JP6641920B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that drives a motor.

  Along with the demand for energy saving in the market, a motor drive control system (hereinafter referred to as a motor drive system), which is often used as a power source for factories and buildings, has a function for adjusting the speed and output of a motor rotor. Power converters are commonly used. In a motor drive system of this type, the introduction of a power converter achieves high functionality, while the system is becoming more complicated. For this reason, there is an increasing possibility that a motor runaway or an accident will occur due to a failure of the power conversion device itself or an associated peripheral device, and it is strongly demanded to prevent such a runaway or an accident. Therefore, safety standards such as IEC61508 and ISO13849, which are international standards, are defined, and a safety function conforming to these safety standards is provided in the power conversion device. For example, with regard to a safety function for a power conversion device that drives and controls a motor, specifications of safety functions such as safe torque-off and safe deceleration are defined in IEC61800-5-2, which is an international standard. Each power converter manufacturer has developed a power converter based on the specifications of this safety function.

  Of these safety functions, the safety deceleration function monitors the speed of the rotor of the motor and decelerates the motor to the specified speed by the specified time from the time when the deceleration command signal is input to the power converter. Is required. When the vehicle is not normally decelerated, such as when the vehicle is not decelerated or when the speed exceeds a specified speed, it is required to forcibly shut off the output of the power converter. In order to realize such a safe deceleration function, a means for accurately detecting the speed and position of the rotor of the motor (hereinafter, simply referred to as the speed and position of the motor) is required. Generally, an encoder is used to detect the speed and position of the motor.

  Here, if the encoder fails, the speed and position of the motor cannot be detected normally, and the safety function cannot be functioned normally. For this reason, a technique for diagnosing the presence or absence of a failure in the encoder and ensuring the reliability of the output of the encoder has been proposed.

  As an example of a technique for diagnosing the presence / absence of a failure in an encoder, there is an encoder disclosed in Patent Document 1. The encoder of Patent Literature 1 includes three detection circuits and a CPU (Central Processing Unit). The CPU of this encoder compares the detection signals output from each of the three detection circuits with each other, and determines which detection signal to adopt based on the majority rule. As a result, in the encoder disclosed in Patent Document 1, a faulty detection circuit among the three detection circuits can be specified.

  However, although the frequency of the failure is lower than that of the detection circuit, the failure may occur in the CPU in the encoder. Therefore, in consideration of such a failure, the reliability of the output of the encoder is further increased. As an example, the CPU in the encoder is duplicated. For example, the encoder is provided with two detection circuits and two CPUs. Each of the two CPUs independently compares the detection signals output from each of the two detection circuits, and mutually diagnoses the result of comparison in each CPU. Further, as another example, an encoder is duplicated such that a plurality of encoders are attached to a motor. In this case, the presence or absence of a failure of the encoder is diagnosed by comparing the output of each encoder with another device different from the encoder.

JP 2010-19575 A

  However, the encoder of Patent Document 1 requires at least three detection circuits, and the cost of the encoder is higher than that of an encoder having two or less detection circuits.

  Further, an encoder with a duplicated CPU requires a plurality of CPUs, and the cost of the encoder is higher than that of a single CPU.

  Further, in a mode in which a plurality of encoders are attached to a motor, a plurality of encoders are required, and the cost for the encoder is higher than in a mode in which only one encoder is attached to the motor.

  The present invention has been made in view of the circumstances described above, and provides a technique capable of satisfying safety performance required in a motor drive system and suppressing the cost of an encoder of the motor drive system. Aim.

  A power conversion device according to the present invention is a device that controls driving of a motor by converting input power and outputting the converted power. A power converter according to the present invention includes a first transmission signal output from an encoder that detects a speed and a position of a rotor of a motor, and a second transmission signal output from an encoder that outputs the first transmission signal. And a safety circuit for determining the presence or absence of an abnormality in the encoder based on the above.

  The power converter according to the present invention determines whether there is an abnormality in the encoder based on the first transmission signal and the second transmission signal output from the same encoder, so that the abnormality in the encoder can be performed without increasing the number of encoders. Can be determined.

  In a preferred aspect, the second transmission signal is a signal generated in the process of generating the first transmission signal. According to the present invention, the first transmission signal is used to determine whether or not the encoder is abnormal based on the first transmission signal and the second transmission signal generated and output in the process of generating the first transmission signal. The determination as to whether the CPU in the encoder used in the process of generating the signal is normal can be made without duplicating the CPU in the encoder. That is, in the present invention, it is possible to determine whether or not the encoder is abnormal without increasing the number of CPUs in the encoder.

  Therefore, by using the power converter of the present invention, it is possible to reduce the cost of the encoder of the motor drive system while satisfying the safety performance required for the motor drive system.

1 is a block diagram illustrating a configuration of a motor drive system 1 according to an embodiment of the present invention. FIG. 3 is a block diagram showing functions of a safety microcomputer 122 of the motor drive system 1. 4 is a flowchart showing the operation of the safety microcomputer 122.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a motor drive system 1 according to one embodiment of the present invention. As shown in FIG. 1, the motor drive system 1 has a power converter 10 and an encoder 20.

  The encoder 20 is a device that detects an operation of the motor 30 such as a speed and a position of the motor 30. The encoder 20 has a disk 32, a first detection circuit 21, a second detection circuit 22, a CPU 23, a bypass transmission circuit 24, an external output terminal 41, and an external output terminal 42. The disk 32 is attached to the rotating shaft 31 of the motor 30 and rotates in the circumferential direction according to the rotation of the motor 30.

  The first detection circuit 21 is a detection circuit that detects a speed and a position of the motor 30 and generates a first detection signal indicating a detection result. The first detection circuit 21 is, specifically, an optical detection circuit, and includes a light emitting element 211, a light receiving element 212, and an amplification circuit 213. On the disk 32, for example, a code pattern having a different light reflectance and corresponding to the angle of the disk 32 is drawn. The light emitting element 211 emits light to the code pattern. The light receiving element 212 receives the reflected light reflected by the code pattern, and outputs an electric signal corresponding to the intensity of the received light to the amplifier circuit 213. The amplification circuit 213 amplifies the amplitude of the electric signal supplied from the light receiving element 212 and generates a first detection signal. The first detection signal generated in this manner is a pulse train signal that rises according to the code pattern drawn on the disk 32, and is an analog signal. Note that the specific configuration of the first detection circuit 21 is not limited to the above example. The first detection circuit 21 is configured to detect the rotation angle (absolute position) of the rotor by reading the code pattern drawn on the disk 32, but is not limited to the configuration that detects the rotation angle of the rotor. Absent. Further, the first detection circuit 21 is not limited to an optical detection circuit.

  The second detection circuit 22 is a detection circuit that detects a speed and a position of the motor 30 and generates a second detection signal indicating a detection result. The second detection circuit 22 is, specifically, a magnetic detection circuit, and includes a magnet (not shown) that generates a magnetic field, a magnetoresistance element 222, and an amplification circuit 223. The magnetoresistive element 222 and the magnet are arranged close to the outer peripheral surface of the disk 32. A plurality of metal protrusions are provided on the outer peripheral surface of the disk 32 along the outer periphery, and the disk 32 is like a gear. When the protrusion on the outer peripheral surface of the disk 32 approaches the magnetoresistive element 222, the strength of the magnetic field received by the magnetoresistive element 222 increases, and the resistance value of the magnetoresistive element 222 increases. On the other hand, when the protrusion on the outer peripheral surface of the disk 32 moves away from the magnetoresistive element 222, the strength of the magnetic field received by the magnetoresistive element 222 decreases, and the resistance value of the magnetoresistive element 222 decreases. The amplifier circuit 223 is supplied with an electric signal whose amplitude increases and decreases in a cycle of a change in the resistance value of the magnetoresistive element 222. The amplifier circuit 223 amplifies the amplitude of the electric signal supplied from the magnetoresistive element 222 and outputs the amplified signal as a second detection signal. The second detection signal generated in this manner is a wave-shaped signal whose amplitude increases and decreases according to a change in the resistance value of the magnetoresistive element 222, and is an analog signal. The specific configuration of the second detection circuit 22 is not limited to the above example. For example, a configuration may be adopted in which a detection coil that generates an induced voltage according to a change in a magnetic field is used instead of the magnetoresistance element 222. Further, the second detection circuit 22 is not limited to a magnetic detection circuit.

  The CPU 23 is, specifically, a microcomputer or an ASIC (Application Specific Integrated Circuit). The CPU 23 performs signal processing on the analog first detection signal output from the first detection circuit 21 and the analog second detection signal output from the second detection circuit 22, This is a detection signal processing unit that generates and outputs a velocity position digital signal that is one of the output signals. Hereinafter, the velocity position digital signal may be referred to as a first transmission signal. The CPU 23 has an A / D (analog / digital) converter 231, an A / D converter 232, a signal processor 233, and an external transmission circuit 234.

  The A / D converter 231 is a circuit that counts pulses of the first detection signal generated by the first detection circuit 21. The pulse count result indicates the rotation angle of the disk 32 (ie, the position of the rotor of the motor 30) and is a digital value. The pulse count result is transferred to the signal processor 233.

  The A / D converter 232 is a circuit that samples the second detection signal generated by the second detection circuit 22 and converts it into a digital signal. The second detection signal converted to a digital signal by the A / D converter 232 is delivered to the signal processor 233.

  The signal processor 233 is a circuit that generates a velocity position digital signal from the processing result of the A / D converter 231 and the processing result of the A / D converter 232. Specifically, the signal processor 233 calculates the speed by time-differentiating the position of the rotor of the motor 30 indicated by the pulse count result of the first detection signal, which is the processing result of the A / D converter 231. . Further, the signal processor 233 calculates the speed from the cycle of the waveform represented by the second detection signal converted into the digital signal which is the processing result of the A / D converter 232. The signal processor 233 compares the speed obtained based on the first detection signal with the speed obtained based on the second detection signal, and compares the speed obtained based on the second detection signal with the first detection circuit 21 and the second detection circuit 22. The presence or absence of abnormalities is determined. Then, the signal processor 233 outputs the position data of the rotor, which is the result of counting the pulses of the first detection signal, the speed data of the rotor obtained based on the first detection signal, and the abnormality of each detection circuit. A frame is generated in which status data indicating the presence / absence of data is stored in the payload. The frame generated in this way is delivered to the external transmission circuit 234. The specific processing of the signal processor 233 is not limited to this example.

  The external transmission circuit 234 is a circuit that outputs the frame generated by the signal processor 233 from the external output terminal 41 as a velocity position digital signal. The external transmission circuit 234 communicates with the power conversion device 10 at a transmission speed of about several Mbps according to serial communication based on RS485. For example, when the external transmission circuit 234 receives a frame in which a request signal is stored from the power conversion device 10, the external transmission circuit 234 causes the signal processor 233 to generate a frame in which speed data, position data, and status data are stored, and generates the frame. Transmit to power converter 10. The communication between the external transmission circuit 234 and the power converter 10 is not limited to serial communication, but may be parallel bus communication or wireless communication.

  The detour transmission circuit 24 is a circuit that outputs a signal generated in the process of the encoder 20 generating the speed position digital signal from the external output terminal 42 as a detour speed analog signal. Specifically, the bypass transmission circuit 24 outputs the first detection signal generated by the first detection circuit 21 as a bypass speed analog signal without passing through the CPU 23. The bypass speed analog signal is another output signal of the encoder 20, and is a signal output separately from the speed position digital signal. Hereinafter, the bypass speed analog signal may be referred to as a second transmission signal. The detour speed analog signal is, for example, an AB pulse signal or a sin / cos signal. The AB pulse method is a method of outputting a two-phase (A-phase and B-phase) pulse signal having a cycle according to the speed of the motor 30 and having a phase difference according to the rotation direction of the motor.

Thus, the encoder 20 outputs the signal output from the CPU 23 and the signal supplied to the CPU 23 as the output signal of the encoder 20. Further, the transmission systems of the two output signals of the encoder 20 are different from each other.
The above is the configuration of the encoder 20.

  The power conversion device 10 is, for example, an inverter device, and is a device that converts the power supplied from the AC power supply 40, supplies the converted power to the motor 30, and controls the driving of the motor 30. The power converter 10 includes a control circuit 11, a safety circuit 12, an inverter main circuit 13, and a gate drive circuit 14.

  The inverter main circuit 13 has a switching element such as an IGBT (Insulated Gate Bipolar Transistor). This switching element is turned on / off according to a gate signal. The inverter main circuit 13 outputs to the motor 30 a current according to the on / off of the switching element. Motor 30 operates according to the current supplied from inverter main circuit 13.

  The control circuit 11 is a circuit that executes a program stored in a storage device (not shown) to perform an operation or the like for controlling the drive of the motor 30. The control circuit 11 includes a command signal terminal block 111, a motor control microcomputer 112, and an LSI (Large Scale Integration) 113. The command signal terminal block 111 receives various command signals (for example, a torque command signal, etc.) from a host controller (not shown) and transfers the command signals to the motor control microcomputer 112. The motor control microcomputer 112 performs a calculation based on the command signal supplied via the command signal terminal block 111 to generate a control signal. The LSI 113 generates a PWM (Pulse Width Modulation) signal by performing pulse width modulation on the carrier signal based on a control signal supplied from the motor control microcomputer 112. The generated PWM signal is output to the gate drive circuit 14. Further, the LSI 113 acquires the velocity position digital signal from the external transmission circuit 234 of the encoder 20 and uses the digital signal for generating the PWM signal.

  The gate drive circuit 14 has, for example, a photocoupler. When no gate stop signal is given, the gate drive circuit 14 turns on the power of the photocoupler, and outputs the PWM signal supplied from the control circuit 11 to the inverter main circuit 13 as a gate signal. On the other hand, when receiving the gate stop signal, the gate drive circuit 14 turns off the power of the photocoupler, and stops the output of the gate signal to the inverter main circuit 13. In addition, the gate drive circuit 14 outputs to the safety circuit 12 a gate stop state signal indicating whether or not the output of the gate signal is stopped.

  The safety circuit 12 outputs a gate stop signal and outputs the gate signal to the gate drive circuit 14 when an abnormality is detected in the motor drive system 1 or when an emergency stop button is pressed by an operator or the like. This circuit performs safety control to stop output. An example of an abnormality in the motor drive system 1 is an abnormality of the encoder 20. The safety circuit 12 compares the speed position digital signal (first transmission signal) output from the CPU 23 of the encoder 20 with the bypass speed analog signal (second transmission signal) output from the bypass transmission circuit 24 of the encoder 20. This is a means for determining whether or not the encoder 20 is abnormal. The determination of the presence or absence of such an abnormality is realized by the safety circuit 12 executing a program stored in a storage device (not shown).

  In the power converter 10, the safety circuit 12 may be duplicated by adding a circuit having the same configuration as the safety circuit 12. In this case, each of the two safety circuits 12 independently compares the speed position digital signal output from the encoder 20 and the bypass speed analog signal, and mutually diagnoses the comparison result in each safety circuit 12.

  The safety circuit 12 includes a safety terminal block 121, a safety microcomputer 122, and an emergency stop circuit 123.

  The safety terminal block 121 receives an emergency stop signal (for example, a signal generated by pressing an emergency stop button) from an external circuit (not shown) and transfers the signal to the safety microcomputer 122 and the emergency stop circuit 123.

  The safety microcomputer 122 acquires the emergency stop signal output from the safety terminal block 121, the gate stop state signal output from the gate drive circuit 14, the speed position digital signal output from the encoder 20, and the bypass speed analog signal. The safety microcomputer 122 is a circuit that determines the presence or absence of an abnormality in the motor drive system 1 based on each of these signals, and outputs an emergency stop command to the emergency stop circuit 123 when it determines that there is an abnormality.

  The emergency stop circuit 123 is a circuit that outputs a gate stop signal to the gate drive circuit 14 when an emergency stop signal output from the safety terminal block 121 or an emergency stop command output from the safety microcomputer 122 is supplied. .

  FIG. 2 is a block diagram showing functions of the safety microcomputer 122. The safety microcomputer 122 includes a data acquisition unit 501, a communication abnormality monitoring unit 502, a position / speed conversion unit 503, a speed comparison unit 504, a pulse counting / A / D conversion unit 505, a speed unit conversion unit 506, and a bypass speed signal monitoring unit 507. , An emergency stop command output unit 508, a motor control microcomputer communication unit 509, an emergency stop signal monitoring unit 510, a gate stop state signal monitoring unit 511, a self-diagnosis processing unit 512, a mutual diagnosis processing unit 513, and an initialization-related processing unit 514. . These components of the safety microcomputer 122 are functions realized by the safety microcomputer 122 executing a program.

  FIG. 3 is a flowchart showing the operation of the safety microcomputer 122. When the power is turned on, the safety microcomputer 122 reads out the program, operates as each functional unit shown in FIG. 2, and sequentially performs the processing of steps S101 to S108 shown in FIG. Thereafter, the safety microcomputer 122 periodically repeats the processing of steps S101 to S108. The operation of the safety microcomputer 122 will be described with reference to FIGS.

  First, the self-diagnosis processing unit 512 makes a self-diagnosis as to whether a runaway or an abnormality of itself (that is, the safety microcomputer 122) occurs (step S101). For example, the self-diagnosis processing unit 512 acquires a result of measuring the temperature of the safety microcomputer 122 and determines whether or not the temperature measurement result is equal to or higher than a predetermined temperature. If the temperature detection result is equal to or higher than the predetermined temperature, the self-diagnosis processing unit 512 outputs the emergency stop command and determines that the safety microcomputer 122 outputs an emergency stop command. The circuit 123 outputs a gate stop signal (omitted in the flowchart of FIG. 3). When the safety microcomputer 122 is duplicated, in addition to the self-diagnosis performed by the self-diagnosis processing unit 512, the mutual diagnosis processing unit 513 of the safety microcomputer 122 determines whether or not the safety microcomputer 122 is abnormal. Diagnosis is performed mutually with step 122 (step S101). If any one of the safety microcomputers 122 has an abnormality, the mutual diagnosis processing unit 513 that has detected the abnormality outputs an emergency stop command and causes the emergency stop circuit 123 to output a gate stop signal (in the flowchart of FIG. 3). Omitted).

  Next, the data acquisition unit 501 acquires a velocity position digital signal (first transmission signal) output from the CPU 23 of the encoder 20 (Step S102). The data acquisition unit 501 acquires a velocity position digital signal by data communication via a communication line from the external output terminal 41 of the encoder 20 to the safety microcomputer 122. Further, the data acquisition unit 501 may acquire a velocity position digital signal via the control circuit 11.

  Next, the communication abnormality monitoring unit 502 changes the unit and bit size of the velocity position digital signal, which is a digital signal, and then checks whether there is an abnormality in communication when acquiring the velocity position digital signal. (Not shown in the flowchart of FIG. 3). For example, the communication abnormality monitoring unit 502 performs a cyclic redundancy check (CRC) using a cyclic redundancy code. When there is an abnormality in the communication (specifically, when an error is detected by CRC), the communication abnormality monitoring unit 502 stores an abnormality flag indicating that an abnormality has occurred in the communication (for example, 1) in the abnormality flag. A signal (hereinafter, simply referred to as an abnormal flag signal) is output to the emergency stop command output unit 508.

  When the communication abnormality monitoring unit 502 determines that there is no abnormality in the communication (specifically, when no error is detected by the CRC), the position / speed conversion unit 503 determines whether the position data stored in the speed / position digital signal is The speed is calculated by differentiating the represented position (step S103). Thus, one speed data to be compared (hereinafter, referred to as a digital speed signal for convenience) is obtained from the speed position digital signal acquired by the digital communication. The position / velocity converter 503 outputs the obtained digital velocity signal to the velocity comparator 504. Note that the position / velocity converter 503 may perform moving averaging on the calculated speed using a moving average filter or the like.

  Next, the pulse counting / A / D converter 505 acquires the bypass speed analog signal (second transmission signal) output from the bypass transmission circuit 24 of the encoder 20, and converts the voltage of the acquired bypass speed analog signal into an operational amplifier. After the adjustment, the pulses of the detour speed analog signal after the adjustment are counted (step S104). The pulse count result indicates the position of the rotor of the motor 30 and is a digital value. The pulse counting / A / D converter 505 outputs the count result to the speed unit converter 506. The pulse counting / A / D converter 505 converts the detour speed analog signal adjusted by an operational amplifier or the like into a digital signal, and then outputs the frequency obtained by frequency conversion to the speed unit converter 506. Is also good.

  Next, the speed unit converter 506 calculates the speed by time-differentiating the pulse count result (or frequency) received from the pulse counting / A / D converter 505 (step S105). As a result, the other speed data to be compared (hereinafter referred to as an analog speed signal for convenience; the analog speed signal is actually digital) is obtained from the detour speed analog signal acquired by the analog communication. Can be Speed unit conversion section 506 outputs the obtained analog speed signal to speed comparison section 504. That is, the safety microcomputer 122 performs the same processing as that performed by the CPU 23 (specifically, the A / D converter 231 and the signal processor 233) of the encoder 20 on the first detection signal into the bypass speed analog signal. Do it for

  At the same time that the pulse counting / A / D converter 505 acquires the bypass speed analog signal, the bypass speed signal monitor 507 also acquires the bypass speed analog signal. Although omitted in the flowchart of FIG. 3, the bypass speed signal monitoring unit 507 checks whether or not there is an abnormality in communication when acquiring the bypass speed analog signal. The detour speed signal monitoring unit 507 determines, for example, whether the detour speed analog signal has been interrupted during communication, or whether the signal value represented by the detour speed analog signal has become indefinite. When there is an abnormality in the communication (specifically, when the communication is interrupted or the signal value becomes indefinite), the bypass speed signal monitoring unit 507 outputs an abnormality flag signal to the emergency stop command output unit 508. .

  Next, the speed comparison unit 504 converts the digital speed signal (speed data obtained from the speed position digital signal) received from the position speed conversion unit 503 and the analog speed signal (detour speed analog signal) received from the speed unit conversion unit 506. The speed of the encoder 20 is compared with the speed data obtained from the above (step S106). If the digital speed signal received from the position / speed converter 503 does not match the analog speed signal received from the speed unit converter 506, the speed comparator 504 considers that an abnormality has occurred in the encoder 20 (S106). : Yes), and outputs an abnormal flag signal to the emergency stop command output unit 508.

  Upon receiving the abnormality flag signal from the speed comparison unit 504, the emergency stop command output unit 508 outputs an emergency stop command to the emergency stop circuit 123 (Step S108). The emergency stop command output unit 508 also outputs an emergency stop command when receiving an abnormality flag signal from the communication abnormality monitoring unit 502 and the bypass speed signal monitoring unit 507. The emergency stop command output unit 508 causes the motor control microcomputer communication unit 509 to output a diagnosis signal indicating that an abnormality has occurred in the motor drive system 1 together with the output of the emergency stop command. The motor control microcomputer 112 recognizes that an abnormality has occurred in the motor drive system 1 by receiving the diagnostic signal output from the motor control microcomputer communication unit 509.

  On the other hand, in step S106, if the digital speed signal received from the position speed converter 503 matches the analog speed signal received from the speed unit converter 506, the speed comparator 504 generates an error in the encoder 20. It is determined that it has not been performed (S106: No).

  After the speed comparison unit 504 determines that no abnormality has occurred in the encoder 20, the emergency stop signal monitoring unit 510 determines whether an emergency stop signal has been supplied via the safety terminal block 121 (step S107). . When the emergency stop signal is supplied, the emergency stop signal monitoring unit 510 outputs an abnormal flag signal to the emergency stop command output unit 508. Then, the emergency stop output unit 508 that has received the abnormality flag signal from the emergency stop signal monitoring unit 510 outputs an emergency stop command to the emergency stop circuit 123 (Step S108). Further, the emergency stop signal monitoring unit 510 also checks whether there is an abnormality in the communication related to the supply of the emergency stop signal. The emergency stop signal monitoring unit 510 outputs an abnormal flag signal to the emergency stop command output unit 508 when there is an abnormality in the communication related to the supply of the emergency stop signal.

  When the emergency stop signal is not supplied and when there is no abnormality in the communication related to the supply of the emergency stop signal (S107: Yes), a series of processing is ended.

  Although omitted in the flowchart of FIG. 3, if the determination result in step S107 is Yes, the gate stop state signal monitoring unit 511 checks whether there is an abnormality in the communication related to the supply of the gate stop state signal. You may go. The gate stop state signal monitoring unit 511 outputs an abnormal flag signal to the emergency stop command output unit 508 when there is an abnormality in the communication related to the supply of the gate stop state signal. The emergency stop output unit 508 that has received the abnormality flag signal from the gate stop state signal monitoring unit 511 outputs an emergency stop command to the emergency stop circuit 123. On the other hand, if there is no abnormality in the communication related to the supply of the gate stop state signal, the series of processing ends.

  Further, the initialization-related processing unit 514 is a functional unit that operates when initializing various setting values used in each functional unit of the safety microcomputer 122.

  As described above, the power conversion device 10 of the motor drive system 1 according to the present embodiment generates the first transmission signal (speed position digital signal) output from the encoder 20 and the first transmission signal in the process of generating the first transmission signal. It is determined whether or not the encoder 20 is abnormal based on the second transmission signal (detour speed analog signal) that is output. Therefore, in the motor drive system 1, it is possible to determine whether the CPU 23 in the encoder 20 used in the process of generating the first transmission signal is normal without duplicating the CPU 23 in the encoder 20. it can. That is, in the present motor drive system, it is possible to determine whether or not the encoder 20 is abnormal without increasing the number of CPUs 23. Further, the power conversion device 10 of the motor drive system 1 determines whether or not the encoder 20 is abnormal based on the first transmission signal and the second transmission signal output from the same encoder 23. For this reason, the motor drive system 1 can determine whether there is an abnormality in the encoder 20 without increasing the number of encoders 20.

  Specifically, even if an abnormality such as thermal runaway or abnormal oscillation occurs in the CPU 23 of the encoder 20, the power conversion device 10 transmits the speed position digital signal output from the CPU 23 and the normal transmission transmitted by bypassing the CPU 23. An abnormality of the CPU 23 can be detected by comparing with the bypass speed analog signal. In addition, even if an abnormality occurs in the detour transmission circuit 24, the power conversion device 10 compares the detour speed analog signal output from the detour transmission circuit 24 with the normal speed position digital signal output from the CPU 23 to perform detour. An abnormality in the transmission circuit 24 can be detected. Further, even if a disconnection or short circuit of the communication path in one of the speed position digital signal and the detour speed analog signal occurs, the power conversion device 10 can perform communication abnormality based on the other transmission signal. Can be detected.

  Therefore, by using the motor drive system 1 of the present embodiment, it is possible to reduce the cost of the encoder 20 of the motor drive system 1 while satisfying the safety performance required for the motor drive system 1.

  Further, in communication using digital signals, there is a possibility that abnormalities specific to digital signals, such as bit errors, may occur. This bit error does not occur in communication using an analog signal. On the other hand, in communication using analog signals, there is a possibility that abnormalities specific to analog signals, such as signal crosstalk, may occur. This crosstalk does not occur in communication using digital signals. In the motor drive system 1 of the present embodiment, the communication using the digital signal and the communication using the analog signal are used in combination, so even if an abnormality specific to the digital signal or the analog signal occurs during the communication, It is unlikely that an abnormality occurs simultaneously in both the communication of the velocity position digital signal and the communication of the bypass speed analog signal. Therefore, in the motor drive system 1, the reliability in communication between the encoder 20 and the power conversion device 10 does not decrease.

  Further, a speed position digital signal output from the encoder 20 is supplied to the control circuit 11 of the power conversion device 10. Since the control circuit 11 controls the drive of the motor 30 using the speed data and the position data included in the speed position digital signal, the power converter 10 can control the drive of the motor in the same manner as the conventional power converter 10. it can.

<Other embodiments>
As described above, one embodiment of the present invention has been described. However, other embodiments of the present invention can be considered. For example:

(1) The encoder 20 of the motor drive system 1 according to the embodiment has two detection circuits (a first detection circuit 21 and a second detection circuit 22). However, the number of detection circuits included in the encoder 20 is not limited to two, and may be one, or may be three or more. For example, in an embodiment in which the encoder has only one detection circuit, the CPU 23 may generate and output a digital first transmission signal (speed position digital signal) based on an analog detection signal of the detection circuit. In this case, an analog detection signal of the detection circuit may be output as a second detection signal (a bypass speed analog signal). Also in this aspect, the same effects as those of the motor drive system 1 of the embodiment can be obtained.

(2) The bypass transmission circuit 24 of the encoder 20 according to the embodiment outputs the first detection signal of the first detection circuit 21 as a second transmission signal. However, the bypass transmission circuit 24 may output the second detection signal of the second detection circuit 22 as a second transmission signal. That is, when the encoder 20 has a plurality of detection circuits, the detour transmission circuit 24 may output the detection signal of any one of the plurality of detection circuits as the second transmission signal.

  DESCRIPTION OF SYMBOLS 1 ... Motor drive system, 10 ... Power converter, 20 ... Encoder, 30 ... Motor, 40 ... AC power supply, 11 ... Control circuit, 12 ... Safety circuit, 13 ... Inverter main circuit, 14 ... Gate drive circuit, 111 ... Command Signal terminal block, 112: Motor control microcomputer, 113: LSI, 121: Safety terminal block, 122: Safety microcomputer, 123: Emergency stop circuit, 21: First detection circuit, 22: Second detection circuit, 23 ... CPU, 24: detour transmission circuit, 31: rotating shaft, 41, 42: external output terminal, 211: light emitting element, 212: light receiving element, 213, 223: amplifier circuit, 222: magnetoresistive element, 231, 232: A / D converter, 233: signal processor, 234: external transmission circuit.

Claims (3)

A power converter that drives and controls a motor by converting and outputting input power,
A first transmission signal output from an encoder that detects a speed and a position of a rotor of the motor, and a second transmission signal output from the encoder from which the first transmission signal is output. It has a safety circuit to determine the presence or absence of an encoder abnormality ,
The first transmission signal output from the encoder is a digital signal,
The second transmission signal output from the encoder is an analog signal,
The safety circuit includes:
Converting the second transmission signal into a digital signal;
A power converter , wherein the first transmission signal is compared with the second transmission signal converted into a digital signal . A power converter that drives and controls a motor by converting and outputting input power,
A first transmission signal output from an encoder that detects a speed and a position of a rotor of the motor, and a second transmission signal output from the encoder from which the first transmission signal is output. It has a safety circuit to determine the presence or absence of an encoder abnormality,
The encoder is
A plurality of detection circuits for detecting the speed and position of the rotor of the motor and generating a detection signal indicating the detection result,
Detection signal processing means for performing signal processing on each detection signal generated by the plurality of detection circuits to generate and output the first transmission signal;
A bypass transmission circuit that outputs a detection signal generated by any one of the plurality of detection circuits as the second transmission signal.
A power converter characterized by the above-mentioned. A power converter that drives and controls a motor by converting and outputting input power,
A first transmission signal output from an encoder that detects a speed and a position of a rotor of the motor, and a second transmission signal output from the encoder from which the first transmission signal is output. It has a safety circuit to determine the presence or absence of an encoder abnormality,
The power converter according to claim 1, wherein the encoder outputs a signal used to generate the first transmission signal as the second transmission signal .

Images