JP2006158089A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device that can maintain drive without stopping a motor 600 by performing overheat protection drive even if an input current sensor 200 is abnormal. <P>SOLUTION: The motor control device is provided with a control means 700 that controls an inverter of the motor 600 by being fed with power from a power supply 100, and also characterized by comprising: the input current sensor 200 that detects an input current fed from the power supply 100 and generates a detected value; an input current estimation means that obtains an estimation value of the input current fed from the power supply 100 by using at least one of a control amount with which the control means 700 controls the motor 600, and an operation amount that indicates the operation state of the motor 600; and a switching means that determines the operation state of the input current sensor 200 and switches a first overheat protection operation mode at a sensor normal time obtained by using the detected value by the input current sensor 200, and a second overheat protection operation mode at a sensor abnormal time obtained by using the estimation value by the input current estimation means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor control device that performs inverter control of a motor, and more particularly to a motor control device that performs an overheat protection operation of a motor.

  By the way, when an abnormality occurs in the inverter-controlled motor, the inverter control circuit detects the motor current and the like, disconnects the motor drive circuit (inverter and the like) and the motor, and stops the motor (for example, patent Reference 1).

There is also a device that detects an input current supplied from an external power source to a motor drive circuit and stops the motor when there is an abnormal current input.
JP 58-2222797 A

  In any case, at the time of abnormality, for example, the motor is stopped for overheat protection, and the system driven by the motor is also stopped.

  At that time, when the input current sensor fails and detects abnormal current, the motor is stopped in the same way even if the system can operate normally, and the system driven by the motor also stops. End up.

  The present invention has been made in view of the above points, and provides a motor control device capable of maintaining the operation without stopping the motor by performing the overheat protection operation even when the input current sensor becomes abnormal. The purpose is to do.

  In order to achieve the above object, the present invention employs technical means described in claims 1 to 7.

According to the motor control device of the present invention as set forth in claim 1, the motor control device includes a control unit that receives power supply and performs inverter control of the motor.
The input current sensor that detects the input current supplied from the power source and generates a detection value, and the control means,
Using at least one of a control amount for controlling the motor and an operation amount indicating the operation state of the motor, input current estimation means for obtaining an estimated value of the input current supplied from the power source, and determining the operation state of the input current sensor Then, switching to switch between the first overheat prevention operation mode when the sensor is normal using the detection value by the input current sensor and the second overheat prevention operation mode when the sensor is abnormal using the estimation value by the input current estimation means Means.

  Accordingly, in the present invention, even when the input current sensor is abnormal, it is possible to continuously operate the motor by estimating the input current and using the substitute value (estimated value) of the input current. In addition, when abnormal overheating of the motor is expected, switching from the first overheat prevention operation mode when the sensor is normal to the second overheat prevention operation mode provided for the sensor abnormality, Different overheat prevention operations can be performed to protect the motor from overload and to reliably suppress abnormal heating.

  According to the second aspect of the present invention, the input current estimation means obtains an estimated value by adding a safety factor that greatly anticipates the input current when estimating the input current supplied from the power source. It is possible to increase the estimated value earlier than normal when the motor load increases, and to switch to the second overheat prevention operation mode when the sensor is abnormal earlier than when the sensor is normal. Thereby, the motor can be operated safely even when the sensor is abnormal.

According to a third aspect of the present invention, the input current estimation means is
Estimated value = N × T / VM / η × SK
However, N is a motor rotation speed, T is an output torque, VM is a power supply voltage, η is a motor / compressor efficiency, and SK is an estimated value of an input current, which is expressed by a safety factor. .

  Accordingly, in the present invention, the estimated value is obtained by using the control amount for controlling the motor that can be acquired by the control means and the operation amount indicating the operation state of the motor without adding a special sensor for estimating the input current. It becomes possible to ask.

  According to the fourth aspect of the present invention, the data indicating the motor / compressor efficiency η is selected from the data map determined in advance according to the motor operating conditions, so that the control means can quickly Data on the compressor efficiency η can be obtained, and the control means can quickly estimate the input current value.

  According to the fifth aspect of the present invention, the switching means determines whether the input current sensor is normal or abnormal, the comparison result between the input current in the no-load state of the motor and the abnormal input current determination value, and the stable load of the motor. It is performed using at least one of the comparison results between the detected value at the time and the abnormal input current determination value under the corresponding operation condition.

  Thereby, it is possible to more reliably determine whether the input current sensor is normal or abnormal by determining the magnitude of the input current in the no-load state or the specific load state.

  According to the invention described in claim 6, the first overheat prevention operation mode is an operation mode for suppressing abnormal overheating of the motor when the detected value exceeds a predetermined threshold value. Therefore, the second overheat prevention operation mode is an operation mode for suppressing abnormal overheating of the motor when the estimated value of the input current estimation means exceeds a predetermined threshold value. By setting a predetermined threshold value common to both modes, it is easy to relate the control characteristics and operation areas of both modes, and it is easy to control switching between both modes.

  Hereinafter, an embodiment of the motor control device of the present invention will be described.

  In the present embodiment, the motor control device of the present invention will be described as an example in which the motor control device of the present invention is applied to a motor control device of an electric compressor in a heat pump cycle of a heat pump type hot water supply device. Is also applicable.

  FIG. 1 is a block diagram showing a schematic configuration of a hot water supply control system including a motor control device.

  In FIG. 1, the external power source 100 includes an input current sensor 200 that is supplied with power from, for example, a commercial power supply of 200 V and detects an input current supplied to the motor drive circuit at the subsequent stage. In this example, the input current sensor 200 rectifies an alternating current signal induced on the secondary coil 201a side of the transformer 201 connected in series to the input line L1 and generates a direct current detection signal (ie, a detection value). And a processing circuit 202 for conversion. The input current sensor 200 may have other configurations besides the transformer method, such as an indirect detection method that detects an induced current from the input line L1.

  An AC voltage from the external power supply 100 is input to the AC / DC converter unit 300 via the input line L1, where it is converted to a DC voltage and input to the inverter unit 500 via the bus L2. As illustrated in FIG. 1, the inverter unit 500 includes power switches (U1,...) And (U2,...) On the upper arm and the lower arm, respectively, which will be described later. Based on a control signal from the control device 700, a voltage having a desired frequency is applied to each phase (U phase, V phase, W phase) of the stator coil of the motor 600, and the rotor in which the magnet is embedded is rotationally driven. Here, the motor 600 is a four-pole three-phase (U, V, W) synchronous motor.

  Further, between the pair of buses L2 and L3, a capacitor 400 of smoothing means for smoothing a DC voltage including a ripple component output from the AC / DC converter unit 300, for example, a film capacitor as an electrolytic capacitor or a snubber capacitor is connected. ing.

  The control device 700 includes a microcomputer, a memory 700a, an input / output circuit, and the like. The control device 700 includes input current information S1 of the input current sensor 200, voltage information S2 between the buses L2 and L3, and at least two phases, here U phase. For example, the inverter unit 500 is controlled in accordance with the command information S4 from the instruction unit 900 which receives the W-phase current information S3 and receives an instruction from the user, and the operation state of the motor 600 (that is, the electric compressor) is controlled. When the control device 700 enters the overheat prevention operation mode, the display device 1000 notifies the user to that effect.

  A heat pump cycle 800 of a heat pump hot water supply apparatus includes a compressor 600a driven by a motor 600, a hot water supply heat exchanger (water refrigerant heat exchanger) 801, a decompression means 802, an accumulator 803, an outdoor heat exchanger (heat source heat exchange). 804) and the internal heat exchanger 805 are connected in a ring shape with refrigerant piping, and provide heat from the high-temperature and high-pressure refrigerant and heat from the outside to the hot water supply side through the hot water heat exchanger 801. Yes. Here, the compressor 600a is an electric compressor that compresses and discharges a gas-phase refrigerant to a critical pressure or higher by operating a refrigerant compression mechanism as a load by a built-in synchronous motor 600.

  Next, overheat prevention operation characteristics when the input current sensor 200 is normal or abnormal (that is, at the time of failure), which is a feature of the present invention, will be described with reference to FIG.

  In FIG. 2, a characteristic A is a characteristic diagram showing a relationship between the motor load L and the input current value iIN obtained by the input current sensor 200. The input current value iIN is an overload protection function, particularly an overheat prevention function. When a predetermined threshold value iX indicating the start of operation is exceeded, this indicates that an overheat prevention operation (that is, a first overheat prevention operation mode) for suppressing (or lowering) abnormal heat generation of the motor 600 is performed. A region I indicates a first overheat prevention operation region when the input current sensor 200 is normal.

  A characteristic B is a characteristic diagram showing a relationship between the motor load L and an input current estimated value iINX (detected value) obtained by an input current estimation formula to be described later. The input current estimated value iINX is an overload protection function, particularly When the threshold value iX indicating the start of operation of the overheat prevention function is exceeded, this indicates that an overheat prevention operation (that is, the second overheat prevention operation mode) for suppressing (or reducing) the abnormal heat generation of the motor 600 is performed. Region II shows a second overheat prevention operation region when the input current sensor 200 is abnormal.

  When the input current sensor 200 is abnormal, for example, when a malfunction occurs in the transformer 201 or the processing circuit 202, the input current value iIN cannot be accurately grasped. Therefore, when calculating the estimated value iINX, the safety factor, that is, the motor load L As compared with the characteristic A, the shift is made to the left (low load side) and the gradient is made higher so that the overheat prevention operation can be started earlier with respect to the increase in. Thereby, when the system is in a state where it can operate normally, even if the sensor 200 becomes abnormal, the motor 600 is not stopped and the motor 600 continues to operate. It becomes possible to prevent reliably.

  The motor load L corresponds to the electric power of the motor 600, and is the product of the voltage and current applied to the motor 600. The threshold value iX is a set value for overload protection that is determined by the original capability and structure of the motor 600.

  Next, the operation of the control device 700 shown in FIG. 1 will be described with reference to FIG.

  FIG. 3 is a flowchart for operating according to the characteristic A or the characteristic B shown in FIG.

  First, when the input current sensor 200 is normal, the current value iIN is acquired from the input current sensor 200 (steps 711 and 712). When the current value iIN is within the threshold value iX, normal operation is performed (steps 713 and 714). ). That is, the voltage information S2 between the buses L2 and L3 and the current information S3 of the U phase and the W phase are fetched, the inverter unit 500 is controlled according to the command information S4 from the instruction unit 900, and the voltage and frequency applied to the motor 600 are determined. To control its operating state.

  On the other hand, when the current value iIN exceeds the threshold value iX, the first overheat prevention operation (first overheat prevention operation mode) is performed and the user is notified of this (steps 713 and 715). That is, when the current value iIN is in the region I, the inverter unit 500 is controlled so as to decrease the rotational speed N of the motor 600 by a predetermined value. If the current value iIN is still in the region I, the rotational speed N is further determined. The inverter unit 500 is controlled so as to decrease the value, and is repeatedly controlled until the current value iIN falls below the region I.

  On the other hand, when the input current sensor 200 is abnormal (that is, failure), the input current estimated value iINX is obtained by estimation calculation described later (steps 711 and 716). When the estimated value iINX is within the threshold value iX, the same normal as step 714 is performed. Driving is performed (steps 717 and 714).

  On the other hand, when the estimated value iINX exceeds the threshold value iX, the second overheat prevention operation (second overheat prevention operation mode) is performed and the fact is notified to the user (steps 717 and 718). That is, when the estimated value iINX is in the region II, the inverter unit 500 is controlled so as to lower the rotational speed N of the motor 600 by a predetermined value. If the estimated value iINX is still in the region II, the rotational speed N is further set to the predetermined value. The inverter unit 500 is controlled so as to decrease the value, and is repeatedly controlled until the estimated value iINX falls below the region II.

  At that time, the rotational speed N may be decreased by a predetermined value in the same manner as in Step 715, but the rotational speed N is further increased from the normal value to increase the response of the overheat prevention operation. You may make it suppress the abnormal heating at the time of sensor abnormality early and reliably.

  In step 715 or 718, the first or second overheat prevention operation is started and the user is notified that the load of the motor 600 is increasing using the alarm device or the display device 1000. It is possible to inform the user that the current operation is in the first or second overheat prevention operation mode and to alert the user to the use of the hot water supply device.

  The processing shown in FIG. 3 corresponds to the switching means described in claim 1 of the present invention.

  Here, step 711 shown in FIG. 3 constitutes a sensor operating state determination unit of the input current sensor 200 and determines whether or not the input current sensor 200 is normal.

  Actually, in another routine of the microcomputer, whether or not the input current sensor 200 is normal is determined in a plurality of confirmation modes by periodic or predetermined priority interrupt processing, and the determination results of each confirmation mode are stored in the memory 700a. Keep it. In step 711, these determination results are confirmed from the stored memory data, and if there is at least one abnormal mode, it is determined as abnormal. Incidentally, in order to reliably determine the operating state of the input current sensor 200, it is desirable to determine by combining a plurality of determination results, and the determination processing in step 711 may be configured as such.

  Therefore, another routine process for determining whether or not the input current sensor 200 is normal will be described with reference to FIG.

  First, in step 721, the U-phase and W-phase current information S3 of the motor 600 and the voltage information S2 between the buses L2 and L3 are fetched to determine the load state (load region) of the motor 600 (step 721). When the motor 600 is in the no-load region, the process proceeds to step 722. When the input current value iIN detected by the input current sensor 200 is larger than the no-load set current value i0 that is an abnormal current determination value, it is determined that there is an abnormality. The first abnormal mode is set and stored in the memory 700a (steps 722 and 723).

  On the other hand, when the input current value iIN is equal to or less than the no-load set current value i0, the process ends. On the other hand, when the motor 600 is in a predetermined load region where a moderate load is applied and the motor 600 is in a stable operation state (that is, a stable load state), the process proceeds to step 724, and when the load is present where the input current value iIN is an abnormal current determination value. When it is smaller than the set current value iS, it is determined that there is an abnormality, and the second abnormality mode is set and stored in the memory 700a (steps 725 and 726).

  Therefore, as described above, in step 711 in FIG. 3, these data are utilized to determine whether the input sensor 200 is normal or abnormal (failure).

  Next, in step 716 shown in FIG. 3, the input current estimated value iINX is acquired. Actually, however, in another routine of the microcomputer, the current input is obtained by estimation calculation by periodic or predetermined priority interrupt processing. The estimated current value iINX is obtained, and is sequentially updated and stored in the memory 700a. In steps 716 and 717, the latest input current estimated value iINX stored in the memory 700a is acquired and used for the magnitude determination with the threshold value iX.

  Therefore, another routine process for estimating and calculating the input current estimated value iINX will be described with reference to FIG.

  First, in step 731, the rotational speed N of the motor 600 is obtained from the current information S 3 including the U-phase and W-phase frequency components of the motor 600, and the output torque T is proportional to the output current. The output torque T can be obtained by estimating the output current.

  Subsequently, the power supply voltage VM is obtained from the voltage information S2 between the buses L2 and L3 (step 732), and the motor / compressor efficiency η is determined from the data map shown in FIG. 6 according to the rotational speed N and the output torque T of the motor 600. Is read (step 733).

  Subsequently, the input current estimated value iINX is calculated using a predetermined calculation formula shown in the following formula 1, and stored in the memory 700a (step 734).

(Equation 1)
Estimated value iINX = rotational speed N × output torque T / power supply voltage VM / efficiency η × safety factor SK

Here, the efficiency η indicates the motor / compressor efficiency η, and the safety factor SK indicates how early the overheat prevention operation is started with respect to the increase in the motor load L as shown in the characteristic B of FIG. This is the design value shown.

  As shown in FIGS. 6 (a), 6 (b), and 6 (c), the efficiency η data map was obtained in advance through experiments or the like to obtain the distribution of efficiency η at the rotational speed N and output torque T for each power supply voltage VM. These are composed of a plurality of two-dimensional tables and are stored in a ROM (not shown) or a rewritable memory 700a. In FIG. 6, the darker region on the center side indicates the higher efficiency region, the peripheral thin region indicates the lower efficiency region, and the middle between them indicates the intermediate efficiency region, and the efficiency gradually increases toward the center side. A higher distribution is shown. In addition, it can be seen that the higher the power supply voltage VM, the larger the high efficiency region. When the power supply voltage VM is between the two tables, the efficiency η is determined by interpolation calculation of the values of both tables. The processing shown in FIG. 5 corresponds to the input current estimating means described in claim 1 of the present invention.

  In the above embodiment, as shown in regions I and II of FIG. 2, the motor 600 operates in the first overheat prevention operation region using the same threshold value iX for the detected value iIN or the estimated value iINX of the input current. I and the second overheat prevention operation region II are determined, but when the input current sensor 200 is abnormal, a threshold different from that when the sensor is normal is set to set the second overheat prevention operation region II. You may make it determine whether it exists in. In this case, the safety factor SK used in the input current estimation formula shown in Formula 1 can be adjusted according to the threshold value. For example, the safety factor SK = 1 can be set and the safety factor SK can be omitted by lowering the threshold value when the sensor is abnormal to the safe side.

  In the above embodiment, the U-phase and W-phase current information S3 is fetched and the motor current of the motor 600 is estimated. However, a current detection resistor is provided in series with the bus L2 or L3, and according to the voltage drop. The motor current may be detected.

  Moreover, in the said embodiment, although the case where it applies to the control apparatus of the motor of the electric compressor in the heat pump cycle of a hot water supply apparatus is taken as an example, even if a load is not a compression mechanism but an electric fan (blower fan), a pump, etc. The present invention can be applied.

It is a block diagram which shows schematic structure of the hot water supply control system containing the motor control apparatus used as one Embodiment of this invention. It is explanatory drawing which shows the overheat prevention driving | operation characteristic at the time of normal of the input current sensor 200 or abnormality. 3 is a flowchart of operation according to the characteristic A or the characteristic B shown in FIG. 2 in the control device 700 according to the operating state of the input current sensor 200. In another routine, it is a flowchart which judges whether input current sensor 200 is normal. It is a flowchart which estimates and calculates the input current estimated value iINX in another routine. 5 is an explanatory diagram showing a data map of motor / compressor efficiency η of a motor 600. FIG.

Explanation of symbols

100 External power supply 200 Input current sensor 300 AC / DC converter unit 300
400 Capacitor 500 Inverter unit 600 Motor 600a Compressor 700 Control device (control means)
800 heat pump cycle

Claims (7)

A motor control device provided with a control means for inverter-controlling a motor upon receiving power supply,
An input current sensor that detects an input current supplied from the power source and generates a detection value;
The control means includes
An input current estimating means for obtaining an estimated value of an input current supplied from the power source using at least one of a control amount for controlling the motor and an operation amount indicating an operation state of the motor;
The operation state of the input current sensor is determined, the first overheating prevention operation mode when the sensor is normal using the detection value by the input current sensor, and the sensor abnormality using the estimation value by the input current estimation means And a switching means for switching between the second overheat prevention operation mode at the time.   The said input current estimation means adds the safety factor which anticipates this input current largely when estimating the input current supplied from the said power supply, and calculated | required the said estimated value, It is characterized by the above-mentioned. Motor control device. The input current estimating means includes
Estimated value = N × T / VM / η × SK
Where N is the motor speed, T is the output torque, VM is the power supply voltage, η is the motor / compressor efficiency, and SK is a safety factor to obtain the estimated value of the input current. The motor control device according to claim 2.   4. The motor control device according to claim 3, wherein the data indicating the motor / compressor efficiency η is selected according to an operating condition of the motor from a data map obtained in advance.   The switching means, when determining whether the input current sensor is normal or abnormal, the comparison result between the input current and the abnormal input current determination value in the no-load state of the motor, and the detection value at the stable load of the motor The motor control device according to any one of claims 1 to 4, wherein the motor control device is performed using at least one of a comparison result with an abnormal input current determination value under a corresponding operation condition.   The motor control device according to claim 5, wherein the first overheat prevention operation mode is an operation mode in which abnormal overheating of the motor is suppressed when the detected value exceeds a predetermined threshold.   6. The motor according to claim 5, wherein the second overheat prevention operation mode is an operation mode in which abnormal overheating of the motor is suppressed when the estimated value of the input current estimation unit exceeds a predetermined threshold. Control device.

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