JP2004032913A - Braking method for servomotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain optimum braking for a motor in an AC servo driver, corresponding to whether or not there is some failure in a power device. <P>SOLUTION: If there is no failure in the power device, a relay 3 is off, so that braking current runs through IGBT4 connected with a motor terminal of which the induced voltage is high, and runs through a motor terminal of which the induced voltage is low, via a diode 5 for reflux. If there is some failure in the power device, on the other hand, the relay 3 turns on, so that two phases of the motor are shortened and the braking current runs through the relay 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an AC servo driver having an inverter for converting a DC voltage into a three-phase voltage and applying the converted voltage to a motor, and more particularly to a servomotor braking method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an AC servo driver performs braking by a dynamic brake that short-circuits motor terminals at the time of motor braking such as emergency stop.
[0003]
In order to reduce the size and cost of the circuit, a method of short-circuiting only two phases of the AC motor terminal may be adopted.
[0004]
Also, as one of the dynamic braking methods by three-phase short-circuit, there is a method in which all three upper or lower arms of a power device are ignited to constitute a circuit together with a reflux diode (Japanese Patent Laid-Open No. 8-149870). .
[0005]
[Problems to be solved by the invention]
The former method has a disadvantage that the coasting distance is longer than the latter method (three-phase short circuit). The latter method has a disadvantage that the dynamic brake function cannot be used when there is an abnormality in the power device such as an overcurrent abnormality.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a servo motor braking method capable of performing optimal braking of a motor in accordance with the presence or absence of an abnormality in a power device while enabling downsizing, low cost, and safety of a circuit. It is in.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a switch for short-circuiting / opening two of the three-phase motor terminals. When an emergency stop is performed when there is no abnormality in the inverter when the brake is applied, all the upper or lower arms of the inverter are fired and dynamic braking is performed together with the freewheeling diode.
[0008]
Therefore, it is possible to perform the optimal braking of the motor in accordance with the presence or absence of the abnormality of the power device, while enabling downsizing of the circuit, low cost, and safety.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a circuit diagram of an AC servo driver according to an embodiment of the present invention. This AC servo driver has an inverter 2 for converting a DC voltage to a three-phase voltage and applying the same to a motor 1, and a relay 3 for short-circuiting / opening two terminals of the three-phase motor terminals. A circuit for turning on / off the relay 3 is not shown. The inverter 2 includes an IGBT (Insulated-gate Bipolar Transistor) that is a power device and a diode 5.
[0011]
FIG. 2A shows the flow of the braking current during the dynamic braking operation when there is no abnormality in the power device. In this example, a case where all the lower arms are fired is shown. Relay 3 is off. The braking current flows to the IGBT 4 connected to the motor terminal having a high induced voltage, passes through the circulating diode 5, and flows to the motor terminal having a low induced voltage. Kinetic energy is consumed by the winding resistance of the motor 1.
[0012]
FIG. 2B shows the flow of the braking current during the dynamic braking operation when the power device is abnormal. In this case, the relay 3 is turned on, the two phases of the motor 1 are short-circuited, and the braking current flows through the relay 3.
[0013]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the size of the circuit, reduce the cost and increase the safety, and perform optimal braking of the motor in accordance with the presence or absence of an abnormality in the power device.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of an AC servo driver according to an embodiment of the present invention.
FIG. 2 shows the flow of a braking current during dynamic braking operation when there is no abnormality in the power device (FIG. 2 (1)) and the flow of braking current when the power device is abnormal in the AC servo driver of FIG. It is a figure which shows FIG.2 (2).
[Explanation of symbols]
1 Motor 2 Inverter 3 Relay 4 Power transistor 5 Diode

Claims (1)

In an AC servo driver having an inverter that converts a DC voltage into a three-phase voltage and applies the voltage to a motor,
A switch for short-circuiting / opening two terminals of the three-phase motor terminals is provided,
If it is determined that there is an abnormality in the inverter, the switch is short-circuited to perform dynamic brake braking. A braking method for a servomotor, characterized in that the servomotor is fired and dynamically braked in combination with a freewheeling diode.

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