JP2000188897A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To brake a plurality of motors in the power failure of a power source without installing a private brake circuit through the use of the regenerative resistor of a regenerative processing circuit and a switching means which makes regenerative current flow in the regenerative resistor. SOLUTION: A regenerative processing circuit is provided with a regenerative resistor 6, a switching means 7 and a control signal generation circuit 8 for outputting a control signal to the switching means 7. When an inter-terminal voltage between the input terminals of inverter circuits 2A-2C is not less than the voltage which was previously decided, the switching means 7 is set to an on-state. When inter-terminal voltage becomes smaller than voltage which was previously decided, the switching means 7 is set to an off-state. When power is cut in the power source, the regenerative transistor 7 goes into on-state, regenerative power supplied from motors 1A-1C through the inverter circuits 2A-2C is consumed in the regenerative resistor 6 as the Joule heat, and the motors are braked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling a plurality of servo motors capable of regenerative control.

[0002]

2. Description of the Related Art In a servomotor or the like used in a machine tool or the like, when a power failure occurs in a power supply of a motor (usually a commercial power supply), it is necessary to stop the rotation of the motor as quickly as possible. As a technology to stop the rotation of the motor quickly and electrically, the brake is applied to the motor by consuming the power generated by the motor that is the generator when the power supply is in a power failure state with the brake resistor. Dynamic brake technology is widely known.

[0003]

In this dynamic braking technique, a special brake circuit is used in which a star-connected brake resistor is connected to a three-phase winding on the stator side of a motor via a relay having normally closed contacts. In this brake circuit, when a power failure occurs in the power supply or the like, the relay closes, a regenerative current flows through the brake resistor, and the motor is braked. However, a brake circuit using a relay and a brake resistor must be provided separately from the motor control circuit, and is relatively large. In addition, providing these separately from the motor control circuit increases the overall price. There's a problem. In particular, when such a brake circuit is provided for each motor when the number of motors to be controlled increases, there is a problem that the overall price is further increased. There is also a problem that the number of uses is limited by the life of the relay.

[0004] It is an object of the present invention to provide a motor control device capable of executing regenerative processing and braking processing for a plurality of motors with a simple configuration.

Another object of the present invention is to provide a motor control device capable of simultaneously applying a brake to a plurality of motors at the time of a power outage without using a dedicated brake circuit.

Another object of the present invention is to provide a motor control which can apply a brake to a plurality of motors at the time of a power failure by using a regenerative resistor of a regenerative processing circuit and a switching means for supplying a regenerative current to the regenerative resistor. It is to provide a device.

It is still another object of the present invention to provide a motor control device which can quickly brake a plurality of motors and does not damage or burn a regenerative resistor during regenerative processing.

[0008]

SUMMARY OF THE INVENTION A motor control device according to the present invention converts a common DC power supply (generally, AC power supplied from a commercial AC power supply into a direct current by a rectifier circuit) to a plurality of motors. Inverter circuit configured to supply drive power and regenerate power regenerated from multiple motors to the power supply side, multiple inverter drive circuits driving multiple inverter circuits, and converting regenerative power to Joule heat And a regenerative processing circuit including a regenerative resistor. Part of the regenerative power is stored in a main circuit capacitor connected between output terminals of a rectifier circuit that rectifies AC power from an AC power supply into DC power. Here, a servo motor is generally used as the plurality of motors, but this motor may be single-phase or multi-phase. The number of the plurality of motors is arbitrary. The inverter circuit configured to regenerate the regenerated power to the power supply side has a circuit configuration in which a flywheel diode is connected in anti-parallel to each of a plurality of semiconductor switching elements normally connected in a bridge. I have.

The regenerative processing circuit monitors input voltages (voltages between terminals of a main circuit capacitor) of a plurality of inverter circuits,
It is provided for the purpose of preventing the voltage between terminals of each inverter circuit (voltage between terminals of the main circuit capacitor) from becoming higher than a predetermined voltage due to regenerative power from a plurality of motors.
Therefore, the regenerative processing circuit is arranged such that a control signal is input to the control terminal to be in a control state, and a current flows through the regenerative resistor during the ON state and cuts off a current flowing through the regenerative resistor during the OFF state. The switching means is turned on when a possible switching means and a terminal-to-terminal voltage between the input terminals of the inverter circuit (a terminal voltage of the main circuit capacitor) are equal to or higher than a predetermined voltage, and the terminal-to-terminal voltage is predetermined. And a control signal generating circuit for outputting a control signal so as to turn off the switching means when the voltage is lower than the set voltage. Note that regenerative monitoring means for monitoring the ON period of the switching means may be provided, and the ON period or the OFF period of the switching means may be controlled based on the monitoring result.

In the present invention, a series circuit of the switching means and the regenerative resistor is commonly connected between respective input terminals of a plurality of inverter circuits. Then, the regenerative processing circuit is configured so that the switching means is turned on when the DC power supply is in a power failure state.

When a normally-off switching means is used as the switching means, the control signal generation circuit of the regenerative processing circuit generates a control signal for turning on the switching means when the DC power supply is cut off. Will be configured. Further, when a normally-on switching means is used as the switching means as described later, it is not necessary to take special measures for the regenerative processing circuit.

According to the present invention, regenerative power from a plurality of inverter circuits can be regenerated by one regenerative resistor and switching means, and the configuration of the control device is simplified. Also, at the time of a power failure or the like, brakes can be applied to a plurality of motors only by turning on one switching unit.

The switching means is turned off when a control signal is input to the control terminal,
It is preferable to use a normally-on structure switching means that is turned on when a control signal is not input to the control terminal. As such a switching means, a normally closed relay or a non-contact semiconductor switching means can be used. As the non-contact semiconductor switching means, a known static induction transistor that is turned off when a voltage is applied to the control terminal (between the gate and the source) can be used. When a normally-on switching device is used, a control signal is not input to the control terminal when the switching device is turned on, and a control signal is input to the control terminal when the switching device is turned off, so that the switching device is controlled. That is, when using this type of switching means, the off state is controlled by a control signal input to the control terminal. When the power supply is lost (when the input of the control signal is lost), the normally-on switching means is turned on. Therefore, when the power supply is in a power failure state, the switching means of the regenerative processing circuit is turned on, and the electric power supplied from the plurality of motors serving as generators via the inverter circuit becomes Joule heat due to the regenerative resistance. And the rotation of the plurality of motors (rotation of the rotor) is braked. Therefore, according to the present invention, it is possible to use the regenerative resistance of one regenerative processing circuit as a brake resistance to apply a brake to a plurality of motors when a common DC power supply is in a power failure state.

When a normally-off switching means is used as the switching means, a control signal for keeping the normally-off switching means in an on state even when the common power supply is interrupted. It is sufficient to prepare a control power supply capable of supplying the power.

In order to apply the brake more quickly, it is necessary to make the resistance value of the regenerative resistor smaller than the resistance value required for normal regenerative processing and to flow a large regenerative current to the regenerative resistor in a short time ( The period during which the current is flowing becomes shorter in inverse proportion to the value of the regenerative resistor.) However, if the resistance value of the regenerative resistor is set small for the purpose of applying the brake quickly, the current flowing through the regenerative resistor during regenerative processing will also increase, and the heat generated by the regenerative resistor will increase too much, and the temperature of the regenerative resistor will decrease. A situation where the temperature exceeds the heat resistant temperature occurs, and the regenerative resistor may be damaged or burnt. Therefore, in such a case, by increasing the off-time of the switching means during the regenerative processing, the temperature of the regenerative resistor is reduced during this off-time, and the temperature of the regenerative resistor rises above the heat-resistant temperature. It should be prevented.

For this purpose, a control signal generating circuit for supplying a control signal to the switching means first outputs a control signal (when power is turned on), and then the voltage between the input terminals of the inverter circuit or the voltage between the terminals of the main circuit capacitor is changed. A first determination operation for determining whether or not the voltage is equal to or higher than a predetermined voltage (regeneration process start voltage) is performed, and in the first determination operation, the terminal voltage becomes equal to or higher than a predetermined voltage. Performing a stop operation of stopping the output of the control signal when it is determined that the terminal voltage is smaller than the predetermined voltage, and then performing a second determination operation to determine whether the inter-terminal voltage is lower than the predetermined voltage. When it is determined that the inter-terminal voltage has become smaller than the predetermined voltage, an output operation of outputting a control signal is performed, and thereafter, after a certain timer time has elapsed, the first determination operation is performed. Be configured so that. Here, the fixed timer time is determined so as to prevent the temperature of the regenerative resistor from rising above the allowable temperature even if regenerative power is repeatedly discharged to the regenerative resistor. The fixed timer time can be determined in advance by calculation or by experiment in consideration of the capacity of the motor to be controlled, the resistance value of the regenerative resistor to be used, and the allowable temperature limit. When such a control signal generating circuit is used, a control signal is output to the control terminal of the switching means while the power is turned on and the terminal voltage is smaller than the predetermined voltage, and the switching means is turned off. Maintained in state. When the number of revolutions of the motor changes rapidly and the voltage between the input terminals of the inverter circuit (the voltage between the terminals of the main circuit capacitor) exceeds a predetermined voltage, the control signal generation circuit stops outputting the control signal and performs switching. The means is turned on. While the switching means is in the ON state, a regenerative current based on the regenerative power flows through the regenerative resistor (the regenerative power is discharged to the regenerative resistor), and the regenerative power is consumed by the regenerative resistor. The inter-voltage decreases. When the voltage between the terminals of the inverter circuit (voltage between the terminals of the main circuit capacitor) becomes lower than a predetermined voltage,
The control signal generation circuit outputs a control signal to a control terminal of the switching means, and the switching means is turned off. After the switching means is turned off, the switching means maintains the off state until a predetermined timer time elapses. That is, during this timer time, even if the voltage between the input terminals of the inverter circuit (the voltage between the terminals of the main circuit capacitor) again becomes equal to or higher than the predetermined voltage, no control signal is output to the switching means, and the switching means is not switched. The means is in the off state. Therefore, the regenerative resistor radiates heat during this timer time. If the voltage between the terminals of the inverter circuit (the voltage between the terminals of the main circuit capacitor) is still smaller than a predetermined voltage when the timer time has elapsed, the off state of the switching means is maintained, and then the voltage between the terminals of the inverter circuit is maintained. When (voltage between terminals of the main circuit capacitor) becomes equal to or higher than a predetermined voltage, the switching means is turned on and the same operation as described above is repeated.

When the change in the load driven by each motor is small, the timer time may be fixed as described above. However, when the fluctuation time of the load is large, the timer time is fixed. Time) becomes longer than necessary, or conversely, the off-time (timer time) becomes shorter than the time required for the temperature drop of the regenerative resistor. Therefore, in such a case, the above-described timer time may be changed according to the state of the regeneration process. In this case, the control signal is determined (determined) according to the time during which the output of the control signal is stopped (the time during which the switching means is turned on and the current flows through the regenerative resistor). Construct a generating circuit. The variable timer time may be determined so as to prevent the temperature of the regenerative resistor from rising above the heat-resistant temperature when the next regenerative power is discharged to the regenerative resistor. That is, when the regenerative power is large (when the ON time of the switching means is long), the timer time is extended,
When the regenerative power is small (when the ON time of the switching means is short), the timer time may be shortened. The time during which the output of the control signal was stopped (the time during which the switching means was turned on and the current was flowing through the regenerative resistor)
Can be detected by providing a regeneration monitor. In order to determine the appropriate timer time, the time during which the output of the control signal is stopped in advance by calculation or test (the time during which the switching means is turned on and the current flows through the regenerative resistor) and the appropriate timer The relationship with time may be obtained, and this may be stored in the memory in the form of a table or a map, or may be stored in the memory in the form of an arithmetic expression.

The control signal generation circuit that operates as described above can be realized using a microcomputer. More specifically, the regenerative processing circuit monitors the switching means and the inter-terminal voltage between the input terminals of the inverter circuit, and outputs a detection signal when the inter-terminal voltage is equal to or higher than a predetermined voltage. What is necessary is just to include a voltage monitoring circuit for outputting, a regenerative monitoring means for monitoring a regenerative state by counting a time when the switching means is in an ON state, and a control signal generating circuit for outputting the above-mentioned control signal. Then, the control signal generation circuit outputs a control signal first, and then performs a first determination operation for determining whether or not a detection signal is output from the voltage monitoring circuit, and the detection signal is generated by the first determination operation. When the output is detected, a stop operation for stopping the output of the control signal is performed, and then a second determination operation for determining whether or not the output of the detection signal from the voltage monitoring circuit is stopped is performed. When the stop of the output of the detection signal is detected by the determination operation of 2, an output operation of outputting a control signal is executed, and thereafter, a predetermined timer time or a time counted by the regenerative monitor means and determined according to a time during which the switching means is in an on state. It is configured to return to the first determination operation after the elapsed timer time has elapsed.

When the regenerative resistor and the brake resistor are completely shared and the braking performance is improved without increasing the number of parts, the resistance value of the regenerative resistor is reduced as described above, and Control to lengthen the off time is required. However, if the number of parts may be slightly increased, the following configuration enables the regeneration process and the braking operation to be performed using the regenerative resistor and the switching means. That is, the regenerative resistor is constituted by a series circuit of the first resistor and the second resistor. Then, the resistance value of the first resistor is set to a resistance value required to convert the electric power generated by the motor into heat in a short time when the power supply is in a power failure state and to quickly stop the motor, The value obtained by adding the resistance value of the second resistor to the resistance value of the first resistor is set to be a resistance value suitable for regenerative processing. Then, a short-circuiting switching means that enters a control state when a control signal is input to the control terminal is connected in parallel to the second resistor.
When the DC power supply enters a power failure state, both the switching means and the short-circuit switching means are turned on. In this way, when there is no power outage in the power supply,
Since the large resistance value obtained by adding the resistance values of the first and second resistors becomes the resistance value of the regenerative resistor, the voltage between the input terminals of the inverter circuit (the voltage between the terminals of the main circuit capacitor) is determined in advance as in the related art. It is sufficient to perform a simple control of turning on the switching means when the voltage becomes equal to or higher than the predetermined voltage and turning off the switching means when the inter-terminal voltage becomes lower than a predetermined voltage. When the power supply is in a power failure state, both the switching means and the short-circuit switching means are turned on, the second resistor is short-circuited, and the first resistor having a small resistance value is used as a brake resistor. As a result, the brake can be quickly applied.

Preferably, similarly to the above-mentioned switching means, the short-circuit switching means is turned off when a control signal is input to the control terminal, and turned on when no control signal is input to the control terminal. A switching means having a normally-on structure is used. In this case, the control signal generating circuit may be configured to always output the control signal to the short-circuit switching means. When such a configuration is employed, the number of components (the number of resistors and the number of switching means) increases, but the configuration of the control signal generation circuit is simplified.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic circuit diagram of an embodiment in which the present invention is applied to a motor control device that controls three three-phase servomotors. In the figure, 1A
Reference numerals 1C to 1C denote three-phase servo motors having a rated 720W in which three-phase windings are wound around a stator. Reference numerals 2A to 2C supply driving power to the motors 1A to 1C and motors 1A to 1C.
This is an inverter circuit configured to regenerate electric power regenerated from the power supply side. These inverter circuits 2A
2C have a configuration in which six semiconductor switching elements including transistors are bridge-connected, and a flywheel diode is connected in anti-parallel to each semiconductor switching element. When a field effect transistor (FET) is used as a transistor, a flywheel diode is structurally attached to each transistor.

Reference numeral 3 denotes a three-phase full-wave rectifier circuit that rectifies three-phase AC power supplied from a three-phase commercial power supply and outputs DC power. Reference numeral 4 denotes a main circuit capacitor having a function of further smoothing the output of the three-phase full-wave rectifier circuit 3 and a function of storing regenerative power regenerated from the motor side. A mechanical power switch MS is connected between the three-phase full-wave rectifier circuit 3 and the main circuit capacitor 4. An inrush prevention resistor R having a large resistance value is connected in parallel to the power switch MS. Power supply to the inverter circuits 2A to 2C is selected between an input terminal having one polarity of the inverter circuits 2A to 2C and one terminal of the main circuit capacitor 4 (or one output terminal of the common power supply). A switch circuit for enabling each is arranged. These switch circuits include transistors TR1 to TR1 each having a collector-emitter circuit connected between an input terminal of one polarity of inverter circuits 2A to 2C and one terminal of main circuit capacitor 4.
3 and a recovery diode D connected in anti-parallel to the emitter-collector circuits of the transistors TR1 to TR3.
1 to D3. These transistors TR
1 to TR3 are controlled so as to maintain the ON state when driving the motor.

When the regenerative power increases, the voltage Vc between the terminals (between PN) of the main circuit capacitor 4, that is, the voltage between the input terminals of the inverter circuits 2A to 2C increases. The terminal voltage Vc is monitored by the voltage monitoring circuit 5. The voltage monitoring circuit 5 is a terminal voltage V between terminals of the main circuit capacitor 4.
It is configured to monitor c and output a detection signal when the inter-terminal voltage Vc is equal to or higher than a predetermined voltage Vref. The voltage monitoring circuit 5 is specifically composed of a resistance voltage dividing circuit, and sets a predetermined voltage based on a voltage dividing ratio. The voltage monitoring circuit 5 may be constituted by a comparator mainly composed of an operational amplifier.

A series circuit of a regenerative resistor 6 and a regenerating transistor 7 (switching means having a normally-on structure) is commonly connected in parallel between input terminals of the inverter circuits 2A to 2C. The series circuit of the regenerative resistor 6 and the regenerating transistor (switching means) 7 constitutes a part of a regenerative processing circuit that converts regenerative power into Joule heat.
In this example, the resistance value of the regenerative resistor 6 converts the electric power generated by the motors 1A to 1C into Joule heat in a short time when the three-phase AC power supply is in a power failure state, and quickly stops the motors 1A to 1C. Is set to the required resistance value. Incidentally, when the rating of each of the motors 1A to 1C is 720W, preferably, the resistance value of the regenerative resistor 6 is 12.5Ω to
It is about 100Ω. The regenerating transistor 7 is turned off in a control state in which a gate voltage (control signal) is applied between a gate G and a source S as control terminals, and a gate voltage is applied between the gate G and the source S. This is an electrostatic induction transistor that is turned on when in a non-control state where no (control signal) is applied.

The regenerating transistor 7 is controlled by a control signal from a control signal generating circuit provided inside the control circuit 8. A microcomputer is arranged inside the control circuit 8. The control circuit 8 outputs a control signal for controlling conduction of a control rectifier such as a thyristor constituting the rectifier circuit 3 by using the microcomputer, and generates a drive signal for each transistor constituting the inverter circuits 2A to 2C. PW in inverter drive circuits 9A-9C
A control signal for M control is output, and a control signal for regenerative control is output to the regenerating transistor 7. The power supply of the control circuit 8 is a control power supply circuit 10 that rectifies an AC from a three-phase commercial power supply and reduces the AC to a DC voltage necessary for driving the microcomputer. The control circuit 8 receives an output from a power supply monitoring circuit 11 that monitors a three-phase AC voltage from a three-phase commercial power supply and monitors a power failure and an open phase. The power supply monitoring circuit performs three-phase full-wave rectification on three-phase alternating current of three-phase commercial power,
The rectified voltage is divided by a resistance voltage dividing circuit, and the divided voltage is output to the control circuit 8. When the voltage becomes equal to or lower than a predetermined voltage, the control circuit 8 determines that a power failure or a phase loss has occurred.

The control circuit 8 counts the time during which the regenerating transistor 7 is on to control the regenerating transistor 7 and monitors the regenerative state. The output of the monitoring circuit 5 is input. The regenerative detection circuit 12 outputs a count start command to start counting by the counter when the regenerating transistor 7 is turned on, and outputs a stop command to stop counting by the counter when the regenerating transistor 7 is turned off. It is configured. The regeneration detection circuit 12 can be most simply constituted by a resistance voltage dividing circuit, but can also be constituted by a comparator using an operational amplifier. When the regenerative detection circuit 12 is constituted by a resistance voltage dividing circuit, the voltage at the voltage dividing point of the resistance voltage dividing circuit (output of the count start command) becomes zero during the period in which the regenerating transistor 7 is in the on state, and the regenerative voltage is reduced. Transistor 7
While the switch is in the off state, a voltage appears at the voltage dividing point of the resistance voltage dividing circuit (count stop command output). The regeneration detection circuit 12 and a counter configured by a microcomputer inside the control circuit 8 constitute a regeneration monitoring means for counting the time during which the regeneration transistor 7 is in the ON state and monitoring the regeneration state. .

The control signal generating circuit for providing a control signal to the regenerating transistor 7 formed inside the control circuit 8 is adapted to output a detection signal from the voltage monitoring circuit 5 (when the voltage between the terminals of the main circuit capacitor 4 is reduced). (When the voltage is equal to or higher than a predetermined voltage), the regenerative transistor 7 is turned on, and the regenerative power stored in the main circuit capacitor 4 and the regenerative power supplied from the inverter circuits 2A to 2C are discharged through the regenerative resistor 6. When the detection signal is not output (when the voltage between the terminals of the main circuit capacitor 4 is smaller than a predetermined voltage), the control signal (voltage signal) is set so that the regeneration transistor 7 is turned off. The voltage is applied between the gate G and the source S of the regenerating transistor 7.

In this example, the control signal generating circuit constituted by the microcomputer inside the control circuit 8
The regenerative transistor 7 is not simply turned on / off according to the output of the voltage monitoring circuit 5. In this example, when a power failure occurs in the power supply, the resistance value of the regenerative resistor 6 is made smaller than the resistance value necessary for normal regenerative processing so that a large current is supplied in a short time in order to quickly apply a brake. The current flows through the regenerative resistor 6. Servo motor 1A-1C
Is a motor having a rated power of 720 W, and when the motor is stopped while the regenerating transistor 7 is maintained in the ON state, a resistor of usually 50Ω · 150 W may be used as the regenerative resistor 6. However, in this example, a resistor of 12.5 Ω · 450 W is used as the regenerative resistor 6 in order to shorten the stop time. When the resistance value of the regenerative resistor 6 is set to such a small value, the current flowing through the regenerative resistor 6 during the regenerative processing increases, and the heat generated by the regenerative resistor becomes too large, so that the temperature of the regenerative resistor exceeds the heat-resistant temperature. Things happen,
The regenerative resistor may be damaged. So in this example,
By forcibly lengthening the off-time of the regenerating transistor 7 during the regenerative processing, the temperature of the regenerative resistor 6 is reduced during this off-time and the temperature of the regenerative resistor 6 is prevented from rising above the heat-resistant temperature. The control signal generating circuit is configured to perform the control signal generation.

Rotation rating 7 rotating at 3000 rpm
3 servo motors of 20W, load inertia of 10
Under the condition that the capacity of the main circuit capacitor was 480 μF and the main circuit power supply was 200 V AC (three-phase commercial power supply), an experiment was performed to stop the motor due to a power failure. In this case, when the regenerative resistor 6 is set to 50Ω, the motor stop time (time from the occurrence of a power failure to when the motor stops) is about 1100 ms, and when the regenerative resistor 6 is set to 25Ω, the motor stop time is about 720 ms and the regenerative resistance 6
Is about 460 when is set to 12.5Ω.
ms. Incidentally, when the regeneration transistor 7 is a normally-off transistor, the motor stop time when the motor is stopped due to a power failure (that is, when no current flows through the regenerative resistor 6 at the time of the power failure) is 7.14.
Seconds.

FIG. 2 is a flowchart showing a basic algorithm of software used when a control signal generating circuit is constituted by a microcomputer inside the control circuit 8. In this algorithm, the off-time after the regenerating transistor 7 is turned on is made variable according to the change in load. Therefore, the control signal generation circuit configured by this algorithm and outputting a control signal firstly starts, that is, when power is turned on (step ST1).
Then, a control signal (a signal for turning off the regenerating transistor 7) is output to the gate G of the regenerating transistor 7 (step ST1). After that, the inverter circuits 2A to 2C
Whether the voltage between the input terminals of the main circuit capacitor 4 or the voltage between the terminals of the main circuit capacitor 4 is equal to or higher than a predetermined voltage (regeneration processing start voltage) is determined by whether a detection signal is output from the voltage monitoring circuit 5 or not. A first determination operation for determination is performed (step ST2). When it is determined in the first determination operation that the inter-terminal voltage is equal to or higher than a predetermined voltage (when it is determined that there is a detection signal), a stop operation for stopping the output of the control signal is performed (step S1). ST
3). As a result, the control signal is not input to the gate G of the regenerating transistor 7, and the normally-on regenerating transistor 7 is turned on. As a result, the regenerative power stored in the main circuit capacitor 4 and the regenerative power regenerated through the inverter circuits 2A to 2C are discharged through the regenerative resistor 6. Since the resistance value of the regenerative resistor 6 is small, the discharge time is shortened and the discharge current is increased. When the output of the control signal is stopped and the regeneration transistor 7 is turned on, the count of the time counter is started based on the count start command output from the regeneration detection circuit 12, and the time during which the output of the control signal is stopped is stopped. That is, the counting of the time during which the regenerating transistor 7 is in the ON state is started (step ST4).

Thereafter, based on the output of the voltage monitoring circuit 5,
A second determination operation is performed to determine whether or not the voltage between the terminals of the main circuit capacitor 4 has become smaller than a predetermined voltage based on whether or not the detection signal is no longer output from the voltage monitoring circuit 5 (step ST5). When it is determined that the inter-terminal voltage has become smaller than the predetermined voltage (when it is determined that the detection signal has disappeared), an output operation of outputting the control signal to the gate G of the regeneration transistor 7 is executed again (step ST6). ), The regeneration transistor 7 is turned off. When the regeneration detection circuit 12 detects that the regeneration transistor 7 has been turned off and a count stop command is input from the regeneration detection circuit 12, the counting of the control signal output stop time is stopped and the count value is reduced. (Control signal stop time or ON time of regeneration transistor 7)
The timer time is determined based on (step ST7).
This timer time is determined so as to prevent the temperature of the regenerative resistor 6 from rising above the heat-resistant temperature when the next regenerative power is discharged to the regenerative resistor 6. That is, when the regenerative power is large (when the ON time of the regenerating transistor 7 is long), the timer time is lengthened, and when the regenerative power is small (when the ON time of the regenerating transistor 7 is short), the timer time is set. Shorten. In this example, in order to determine an appropriate timer time according to the motors 1A to 1C to be controlled and their loads, the time during which the output of the control signal is stopped in advance by calculation or by a test (regeneration transistor 7) Is turned on and the current is flowing through the regenerative resistor 6) and an appropriate timer time is obtained in advance, and this is stored as a table in the ROM of the microcomputer. Therefore, when the count value of the stop time of the control signal is determined, the timer time is automatically determined. Then, the timer time is counted by the timer means, and after the timer time has elapsed (step ST8), the process returns to step ST2. Thereafter, the control signal generation circuit returns to step ST
2 to ST8 are repeated.

When the timer time is changed according to the on-time of the regenerating transistor 7 as in the control signal generating circuit used in this example, the off-time of the regenerating transistor 7 is required even when the load fluctuates. Longer than
Conversely, it is possible to effectively prevent the off time from becoming shorter than the time required for lowering the temperature of the regenerative resistor 6.

In the example shown in FIG. 1, when a power failure occurs in the three-phase AC power supply or when the line connecting this device to the three-phase AC power supply is disconnected, all of the inverter circuits 2A to 2C, the control circuit 8, etc. The power supply of the circuit is lost. The output of the control signal from the control circuit 8 also disappears. However, since the regenerating transistor 7 has a normally-on structure, it is turned on at the same time as the occurrence of a power failure, and the regenerative power regenerated from the motors 1A to 1C, which have been generators, is turned on. And, it is discharged through the regenerative resistor 6 and consumed as heat. Since the value of the regenerative resistor 6 is set small so that a large current can flow in a short time, the motor can be stopped in a short time. After the power outage is recovered, a control signal is output from the control signal generation circuit provided inside the control circuit 8 in accordance with the flowchart shown in FIG. 2, and the above-described regenerative operation is executed.

In the above example, the regeneration transistor 7
The time for forcibly turning off after turning on, that is, the off-time (timer time) is changed according to the on-time. However, when controlling a motor used for an application in which there is not much load variation, The off-time (timer time) may be fixed, or the off-time (timer time) may not be set when the regenerative resistor 6 is increased. When the off time (timer time) is made constant, the timer time needs to be determined so as to prevent the temperature of the regenerative resistor from rising above the heat resistant temperature even if regenerative power is repeatedly discharged to the regenerative resistor. The fixed timer time is determined in advance by calculation or by experiment in consideration of the capacity of the motor to be controlled, the resistance value of the regenerative resistor to be used, and the allowable temperature limit. By the way, in the case of the example of FIG. 1, if the timer time is fixed, it may be set in the range of 2 ms to 4 ms. FIG. 3 shows the algorithm of the software used when the control signal generation circuit used to make the timer time constant is realized using a microcomputer inside the control circuit 8.

The control signal generating circuit constituted by the software of the algorithm of FIG. 3 also outputs a control signal first (when power is turned on) (step ST11), and thereafter the voltage between the input terminals of the inverter circuits 2A to 2C or the main signal. The voltage monitoring circuit 5 determines whether or not the voltage between the terminals of the circuit capacitor 4 is equal to or higher than a predetermined voltage (start voltage of the regenerative processing).
Is performed (step ST12), and when it is determined that the inter-terminal voltage is equal to or higher than a predetermined voltage, the control signal is output. A stop operation for stopping is executed (step ST13). Thereafter, a second determination operation is performed to determine whether or not the inter-terminal voltage is lower than a predetermined voltage based on the output of the voltage monitoring circuit 5 (step ST).
14) When it is determined that the inter-terminal voltage has become smaller than a predetermined voltage, an output operation of outputting a control signal is executed (step ST15). Thereafter, after a predetermined timer time previously stored in the ROM has elapsed, the process returns to step ST12, and the same operation is repeated thereafter. Even if the timer time is kept constant, the operation can be performed without any trouble unless the load changes greatly. In this case, the regeneration detection circuit 12 is unnecessary.

In the above example, the on-time of the regenerating transistor 7 is detected by using the regenerative detection circuit 12. However, a counter for counting the time during which the control signal is not output is provided in the control circuit 8. Of course, the output of the counter may be used as the ON time of the regenerating transistor 7.

In the above example, since the regenerating transistor 7 as the switching means is formed by using a semiconductor switching element having a normally-on structure, the structure is simpler than when the switching means is formed by using a relay. However, it is a matter of course that the switching means may be constituted by a relay.

In the above example, the regenerative resistor 6 is completely used as a brake resistor. However, if the number of parts can be increased slightly, the configuration shown in FIG.
The regenerative processing and the brake operation can be performed by using the regenerative resistor and the switching means (regeneration transistor). That is, the regenerative resistor 6 is constituted by a series circuit of the first resistor 6a and the second resistor 6b. And the first resistor 6
a when the power supply is in a power failure state.
The resistance value of the second resistor 6b is set to the resistance value of the first resistor 6a by setting the resistance value required to convert the electric power generated by the 1C into heat in a short time and quickly stop the motor. The added value is set to be a resistance value suitable for the regenerative processing. After that, a control signal is input to the control terminal of the second resistor 6b, and a transistor 13 is connected in parallel as a short-circuit switching means to be in a control state. Similarly to the regenerating transistor 7, the transistor 13 constituting the short-circuit switching means is turned off when a control signal is input to the control terminal, and turned on when no control signal is input to the control terminal. A normally-on transistor is used. In the case where such a circuit is employed as an operation unit of the regenerative processing circuit, the control signal generation circuit configured inside the control circuit 8 always outputs a control signal to the transistor 13,
For the regeneration transistor 7, a voltage monitoring circuit 5
May be configured to stop outputting the control signal when the detection signal is being output, and to output the control signal when the voltage monitoring circuit 5 is not outputting the detection signal. With this configuration, when a power failure does not occur in the power supply, a large resistance value obtained by adding the resistance values of the first and second resistors 6a and 6b becomes the resistance value of the regenerative resistor 6, and thus, as in the related art, When the voltage between the input terminals of the inverter circuit (the voltage between the terminals of the main circuit capacitor) becomes equal to or higher than a predetermined voltage, the regenerating transistor 7 is turned on, and when the voltage between the terminals becomes smaller than the predetermined voltage. A simple regenerative process control for turning off the regenerating transistor 7 may be performed. When the power supply goes into a power failure state, both the regenerating transistor 7 and the transistor 13 are turned on, and the second
Is short-circuited, and the first resistor 6a having a small resistance value is short-circuited.
Is used as a brake resistor. As a result, the brake can be quickly applied. If such a configuration is adopted, the number of components (the number of resistors and the number of switching means)
However, there is an advantage that the configuration of the control signal generation circuit is simplified.

In each of the above examples, the value of the regenerative resistor used as the brake resistor is set to a small value. However, when the regenerative resistor is used for applications in which the braking performance may be slightly reduced, the existing regenerative resistor can be used as it is. Of course it is good.

In the above example, the power supply to each of the motors 1A to 1C can be individually selected. However, as shown in FIG. 5, the power supply to each of the motors 1A to 1C cannot be selected individually. Is also good. In FIG. 5, the control signal generation circuit is omitted.

In the above example, a normally-on transistor is used as the switching means (regeneration transistor 7). However, a normally-off switching means (regeneration transistor in FIG. 6) is used as the switching means (regeneration transistor 7). Transistor 7 ') can also be used. However, when a normally-off transistor is used, if the control power supply circuit 10 for rectifying three-phase AC power is used as it is as in the example of FIG. 1, the normally-off transistor is maintained in an on state during a power failure. Can not do it. Therefore, a circuit as shown in FIG. 6 may be added. In FIG. 6, only one inverter circuit 1 is shown. In this circuit, when the commercial power supply is not interrupted, the control circuit 8 'outputs a control signal for maintaining the normally-off transistor 7' in an on state by the output of the control power supply 10 '. The occurrence of a power failure is confirmed by the control circuit 8 'determining whether or not there is a voltage at the voltage dividing point of the voltage dividing circuit composed of the resistors R1 and R2. Then, when a power failure occurs and the back electromotive force is regenerated from the motor through the inverter circuit 1,
Driving power is supplied to the control circuit 8 'through the resistor R3 and the diode D4. When the regenerated back electromotive force is reduced or low, the electric charge stored in the capacitor 4 or the capacitor C is discharged, and the driving power is supplied to the control circuit 8 '. In this circuit, the capacitor C is normally charged through the diode 5. The Zener diode ZD makes the voltage input to the control circuit 8 'constant. By using such a circuit, by appropriately selecting the capacity of the capacitor C, it is possible to reliably supply the control signal to the transistor 7 'until the motor stops. Of course, an uninterruptible power supply with a built-in battery may be used as the power supply for the control circuit. When a circuit as shown in FIG. 6 or an uninterruptible power supply is used, a normally-off switching means may be used as the switching means 7 and the short-circuit switching means 13 of the circuit shown in FIG. It is.

[0042]

According to the present invention, the regenerative power from a plurality of inverter circuits can be regenerated by one regenerative resistor and switching means, so that the configuration of the control device is simplified and the regenerative processing circuit Since the regenerative resistor can be used as a brake resistor and a plurality of motors can be braked when the power supply goes out of power, there is an advantage that it is not necessary to provide a dedicated brake circuit.

Further, by setting the resistance value of the regenerative resistor smaller than the resistance value necessary for normal regenerative processing, a large current is supplied to the regenerative resistor within a short time so that the brake can be quickly applied. Even in this case, in the present invention, by increasing the off-time of the switching means during the regenerative processing, the temperature of the regenerative resistor is lowered during this off-time, and the temperature of the regenerative resistor is prevented from rising above the heat-resistant temperature. Therefore, there is an advantage that the regenerative resistor is not damaged or burnt.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram of an embodiment in which the present invention is applied to a motor control device that controls a plurality of three-phase servomotors.

FIG. 2 is a flowchart showing a basic algorithm of software used when a control signal generation circuit is configured by a microcomputer inside the control circuit.

FIG. 3 is a flowchart showing a basic algorithm of software used when a control signal generation circuit of another example is configured by a microcomputer inside the control circuit.

FIG. 4 is a circuit diagram of a main part of a regenerative processing circuit used in another embodiment of the present invention.

FIG. 5 is a circuit diagram showing a modification of the embodiment of FIG. 1;

FIG. 6 is a circuit diagram showing an example of a control power supply circuit when a normally-off switching means is used as the switching means.

[Explanation of symbols]

 1A-1C Motor 2A-2C Inverter circuit 3 Rectifier circuit 4 Main circuit capacitor 5 Voltage monitoring circuit 6 Regenerative resistor 7,7 'Regeneration transistor (switching means) 8,8' Control circuit (control signal generation circuit) 9A-9C Inverter Drive circuit 10 Control power supply circuit 11 Power supply monitoring circuit 12 Regenerative detection circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H530 AA07 BB32 CC26 CD34 CE15 CE16 DD03 DD12 DD13 DD14 DD16 DD22 DD28 EE01 EE05 EF04 5H572 AA14 BB07 BB10 CC05 DD05 DD09 HA07 HA08 HA09 HA11 HB09 HC07 HC10 JJ03 JJ24 JJ17 JJ17 JJ17 JJ18 MM03 MM13 5H576 AA17 BB06 BB10 CC05 DD02 DD07 EE09 EE11 HA01 HA02 HA03 HA05 HA10 HB02 HB05 JJ03 JJ12 JJ17 JJ18 LL24 LL60 MM01 MM03 MM10 MM13

Claims (8)

[Claims] 1. A plurality of inverter circuits configured to supply drive power to a plurality of motors from a common DC power supply and to regenerate power regenerated from the plurality of motors to the DC power supply, respectively. A plurality of inverter drive circuits for driving the plurality of inverter circuits, and a regenerative processing circuit including a regenerative resistor for converting the regenerative power to Joule heat, wherein the regenerative processing circuit receives a control signal input to a control terminal. A controllable switching means arranged to supply a current to the regenerative resistor during an on state and to interrupt a current flowing to the regenerative resistor during an off state; and an input terminal of the inverter circuit. When the inter-terminal voltage is higher than or equal to a predetermined voltage, the switching unit is turned on, and the inter-terminal voltage is set to the predetermined value. A control signal generating circuit that outputs the control signal so as to turn off the switching means when the voltage is lower than a predetermined voltage, wherein the series circuit of the switching means and the regenerative resistor includes A motor control device, wherein the regenerative processing circuit is connected in common between the input terminals of the respective inverter circuits, and the switching means is turned on when the DC power supply is in a power failure state. . 2. A normally-on switching device which is turned off when the control signal is input to the control terminal and is turned on when the control signal is not input to the control terminal. 2. The motor control device according to claim 1, wherein means is used. 3. A switch circuit for selectively supplying power to the plurality of inverter circuits is arranged between the common DC power supply and the plurality of inverter circuits. Or the motor control device according to 2. 4. The resistance value of the regenerative resistor is necessary for converting the electric power generated by the plurality of motors into heat in a short time when the power supply is in a power outage state, and quickly stopping the motors. The control signal generation circuit first outputs the control signal, and then determines whether the inter-terminal voltage is equal to or higher than the predetermined voltage. Performing a determining operation, performing a stopping operation of stopping the output of the control signal when determining that the inter-terminal voltage is equal to or higher than the predetermined voltage in the first determining operation, and thereafter performing the stopping operation. When a second determination operation is performed to determine whether or not the inter-terminal voltage is lower than the predetermined voltage, and when it is determined that the inter-terminal voltage is lower than the predetermined voltage, the control signal is output. Output to output Operation, and then returns to the first determination operation after a lapse of a predetermined timer time. The timer time is set when the regenerative power is repeatedly discharged to the regenerative resistor. The motor control device according to claim 2, wherein the motor control device is set so as to prevent the temperature of the resistor from rising above the allowable temperature limit. 5. The resistance value of the regenerative resistor is required to convert electric power generated by the motor into heat in a short time when the power supply is in a power outage state, and to quickly stop the motor. The control signal generating circuit outputs the control signal first, and then determines whether or not the inter-terminal voltage is equal to or higher than the predetermined voltage. Executing a stop operation of stopping the output of the control signal when it is determined in the first determination operation that the inter-terminal voltage is equal to or higher than the predetermined voltage, and thereafter, the inter-terminal voltage Performs a second determination operation of determining whether the voltage is smaller than the predetermined voltage, and outputs the control signal when it is determined that the inter-terminal voltage is smaller than the predetermined voltage. Output operation And then returns to the first determination operation after the elapse of a timer time set according to the time during which the output of the control signal has been stopped. 3. The motor control device according to claim 2, wherein when the regenerative electric power is discharged, the temperature of the regenerative resistor is prevented from rising to a temperature equal to or higher than an allowable temperature. 6. A rectifier circuit for rectifying AC power; a main circuit capacitor connected in parallel between output terminals of the rectifier circuit; and a drive power supply from the rectifier circuit to a plurality of motors and from the plurality of motors. A plurality of inverter circuits configured to charge the main circuit capacitor with regenerated power; a plurality of inverter drive circuits driving the plurality of inverter circuits; and a plurality of inverter circuits connected between terminals of the main circuit capacitor. A regenerative processing circuit including a regenerative resistor that converts regenerative electric power into Joule heat, wherein the regenerative processing circuit enters a control state when a control signal is input to a control terminal, and supplies current to the regenerative resistor during an ON state. Controllable switching means arranged to cut off the current flowing through the regenerative resistor during a period in which the current flows and is in an off state; A voltage monitoring circuit that outputs a detection signal when the inter-terminal voltage is equal to or higher than a predetermined voltage, and a regenerative device that monitors a regenerative state by counting a time during which the switching means is on. Monitoring means, when the detection signal is output from the voltage monitoring circuit, turns on the switching means to discharge the regenerative power through the regenerative resistor; and when the detection signal is not output, the switching is performed. A control signal generating circuit for outputting the control signal so as to turn off the means, wherein a series circuit of the switching means and the regenerative resistor is shared between the respective input terminals of the plurality of inverter circuits. The regenerative processing circuit is connected so that the switching means is turned on when the DC power supply is in a power failure state. A motor control device, comprising: 7. A plurality of inverter circuits configured to supply driving power to a plurality of motors from a common DC power supply and to regenerate power regenerated from the plurality of motors to the DC power supply side; A plurality of inverter drive circuits for driving the inverter circuits; a main circuit capacitor connected between input terminals of the plurality of inverter circuits to store power regenerated from the plurality of motors; and an input of the plurality of inverter circuits. A regenerative processing circuit including a regenerative resistor commonly connected between the terminals and converting regenerative power stored in the main circuit capacitor into Joule heat, wherein the regenerative processing circuit receives a control signal input to a control terminal. A control state is established so that a current flows through the regenerative resistor during the on-state and a current flows through the regenerative resistor during the off-state. Controllable switching means, and the switching means is turned on when the terminal voltage of the main circuit capacitor is equal to or higher than a predetermined voltage, and the terminal voltage becomes smaller than the predetermined voltage. And a control signal generation circuit that outputs the control signal so as to turn off the switching means when the switching means is in the off state, wherein a series circuit of the switching means and the regenerative resistor is provided for each of the plurality of inverter circuits. The regenerative resistor is connected in common between the input terminals, and the regenerative resistor is configured by a series circuit of a first resistor and a second resistor. Is set to a resistance value required to convert the electric power generated by the motor into heat in a short time to quickly stop the plurality of motors, A value obtained by adding the resistance value of the resistor to the resistance value of the first resistor is set to be a resistance value suitable for regenerative processing, and a control signal is input to a control terminal of the second resistor for control. The short-circuit switching means to be in a state is connected in parallel, and the regenerative processing circuit is configured such that when the DC power supply is in a power failure state, both the switching means and the short-circuit switching means are turned on. Motor control device. 8. The switching means and the short-circuiting switching means are turned off when the control signal is input to the control terminal, and turned on when the control signal is not input to the control terminal. 8. The motor control device according to claim 7, wherein the control signal generating circuit is configured to always output the control signal to the short-circuiting switching unit using a switching unit having a normally-on structure.