JP2009011042A - Method for protecting rush current prevention circuits, and inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for protecting a rush current prevention circuit wherein burnout of a rush current prevention resistor can be prevented through conventional circuitry and the operating state of a relay can be determined, and to provide an inverter device incorporating this method. <P>SOLUTION: The inverter device includes: a relay 41 that supplies power from an alternating-current power supply 1 through a converter unit 2 and has an answerback function; a rush current prevention resistor 3 connected in parallel with the relay 41; a smoothing capacitor 5 connected to the rush current prevention resistor 3; a direct-current bus voltage detection unit 8 that detects the voltage between the terminals of the smoothing capacitor 5; and a control circuit unit 9 having a torque limit function. The set value of a motor-side torque limiter is reduced according to an answerback signal from the relay 41 and burnout of the rush current prevention resistor 3 in a rush current prevention circuit 10 is thereby prevented at the time of relay operation failure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inrush current prevention circuit for an inverter device, and a protection method for an inrush current prevention circuit for preventing burning of an inrush current suppression resistor when a relay in the inrush current prevention circuit malfunctions, and an inverter having the same Relates to the device.

A smoothing capacitor is connected to the power supply of the inverter device in order to stabilize the voltage. In order to charge the smoothing capacitor when the power is turned on, an inrush current several times that in the steady state flows, and it is composed of a resistor and a relay. The inrush current prevention circuit suppresses the inrush current.
FIG. 3 is an example of a conventional inrush current prevention circuit.
In FIG. 3, 1 is an AC power source, and 2 is a converter unit for converting AC to DC. 3 is an inrush current suppression resistor, 4 is a relay, 5 is a smoothing capacitor that stabilizes the DC voltage, 6 is an inverter unit that converts the DC voltage into a variable voltage of a variable frequency, and 7 is a motor as a load.
When the AC power supply 1 is turned on, the operation of the inrush current prevention circuit charges the smoothing capacitor 5 while suppressing the inrush current by the inrush current suppression resistor 3 via the converter unit 2. When charging of the smoothing capacitor 5 is started and the DC bus voltage rises, the relay 4 is operated to short-circuit the contact portion of the relay 4. After the relay contact is short-circuited, a load current flows through the contact of the relay 4.
Thus, the inrush current prevention circuit suppresses the charging current of the smoothing capacitor 5 when the power is turned on by the inrush current suppression resistor 3, and when charging is completed, the relay 4 short-circuits the inrush current suppression resistor 3 and the relay 4 The load current is passed through the contact portion.

Conventionally, a relay having an answer back signal output function is used as means for determining the operation state of the relay 4 for protection of the inrush current prevention circuit.
Further, the comparison of the DC bus voltage value calculated from the output signal of the DC bus voltage detection unit 8 and the output signal of the load current detection unit 11 and the output signal value of the DC bus voltage detection unit 8 as shown in FIG. There is also one that detects a malfunction (see, for example, Patent Document 1).
JP 2006-340532 A (page 3-5, FIG. 1)

When an abnormality occurs in the relay or relay drive circuit in the inrush current prevention circuit and the relay does not operate normally, the load current of the motor 7 serving as a load always flows in the inrush current suppression resistor 3 in the circuit of FIG. There is a problem that the inrush current suppression resistor 3 is burned out.
As a solution to this problem, there is a method of using a relay having an answer back function and confirming the operation state of the relay. In the conventional method using this relay, the procedure of checking the matching of the relay drive command signal and the answer back signal is taken. When the power is turned off, the relay drive power is turned off, and the relay drive command signal and the answer back signal are Since inconsistency may occur, a certain amount of monitoring time is required, and there is a problem that it is not possible to immediately determine a relay operation failure due to inconsistency. If the relay operation is defective, the inrush current suppression resistor may be burned out during this monitoring time.
Further, the conventional technique as shown in FIG. 4 requires complicated calculation processing, and it is necessary to flow a load current in a steady state through the inrush current suppression resistor until a malfunction of the relay is detected.
The present invention has been made in view of such problems, and a protection method for an inrush current prevention circuit that can prevent the inrush current suppression resistor from burning out and determine the operation state of the relay with a conventional circuit configuration, and An object is to provide an inverter device including the same.

In order to solve the above problems, the present invention has the following method and configuration.
The invention according to claim 1 is connected to a relay having an answer back function for supplying electric power from an AC power source via a converter unit, an inrush current suppression resistor connected in parallel to the relay, and the inrush current suppression resistor. In an inverter device comprising a smoothing capacitor, a DC bus voltage detection unit for detecting a voltage between terminals of the smoothing capacitor, and a control circuit unit having a torque limit function, an electric side torque limiter according to an answer back signal of the relay Is set to a value that is less than or equal to the current value that allows continuous energization of the inrush current suppression resistor to prevent burning of the inrush current suppression resistor in the inrush current prevention circuit at the time of relay operation failure. is there.
According to a second aspect of the present invention, in the inverter device according to the first aspect, the protection function of the inrush current prevention circuit of the inverter device sets the set value of the electric side torque limiter according to the answer back signal of the relay. When the DC bus voltage detection value does not decrease below the preset DC bus voltage setting value when the value is lowered to the above value, there is provided means for determining that the operating state of the inrush current prevention circuit is defective.
According to a third aspect of the present invention, in the inverter device according to the first aspect, the protection function of the inrush current prevention circuit of the inverter device sets the set value of the electric side torque limiter according to the answer back signal of the relay. When the DC bus voltage detection value is lower than the preset DC bus voltage setting value when the value is lowered to the above value, the power source is recognized as being in a cut-off state and has a function of shifting to a power failure processing operation. It is.
According to a fourth aspect of the present invention, in the inverter device according to the second aspect, when the means for determining the operating state of the inrush current prevention circuit determines that the inrush current prevention circuit is malfunctioning, An alarm is displayed on the display unit to indicate that the inrush current prevention circuit is malfunctioning.
According to a fifth aspect of the present invention, in the inverter device according to the second aspect, when the means for determining the operating state of the inrush current preventing circuit determines that the inrush current preventing circuit is malfunctioning, The main circuit switching element is blocked and the supply of power is stopped.
According to a sixth aspect of the present invention, in the inverter device according to any one of the first to third aspects, instead of the relay, a contactor having an output function capable of determining an on / off state, or a semiconductor such as a thyristor A switching element is used in the inrush current prevention circuit.

According to a seventh aspect of the present invention, there is provided a relay having an answer back function for supplying electric power from an AC power source via a converter unit, an inrush current suppression resistor connected in parallel to the relay, and the inrush current suppression resistor. In the method for protecting an inrush current prevention circuit of a device comprising: a smoothing capacitor; a DC bus voltage detection unit for detecting a voltage across the terminals of the smoothing capacitor; and a control circuit unit having a current limit function of the converter unit. The inrush current prevention circuit protection method is configured to lower the set value of the current limit function to a value that is equal to or less than a current value at which the inrush current suppression resistor can be continuously energized according to the answerback signal.
According to the present invention, the inrush current of the converter unit at the time of power-on is not limited to the inverter device according to any one of claims 1 to 6, but a semiconductor switching element such as a relay, a contactor or a thyristor and an inrush current suppression resistor. The inrush current prevention circuit that suppresses AC can be widely applied to a DC power supply device that obtains a DC power by converting AC to DC.
According to an eighth aspect of the present invention, in the method for protecting an inrush current preventing circuit according to the seventh aspect, when the set value of the current limit function is lowered to the value in accordance with the answer back signal of the relay, the preset value is set in advance. When the detected value of the DC bus voltage is not lower than the set value of the DC bus voltage, there is provided means for determining that the operating state of the inrush current prevention circuit is defective.
According to a ninth aspect of the present invention, in the method for protecting an inrush current preventing circuit according to the seventh aspect, when the set value of the current limit function is lowered to the value in accordance with the answer back signal of the relay, the preset value is set in advance. When the detected value of the DC bus voltage is lower than the set value of the DC bus voltage, the function recognizes that the power source is in a cut-off state and shifts to a power failure processing operation.
According to a tenth aspect of the present invention, in the method for protecting an inrush current preventing circuit according to the eighth aspect, when the means for judging the operating state of the inrush current preventing circuit judges that the inrush current preventing circuit is malfunctioning. In this case, an alarm is displayed to the effect that the inrush current prevention circuit is malfunctioning.
According to an eleventh aspect of the present invention, in the method for protecting an inrush current preventing circuit according to the ninth aspect, the means for judging the operating state of the inrush current preventing circuit recognizes that the power supply is in a cut-off state, and When transitioning to operation, an alarm is displayed to indicate that a power failure is occurring.
According to a twelfth aspect of the present invention, in the inrush current protection circuit protection method according to any of the seventh to ninth aspects, a contactor having an output function capable of determining an on / off state instead of the relay, Alternatively, a semiconductor switching element such as a thyristor is used in the inrush current prevention circuit.

  According to the present invention, it is possible to prevent the inrush current suppression resistor from burning out by suppressing the current flowing through the inrush current suppression resistor when the relay operation is defective in the conventional circuit configuration. Further, it is possible to determine abnormality of the inrush current prevention circuit.

  Hereinafter, specific examples of the method of the present invention will be described with reference to FIGS.

FIG. 1 is a configuration diagram of an inverter device that implements a method for protecting an inrush current prevention circuit according to the present invention. In the figure, 1 is an AC power source, 2 is a converter unit, 3 is an inrush current suppression resistor, 41 is a relay having an answer back function indicating that the contact is turned on, 5 is a smoothing capacitor, 6 is an inverter unit, and 7 is A motor serving as a load, 8 is a DC bus voltage detection unit, and 9 is a control circuit unit. The control circuit unit 9 has an inverter control unit having a torque limit function, a DC voltage monitoring by the DC bus voltage detection unit 8, a relay 4 drive command and an answer back signal monitoring function.
The inrush current prevention circuit 10 includes an inrush current suppression resistor 3, a relay 41, a DC bus voltage detection unit 8, and a control circuit unit 9. The basic operation is the same as that of the conventional example shown in FIG. 3 except that the relay 4 is a relay 41 having an answer back function and a DC bus voltage detector 8 is added. is there.

FIG. 2 is a flowchart showing a method for protecting the inrush current prevention circuit 10 in the embodiment, and more specifically, a processing procedure for preventing the inrush current suppression resistor from burning out. Hereinafter, the protection method of the inrush current prevention circuit 10 of the present invention will be described with reference to FIG.
First, in step 1 (described as S1 in FIG. 2), the answer back signal of the relay 4 is monitored, and when the answer back signal is turned OFF, the set value of the electric torque limiter is lowered in step 2, that is, Then, the load current to the motor 7 serving as a load is suppressed by lowering the inrush current suppression resistor 3 to a value that is equal to or less than a current value that allows continuous energization. This prevents the inrush current suppression resistor 3 from burning out when the inrush current prevention circuit 10 is abnormal. If the answerback signal is not OFF, the process returns to step 1.

  Note that the current value that can be continuously energized depends on the allowable temperature rise of the inrush current suppression resistor 3, the cooling conditions, the installation environment, and the like, and is determined so as to meet the design conditions of the inverter device. Also, depending on the application on the side of the machine driven by the motor that is the load, there may be no problem even if it stops instantaneously when an abnormality occurs, but in general, a sudden stop is not preferable for the machine. The set value of is processed so as to gradually decrease. If the machine can tolerate a sudden stop, the torque limiter set value may be set to zero and the motor current may be set to substantially zero simultaneously with turning off the answerback signal. Furthermore, depending on the application of the machine, even when an abnormality occurs, it may be necessary to maintain the driving state as much as possible. In such a case, the set value of the torque limiter is maintained as it is for a predetermined period after the answer back signal is informed until the evacuation process on the machine side is completed, and then the set value is gradually increased. Take measures such as lowering.

  Next, in step 3, the DC bus voltage is monitored by the DC voltage detector 8, and it is determined whether or not the voltage is lower than a preset voltage value. That is, when the input power is cut off, if the answer back signal of the relay 41 is turned OFF and the DC bus voltage drops, it is determined that the DC bus voltage has dropped because the power supply is cut off, and the answer back signal is turned OFF. Nevertheless, if the DC bus voltage does not decrease, it can be determined that some malfunction has occurred in the contact portion of the relay 41 or the drive circuit of the relay 41.

In addition, the following cases can be considered as abnormal contents in the inrush current prevention circuit 10. For example, when the drive current of the relay 41 is interrupted while the load current is flowing through the contact of the relay 41 during the inverter operation, the contact of the relay 41 is turned off and connected to the relay 41 in parallel. The load current flows through the inrush current suppression resistor 3 that is provided. If this load current continues to flow, it leads to a burnout accident of the inrush current suppression resistor 3.
Further, when the DC bus voltage does not decrease even though the answer back signal of the relay 41 is turned off, the answer back signal is abnormal, the contact welding of the relay 41, and the relay 41 is turned off via the inrush current suppression resistor 3. An abnormal condition such as a load current continuing to flow is considered.

  In the present invention, since the load current is suppressed when the answer back signal of the relay 41 is detected to be OFF, even if the inrush current prevention circuit 10 is abnormal, the inrush current suppression resistor 3 is prevented from being burned out. Therefore, the abnormality of the inrush current prevention circuit 10 can be determined.

Further, if the inrush current prevention circuit 10 is determined to be abnormal, an alarm is displayed on the display unit of the inverter device in step 4 to indicate that the inrush current prevention circuit 10 is malfunctioning, and in step 5, the main circuit switching element of the inverter device is displayed. To stop the operation of the inverter.
When it is determined that the inrush current prevention circuit 10 is normal, a normal power failure process is executed in step 6.

  Inrush current prevention circuit that suppresses the inrush current of the converter section when power is turned on using a semiconductor switching element such as a relay, contactor or thyristor and an inrush current suppression resistor is a DC power supply that converts AC to DC to obtain DC power The present invention is widely used in devices, inverter devices for controlling motors, and the like, and the present invention can be executed by a conventional circuit configuration and software processing, and can be easily applied to these devices.

The block diagram of the inverter apparatus which applies the protection method of the inrush current prevention circuit of this invention The flowchart which shows the process sequence of the protection method of the inrush current prevention circuit of this invention Configuration diagram of an inverter device having a conventional inrush current prevention circuit Configuration diagram of an inverter device to which a conventional inrush current prevention circuit protection method is applied

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter part 3 Inrush current suppression resistance 4 Relay 5 Smoothing capacitor 6 Inverter part 7 Motor 8 DC bus voltage detection part 9 Control circuit part 10 Inrush current prevention circuit 41 Relay with an answerback function

Claims (12)

  A relay having an answer-back function for supplying power from an AC power supply via a converter unit; an inrush current suppression resistor connected in parallel to the relay; a smoothing capacitor connected to the inrush current suppression resistor; In an inverter device having a DC bus voltage detection unit for detecting a voltage between terminals and a control circuit unit having a torque limit function, the set value of the electric side torque limiter is controlled in accordance with the answerback signal of the relay. An inverter device having a protection function for an inrush current prevention circuit, wherein the resistance is lowered to a value that is equal to or less than a current value that allows continuous energization of the resistor.   The protection function of the inrush current prevention circuit of the inverter device is that when the set value of the electric torque limiter is lowered to the value in accordance with the answer back signal of the relay, the DC bus voltage is set to be lower than the preset DC bus voltage setting value. 2. The inverter device according to claim 1, further comprising means for determining that the operating state of the inrush current prevention circuit is defective when the detected value does not decrease.   The protection function of the inrush current prevention circuit of the inverter device is that when the set value of the electric torque limiter is lowered to the value in accordance with the answer back signal of the relay, the DC bus voltage is set to be lower than the preset DC bus voltage setting value. The inverter device according to claim 1, further comprising a function of recognizing that the power source is in a cut-off state and shifting to a power failure processing operation when the detected value decreases.   When the means for determining the operating state of the inrush current prevention circuit determines that the inrush current prevention circuit is inoperative, an alarm display indicating that the inrush current prevention circuit is in malfunction is displayed on the display unit of the inverter device. The inverter device according to claim 2.   The means for determining the operating state of the inrush current prevention circuit, when it is determined that the inrush current prevention circuit is defective, blocks the main circuit switching element of the inverter device and stops supplying power. The described inverter device.   The inverter according to any one of claims 1 to 3, wherein a semiconductor switching element such as a contactor or a thyristor having an output function capable of discriminating an on / off state is used in the inrush current prevention circuit instead of the relay. apparatus.   A relay having an answer-back function for supplying power from an AC power supply via a converter unit; an inrush current suppression resistor connected in parallel to the relay; a smoothing capacitor connected to the inrush current suppression resistor; In a method for protecting an inrush current prevention circuit of a device comprising a DC bus voltage detection unit for detecting a voltage between terminals and a control circuit unit having a current limit function of the converter unit, the current according to the answer back signal of the relay A method for protecting an inrush current prevention circuit, wherein a set value of a limit function is lowered to a value that is equal to or less than a current value that allows continuous energization of the inrush current suppression resistor.   According to the protection method of the inrush current prevention circuit, when the set value of the current limit function is lowered to the value according to the answer back signal of the relay, the detected DC bus voltage value is lower than the preset DC bus voltage setting value. 8. The method for protecting an inrush current prevention circuit according to claim 7, further comprising means for judging that the operation state of the inrush current prevention circuit is defective when the current does not decrease.   According to the protection method of the inrush current prevention circuit, when the set value of the current limit function is lowered to the value according to the answer back signal of the relay, the detected DC bus voltage value is lower than the preset DC bus voltage setting value. 8. The method for protecting an inrush current prevention circuit according to claim 7, further comprising a function of recognizing that the power source is in a cut-off state and shifting to a power failure processing operation when the power supply voltage is lowered.   The means for determining an operating state of the inrush current prevention circuit displays an alarm indicating that the inrush current prevention circuit is in malfunction when the inrush current prevention circuit is judged to be in malfunction. Protection method for inrush current prevention circuit.   The means for determining the operation state of the inrush current prevention circuit recognizes that the power supply is in a cut-off state, and displays an alarm indicating that a power outage is occurring when the power transfer processing operation is performed. Inrush current protection circuit protection method.   10. The inrush according to claim 7, wherein a semiconductor switching element such as a contactor or a thyristor having an output function capable of discriminating an on / off state is used in the inrush current prevention circuit instead of the relay. Protection method of current prevention circuit.

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