JPS61189191A - Inverter of induction motor - Google Patents

Abstract

PURPOSE:To hardly trip by observing a DC voltage of a converter, and pausing an inverter operation when it decreases lower than the special value, thereby eliminating the occurrence of an abnormal operation even if a power is momentarily stopped. CONSTITUTION:A power source 19 receives power from a DC voltage VDC of a converter 14, and supplies power voltage to a base driver 18, a controller 17 and a DC voltage detector 20. The detector 20 detects whether the voltage VDC is higher than the specified value or not, applies a signal to the controller 17, sets an inverter to a pause state by an input voltage that a voltage stabilization does not operated in the full-load state, and resets the operation by the frequency immediately before entering the pause state when the input voltage is reset.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inverter device that controls the number of revolutions of an induction motor by changing the voltage and frequency applied to the motor.

Conventional technology An inverter device for controlling the rotation speed of an induction motor (hereinafter abbreviated as motor) has a diode 1.
Converter section 3 consisting of a capacitor 2. transistor 4
．． Inverter section 6 consisting of diode 6. Base drive circuit 7 that supplies the base current of transistor 4. A control circuit 8 that controls the entire inverter device and supplies the base signal to the base drive circuit 7 in an insulated manner. A power supply circuit 9 that supplies power and power signals to the control circuit 8 and base drive circuit 7. The inverter device 10 is composed of the following. Note that the converter section 3 and the power supply circuit 9 are connected to a power source 16 or a single-phase power source 16, the inverter section 6 is connected to the motor 11, and the rotation speed command 12 is connected to the control circuit 8.

Traditionally, inverter devices stop operating when a momentary power outage or instantaneous voltage drop (hereinafter collectively referred to as a momentary power outage) occurs, and when the power supply voltage is restored, it returns to its original state. A method of restarting the device or a method called ``trip'' in which the device remains in a stopped state unless it is determined to be in an abnormal state and reset is adopted.

3. It prevents the microcomputer and logic IC in the control circuit from malfunctioning due to a drop in the voltage supplied from the power supply circuit 9 to the control circuit 8 and base drive circuit 7 due to a power supply voltage stoppage or shortage. This is to prevent the transistor 4 from entering the active region if the base current supplied from the base drive circuit 7 to the base of the transistor 40 is insufficient, resulting in destruction of the transistor due to excessive wattage.Problems to be Solved by the InventionMomentary power failure Although it is unavoidable for the safety of the equipment for the inverter to stop all operations when a Considering the load,
Since the rotation speed did not decrease during the momentary power failure, when the power supply voltage returns and the inverter resumes operation from the initial state,
Since the frequency supplied from the inverter to the motor is lower than the rotation speed of the motor, the motor operates as a generator, a so-called regenerative state, and a large current flows through the transistor 4 and diode 6 of the inverter, and the regenerated power from the motor This is because the voltage of the capacitor 2 increases abnormally, causing an abnormal protection operation called an overcurrent trip or an overvoltage trip, respectively.

If you apply a frequency that matches the rotational speed to the motor, there will be no problem as large current will not flow or regenerative power will be generated. is not allowed.

As described above, conventional inverters have the problem of tripping when a momentary power outage occurs. Therefore, an object of the present invention is to provide an inverter that is unlikely to trip even when a momentary power failure occurs.

Means for Solving Problems The present invention is based on a DC-DC converter that uses the DC voltage vDc of the converter as input to generate various DC voltages via a high-frequency transformer, and observes the DC voltage vDc on 6 pages and determines whether it exceeds a specified value. means for detecting whether or not the
It is constituted by means for stopping the inverter operation when the DC voltage vDc falls below a specified value.

Effect: According to the above configuration, even if a momentary power outage occurs, unnecessary trips can be prevented from occurring.

Embodiment Next, an embodiment of the present invention will be explained based on FIGS. 1 to 4.

In Fig. 1, 13 is a single-phase or three-phase power supply, 14 is a converter section consisting of a single-phase/three-phase rectifier and a smoothing capacitor 16, 15 is an inverter section consisting of transistors and diodes, and 16 is a motor. be. The entire inverter is controlled by the control circuit 17, which supplies the signal to the base drive circuit 18 after insulating it with a photocoupler, etc., and turns the transistor ON/OFF as a base signal for the transistor of the inverter section 15.

The power supply circuit 19 receives power from the DC voltage vDc of the converter section 14, and supplies power to the base drive circuit 18 and the 6-beam control circuit 17. Supply voltage to the DC voltage detection circuit 2o. Note that the DC voltage detection circuit 2o detects whether the DC voltage vDc is equal to or higher than a specified value and sends a signal to the control circuit 17.

Next, the power supply circuit 19 will be explained. As shown in FIG. 2, this is a power supply circuit known as a self-excited DC-DC converter using a ringing choke converter type to which a voltage stabilizing circuit is added. Using this DC-DC converter, the outputs E1 to E4 are used as the power source for the base drive circuit 18 shown in FIG. 1, and output E6 is used as the power source for the control circuit 17. The power supply current of the base drive circuit 18 depends on the so-called operating state in which voltage and frequency are supplied from the inverter section 16 to the motor 16, and the so-called operating state when the transistor of the inverter section 15 is OFF.
L: No power is being supplied to the motor. It is completely different in the so-called stopped state, in which the pace current of the transistor is unnecessary, so almost no current flows. When the load condition is largely divided into two in this way, the output voltage of the ringing choke type self-excited DC-DC converter is stabilized.As shown in Figure 3, when the inverter is in operation, the DC voltage vDc is
This shows that the output voltage can be stabilized up to a low input voltage up to point B, which is lower than point A, when the inverter is in a stopped state.

Next, the DC voltage detection circuit 20 will be explained. This is a voltage that is obtained by insulating the output voltage vDc of the converter section (14 in FIG. 1) directly or with a V/F, F/V converter, etc. It has a function of determining whether the voltage is higher than or equal to the voltage shown at point A in the figure and notifying the control circuit.

Next, the overall control contents will be explained based on the time chart of FIG. 4.

The power supply 13 shown in FIG. 1 is turned on at time t. When an instantaneous power outage with width T1 occurs, the output voltage vDc of the converter section 14 decreases at a slope determined by the motor load.

When the power supply is restored at tl, the DC voltage VDc rises again, but at that time t1, the DC voltage vDc is as shown in Figure 2 A.
If the voltage is higher than the voltage at the point, the power supply voltage of the control circuit 17 and the base drive circuit 18 is stable, and malfunctions of microcomputers and ICs, transistor breakdown due to insufficient base current of transistors, etc. do not occur. Therefore, the inverter applies the motor applied voltage V.

However, the inverter does not need to suspend or stop operation due to tripping, etc.

Next, at time t2, when a 12-width instantaneous power outage occurs, which is longer than the time width TA during which vDc drops to point A in Figure 3, and shorter than the time width TB during which the DC voltage vDc drops to point B in Figure 3. , the inverter is operated until time t3 when the DC voltage vDc becomes the voltage at point A, and at time t3 the base drive circuit (18 in Figure 1) is connected to the inverter section (16 in Figure 1).
The base current supplied to the transistor is stopped, and the transistor is turned off and placed in a resting state. that way,
As shown in Figure 4, the power supply voltage of the control circuit is a DC voltage vDc.
It remains stable until the voltage drops to point B, and no malfunctions of the microcomputer or logic IC occur.

When the instantaneous power failure ends at time t'''C, the DC voltage vDc is A
The inverter restarts when it detects that the voltage exceeds this point.

At that time, the frequency 9.number at time 13 is applied. It is often better to apply a slightly lower frequency to the motor depending on the inertia of the load.

If the output voltage is increased at a constant gradient to a predetermined voltage as shown in the figure, a large current will not flow to the motor and a current trip of the inverter will not occur.

Therefore, the inverter completely stops when the DC voltage vDc
is the voltage below point B in Figure 3, which is the voltage at point 6.
As shown in the figure, this occurs only when there is a momentary power outage that is longer than the time width TB.

The slope at which the DC voltage vDc decreases from time t3 to time t4 in FIG. 4 is determined by the capacitance of the capacitor 15 in the converter section 14 in FIG. Since it is determined by the output capacitance of the capacitor (shown in FIG. 3), even if an instantaneous power failure occurs, if it is desired to extend the rest state, it is possible to do so simply by increasing the capacitance of the capacitor 16.

Further, the operating frequency when the input voltage is restored is 3 to 1 ohz lower than the frequency immediately before entering the hibernation state.

Effects of the Invention As explained above, the inverter device of the present invention does not cause abnormal operation even if a momentary power outage occurs, resulting in an inverter that is unlikely to trip.

[Brief explanation of drawings]

Figure 1 is a block diagram of an inverter according to an embodiment of the present invention, Figure 2 is a circuit diagram of a power supply circuit used in the present invention, and Figure 3 is a diagram of input/output characteristics of the power supply circuit in Figure 2. 4 is a time chart of an embodiment of the invention, and FIG. 6 is a block diagram of a conventionally used inverter. 14...Converter section, 16...Inverter section, 16...Motor, 17...
Control circuit, 19... Mountain/power supply circuit, 2o... DC voltage detection circuit. Name of agent: Patent attorney Toshio Nakao and one other person
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Claims (1)

[Claims] (1) A power supply circuit consisting of a self-excited DC-DC converter using a ringing choke converter type with a voltage stabilization circuit added, a detection circuit that detects the input voltage and compares it with a specified value, and a signal from this detection circuit. An induction motor equipped with a control circuit that puts the inverter into a hibernation state at an input voltage that causes voltage stabilization to fail under full load conditions, and resumes operation at the frequency immediately before entering the hibernation state when the input voltage returns. inverter device.