Motor control device

Abstract

To provide a motor controller with a fault detection function and a monitoring function of a dynamic brake circuit.SOLUTION: A motor controller comprises: a motor 1; an inverter circuit 2 which drives the motor 1; first wiring L1 which connects the motor 1 with the inverter circuit 2; second wiring L2 which connects the motor 1 with the inverter circuit 2; a first sensor S1 which detects first current flowing to the first wiring L1; a second sensor S2 which detects second current flowing to the second wiring L2; and a dynamic brake circuit 3. The dynamic brake circuit 3 is connected between the first sensor S1 and the motor 1, and between the second sensor S2 and the inverter circuit 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a motor control device.

Background Art

[0002] In a motor control device, a dynamic brake circuit is known that short-circuits between the terminals of a motor via a resistor when a power failure occurs or when an amplifier fails, and dissipates rotational energy as heat to quickly stop the motor. Further, a failure detection device that detects a failure of the dynamic brake circuit due to welding of a relay or the like is known.

[0003] For example, Patent Document 1 discloses a motor control device having a failure detection function for determining the presence or absence of a failure in a dynamic brake circuit by applying a predetermined DC voltage to the dynamic brake circuit and comparing the current value flowing in the dynamic brake circuit with a threshold value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the dynamic brake circuit is wired closer to the motor side than the current detection circuit composed of a current detection resistor and a current sensor, it is not possible to measure the current value of the dynamic brake current flowing through the dynamic brake circuit due to the induced voltage of the motor. Therefore, there has been a problem that it is not possible to detect a failure due to a short circuit of the resistor in the dynamic brake circuit or to monitor the state (monitoring) of the dynamic brake circuit.

[0006] The present disclosure aims to provide a motor control device having a failure detection function and a monitoring function for a dynamic brake circuit.

Means for Solving the Problems

[0007] A motor control device according to one aspect of the present disclosure includes a motor and an inverter circuit that drives the motor, a first wiring that connects the motor and the inverter circuit, a second wiring that connects the motor and the inverter circuit, a first sensor that detects a first current flowing through the first wiring, a second sensor that detects a second current flowing through the second wiring, a dynamic brake circuit, and is provided with The dynamic brake circuit is connected between the first sensor and the motor and between the second sensor and the inverter circuit.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a motor control device having a failure detection function and a monitoring function for a dynamic brake circuit.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Best Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For members having the same reference numerals as those already described in the description of the embodiments, the description thereof will be omitted for convenience of explanation. Also, the dimensions of each member shown in the drawings may be different from the actual dimensions of each member for convenience of explanation.

[0011] (Configuration of Motor Control Device) FIG. 1 is a schematic diagram of a motor control device according to an embodiment of the present invention. As shown in FIG. 1, the motor control device includes a motor 1, an inverter circuit 2, first wiring L1, second wiring L2, third wiring L3 connecting the motor 1 and the inverter circuit, first sensor S1, second sensor S2, and a dynamic brake circuit 3.

[0012] The inverter circuit 2 drives the motor 1. The inverter circuit 2 outputs a three-phase alternating current (U-phase, V-phase, W-phase). The inverter circuit 2 generates a three-phase alternating current from a commercial power source. For example, the inverter circuit 2 outputs the current of the U-phase to the first wiring L1, the current of the V-phase to the second wiring L2, and the current of the W-phase to the third wiring L3.

[0013] The three-phase alternating current output from the inverter circuit 2 flows through the first wiring L1, the second wiring L2, and the third wiring L3, respectively. The current flowing through the first wiring L1 is called the first current. The current flowing through the second wiring L2 is called the second current. A first sensor S1 for detecting the first current is provided on the first wiring L1. A second sensor S2 for detecting the second current is provided on the second wiring L2. For the first sensor S1 and the second sensor S2, a resistance detection type such as a current detection resistor or a magnetic field detection type such as a Hall element can be adopted.

[0014] In the normal state where the dynamic brake circuit 3 does not operate, a three-phase alternating current is supplied from the inverter circuit 2 to the motor 1 via the first wiring L1, the second wiring L2, and the third wiring L3. At this time, the first current flowing through the first wiring L1 can be measured by the first sensor S1. Also, the second current flowing through the second wiring L2 can be measured by the second sensor S2.

[0015] The dynamic brake circuit 3 includes a dynamic brake resistor R1 and a dynamic brake relay SW1 connected in series. When the dynamic brake relay SW1 is turned ON, the terminals of the motor 1 are short-circuited via the dynamic brake resistor R1. That is, a dynamic brake current flows through a circuit composed of the first wiring L1, the dynamic brake circuit 3, and the second wiring L2 from the motor 1. As a result, the induced current generated by the rotation of the motor 1 is converted into thermal energy in the dynamic brake resistor R1, and the dynamic brake circuit 3 functions as a dynamic brake.

[0016] Incidentally, the dynamic brake circuit 3 of the present embodiment is connected to a first contact point P1 between the first sensor S1 and the motor 1 and a second contact point P2 between the second sensor S2 and the inverter circuit 2. Therefore, when the dynamic brake relay SW1 is turned ON, a dynamic brake current flows through a path composed of the first wiring L1, the first contact point P1, the dynamic brake relay SW1, the dynamic brake resistor R1, the second contact point P2, the second sensor S2, and the second wiring L2 from the motor 1. That is, since the dynamic brake current flows through the second sensor S2, the dynamic brake current flowing through the dynamic brake circuit 3 when the dynamic brake relay SW1 is ON can be measured by the second sensor S2. Also, when the inverter circuit is operated with the dynamic brake relay SW1 inadvertently turned on, for example, when the contacts of the dynamic brake relay SW1 are welded due to a failure, the dynamic brake relay SW1 will close. In this case as well, the inverter circuit current flows through the dynamic brake circuit 3. The first sensor S1 can measure the inverter circuit current flowing through the dynamic brake circuit 3 when the dynamic brake circuit 3 fails.

[0017] FIG. 2 is a block diagram of an alarm control device according to an embodiment of the present disclosure. As shown in FIG. 2, the alarm control device includes an alarm display control unit 4 and an alarm display unit 10.

[0018] The alarm control device has two functions: a failure detection mode and a monitoring mode of the dynamic brake circuit 3. In the failure detection mode, abnormalities such as overcurrent due to contact welding of the dynamic brake relay SW1 and overcurrent due to resistance short - circuit of the dynamic brake resistor R1 are detected. In the monitoring mode, the amount of heat generated in the dynamic brake resistor R1 and the number of times the dynamic brake relay SW1 is turned on are monitored to detect abnormalities. When an abnormality is detected, the alarm display control unit 4 notifies a predetermined alarm to the alarm display unit 10 for display to the user.

[0019] The sensor control unit 5 acquires the current value of the first current detected by the first sensor S1 and the current value of the second current detected by the second sensor S2, and transmits the current values of the second current and the first current to the arithmetic unit 7. The counter 6 counts the number of times the dynamic brake relay SW1 is turned on, and transmits the number of on-times to the arithmetic unit 7. Based on the current value of the second current received from the sensor control unit 5 and the number of on-times received from the counter 6, the arithmetic unit 7 calculates the amount of heat generated in the dynamic brake resistor R1, and transmits the current values of the first current and the second current and the calculated amount of heat to the determination unit 8. The determination unit 8 receives the current values of the first current and the second current, the amount of heat calculated, and the number of on-times from the arithmetic unit 7, reads out the threshold value preset from the storage unit 9, compares the received values with the read threshold value, and determines the presence or absence of overcurrent, generation of abnormal heat amount, and abnormal number of on-times. When it is determined that there is any of the above abnormalities, the determination unit 8 notifies and displays a predetermined alarm on the alarm display unit 10.

[0020] (Fault detection mode) FIG. 3 is a flowchart of fault detection of the dynamic brake circuit 3. The processing flow of the fault detection mode will be described while also referring to the internal blocks of the alarm display control unit 4 shown in FIG. 2.

[0021] After the start of the failure detection mode, the alarm display control unit 4 loads the first threshold value and the second threshold value specified in advance by the user into the storage unit 9 composed of a volatile memory or the like, and performs initialization settings (S100). The first threshold value and the second threshold value are recorded in a non-volatile memory or the like by the user in advance. Next, the sensor control unit 5 acquires the current value of the first current from the first sensor S1 and the current value of the second current from the second sensor S2 (S101, S102). The acquired current values of the first current and the second current are transmitted from the sensor control unit 5 to the determination unit 8 via the calculation unit 7. The determination unit 8 determines whether the current value of the first current exceeds the first threshold value read from the storage unit 9 (S103). If it exceeds, the first alarm is notified to the alarm display unit 10 for display (S104). Next, the determination unit 8 determines whether the current value of the second current exceeds the second threshold value read from the storage unit 9 (S105). If it exceeds, the second alarm is notified to the alarm display unit 10 for display (S106). By periodically repeating the steps of S101 to S106, the current values of the first current and the second current are monitored, and overcurrents due to contact welding of the dynamic brake relay SW1 and overcurrents due to resistance short-circuit of the dynamic brake resistor R1 are detected.

[0022] According to the above processing flow, a short circuit of the inverter circuit current due to melting point adhesion of the dynamic brake relay SW1 and a short circuit of the dynamic brake resistor R1 during the operation of the dynamic brake circuit 3 can be determined, and an alarm can be notified to the user.

[0023] (Monitoring mode) FIG. 4 is a flowchart for monitoring the amount of heat generated in the dynamic brake resistor R1. The processing flow of the failure detection mode will be described with reference to the internal blocks of the alarm display control unit 4 shown in FIG. 2 as well.

[0024] After the start of the monitoring mode, the alarm display control unit 4 loads a third threshold value specified in advance by the user into the storage unit 9 and performs initialization settings (S200). Next, the sensor control unit 5 acquires the current value of the second current from the second sensor S2 (S201). The acquired current value of the second current is transmitted from the sensor control unit 5 to the arithmetic unit 7. The arithmetic unit 7 calculates the amount of heat generated in the dynamic brake resistor R1 from the current value of the second current (S202). Here, the "amount of heat" may be the amount of heat generated per unit time or the total amount of heat generated so far. The arithmetic unit 7 transmits the calculated amount of heat to the determination unit 8. Next, the determination unit 8 determines whether the transmitted amount of heat exceeds the third threshold value read from the storage unit 9 (S203). If it exceeds, the third alarm is notified to the alarm display unit 10 and displayed (S204). By periodically repeating the steps of S201 to S204, the amount of heat generated in the dynamic brake resistor R1 is monitored and a circuit abnormality is detected.

[0025] Figure 5 is a flowchart for monitoring the number of ON times of the dynamic brake relay SW1. The processing flow in the failure detection mode will be described with reference to the internal blocks of the alarm display control unit 4 shown in FIG. 2.

[0026] After the start of the monitoring mode, the alarm display control unit 4 loads a fourth threshold value specified in advance by the user into the storage unit 9 and performs initialization settings (S300). Next, the counter 6 monitors whether the dynamic brake relay SW1 is turned ON (S301). If it is turned ON, the counter for the number of ON times is incremented (S302). The incremented number of ON times is transmitted from the counter 6 to the determination unit 8 via the arithmetic unit 7. Next, the determination unit 8 determines whether the transmitted number of ON times exceeds the fourth threshold value read from the storage unit 9 (S303). If it exceeds, the fourth alarm is notified to the alarm display unit 10 and displayed (S304). By periodically repeating the steps of S301 to S304, the number of ON times of the dynamic brake relay SW1 is monitored and an abnormality in the number of operations of the dynamic brake is detected.

[0027] According to the above processing flow, an alarm can be notified to the user before the dynamic brake resistor R1 fails based on the amount of heat generated in the dynamic brake resistor R1. Also, an alarm can be notified to the user before the dynamic brake relay SW1 fails based on the number of ON times of the dynamic brake relay SW1.

[0028] As described above, the embodiments of the present invention have been explained. Needless to say, the technical scope of the present invention should not be construed in a limited manner by the description of these embodiments. These embodiments are merely examples, and those skilled in the art will understand that various modifications of the embodiments are possible within the scope of the invention described in the claims. The technical scope of the present invention should be determined based on the scope of the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0029] 1 Motor 2 Inverter Circuit 3 Dynamic Brake Circuit 4 Alarm Display Control Unit 5 Sensor Control Unit 6 Counter 7 Arithmetic Unit 8 Determination Unit 9 Storage Unit 10 Alarm Display Unit L1 First Wiring L2 Second Wiring L3 Third Wiring S1 First Sensor S2 Second Sensor P1 First Contact P2 Second Contact R1 Dynamic Brake Resistor SW1 Dynamic Brake Relay

Claims

1. A motor and an inverter circuit for driving the motor, a first wiring for connecting the motor and the inverter circuit, a second wiring for connecting the motor and the inverter circuit, a first sensor for detecting a first current flowing through the first wiring, a second sensor for detecting a second current flowing through the second wiring, a dynamic brake circuit, an alarm display unit, an alarm display control unit, comprising: The dynamic brake circuit is connected between the first sensor and the motor and between the second sensor and the inverter circuit, The dynamic brake circuit has a dynamic brake resistor, When the alarm display control unit determines that the current value of the first current detected by the first sensor exceeds a predetermined first threshold value, the alarm display unit displays a first alarm indicating an abnormal current in the inverter circuit due to a failure of the dynamic brake circuit, The alarm display control unit, when determining that the current value of the second current detected by the second sensor exceeds a predetermined second threshold value, displays a second alarm indicating an abnormal current in the dynamic brake circuit due to a short circuit of the dynamic brake resistor on the alarm display unit. A motor control device.

2. The alarm display control unit calculates the amount of heat generated in the dynamic brake resistor from the current value of the second current, and when determining that the amount of heat exceeds a predetermined third threshold value, displays a third alarm on the alarm display unit. The motor control device according to Claim 1.

3. The dynamic brake circuit has a dynamic brake relay, The alarm display control unit counts the number of times the dynamic brake relay is turned on, and when determining that the number of times exceeds a predetermined fourth threshold value, displays a fourth alarm on the alarm display unit. The motor control device according to Claim 1 or 2.

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