LOAD MONITORING DEVICE AND LOAD MONITORING METHOD

Abstract

To provide a load monitoring device and a load monitoring method that can bring out the essential performance of a motor or a driver as much as possible.SOLUTION: A load monitoring device comprises: a load determination unit that has a first control structure having first load characteristics indicating, for a motor, an application allowed time for the value of a predetermined current supplied to the motor and a second control structure having second load characteristics, for a driver, indicating an application allowed time for the value of the predetermined current; and a correction unit that corrects the first load characteristics in the first control structure and the second load characteristics in the second control structure based on a first ambient temperature being the ambient temperature of the motor and a second ambient temperature being the ambient temperature of the driver.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a load monitoring device and a load monitoring method for monitoring a motor and a load of a driver that controls the operation of the motor. [Background technology]

[0002] Conventionally, various methods have been considered for overheat protection of motors used in machine tools and the like and drivers that control the operation of the motors. For example, Patent Document 1 describes a method of controlling a motor by referring to a control table using control instruction information and the ambient temperature of the motor detected by a temperature sensor, reading out the corresponding control amount (motor torque). Patent Document 2 describes a method of calculating the temperature rise of a motor based on the current passed through the motor and the heat dissipated from the motor, and correcting the control parameters of the motor (such as the torque constant and resistance value of the motor) based on the temperature rise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-163182 [Patent Document 2] JP 2004-318709 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method of Patent Document 1, the control table is used to prevent the generation of motor torque more than necessary, so the motor's original performance cannot be exhibited.In addition, in the method of Patent Document 2, the control parameters are corrected to output accurate motor torque, so the motor's original performance cannot be exhibited.

[0005] The present invention has been made in view of the above problems, and has an object to provide a load monitoring device and a load monitoring method that can maximize the inherent performance of a motor and a driver. [Means for solving the problem]

[0006] In the present invention, in order to solve the above problems, a load monitoring device that monitors the load on a motor and a driver that controls the operation of the motor employs the following configuration: That is, the load monitoring device includes a current value acquisition unit that acquires a current value supplied to the motor, a first temperature estimation unit that estimates the temperature of the motor as a first temperature using a first thermal model that indicates the relationship between the current value and the amount of heat generated by the motor, a second temperature estimation unit that estimates the temperature of the driver as a second temperature using a second thermal model that indicates the relationship between the current value and the amount of heat generated by the driver, a first control structure that is configured to compare the first temperature with a first threshold value for the motor to determine whether or not the motor is in an overloaded state, and has a first load characteristic that indicates an applicable time for a predetermined current value for the motor, and a second control structure that estimates the second temperature and the driver. the load determination unit having a second control structure configured to determine whether or not the driver is in an overload state by comparing a first threshold value for the motor with a second threshold value for the motor, the second control structure having a second load characteristic indicating an applicable time for a predetermined current value for the driver; an output unit which outputs abnormality information relating to an overload state when the load determination unit determines that at least one of the motor and the driver is in an overload state; and a correction unit which corrects the first load characteristic in the first control structure and the second load characteristic in the second control structure based on a first ambient temperature which is the ambient temperature of the motor and a second ambient temperature which is the ambient temperature of the driver.

[0007] The present invention relates to a load monitoring method, a load monitoring program, and a load monitoring device having the same features as the above load monitoring device. This also includes programs, recording media on which such programs are recorded, etc.

[0008] According to the above configuration, the first load characteristic and the second load characteristic are corrected based on the ambient temperature of the motor and the ambient temperature of the driver, respectively. As a result, it is determined whether a current larger than the rated current is applied to the motor and the driver for longer than the applicable time based on a threshold value corresponding to the corrected load characteristic. In this way, by adjusting the applicable time to the motor and the driver, i.e., adjusting the load on the motor and the driver, it is possible to bring out the original performance of the motor and the driver as much as possible according to the ambient temperature of the motor and the ambient temperature of the driver.

[0009] In the above-described load monitoring device, the correction unit may correct the first load characteristic so that the applicable time under the first load characteristic becomes longer as the first ambient temperature becomes lower while maintaining the rated current of the motor, and may correct the second load characteristic so that the applicable time under the second load characteristic becomes longer as the second ambient temperature becomes lower while maintaining the rated current of the driver.

[0010] According to the above configuration, by correcting the first load characteristic and the second load characteristic, while maintaining the rated current of the motor and the driver, the lower the first ambient temperature and the second ambient temperature, respectively, the longer the application time for the first load characteristic and the second load characteristic.

[0011] In the above-described load monitoring device, the correction unit may correct the first load characteristics so that the rated current of the motor is increased and the application time under the first load characteristics is extended as the first ambient temperature decreases, and may correct the second load characteristics so that the rated current of the driver is increased and the application time under the second load characteristics is extended as the second ambient temperature decreases.

[0012] According to the above configuration, by correcting the first load characteristic and the second load characteristic, the lower the first ambient temperature and the second ambient temperature, respectively, the higher the rated current of the motor and the driver, and the longer the application time for each of the first load characteristic and the second load characteristic.

[0013] In the above-mentioned load monitoring device, the load determination unit may calculate a first current value as an allowable current value of the motor and driver and a first applicable time corresponding to the first current value from the first load characteristic and the second load characteristic corrected by the correction unit, calculate a second current value as an allowable current value of the power cable from the first applicable time and information regarding the configuration of the power cable connecting the motor and driver, compare the second current value with the first current value, and output information indicating an overload state of the power cable when the second current value is less than or equal to the first current value.

[0014] According to the above configuration, after correcting the first load characteristic and the second load characteristic graph, the load determination unit determines whether the allowable current value (second current value) of the power cable is equal to or less than the allowable current value (first current value) of the motor and the driver based on the corrected first load characteristic and the second load characteristic, and outputs information indicating an overload state when the second current value is equal to or less than the first current value. This makes it possible to avoid the possibility of the power cable being burned due to an excessive rise in temperature caused by the second current value falling below the first current value. This makes it possible to protect not only the motor and the driver but also the power cable while drawing out the original performance of the motor and the driver as much as possible.

[0015] The above load monitoring device may further include a receiving unit that receives input of information relating to the configuration of the power cable.

[0016] According to the above configuration, by making it possible to input information relating to the configuration of the power cable, it is possible to provide protection for the power cable in an appropriate manner according to the type of the power cable and the installation conditions. Effect of the Invention

[0017] According to the present invention, the inherent performance of the motor and the driver can be maximized. [Brief description of the drawings]

[0018] [Figure 1]FIG. 1 is a diagram showing a schematic configuration of a motor control system. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a control system in which a motor is incorporated. [Diagram 3] FIG. 3 is a diagram showing a control structure formed by the driver of the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the configuration of a calculation model for a motor. [Diagram 5] FIG. 5 is a diagram showing an example of the configuration of a calculation model for a driver. [Figure 6] FIG. 6 is a flowchart showing a first example of processing by the electronic thermal unit. [Figure 7] FIG. 7A is an explanatory diagram of an overload characteristic graph of each of the motor and the driver, and FIG. 7B is an explanatory diagram of an overload characteristic graph of the entire system. [Figure 8] FIG. 8 is a flowchart illustrating an example of processing by the setting unit. [Figure 9] FIG. 9 is a graph showing the overload characteristics of the entire system when corrected by the first correction method. [Figure 10] FIG. 10 is a graph showing the overload characteristics of the entire system when corrected by the second correction method. [Figure 11] FIG. 11 is a flowchart showing a second processing example of the electronic thermal unit. [Figure 12] FIG. 12 is a flowchart showing a third example of processing by the electronic thermal unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A load monitoring device according to an embodiment of the present invention will be described below with reference to the drawings. The configuration of the embodiment is an example, and the present invention is not limited to the configuration of the embodiment.

[0020] <Embodiment> FIG. 1 is a schematic diagram of a control system including a driver 4 that also operates as a load monitoring device of this embodiment. The control system includes a network 1, a motor 2, a load device 3, the driver 4, a PLC (Programmable Logic Controller) 5, a power cable 8, and a terminal It has a final number of 9.

[0021] The control system is a system for driving and controlling a load device 3 together with a motor 2. The motor 2 and the load device 3 are treated as a control target 6 controlled by the control system. Here, examples of the load device 3 include various types of mechanical devices (for example, an arm of an industrial robot or a conveying device). The motor 2 is incorporated in the load device 3 as an actuator that drives the load device 3. For example, the motor 2 is an AC servo motor having a stator wound with a winding and a rotor. The motor 2 may have a configuration in which the stator is wound with a winding and has a rotor, and the specific configuration is not limited to an AC servo motor.

[0022] An encoder (not shown) is attached to the motor 2, and the encoder transmits a parameter signal related to the operation of the motor 2 as feedback to the driver 4. The parameter signal transmitted as feedback (hereinafter referred to as a feedback signal) includes, for example, position information on the rotational position (angle) of the rotating shaft of the motor 2, information on the rotational speed of the rotating shaft, etc.

[0023] The driver 4 receives an operation command signal related to the operation (motion) of the motor 2 from the PLC 5 via the network 1, and also receives a feedback signal output from an encoder connected to the motor 2. The driver 4 performs servo control related to the drive of the motor 2, i.e., calculates a command value related to the operation of the motor 2, based on the operation command signal from the PLC 5 and the feedback signal from the encoder, and supplies three-phase drive currents of u, v, and w to the motor 2 via a power cable 8 so that the operation of the motor 2 follows the command value. The drive current supplied to the motor 2 utilizes AC power sent from an AC power source 7 to the driver 4.

[0024] In this embodiment, the driver 4 is of a type that receives three-phase AC, but may be of a type that receives single-phase AC. The servo control by the driver 4 is feedback control that utilizes a position controller 41, a speed controller 42, and a current controller 43 that the driver 4 has.

[0025] 1, the driver 4 includes a position controller 41, a speed controller 42, and a current controller 43, which perform the above-mentioned servo control. The driver 4 also includes an electronic thermal unit 150 (see FIG. 2) to protect the motor 2 and the driver 4 from damage due to overheating.

[0026] The electronic thermal unit 150 estimates the temperature of the windings of the motor 2 and the temperature of the driver 4, and judges whether the motor 2 is in an overheated state based on the estimated temperatures.

[0027] 2, the servo control by the driver 4 and the protection control of the motor 2 by the electronic thermal unit 150 will be described. The control structure is formed by executing a predetermined control program in the driver 4 having a predetermined arithmetic unit, memory, etc.

[0028] The position controller 41 performs, for example, proportional control (P control). Specifically, a speed command is calculated by multiplying a position deviation, which is a deviation between a position command notified from the PLC 5 and a detected position, by a position proportional gain Kpp. The position controller 41 has a position proportional gain Kpp in advance as a control parameter. Next, the speed controller 42 performs, for example, proportional integral control (PI control). Specifically, an integral amount of a speed deviation, which is a deviation between a speed command calculated by the position controller 41 and a detected speed, is multiplied by a speed integral gain Kvi, and a sum of the calculation result and the speed deviation is multiplied by a speed proportional gain Kvp to calculate a torque command. The speed controller 42 has a speed integral gain Kvi and a speed proportional gain Kvp in advance as control parameters. The speed controller 42 may perform P control instead of PI control. In this case, the speed controller 42 has a speed proportional gain Kvp in advance as a control parameter. Next, the current controller 43 generates a command voltage for driving the amplifier 44 based on the torque command calculated by the speed controller 42. The amplifier 44 outputs a drive current for driving the motor 2 in accordance with the generated command voltage, thereby controlling the drive of the motor 2. The current controller 43 includes a filter (first-order low-pass filter) related to the torque command and one or more notch filters, and has cutoff frequencies related to the performance of these filters as control parameters. The current controller 43 also includes a current detector that detects the current command supplied from the amplifier 44 to the motor 2, and the current command detected by the current detector is fed back to the subtractor.

[0029] The control structure of the driver 4 includes a speed controller 42, a current controller 43, and a speed feedback system in which the controlled object 6 is a forward element, and further includes a position feedback system in which the speed feedback system and the position controller 41 are forward elements. The control structure enables the driver 4 to servo-control the motor 2 to follow position commands provided by the PLC 5 .

[0030] When the motor 2 is servo-controlled in this manner, if an excessive load (for example, a load exceeding the rated load of the motor 2) is applied to the motor 2 for a relatively long period of time, an excessive current will flow through the windings of the motor 2 for a long period of time. This may cause the temperature of the windings to rise excessively, resulting in burnout. Furthermore, if a current above the rated value is supplied from the driver 4 to the motor 2 for a long period of time, the temperature of the driver 4 or the power cable 8 may rise excessively, resulting in burnout. In order to protect the motor 2, driver 4, and power cable 8 from such damage, such as burnout, the driver 4 has an electronic thermal unit 150.

[0031] Specifically, the electronic thermal unit 150 has a calculation model 100 and an overload determination unit 110. As shown in Fig. 3, the calculation model 100 includes a calculation model 100a for the motor 2 and a calculation model 100b for the driver 4. The overload determination unit 110 also includes an overload determination unit 110a for the motor 2 corresponding to the calculation model 100a, and an overload determination unit 110b for the driver 4 corresponding to the calculation model 100b.

[0032] FIG. 4 shows a schematic structure of the calculation model 100a of the motor 2. The calculation model 100a is a program that calculates the winding temperature of the motor 2 in the electronic thermal unit 150, and outputs the winding temperature of the motor 2 when a heat flow in the motor 2 is given as an input. The heat flow can be regarded as a so-called copper loss caused by the electrical resistance of the winding coil of the motor 2, and is proportional to the square of the current flowing through the winding coil. The calculation model 100a is a thermal model that shows the relationship between the current value supplied to the motor 2 and the heat generation amount of the motor 2. For example, the calculation model 100 detects the current (current command) supplied to the motor 2 by the command voltage of the power control unit 43, thereby acquiring the current value, and calculates the heat flow by calculating the heat amount per unit time from the current value. The calculation model 100 operates as a current value acquisition unit that acquires the current value supplied to the motor 2.

[0033] 4, the calculation model 100a includes, as sub-models constituting the calculation model 100a itself, a winding temperature characteristic model 101 and a stator temperature characteristic model 102. The winding temperature characteristic model 101 is a model for calculating the temperature characteristics of the windings in the motor 2 when the thermal effect of the stator is virtually removed.

[0034] The stator temperature characteristic model 102 includes a reference model 102' and an iron loss coefficient Kr that uses as an argument the rotation speed (rpm) of the rotor of the motor 2. The reference model 102' is a model for calculating the temperature characteristics of the stator when the thermal influence of the windings is virtually removed in the motor 2. The value of the iron loss coefficient Kr can vary depending on the rotation speed of the rotor.

[0035] In the stator temperature characteristic model 102, the input heat flow is multiplied by (1+Kr) and input to the reference model 102' to calculate the output of the stator temperature characteristic model 102. By having such a stator temperature characteristic model 102 in the calculation model 100a, it is possible to reflect the iron loss caused by the rotation of the rotor in the temperature characteristics of the stator, and it is possible to more suitably realize the estimation of the winding temperature of the motor 2 for overload protection.

[0036] In this way, the calculation model 100a includes the winding temperature characteristic model 101 and the stator temperature characteristic model 102, and as shown in Fig. 4, the sum of the outputs of each model is calculated as the winding temperature of the motor 2. In this way, the winding temperature of the motor is calculated taking into account the correlation between the stator and the windings.

[0037] Here, the winding temperature characteristic model 101 will be described. The winding temperature characteristic model 101 is The following formula 1 is expressed including the thermal resistance Ra and thermal time constant Ta of the winding, which are parameters related to the temperature characteristics of the winding (winding-related parameters). The thermal resistance Ra is a value indicating the difficulty of heat transfer, and is a parameter indicating the amount of temperature rise per amount of heat generated per unit time. In this embodiment, the thermal resistance when the winding of the motor 2 is regarded as a thermally homogeneous object is used. The thermal time constant Ta is a parameter indicating the degree of responsiveness of the winding to temperature changes, and is defined as the time required for the temperature of the winding to change by 63.2% when transitioning from an initial thermal equilibrium state to another thermal equilibrium state. Winding temperature characteristic model = Ra / (Ta s+1) (Equation 1)

[0038] Next, the stator temperature characteristic model 102 will be described. The reference model 102' of the stator temperature characteristic model 102 includes the thermal resistance Rb and thermal time constant Tb related to the stator, which are parameters related to the temperature characteristics of the stator (stator-related parameters), and is expressed by the following formula 2. The definition of the thermal resistance Rb is the same as the definition of the thermal resistance Ra above, and in this embodiment, the thermal resistance when the stator of the motor is regarded as a thermally homogeneous object is adopted. The thermal time constant Tb is a parameter representing the degree of responsiveness of the stator to temperature changes, and is the same as the definition of the thermal time constant Ta above. Stator temperature characteristic model = Rb / (Tb s+1) (Equation 2)

[0039] In the calculation model 100a, the input (heat flow in the motor 2) is passed to the winding temperature characteristic model 101 and the stator temperature characteristic model 102. The outputs of the models are then added together to obtain the output of the calculation model, i.e., the estimated temperature of the motor windings. When the outputs of the models 101, 102 are added together, a value obtained by multiplying the output of each model 101, 102 by a predetermined gain may be added. By configuring the calculation model 100a in this manner, the winding temperature of the motor is estimated taking into account the correlation between the stator and the windings.

[0040] 5 shows a configuration example of a calculation model 100b for the driver. The calculation model 100b is a model for calculating temperature characteristics at a predetermined position of the driver 4 in the electronic thermal unit 150. The predetermined position may be any position that generates heat in response to the supply of current to the motor 2, and may be, for example, a position where a predetermined circuit such as an IGBT or a current detector provided in the driver 4 is mounted.

[0041] 5, the calculation model 100b includes a detection resistor section temperature characteristic model 103 and a board section temperature characteristic model 104 as sub-models constituting the calculation model 100b itself. The detection resistor section temperature characteristic model 103 is a model for calculating the temperature characteristic of the current detector (current detection resistor) when the thermal influence of the entire board of the driver 4 is virtually removed in the driver 4. The board section temperature characteristic model 104 is a model for calculating the temperature characteristic of the entire board of the driver 4 including the peripheral board of the current detection resistor when the thermal influence of the current detection resistor is virtually removed in the driver 4.

[0042] Here, the detection resistor temperature characteristic model 103 will be described. The detection resistor temperature characteristic model 103 is expressed by the following formula 3, including the thermal resistance Rc and thermal time constant Tc related to the current detection resistor, which are parameters related to the temperature characteristics of the detection resistor (detection resistor related parameters). The definition of the thermal resistance Rc is the same as the definition of the thermal resistance Ra above, and in this embodiment, the thermal resistance when the current detection resistor is regarded as a thermally homogeneous object is adopted. The thermal time constant Tc is a parameter that indicates the degree of responsiveness of the current detection resistor to temperature changes, and is the same as the definition of the thermal time constant Ta above. Temperature characteristic model of detection resistor = Rc / (Tc·s+1) (Equation 3)

[0043] Next, the substrate temperature characteristic model 104 will be described. The substrate temperature characteristic model 104 is a parameter related to the temperature characteristic of the substrate (substrate-related parameter) of the driver 4. It is expressed by the following formula 4 including the thermal resistance Rd and thermal time constant Td related to the board. The definition of thermal resistance Rd is the same as the definition of thermal resistance Ra above, and in this embodiment, the thermal resistance when the entire board of the driver 4 is regarded as a thermally homogeneous object is adopted. The thermal time constant Td is a parameter representing the degree of responsiveness to temperature changes of the board of the driver 4, and is the same as the definition of the thermal time constant Ta above. Board temperature characteristic model = Rd / (Td s+1) (Equation 4)

[0044] The calculation model 100b is a thermal model that indicates the relationship between the value of the current supplied to the motor 2 and the amount of heat generated by the driver 4, and a heat flow that depends on the current (detected current) detected as the output of the amplifier 44 is passed as an input to the detection resistor temperature characteristic model 103 and the board temperature characteristic model 104. The outputs of the models are added together to obtain the output of the calculation model, that is, the temperature of the driver 4 (referred to as the "driver temperature"). When the outputs of the models 103 and 104 are added together, a value obtained by multiplying the output of each model 103 and 104 by a predetermined gain may be added. By configuring the calculation model 100b in this manner, the driver temperature is estimated taking into account the correlation between the current detection resistor and the board.

[0045] As described above, each of the calculation models 100a and 100b outputs the temperature and the driver temperature of the motor 2. The overload determination unit 110a of the overload determination unit 110 determines whether the motor 2 is likely to reach an overload state, in other words, whether the windings of the motor 2 are likely to become excessively heated, based on the temperature of the motor 2 (referred to as the "motor temperature") which is the output of the calculation model 100a.

[0046] The overload determination unit 110b of the overload determination unit 110 determines, based on the driver temperature, which is the output of the calculation model 100b, whether the driver 4 is likely to reach an overload state, in other words, whether the driver 4 is likely to become excessively warm either overall or locally.

[0047] When the overload determination units 110a and 110b determine that either the motor 2 or the driver 4 is in an overload state, the driver 4 can stop driving in order to protect the system including the motor 2 and the driver 4. The calculation model 100 corresponds to a heat generation amount estimation unit, and the overload determination unit 110 corresponds to a load determination unit and an output unit.

[0048] 6 is a flowchart showing a first processing example of the electronic thermal unit 150. In step S101, the calculation models 100a and 100b of the electronic thermal unit 150 calculate the motor temperature and the driver temperature. That is, the calculation model 100a calculates the motor temperature (estimated value) according to the heat flow as a heat load calculation of the motor 2. The calculation model 100b calculates the driver temperature (estimated value) according to the heat flow as a heat load calculation of the driver 4. The order of calculation of each temperature is arbitrary, and may be executed in parallel.

[0049] In step S102, the overload determination unit 110 determines whether either the motor temperature or the driver temperature exceeds a threshold value. That is, the overload determination unit 110a determines whether the motor temperature exceeds a threshold value for the motor 2, and the overload determination unit 110b determines whether the driver temperature exceeds a threshold value for the driver 4. The order of these determinations is arbitrary, and these determinations may be performed in parallel. When it is determined that either of the threshold values ​​is exceeded, the remaining determinations may be canceled or stopped. If it is determined that either of the motor temperature and the driver temperature exceeds a threshold value, the process proceeds to step S103, and if not, the process proceeds to step S101. Here, the threshold value for the motor 2 is, for example, the maximum allowable temperature defined by the insulation class of the motor 2. For example, when the insulation class of the motor 2 is type F, the maximum allowable temperature is 155°C. Moreover, the threshold value for the driver 4 is, for example, the maximum allowable temperature set for protecting the IGBT in the driver 4.

[0050] In step S103, the electronic thermal unit 150 detects an abnormal temperature rise in the motor 2 and the driver 4 and outputs information indicating an overheated state (abnormality or warning) of the motor 2 and the driver 4. The information is output by emitting or blinking LEDs, outputting an alarm sound, displaying information on a display, etc. The configuration for outputting the information may be provided in the driver 4, or the information may be notified (displayed, etc.) using a display or speaker provided in the terminal 9. The electronic thermal unit 150 may also have a configuration for automatically stopping the operation of the driver 4 along with outputting the information indicating an abnormality or warning. However, the operation of the driver 4 may also be stopped manually by a user who receives the information.

[0051] The terminal 9 is used by the user to make various settings for the electronic thermal unit 150 through the setting unit 120 provided in the driver 4. The terminal 9 is also used to notify the user of various information by displaying the information indicating the above-mentioned abnormalities and warnings, etc. The setting unit 120, like the electronic thermal unit 150, may be realized by program execution by a processor (CPU) provided in the driver 4, or may be realized by a dedicated circuit (hardware) implemented in the driver 4.

[0052] The terminal 9 has a processor, a memory, an input device, a display, a communication interface, etc. By executing a program stored in the memory, the processor reads and writes information from and to the memory, accepts information input by a user using the input device, displays the information on the display, and transmits and receives information to and from the setting unit 120 by controlling the communication interface.

[0053] For example, the user can turn on and off the heat load calculations for the motor 2 and the driver 4. That is, the user can input information indicating the on or off status of each of the calculation models 100a and 100b from the input device to the terminal 9.

[0054] The information indicating on or off is sent to the setting unit 120 via the network 1. The setting unit 120 turns on or off the corresponding calculation models 100a and 100b based on the information indicating on or off. This makes it possible to turn on or off (set enable / disable) the heat load calculation for each of the motor 2 and the driver 4. Turning off the heat load calculation can reduce the calculation load on the processor (CPU).

[0055] Furthermore, the memory of the driver 4 (which may be the memory of the terminal 9) stores one or more sets of parameters (such as thermal resistances Ra-Rd and time constants Ta-Td) to be set in the calculation models 100a and 100b of the motor 2 and the driver 4. The user turns on the thermal load calculation for each of the motor 2 and the driver 4 on the terminal 9 and inputs the types of the motor 2 and the driver 4, whereby the setting unit 120 sets the parameters corresponding to the types of the motor 2 and the driver 4 in the calculation models 100a and 100b, and sets the thresholds corresponding to the types of the motor 2 and the driver 4 in the overload determination units 110a and 100b.

[0056] Furthermore, the setting unit 120 can automatically change the parameters (such as thermal time constant) and thresholds of the thermal load calculation according to the operating time (power supply time) of the motor 2 or the ambient temperatures of the motor 2 and the driver 4. The driver 4 measures the operating time (power supply time) of the motor 2, and the measured value can be used to change the parameters and thresholds. Furthermore, the ambient temperature may be predicted from the value of a temperature sensor in the encoder of the motor 2 or the value of a temperature sensor of a heat sink in the driver 4, or the value of a temperature sensor that measures the outside air temperature may be used as the ambient temperature.

[0057] As an example of a change in a parameter, when the operation time exceeds a predetermined time, the setting unit 120 changes the heat The value of the time constant is made smaller than the reference value. Furthermore, if the ambient temperature is higher than the reference temperature or the range of the reference temperature, the setting unit 120 lowers the threshold value. Conversely, if the ambient temperature is lower than the range of the reference temperature, the setting unit 120 raises the threshold value. In this way, the motor 2 and the driver 4 can be protected while the motor 2 is used appropriately according to the usage conditions of the motor 2.

[0058] Moreover, the setting unit 120 operates as a "control unit" and can generate and output information showing thermal curves (overload characteristic graphs) for the motor 2 and the driver 4, respectively, using parameters and thresholds for thermal load calculation for the motor 2 and the driver 4. Furthermore, the setting unit 120 can generate and output information obtained by combining information showing the overload characteristic graph of the motor 2 and information showing the overload characteristic graph of the driver 4. The overload characteristic graph is a graph showing the change in the time (detection time) until an overheating state is detected when a current larger than the rated current is applied. The overload characteristic is usually expressed as a graph with the horizontal axis showing a current equal to or larger than the rated current and the vertical axis showing the time (detection time) until an overload (overheating state) is detected. It should be noted that the time (detection time) until an overload is detected is the time (applicable time) during which a predetermined current larger than the rated current is allowed to be continuously applied to the motor 2 and the driver 4. For this reason, in the following overload characteristic graph, the vertical axis shows the applicable time instead of the detection time.

[0059] FIG. 7A shows a graph M indicating the overload characteristics of the motor 2 and a graph D indicating the overload characteristics of the driver 4. In the overload characteristics graph, the larger the current, the shorter the application time. The numerical values ​​on which the graphs M and D are based may be generated in the driver 4 or in the terminal 9. The processor of the terminal 9 displays the graphs M and D on the display of the terminal 9. This allows the user to grasp the overload characteristics of the motor 2 and the driver 4. Also, FIG. 7B shows a graph S which is a composite of the graph M indicating the overload characteristics of the motor 2 and the graph D indicating the overload characteristics of the driver 4. The processor of the terminal 9 displays the graph S on the display of the terminal 9. This allows the user to grasp the overload characteristics of the entire system including the motor 2 and the driver 4 which satisfies the overload characteristics of both the motor 2 and the driver 4.

[0060] In addition, the setting unit 120 can correct the overload characteristic graphs of the motor 2 and the driver 4, respectively, by using the value of the temperature sensor in the encoder as the ambient temperature of the motor 2, and the value of the temperature sensor of the heat sink of the driver 4 as the ambient temperature of the driver 4.

[0061] Fig. 8 is a flowchart showing a processing example of the setting unit 120. In this processing example, it is assumed that, as an initial state, the overload characteristic graphs M and D of the motor 2 and the driver 4, respectively, and the overload characteristic graph S of the entire system, as shown in Fig. 7, have been generated. In step S201, the setting unit 120 acquires the ambient temperature of the motor 2 and the ambient temperature of the driver 4 from the temperature sensor in the encoder and the temperature sensor in the heat sink.

[0062] In step S202, the setting unit 120 corrects the overload characteristic graphs of the motor 2 and the driver 4 based on the ambient temperature of the motor 2 and the ambient temperature of the driver 4 acquired in step S201. Then, in step S203, the setting unit 120 sets parameters corresponding to the overload characteristic graphs of the motor 2 and the driver 4 corrected in step S203 in the calculation models 100a and 100b, respectively, and sets threshold values ​​in the overload determination units 110a and 100b, respectively.

[0063] Here, the correction of the overload characteristic graph performed in step S202 will be described.

[0064] First, a method for generating an overload characteristic graph will be described. Here, a method for generating an overload characteristic graph M of the motor 2 will be described as an example. First, the setting unit 120 generates the overload characteristic graph M The setting unit 120 outputs a command to the current controller 43 to perform a first voltage application for generating a current corresponding to 200% of the rated current of the motor 2. In the first voltage application, a voltage is applied to supply the motor 2 with a current that is 200% of the rated current of the motor 2. The setting unit 120 then calculates the ambient temperatures of the motor 2 3 seconds, 10 seconds, and 20 seconds after the first voltage application (energization) is performed. The ambient temperatures of the motor 2 after energization are calculated by a resistance method using the resistance temperature coefficient of copper, which is expressed by the following equation 5. t2 = (R2 / R1-1)(234.5+t1)±Δt (Formula 5) In Equation 5, R1 is the winding resistance value of motor 2 when current begins to flow, and R2 is the winding resistance value of motor 2 after current begins to flow. These winding resistance values ​​are calculated from the current value detected by the current detector. Additionally, t1 is the ambient temperature of motor 2 when current begins to flow, and t2 is the ambient temperature of motor 2 after current begins to flow. Here, the value of the temperature sensor in the encoder is used for t1. And Δt is the change in the ambient temperature of motor 2 between when current begins to flow and after current begins to flow. For Δt, the value of the temperature sensor in the encoder is used. When the ambient temperature rises after current begins to flow, Δt is subtracted, and when the ambient temperature drops, Δt is added.

[0065] Next, the setting unit 120 generates an overload rate curve passing through three points of the ambient temperature t2 of the motor 2 at 3 seconds, 10 seconds, and 20 seconds after the current is turned on, when the first voltage is applied. Then, from this overload rate curve, the setting unit 120 calculates a thermal time constant Ta for the winding of the motor 2, a thermal time constant Tb for the stator, and a thermal resistance ratio time constant which is the ratio between the thermal time constant Ta and the thermal time constant Tb.

[0066] Next, the setting unit 120 outputs a command to perform the second voltage application to the current controller 43. In the second voltage application, a voltage is applied to supply a current that is 300% of the rated current of the motor 2 to the motor 2. Then, the setting unit 120 calculates the ambient temperature t2 of the motor 2 three seconds after the second voltage application (energization) is performed. The ambient temperature t2 of the motor 2 after energization is calculated by the resistance method represented by the above-mentioned equation 5.

[0067] Next, the setting unit 120 generates a curve of the overload rate when the second voltage is applied from the thermal time constant Ta, thermal time constant Tb, and thermal resistance ratio time constant Tr calculated from the result of the first voltage application. Note that the setting unit 120 may check whether the generated curve of the overload rate when the second voltage is applied is appropriate based on the ambient temperature t2 of the motor 2 three seconds after the second voltage application and the threshold value for the motor 2.

[0068] Then, the setting unit 120 obtains an overload characteristic graph M of the motor 2 by combining the curve of the overload rate when the first voltage is applied and the curve of the overload rate when the second voltage is applied.

[0069] In addition, the overload characteristic graph D of the driver 4 is generated using the formula 5 in the same manner as the overload characteristic graph M of the motor 2. However, in the formula 5, R1 is the current detection resistance value of the driver 4 at the start of energization, and R2 is the current detection resistance value of the driver 4 after energization. These current detection resistance values ​​are calculated from the current value detected by the current detector. t1 is the ambient temperature of the driver 4 at the start of energization, and t2 is the ambient temperature of the driver 4 after energization. Here, the value of the temperature sensor of the heat sink in the driver 4 is used for t1. And, Δt is the change in the ambient temperature of the driver 4 between the start of energization and after energization. The value of the temperature sensor of the heat sink is used for Δt. In addition, the setting unit 120 calculates the thermal time constant Tc of the detection resistor part of the driver 4, the thermal time constant Td of the board part, and the thermal resistance ratio time constant which is the ratio of the thermal time constant Tc to the thermal time constant Td from the curve of the overload rate at the time of the first voltage application. In addition, the setting unit 120 may check whether the generated curve of the overload rate when the second voltage is applied is appropriate based on the ambient temperature t2 of the motor 2 3 seconds after the application of the second voltage and the threshold value for the driver 4.

[0070] Next, a method for correcting the overload characteristic graph will be described. In the first correction method, The setting unit 120 regenerates the overload characteristic graphs of the motor 2 and the driver 4, respectively, using the ambient temperature of the motor 2 and the ambient temperature of the driver 4 acquired in step S201. In this regeneration, the setting unit 120 corrects the overload characteristic graph of the motor 2 so that the application time in the overload characteristic graph of the motor 2 becomes longer as the ambient temperature of the motor 2 becomes lower while maintaining the rated current of the motor 2. The setting unit 120 also corrects the overload characteristic graph of the driver 4 so that the application time in the overload characteristic graph of the driver 4 becomes longer as the ambient temperature of the driver 4 becomes lower while maintaining the rated current of the driver 4. Then, the setting unit 120 combines the regenerated overload characteristic graph of the motor 2 and the overload characteristic graph of the driver 4 to regenerate the overload characteristic graph of the entire system.

[0071] FIG. 9 shows an overload characteristic graph of the entire system when corrected by the first correction method. In FIG. 9, in addition to the overload characteristic graph of the entire system after correction, an overload characteristic graph of the entire system before correction, for example, the overload characteristic graph S shown in FIG. 8B, is also shown. As shown in FIG. 9, the overload characteristic graph S1 of the entire system after correction has a longer applicable time (D1 before correction, D2 after correction) when compared at a predetermined current value (R1) greater than the rated current, compared with the overload characteristic graph S of the entire system before correction. For example, when a current of 250% of the rated current is applied, the applicable time is about 0.9 seconds in the overload characteristic graph S of the entire system before correction, whereas the applicable time is about 10 seconds in the overload characteristic graph S1 of the entire system after correction. Also, when a current of 350% of the rated current is applied, the applicable time is about 0.2 seconds in the overload characteristic graph S of the entire system before correction, whereas the applicable time is about 2 seconds in the overload characteristic graph S1 of the entire system after correction.

[0072] In the second correction method, the setting unit 120 moves the asymptote of the overload characteristic graph using the ambient temperature of the motor 2 and the ambient temperature of the driver 4 acquired in step S201, without basically changing the shape of each of the overload characteristic graphs of the motor 2 and the driver 4 before correction. In this movement, the setting unit 120 increases the rated current of the motor 2 and moves the asymptote so that the application time in the overload characteristic graph of the motor 2 becomes longer as the ambient temperature of the motor 2 becomes lower. In addition, the setting unit 120 increases the rated current of the driver 4 and moves the asymptote so that the application time in the overload characteristic graph of the driver 4 becomes longer as the ambient temperature of the driver 4 becomes lower. Then, the setting unit 120 combines the overload characteristic graph of the motor 2 with the asymptote moved and the overload characteristic graph of the driver 4 to regenerate the overload characteristic graph of the entire system.

[0073] FIG. 10 shows an overload characteristic graph of the entire system when corrected by the second correction method. In FIG. 10, in addition to the overload characteristic graph of the entire system after correction, an overload characteristic graph of the entire system before correction, for example, the overload characteristic graph S shown in FIG. 8B, is also shown. As shown in FIG. 10, the overload characteristic graph S2 of the entire system after correction has a larger current value (R1 before correction, R2 after correction) when compared with the overload characteristic graph S of the entire system before correction, when compared at a predetermined applicable time (D1). For example, the current value at which the applicable time is 100 seconds is about 130% of the rated current in the overload characteristic graph S of the entire system before correction, whereas it is about 170% of the rated current in the overload characteristic graph S2 of the entire system after correction. Also, the current value at which the applicable time is 10 seconds is about 160% of the rated current in the overload characteristic graph S of the entire system before correction, whereas it is about 230% of the rated current in the overload characteristic graph S2 of the entire system after correction.

[0074] In the second correction method, the setting unit 120 determines the amount of movement (increase) of the asymptote based on the ambient temperature of the motor 2 and the ambient temperature of the driver 4. For example, the asymptote A of the overload characteristic graph S of the entire system before correction is a straight line that passes through a current value that is 115% of the rated current among straight lines parallel to the axis indicating the detection time. For example, when the insulation class of the motor 2 is Class F, when the ambient temperature of the motor 2 is 40°C (the upper limit of the range of the operating environment temperature defined by the specifications of the motor 2), Even if a current of 115% of the rated current continues to flow through the motor 2 at a certain time, the temperature of the motor 2 is set to be within 155°C, which is the maximum allowable temperature for class F. The current value of 115% of the rated current, which is the current value of asymptote A, is such a current value. Therefore, if the insulation class of the motor 2 is a type other than class F (for example, class B or class H), the current value of the asymptote will be a current value other than 115% of the rated current. Here, if the insulation class of the motor 2 is class F, and the ambient temperature of the motor 2 is 0°C (the lower limit of the range of the operating environment temperature specified by the specifications of the motor 2), the motor 2 has a temperature margin of 40°C. In the case of asymptote A, a temperature margin of 40°C corresponds to a current value of 29.68% of the rated current, because a temperature of 1°C corresponds to a current value of 0.74% of the rated current. That is, the setting unit 120 can move the asymptote A in the direction in which the current increases (to the right in FIG. 10) by a maximum current value of 29.68% of the rated current to obtain the asymptote A2. In accordance with this movement of the asymptote A, the setting unit 120 can move the overload characteristic graph S of the entire system before correction in the direction in which the current increases to obtain the overload characteristic graph S2 of the entire system after correction. However, the instantaneous allowable current value of the motor 2 is specified based on the specifications of the motor 2. For this reason, the setting unit 120 adjusts (shortens) the length in the axial direction indicating the current in the overload characteristic graph S2 of the entire system after correction so that the maximum current value of the overload characteristic graph does not exceed the instantaneous allowable current value of the motor 2 even if the overload characteristic graph S of the entire system before correction is moved in the direction in which the current increases.

[0075] 11 is a flowchart showing a second processing example of the electronic thermal unit 150. In step S301, the overload determination units 110a and 100b acquire thresholds (applicable time for a predetermined current value greater than the rated current) corresponding to the overload characteristic graphs of the motor 2 and the driver 4 after correction from the setting unit 120. In step S302, the overload determination units 110a and 100b determine whether a current greater than the rated current has been applied to the motor 2 and the driver 4 for a period exceeding the applicable time. That is, the overload determination unit 110a determines whether a current greater than the rated current has been applied to the motor 2 for a period exceeding the applicable time for the motor 2, and the overload determination unit 110b determines whether a current greater than the rated current has been applied to the driver 4 for a period exceeding the applicable time for the driver 4. If it is determined that a current larger than the rated current has been applied to at least one of the motor 2 and the driver 4 for a period exceeding the application time, the process proceeds to step S303, and if not, the process proceeds to step S301. In step 303, the overload determination unit 110 determines that an overload has occurred in the motor 2 and the driver 4, and outputs information indicating an overload (abnormality or warning). The information is output by lighting or blinking an LED, outputting a warning sound, displaying information on a display, etc.

[0076] According to this embodiment, the setting unit 120 corrects the overload characteristic graphs of the motor 2 and the driver 4 based on the ambient temperature of the motor 2 and the ambient temperature of the driver 4. As a result, the overload determination unit 110 determines whether a current larger than the rated current has been applied to the motor 2 and the driver 4 for longer than the applicable time based on the threshold value corresponding to the corrected overload characteristic graph. In this way, by adjusting the applicable time to the motor 2 and the driver 4, that is, by adjusting the load on the motor 2 and the driver 4, the original performance of the IGBTs of the motor 2 and the driver 4 can be brought out as much as possible according to the ambient temperature of the motor 2 and the ambient temperature of the driver 4. Therefore, the motor 2 and the driver 4 can be used efficiently while being protected.

[0077] <Modification> Next, a modified example will be described. Since this modified example has a similar configuration to the embodiment, differences will be mainly described.

[0078] In the above-described embodiment, the overload characteristic graphs of the motor 2 and the driver 4 are corrected. This allows a current larger than the rated current to be applied to the motor 2 and the driver 4 for an application time that corresponds to the ambient temperature of the motor 2 and the ambient temperature of the driver 4. However, applying a current larger than the rated current for the application time may cause the instantaneous allowable current value of the motor 2 to exceed the instantaneous allowable current value of the power cable 8.

[0079] Here, the instantaneous allowable current value I of the power cable 8 is expressed by the following formula 6.

number

[0080] Therefore, in the load monitoring device according to this modification, in addition to monitoring the overload of the motor 2 and the driver 4, the overload of the power cable 8 is also monitored.

[0081] In this modification, the user can set the protection level of the power cable 8 by inputting the type of the power cable and the power cable installation conditions into the terminal 9. For example, when some of the following requirements are input, the processor of the terminal 9 or the setting unit 120 of the driver 4 calculates the protection level of the power cable 8 corresponding to the input information. Cable jacket material, thermal resistance of jacket material, or maximum operating temperature of cable - Cable wire outer diameter and length · Cable wire conductor material or electrical resistivity (resistivity, specific resistance) [Ω·m] Cable conductor diameter (AWG, sq.) or cross-sectional area Ambient temperature when laying the cable In case of multiple installation, multiple installation conditions If wiring is done through a wiring duct, the material of the wiring duct or the maximum operating temperature of the wiring duct material

[0082] For example, the terminal 9 is configured to display the above menu on a display and allow the user to select an option or input a value. -Cable sheath material (options: CV cable, OF cable, solid cable, vinyl cable) Or maximum operating temperature of the cable (options: 80℃, 85℃, 105℃) Cable conductor diameter (enter value: AWG / SQ) Ambient temperature when laying the cable (options: 0℃ 25℃ 40℃ 55℃ 70℃ 85℃) Multiple laying (Yes, No) Maximum operating temperature of wiring duct material when multiple wiring is used (Options: 65℃, 80℃, 85℃, 105 °C)

[0083] The memory of the driver 4 (or the terminal 9) stores one or more sets of parameters (thermal resistances Ra-Rd, time constants Ta-Td, etc.) to be set in the calculation models 100a and 100b of the motor 2 and the driver 4 corresponding to the protection level, and the setting unit 120 sets the parameters corresponding to the protection level acquired by its own calculation or acquired from the terminal 9 by operating as a "reception unit" in the calculation models 100a and 100b. For example, the values ​​of the thermal resistances Ra-Rd are set to be smaller as the conductor diameter of the cable wire becomes thicker. Also, for example, the values ​​of the time constants Ta-Td are set to be smaller as the number of wires increases. The set of parameters may be calculated using a parameter calculation algorithm based on the input information. Also, the setting unit 120 acquires threshold values ​​corresponding to the protection level stored in advance in the memory, and sets them in the overload determination units 110a and 110b. This makes it possible to calculate the thermal load and determine overload of the motor 2 and driver 4 while taking into account the power cable 8, allowing the motor 2 and driver 4 to be used efficiently while protecting the power cable 8 in addition to the motor 2 and driver 4.

[0084] FIG. 12 is a flowchart showing a third processing example of the electronic thermal unit 150. In step S401, the overload determination units 100a and 100b obtain the corrected overload characteristic graphs of the motor 2 and the driver 4 from the setting unit 120. In step S402, the overload determination units 100a and 100b calculate the allowable current values ​​of the motor 2 and the driver 4 and the applicable time corresponding to the allowable current values ​​from the corrected overload characteristic graphs of the motor 2 and the driver 4. In step S403, the overload determination units 100a and 100b obtain the cable coating material type and conductor diameter as information on the configuration of the power cable 8 from the setting unit 120. In step 404, the overload determination units 100a and 100b calculate the allowable current value of the power cable 8 from the calculated applicable time and the obtained information on the configuration of the power cable 8 using Equation 6. In step S405, the overload determination units 100a and 100b determine whether the allowable current value of the power cable 8 is equal to or less than the allowable current value of the motor 2 and the driver 4. If the allowable current value of the power cable 8 is equal to or less than the allowable current value of the motor 2 and the driver 4, the process proceeds to step S406, and if not, the process proceeds to step S401. In step S406, the overload determination units 100a and 100b output information indicating an overload (abnormality or warning) as an overload has occurred in the power cable 8. The information is output by lighting or blinking an LED, outputting a warning sound, displaying information on a display, etc.

[0085] According to this modification, after correcting the overload characteristic graphs of the motor 2 and the driver 4, the overload determination unit 110 determines whether the allowable current value of the power cable 8 is equal to or lower than the allowable current value of the motor 2 and the driver 4 based on the corrected overload characteristic graphs of the motor 2 and the driver 4, and outputs information indicating an overload when it is determined that the allowable current value of the power cable 8 is equal to or lower than the allowable current value of the motor 2 and the driver 4. As a result, the allowable current value of the power cable 8 falls below the allowable current value of the motor 2 and the driver 4, thereby preventing the power cable 8 from excessively increasing in temperature and burning out. Therefore, the motor 2 and the driver 4 can be used efficiently while protecting not only the motor 2 and the driver 4 but also the power cable 8.

[0086] <Additional Notes> A load monitoring device (4) for monitoring a load between a motor (2) and a driver (4) that controls the operation of the motor (2), a current value acquisition unit (150) that acquires a current value supplied to the motor (2); a first temperature estimation unit (100) that estimates the temperature of the motor (2) as a first temperature using a first thermal model (100a) that indicates the relationship between the current value and the amount of heat generated by the motor (2); and, a second temperature estimation unit (100) that estimates a temperature of the driver (4) as a second temperature using a second thermal model (100b) that indicates a relationship between the current value and the amount of heat generated by the driver (4); a load determination unit (110) configured to determine the presence or absence of an overload state of the motor (2) by comparing the first temperature with a first threshold value for the motor (2), the load determination unit (110) having a first control structure having a first load characteristic (M) indicating an applicable time for a predetermined current value for the motor (2), and a second control structure configured to determine the presence or absence of an overload state of the driver (4) by comparing the second temperature with a second threshold value for the driver (4), the second load characteristic (D) indicating an applicable time for the predetermined current value for the driver (4); an output unit (100) that outputs abnormality information relating to an overload state when the load determination unit determines that at least one of the motor (2) and the driver (4) is in an overload state; a correction unit (120) that corrects the first load characteristic (M) in the first control structure and the second load characteristic (D) in the second control structure based on a first ambient temperature that is an ambient temperature of the motor (2) and a second ambient temperature that is an ambient temperature of the driver (4); A load monitoring device (4). [Explanation of symbols]

[0087] 1. Network 2. Motor 3...Loading device 4. Driver 5. PLC 6. Control Object 7...AC power supply 8. Power cable 9. Terminal 41 Position controller 42 Speed ​​controller 43 Current controller 44 Amplifier 100···Calculation model 110...Overload judgment section 120 Setting section 150···Electronic thermal section

Claims

1. A load monitoring device that monitors a load between a motor and a driver that controls the operation of the motor, a current value acquisition unit that acquires a value of a current supplied to the motor; a first temperature estimator that estimates a temperature of the motor as a first temperature using a first thermal model that indicates a relationship between the current value and a heat generation amount of the motor; a second temperature estimator that estimates a temperature of the driver as a second temperature using a second thermal model that indicates a relationship between the current value and a heat generation amount of the driver; a load determination unit configured to determine the presence or absence of an overload state of the motor by comparing the first temperature with a first threshold value for the motor, the load determination unit having a first control structure having a first load characteristic indicating an application time for a predetermined current value for the motor, and a second control structure configured to determine the presence or absence of an overload state of the driver by comparing the second temperature with a second threshold value for the driver, the second load characteristic indicating an application time for the predetermined current value for the driver; an output unit that outputs abnormality information related to an overload state when the load determination unit determines that at least one of the motor and the driver is in an overload state; a correction unit that corrects the first load characteristic in the first control structure and the second load characteristic in the second control structure based on a first ambient temperature that is an ambient temperature of the motor and a second ambient temperature that is an ambient temperature of the driver; A load monitoring device comprising:

2. the correction unit corrects the first load characteristic such that the application possible time under the first load characteristic becomes longer as the first ambient temperature becomes lower while maintaining a rated current of the motor, and corrects the second load characteristic such that the application possible time under the second load characteristic becomes longer as the second ambient temperature becomes lower while maintaining a rated current of the driver.

2. The load monitoring device of claim 1.

3. the correction unit corrects the first load characteristic so that the rated current of the motor increases and the application possible time under the first load characteristic becomes longer as the first ambient temperature decreases, and corrects the second load characteristic so that the rated current of the driver increases and the application possible time under the second load characteristic becomes longer as the second ambient temperature decreases.

2. The load monitoring device of claim 1.

4. the load determination unit calculates a first current value as an allowable current value of the motor and the driver and a first applicable time corresponding to the first current value from the first load characteristic and the second load characteristic corrected by the correction unit, calculates a second current value as an allowable current value of the power cable from the first applicable time and information on the configuration of a power cable connecting the motor and the driver, compares the second current value with the first current value, and outputs information indicating an overload state of the power cable when the second current value is equal to or less than the first current value. The load monitoring device according to any one of claims 1 to 3.

5. a receiving unit that receives an input of information regarding a configuration of the power cable; Further equipped with 5. A load monitoring device according to claim 4.

6. A load monitoring method for monitoring a load between a motor and a driver that controls the operation of the motor, comprising the steps of: Acquire a current value supplied to the motor; estimating a temperature of the motor as a first temperature based on a first thermal model that indicates a relationship between the current value and a heat generation amount of the motor; estimating a temperature of the driver as a second temperature using a second thermal model that indicates a relationship between the current value and a heat generation amount of the driver; generating a first load characteristic indicating an application time for a given current value for the motor; correcting a first threshold value for the motor from the first temperature; comparing the corrected first threshold value for the motor with a current output current value to determine whether the motor is in an overload state; generating a second load characteristic indicating an application time for a given current value for the driver; calibrating a second threshold for the driver from the second temperature; comparing a current output current value to a second corrected threshold value for the driver to determine whether or not the driver is in an overload state; When it is determined that at least one of the motor and the driver is in an overload state, abnormality information relating to the overload state is output; correcting the first load characteristic in the first control structure and the second load characteristic in the second control structure based on a first ambient temperature which is an ambient temperature of the motor and a second ambient temperature which is an ambient temperature of the driver; Load monitoring method.

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