value Y2 is rewritten to the value of the all-phase coil current integrated value Y1 (step) S27).

  Next, the single-phase coil current integrated value Y2 with the value maintained or the single-phase coil current integrated value Y2 with the value rewritten is the overload level O.D. It is determined whether or not L has been reached (step S28). If it is determined that it has not reached L, the operation of calculating the single-phase coil current integrated value Y2 (steps S20 to S27) is repeated. On the other hand, the overload level O.D. If it is determined that the value has reached L, a state in which the single-phase coil of the motor 30 is overheated is detected, an overload alarm 13a is output (step S29), and this single-phase coil overheat detection operation is performed. Is terminated. Note that the single-phase coil overheat detection operation is started again, for example, when a return signal is input from the outside to the motor driver 10.

  In the first embodiment, each overheat detection unit 12 and 13 has been described as directly detecting the current value command Icmd and the rotation speed command Rcmd output from the drive control unit 11, but each overheat detection is performed. The unit may indirectly detect the current value command Icmd and the rotation speed command Rcmd via a current detector and a rotation detector attached to the motor.

DESCRIPTION OF SYMBOLS 11 Drive control part 12 All-phase coil overheat detection part 12a Overload alarm 13 Single-phase coil overheat detection part 13a Overload alarm Icmd Current value command Rcmd Rotational speed command

Claims (3)

Using the first thermal time constant which is the thermal time constant of the coils of all phases of the motor (30), an all-phase coil current integrated value Y1 which is an integrated value of the current value command Icmd to the motor (30) is obtained, All-phase coil current integrated value Y1 is overload level O.D. An all-phase coil overheat detection unit (12) for detecting a state in which all the phase coils of the motor (30) are overheated when L is reached and outputting an overload alarm (12a);
In order to monitor the heat generation in the stall state of the motor (30), a second thermal time constant τ2, which is a thermal time constant of a single-phase coil of the motor (30), and a rotational speed command to the motor (30) Rcmd is used to determine a single-phase coil current integrated value Y2 that is an integrated value of the current value command Icmd, and the single-phase coil current integrated value Y2 is determined as an overload level O.D. A single-phase coil overheat detection unit (13) for detecting a state where the single-phase coil of the motor (30) is overheated and outputting an overload alarm (13a) when L is reached. The motor overload detection apparatus characterized by the above-mentioned. The single-phase coil overheat detection unit (13)
When the rotational speed command Rcmd is equal to or less than a predetermined threshold Th, the current value I for integration is set as the current value command Icmd, and when the rotational speed command Rcmd is larger than the threshold Th, the current value I for integration is set. As 0
Y2 = {1-e ^{(−t / τ2)} } × {I−Y2 _(n−1) } + Y2 _(n−1)
(Where t is the time, τ2 is the second thermal time constant, I is the current value for integration, and Y2 _(n-1) is the single-phase coil current integration value immediately before the integration current value I changes). The motor overload detection device according to claim 1, wherein a phase coil current integrated value Y2 is obtained. The single-phase coil overheat detection unit (13)
It is determined whether the all-phase coil current integrated value Y1 obtained by the all-phase coil overheat detecting unit (12) is smaller than the single-phase coil current integrated value Y2, and the all-phase coil current integrated value Y1 is When the value is smaller than the single-phase coil current integrated value Y2, the obtained single-phase coil current integrated value Y2 is maintained, and the all-phase coil current integrated value Y1 is equal to or greater than the single-phase coil current integrated value Y2. In some cases, the value of the single-phase coil current integrated value Y2 is rewritten to the value of the all-phase coil current integrated value Y1,
The single-phase coil current integrated value Y2 with the value maintained or the single-phase coil current integrated value Y2 with the value rewritten is overload level O.D. The motor overload detection device according to claim 1, wherein it is determined whether or not L has been reached.

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