JP2010233414A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device capable of protecting a regenerative resistor at low cost without requiring the setting of a special protective function on the outside by a final user. <P>SOLUTION: The motor control device includes: a charging-current limiting means 6 limiting the charging current of an electrolytic capacitor 3 for smoothing for a fixed period after power-on; and a regenerative resistor 4 consuming a regenerative power supplied through an inverter 2 from a motor 11 by heat. The motor control device further includes a semiconductor switching element 5 being connected in series with the regenerative resistor 4 and consuming the regenerative power in the regenerative resistor 4 by an ON operation, and a fault detection means 7 controlling the ON/OFF operation of the semiconductor switching element 5 and detecting a short circuit fault in case of an OFF operation. The charging-current limiting means 6 consists of a current limiting resistor 6a and a relay 6b connected in parallel. The fault detection means 7 continuously makes a current flow through the current limiting resistor 6a by opening the relay 6b when detecting the short circuit fault of the semiconductor switching element 5, overload-disconnects the current limiting resistor 6a and prevents the burning of the regenerative resistor 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor control device having a charging current limiting means and a regenerative power processing circuit, and more particularly to burnout protection of a regenerative resistor against a short circuit failure of a semiconductor switching element for regenerative processing.

  Conventionally, in a motor control device such as a servo amplifier or an inverter, especially a small device, a method of converting heat energy by a resistor is generally used as means for consuming regenerative power of the motor.

  FIG. 3 is a principal block diagram of a conventional motor control device. When the motor control device rectifies the AC power supply 10 as an input by the diode bridge 1 and supplies it to the DC bus, the inverter unit 2 uses the electrolytic capacitor 3 for smoothing connected between the positive and negative DC buses as a power source to generate DC power. It is converted into AC power and supplied to the motor 11 for driving.

  On the other hand, as a protection function of the motor control device, the regenerative resistor 4 and the semiconductor switching element 5 are connected in series between the positive and negative DC buses with respect to the regenerative power supplied from the motor 11 via the inverter unit 2 to perform semiconductor switching. Heat is consumed by the regenerative resistor 4 by ON / OFF control of the element 5. The charging current limiting means 6 for limiting the charging current of the electrolytic capacitor 3 for a certain period after the power is turned on is composed of a current limiting resistor 6a and a relay 6b connected in parallel, and the relay 6b is turned on. Immediately after that, the charging current of the electrolytic capacitor 3 flows through the current limiting resistor 6a in an open state, and after charging is completed, the relay 6b is operated by a command from the CPU 8 to short-circuit the current limiting resistor 6a. Thereafter, the current flows through the relay 6b.

  In the motor control device configured as described above, when considering a case where the semiconductor switching element 5 is short-circuited, current continuously flows through the regenerative resistor 4 through the diode bridge 1 and the relay 6b. When the semiconductor switching element 5 has an open failure, the voltage across the electrolytic capacitor 3 rises abnormally, so the CPU 8 detects and trips the overvoltage.

  In general, the regenerative resistor 4 is designed so that a current is intermittently supplied when regenerative power is generated, and a resistor having a capacity corresponding to the current is selected. Therefore, when a current is continuously supplied to the regenerative resistor 4, the resistor may overheat and in the worst case, burnout may occur.

  For this reason, various proposals have been made for the function of preventing the burnout of the regenerative resistor. For example, Patent Document 1 proposes a method for detecting a short-circuit fault in a semiconductor switching element.

  However, the technique of Patent Document 1 does not describe the protection method after the detection of the short-circuit fault, and it is generally assumed that the motor control device outputs a short-circuit fault detection signal to the outside for the final use. This is a method in which a person operates an electromagnetic contactor or the like installed between a motor control device and a power source to cut off the power source.

  On the other hand, a method for specifically preventing burnout of the regenerative resistor by detecting a short circuit failure of the semiconductor switching element and adding a thyristor, a current fuse, or the like has been proposed (for example, see Patent Document 2).

Alternatively, a method of detecting overheating by incorporating a temperature detection element such as a fuse or a thermostat in the regenerative resistor itself has been conventionally performed.
JP 2002-191178 A JP-A-5-336758

  As described above, various methods have been tried for preventing the burnout of the regenerative resistor against a short circuit failure of the semiconductor switching element. However, in the method of detecting the failure and outputting the signal to the outside, the power supply is shut off to regenerate the resistance. The means for preventing the burnout of the vessel was left to the end user, and it was up to the end user to ensure that it could be protected.

  Also, the method of incorporating the temperature detection element in the regenerative resistor itself is left to the judgment of the end user when the regenerative resistor is selected by the end user, and the protection function is completed with the motor control unit alone. I did not. In addition, adding a thyristor, a current fuse, etc. is disadvantageous in terms of cost and shape.

  The present invention solves the above-mentioned conventional problems, and it is not necessary for the end user to provide a special protection function for the short circuit failure of the semiconductor switching element, and the motor control that can protect the regenerative resistor at low cost. An object is to provide an apparatus.

  In order to solve the above problems, a motor control device according to claim 1 is a current limiting resistor and a relay for limiting a charging current of a smoothing electrolytic capacitor connected between positive and negative DC buses for a certain period after power-on. Charging current limiting means comprising a parallel circuit, a regenerative resistor that consumes regenerative power supplied from a motor via an inverter unit by heat, and the regenerative resistor that is connected in series to the regenerative resistor and that is turned ON A semiconductor switching element that consumes regenerative power at the same time, a failure monitoring means that is connected to both ends of the regenerative resistor and that monitors a short-circuit fault of the semiconductor switching element, controls the ON / OFF operation of the semiconductor switching element, and is OFF A microprocessor (hereinafter referred to as a CPU) that detects a short-circuit failure by an operation and an output of the failure monitoring means; And detecting a short-circuit fault in the semiconductor switching element, the relay in the charging current limiting means is opened, a current is continuously passed through the current limiting resistor, and the current limiting resistor is overloaded, thereby causing the regeneration. Prevent resistor burnout.

  According to a second aspect of the present invention, a temperature control fuse is connected in series to the current limiting resistor and the temperature fuse is blown prior to the current limiting resistor.

  According to the motor control device of the first aspect, it is possible to realize a short circuit failure of the semiconductor switching element without disconnecting the current limiting resistor and protecting the regenerative resistor without adding new components. Therefore, cost reduction can be achieved. Further, the regenerative resistor can be protected without depending on the judgment of the end user. Furthermore, it can be realized without greatly changing the conventional configuration and the number of parts.

  According to the motor control device of the second aspect, since the thermal fuse is blown before the current limiting resistor, the regenerative resistor can be reliably protected.

Charging current limiting means consisting of a parallel circuit of a current limiting resistor and a relay that limits the charging current of the electrolytic capacitor for smoothing connected between the positive and negative DC buses for a certain period after turning on the power, and supplied from the motor via the inverter unit A regenerative resistor that consumes the regenerative power that is generated by heat, a semiconductor switching element that is connected in series to the regenerative resistor and that consumes the regenerative power by the regenerative resistor by an ON operation, and is connected to both ends of the regenerative resistor A failure monitoring means for monitoring a short-circuit fault of the semiconductor switching element; and a microprocessor for controlling an ON / OFF operation of the semiconductor switching element and detecting a short-circuit fault by an OFF operation and an output of the failure monitoring means (hereinafter referred to as a “short-circuit fault”). The CPU), the CPU detects the short circuit failure of the semiconductor switching element and detects the short circuit failure. Electric current continuously to the current limiting resistor opens the relays in current limiting means, to prevent burnout of the regenerative resistor by overload break the current limiting resistor. Hereinafter, specific embodiments will be described.

(Embodiment 1)
FIG. 1 is a block diagram of a main part of a motor control device according to Embodiment 1 of the present invention. In FIG. 1, a motor control device includes a diode bridge 1 that rectifies an AC power supply 10 and supplies a DC bus, an inverter unit 2 that converts DC power into AC power, and a smoothing connected between positive and negative DC buses. The electrolytic capacitor 3, the regenerative resistor 4 that consumes the regenerative power supplied from the motor via the inverter unit 2, the semiconductor switching element 5 that controls the energization of the regenerative resistor 4, and the charging current of the electrolytic capacitor 3 The charging current limiting means 6 is configured to limit for a certain period after the power is turned on.

  The charging current limiting means 6 comprises a current limiting resistor 6a and a relay 6b connected in parallel. Immediately after the power is turned on, the relay 6b is in an open state, the charging current of the electrolytic capacitor 3 flows through the current limiting resistor 6a, and charging ends. Later, the relay 6b is closed by a command from the CPU 8 to short-circuit the current limiting resistor 6a, so that the current flows through the relay 6b thereafter.

  On the other hand, in response to a command from the CPU 8 that detects that the voltage between the positive and negative DC buses has increased due to the regenerative power of the motor 11, the semiconductor switching element 5 is turned on and a current flows through the regenerative resistor 4. The process up to this point is the same as the conventional one.

  The feature of the present invention is that the failure monitoring means 7 and the CPU 8 detect a short-circuit failure of the semiconductor switching element 5 and open the relay 6b of the charging current limiting means 6 to protect the regenerative resistor 4 from burning. is there.

  The fault monitoring means 7 of the present invention has a configuration in which, for example, a photocoupler and a resistor for limiting the current flowing through the photocoupler are connected in parallel with the regenerative resistor 4, and monitors the potential difference between both ends of the regenerative resistor 4. As a result, the conduction and non-conduction of the semiconductor switching element 5 are detected and a signal is output to the CPU 8. When the CPU 8 receives a signal indicating that the semiconductor switching element 5 is conductive from the failure monitoring means 7 even though it does not issue an ON command to the semiconductor switching element 5, it is a short circuit failure of the semiconductor switching element 5. And relay 6b is turned OFF (contact is opened). As a result, the current flowing through the regenerative resistor 4 also flows through the current limiting resistor 6a connected in parallel with the relay 6b.

  Here, the difference in design between the regenerative resistor 4 and the current limiting resistor 6a will be described. The regenerative resistor 4 consumes the regenerative power of the motor 11 and is designed to withstand a certain amount of continuous energization depending on the type of motor, the inertia of the load, the operation pattern of the motor, and the like. It is common.

  For this purpose, it is necessary to increase the weight of the resistance wire inside the resistor. For this reason, the resistance wire can be easily overloaded even in a situation where a short circuit failure occurs in the semiconductor switching element 5 and current flows continuously. Otherwise, the resistor may overheat abnormally and may be burned out.

Since one current limiting resistor 6a is energized only during the charging period of the electrolytic capacitor 3 when the power is turned on, it is not necessary to consider that it can withstand energization for a long time, and it is relatively easy for continuous energization. It can be designed to break overload. For this reason, the regenerative resistor 4 is more expensive than the current limiting resistor 6a.

  The current limiting resistor 6a designed in this way is incorporated in the charging current limiting means 6, and when the semiconductor switching element 5 is short-circuited as described above, the current flowing through the regenerative resistor 4 is also passed through the current limiting resistor 6a. As a result, the current limiting resistor 6a is forcibly overloaded.

  Thereby, even if the power supply is operating normally, the relay 6b is in an open state, so that the DC power to the regenerative resistor 4 is cut off and can be protected from burning. In addition, since the semiconductor switching element 5 has a short circuit failure, the regenerative power is continuously consumed by the regenerative resistor 4, so that the electrical connection between the motor control device and the motor is cut off.

Although the above-described failure monitoring means 7 is for observing the voltage across the regenerative resistor 4, the same applies to the method of detecting the current flowing through the regenerative resistor 4 and the semiconductor switching element 5 connected in series. The function is configurable.
(Embodiment 2)
FIG. 2 is an explanatory diagram of a current limiting resistor according to Embodiment 2 of the present invention. The only difference from the first embodiment is the configuration of the current limiting resistor.

  The current limiting resistor 12 according to the second embodiment includes a thermal fuse 13 and a resistor 14 connected in series.

  Similarly to the first embodiment, when the semiconductor switching element 5 connected to the regenerative resistor 4 is short-circuited, the contact of the relay 6b is opened, and the resistor constituting the regenerative resistor 4 and the current limiting resistor 12 A current also flows through 14 and the thermal fuse 13. At this time, the thermal fuse 13 is blown before the resistor 14 is disconnected due to overload.

  Similarly to the first embodiment, the relay 6b is in an open state even when the power supply is operating normally, and the regenerative resistor 4 can be protected.

  In the first embodiment, the current limiting resistor 6a may not be immediately disconnected by a DC arc. Therefore, if the current limiting resistor 12 of the second embodiment is configured, the charging current limiting means is reliably opened by fusing. Can be. Therefore, the regenerative resistor 4 can be protected.

  Although Embodiments 1 and 2 have been described with reference to an example of a motor control device that converts AC power into DC power, it goes without saying that the input of the motor control device may be a DC power supply.

  The motor control device of the present invention is useful for industrial equipment such as servo amplifiers and inverters.

Block diagram of main parts of the motor control device according to Embodiment 1 of the present invention. Explanatory drawing of the current limiting resistor in Embodiment 2 of this invention Main part block diagram of motor control device in conventional example

DESCRIPTION OF SYMBOLS 1 Diode bridge 2 Inverter part 3 Electrolytic capacitor 4 Regenerative resistor 5 Semiconductor switching element 6 Charging current limiting means 6a Current limiting resistor 6b Relay 7 Failure monitoring means 8 CPU
DESCRIPTION OF SYMBOLS 10 AC power source 11 Motor 12 Current limiting resistor 13 Thermal fuse 14 Resistor

Claims (2)

A charging current limiting means comprising a parallel circuit of a current limiting resistor and a relay for limiting the charging current of the smoothing electrolytic capacitor connected between the positive and negative DC buses over a certain period after power-on,
A regenerative resistor that consumes regenerative power supplied from the motor via the inverter unit with heat;
A semiconductor switching element connected in series to the regenerative resistor and consuming regenerative power in the regenerative resistor by an ON operation;
Fault monitoring means connected to both ends of the regenerative resistor and monitoring a short-circuit fault of the semiconductor switching element;
A microprocessor (hereinafter referred to as a CPU) that controls the ON / OFF operation of the semiconductor switching element and detects a short-circuit failure by the OFF operation and the output of the failure monitoring means,
When the CPU detects a short-circuit fault of the semiconductor switching element, the CPU opens the relay in the charging current limiting means and continuously supplies a current to the current limiting resistor, thereby overloading the current limiting resistor. A motor control device characterized by preventing burnout of the regenerative resistor.   2. The motor control device according to claim 1, wherein a thermal fuse is connected in series to the current limiting resistor, and the thermal fuse is blown prior to the current limiting resistor.

Images