JPH0715989A - Motor controller - Google Patents

Abstract

PURPOSE:To reduce the damage on a braking resistor in the stopped state of this controller by a method wherein the generated voltage of a motor is applied to the braking resistor when a braking signal is input in the driven state of an inverter and the voltage is not applied in the non-driven state of the inverter irrespective of whether the braking signal exists or not. CONSTITUTION:When an input voltage is larger than a rated voltage due to the situation of a power supply during the drive of an inverter means (IV), a bus voltage at a prescribed voltage or higher is detected, and a braking signal is detected. However, since the output of an AND circuit A2 for a suppression discrimination means 15 is at L, the drive of the IV 3 is not suppressed irrespective of whether the braking signal exists or not as long as an operating switch 9 is turned on. On the other hand, when the operating switch 9 is turned off, the frequency of the IV 3 is lowered quickly, and the bus voltage at the prescribed voltage or higher is detected due to the power-generation action of a motor 4, the braking signal is detected. In addition, since the output of the AND circuit A2 is set to H, the drive of the IV 3 is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor control device for frequency controlling the rotational speed of an electric motor.

[0002]

2. Description of the Related Art Generally, an electric motor control device of this type includes
The AC input voltage is rectified and smoothed by the converter means to output a DC voltage, and the DC voltage of the converter means is converted into the AC voltage by the inverter means and supplied to the electric motor,
There is one in which the frequency supplied to the electric motor is changed by the drive control of the inverter means to change the rotation speed of the electric motor. In the drive control of the inverter means, the control means gradually accelerates the inverter means to a predetermined frequency in response to the ON operation of the operation switch, and then drives the inverter means at the predetermined frequency to drive the electric motor at a desired rotation speed. In response to the operation of turning off the operation switch, the inverter means is gradually decelerated from a predetermined frequency to operate the electric motor. In this motor control device, when the inverter means is gradually decelerated from a predetermined frequency, various loads such as a load with a large inertia or a light load may be connected to the motor, so that regenerative voltage, regenerative current, etc. are detected. Then, a stall function for varying the deceleration speed of the inverter means is provided based on this detected state to protect the control device against overvoltage generated by the power generation action of the electric motor and to stop the electric motor early. Further, in order to further stop the motor early, a voltage discriminating means for detecting an input voltage of the inverter means and outputting a brake signal when the voltage exceeds a predetermined value, and an inverter in response to the brake signal of the voltage discriminating means. Brake means for energizing the brake resistance connected in parallel to the input of the means is provided, and the voltage generated by the power generation action of the electric motor is applied to the brake resistance to consume the electric power and to stop the electric motor early.

[0003]

However, in the above-described electric motor control device, the voltage discriminating means and the braking means provided for the purpose of early stopping of the electric motor are the input voltage of the inverter means, that is, the converter means. A brake signal is output when the DC voltage exceeds a specified value.For example, when the input AC voltage fluctuates significantly or an abnormal voltage is input, a brake signal is output and the brake resistance is energized. May start, and if this energization continues, there is a risk that the brake resistance will burn out.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device in which damage to the brake resistance is reduced in a stopped state.

[0005]

In order to solve such a problem, a motor control device according to the present invention uses a converter means for rectifying and smoothing an AC input voltage and outputting a DC voltage, and a DC voltage of the converter means for AC. Inverter means for converting the voltage to supply to the electric motor and control means for driving the inverter means in response to the operation of the operation switch including acceleration and deceleration and outputting an operation signal while the inverter means is being driven. A voltage discriminating means for detecting the input voltage of the inverter means and outputting a brake signal when the voltage exceeds a predetermined value, and a brake means for energizing a brake resistor connected in parallel to the input of the inverter means at the time of signal input,
In the electric motor control device including: a suppression determination unit that inputs the brake signal of the voltage determination unit and the operation signal of the control unit and outputs the brake signal only when the operation signal is generated. The output of the discriminating means is input to the braking means.

[0006]

According to the structure of the present invention, when the inverter means is being driven, when the brake signal is input, the brake signal is input to the brake means and the generated voltage of the electric motor is applied to the brake resistance. In the state where is not driven, it is not applied to the brake resistor regardless of the presence or absence of the brake signal.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. That is, this motor control device rectifies and smoothes the AC input voltage of the three-phase AC power supply 1 by the converter means 2 to output a DC voltage, and converts this DC voltage into an AC voltage by the inverter means 3 (power circuit). Electric motor 4
Is being supplied to. The converter means 2 is composed of a diode bridge connecting a plurality of diodes, rectifies the AC input voltage of the three-phase AC power supply 1 into a pulsating current, and smoothes this pulsating current with a smoothing capacitor to output it as a DC voltage. There is. The inverter means 3 is formed by connecting a transistor and a diode in parallel to form an arm and connecting three pairs of these arms in parallel. The inverter means 3 inputs a DC voltage which is an output voltage of the converter means 2 and operates a control means 5 described later. According to the operation of the switch, the AC voltage of the set frequency is converted to drive the electric motor 4, which is an induction motor.

Reference numeral 5 is a control means, which is a RAM or EEPR for storing frequency data of alternating current supplied to the inverter means 3.
It has an inverter control microcomputer 6 having a data storage means, which is a rewritable memory composed of OM, and responds to an ON operation of an operation switch 9 and gradually drives the inverter means 3 up to a predetermined frequency via a power Tr drive circuit 7. After acceleration, the inverter means 3 is driven at a predetermined frequency to drive the electric motor.
4 is driven at a desired rotational speed, and in response to the operation of turning off the operation switch 9, the inverter means 3 is gradually decelerated from a predetermined frequency to operate the electric motor 4 to stop. In addition, this control means 5 is provided with a protection circuit 8 (stall function) so that the rotation speed of the inverter circuit 3 does not decrease when the rotation speed of the motor 4 does not decrease easily due to the connection of a load with large inertia. Is gradually lowered to protect the inverter control microcomputer 6 against overvoltage generated by the power generation action of the electric motor 4. This control means 5 operates the inverter switch 3 by turning on the operation switch 9.
Drive including acceleration and deceleration, and inverter means 3
The driving signal is output while driving.

The control means 5 will be described with reference to FIG. 2. The frequency and drive time for driving the inverter means 3 are selected (S1) in advance. Then, it is judged whether the operation switch 9 (see FIG. 1) is on or off (S2), and if it is on, the control means 5 outputs an operation signal (S3) to drive the inverter means 3 (S4). This inverter means 3 is continuously driven until the operation switch 9 is turned off. Also,
If the operation switch (S2) is off, inverter means 3
The driving signal for discriminating whether or not is driven is discriminated (S5), and if 0, the inverter means 3 is stopped, and this state is continued until the driving switch (S2) is turned on. If the operation signal judgment (S5) is 1, deceleration stop control (S6) is performed to judge whether the inverter means 3 has stopped.
(S7), if stopped (S8), the operation signal becomes 0 and the stopped state continues until the operation switch (S2) turns on.
If not stopped, the deceleration control is continued through (S2), (S5), (S6).

Reference numeral 10 is a voltage discriminating means, which lowers the frequency of the inverter means 3 by turning off the operation switch 9, but due to the large inertia of the load of the electric motor 4, the frequency of the inverter means 3 is lowered. The rotation speed of the electric motor 4 may not catch up. In this case, the electric motor 4
The voltage generated by the power generation action of is applied to the inverter means 3, and when this voltage exceeds a predetermined value (voltage necessary for passing current through the brake resistor), a brake signal is output.

Reference numeral 11 is a brake drive means, which is a voltage determination means 10
When the brake signal is output by
The drive of the inverter means 3 is controlled by driving the magnet 13 by means of the electric current and passing a current through the brake resistor 14.

When the power supply situation is bad and the AC input voltage of the three-phase AC power supply 1 fluctuates significantly or an abnormal voltage is input, the brake signal is detected and the brake resistor 14 is used to early stop the electric motor 3. Therefore, in order to prevent this, the suppression determination means 15 is provided in the approximate center of FIG. The suppression determination means 15 is provided between the voltage determination means 10 and the brake driving means 11, and when the brake signal of the voltage determination means 10 and the operation signal of the control means 5 are input, the operation signal is generated. By outputting the brake signal only to the
It is applied to 14 to consume electric power and the motor 4 is stopped early. This suppression determination means 15 has a configuration in which a NOT circuit N1 arranged between the output of the operation switch 9 and the input of the control means 5,
The output of this N1 and the operation signal of the control means 2 were used as the input side.
It is composed of an AND circuit A1 and an AND circuit A2 having the output and brake signal of A1 as an input side.

Next, the operation of this embodiment will be described with reference to FIG. That is, when the switch means 1 is turned on,
The ON waveform shown in Fig. 3 (a) is output. At this time, as shown in (b), the frequency rapidly rises from the stopped state of the inverter means 3 and reaches the set frequency stored in the inverter control microcomputer 6. Further, the control means 5 outputs the operation signal (c). Here, when the input voltage is higher than the rated voltage due to the power supply situation, a bus voltage equal to or higher than a predetermined value is detected as shown in (e), and a brake signal f1 is detected as shown in (f). However, since the output (g) of the AND circuit A2 of the suppression determination means 15 is at the L level, the drive of the inverter means 3 is not suppressed when the operation switch 9 is on regardless of the presence or absence of the brake signal.

Next, when the operation switch 9 is turned off while the inverter means 3 is being driven at the set frequency, the frequency of the inverter means 3 is rapidly lowered as shown in (b). At this time, the operation signal (c) indicating the state of driving the inverter means 3 is detected. Further, the electric motor 4 generates electricity to detect a bus voltage equal to or higher than a predetermined value, and the brake signal f1 is detected as shown in (f). Also, the suppression determination means
Since the output (g) of the AND circuit A2 of 15 becomes the H level, the drive of the inverter means 3 is suppressed when the brake signal f1 is detected when the operation switch 9 is in the OFF state.

As described above, the suppression discriminating means 15 is provided between the voltage discriminating means 10 and the brake driving means 11 so that when the AC voltage fluctuates drastically or when an abnormal voltage is inputted, the brake is discriminated. Since no signal is output, damage to the brake resistor can be reduced.

[0016]

According to the inverter device of the present invention, when the inverter means is being driven, when the brake signal is input, the brake signal is input to the brake means and the generated voltage of the electric motor is applied to the brake resistor. , When the inverter means is not driven, it is not applied to the brake resistance regardless of the presence or absence of the brake signal, so the brake signal is output when the input AC voltage fluctuates significantly or when an abnormal voltage is input. Therefore, it is possible to reduce the damage of the brake resistance in the stopped state.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the control means of FIG.

FIG. 3 is a waveform diagram for explaining the operation of FIG.

[Explanation of symbols]

 2 converter means 3 inverter means 4 electric motor 5 control means 10 voltage determination means 11 brake drive means 14 brake resistance 15 suppression determination means

Claims (1)

[Claims] 1. A converter means for rectifying and smoothing an AC input voltage to output a DC voltage, an inverter means for converting the DC voltage of the converter means into an AC voltage and supplying it to an electric motor, and an inverter switch for operating the inverter means. Control means for performing driving including acceleration and deceleration in response to an operation and outputting an operation signal while driving the inverter means,
A motor provided with a voltage determining means for detecting an input voltage of the inverter means and outputting a brake signal when the voltage exceeds a predetermined value, and a brake means for energizing a brake resistor connected in parallel with the input of the inverter means at the time of signal input. The control device is provided with suppression determination means for inputting the brake signal of the voltage determination means and the operation signal of the control means and outputting the brake signal only when the operation signal is generated, and the output of the suppression determination means Is input to the braking means.