JPH02133072A - Control method of inverter device - Google Patents

Abstract

PURPOSE:To prevent the easy trouble of an inverter device even by the recovery of a power supply from a level close to an undervoltage level by arithmetically operating the degree of the DC voltage drop of a converter section, deenergizing an electromagnetic contactor and charging a capacitor through a resistor for inhibiting currents at the time of the recovery of the power supply when the input voltage of the inverter device instantaneously drops. CONSTITUTION:When input supply voltage instantaneously drops, the DC voltage of a converter section 2 suddenly lowers gradually because a load AC motor 8 is supplied with energy. A microprocessor 12 transmits a signal over a control circuit 10, and the control circuit 10 turns the (a) contact 3 of an electromagnetic contactor 4 ON. Consequently, the charging currents of a capacitor 6 are made to flow through a resistor 5 for inhibiting currents. Even when an input power supply is recovered, the charging currents of the capacitor 6 are made to flow through the resistor 5 for inhibiting currents, thus suppressing excess capacitor charging currents.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides control of an inverter device configured to prevent the inverter device from failing when the input voltage of the inverter device recovers from a momentary power failure or drop. It is about the method.

[Conventional technology]

Figure 3 shows an elliptical example of a conventional inverter device, where (1) is a three-phase input AC power supply, (2) is a converter circuit that converts AC to DC, and (3) is an electromagnetic circuit connected to the input power supply. Regular contact (hereinafter referred to as a contact) of the contactor (4), (
5) What? U current suppression resistor, (6) is a smoothing capacitor, (
7) is an inverter circuit (8) for converting direct current to alternating current, an AC motor, (9) a DC/DC power supply circuit, and (10) a control circuit. Next, the operation will be explained. If the smoothing capacitor (6) is not charged when the input power is turned on,
Since the smoothing capacitor (6) short-circuits the power supply, an excessive current may flow into the converter circuit (2) and damage the converter circuit (2). For this purpose, the a contact (3) of the magnetic contactor (4) and the current suppression resistor (5) are connected between the converter circuit (2) and the smoothing capacitor (6), and the T4 magnetic contactor (4) is A circuit is configured to charge the smoothing capacitor (6) through the current suppressing resistor (5) until the a contact (3) closes during the operation time.

[Problem to be solved by the invention]

Conventional inverter equipment is configured with a circuit that ensures sufficient control power so that it does not easily stop due to instantaneous interruptions or drops in the input power supply voltage, and where the undervoltage level is set at a fairly low level. There are many. However, for some reason the input power supply voltage may cause instantaneous power outages, instantaneous drops, etc.
) occurs at a voltage and time that are not deenergized, an excessive capacitor current will flow through the a contact (3) of the magnetic contactor (4) when the power is restored, causing damage to the capacitor part (2).
There were problems such as deterioration of the A contact (3) of the electromagnetic contactor (4) and causing inverter failure.

This invention was made to solve the above-mentioned problems, and aims to provide a control method for an inverter that does not easily cause the inverter to malfunction even when the power is restored from around an undervoltage level. purpose.

[Means to solve the problem]

The method for controlling an inverter device according to the present invention is to detect the DC voltage of the inverter section (2) with a detection circuit (11), and to detect the constant average DC voltage (hereinafter referred to as v) with a microprocessor (12).
1) is calculated. When the DC voltage of the converter suddenly decreases due to fluctuations in the input power supply voltage, instantaneous power outages, instantaneous drops, etc., if the DC voltage at this time is V, then V, -V, - ΔV
If the value exceeds a predetermined value, the microprocessor outputs a signal and the control circuit (10
), the control configuration is such that it is output from

[Effect]

According to the control method according to the present invention, the inverter device does not easily fail even when the power is restored from around the undervoltage level.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. In FIG. 1, (1) to (9) are the same as shown in FIG. 3. (10) is a control circuit (I1) that excites or deenergizes the electromagnetic contactor (4), and (12) is a detection circuit that detects the DC voltage of the converter section (2). V.) means for calculating
means for calculating changes in DC voltage (ΔV=V, -V,);
Next, the operation of the embodiment L, which is provided with a control means for controlling the control circuit (10) to output when ΔV exceeds a predetermined value, will be described. First, during the operation of the inverter device, time t occurs as shown in FIG. Assuming that the input power supply voltage drops instantaneously at , and is restored at time t, before time t0, the converter average DC voltage (V,) is read from the detection circuit (11) to the microprocessor (l2). It is calculated. Further, the electromagnetic contactor (4) is excited by the output of the control circuit (lO), and the a contact (3) is inactive. From time t0, the converter DC voltage rapidly drops to supply power to the load AC motor (8). When the converter DC voltage calculated by the microprocessor (l2) at time t1 reaches the value of V, that is, ΔV=V. −V, ≧
When the predetermined value is reached, the microprocessor (12) sends a signal to the control circuit (1G). The control circuit (10) deenergizes the electromagnetic contactor (4) and opens the a contact (3). As a result, the capacitor charging current flows through the current suppressing resistor (5). Even if the input power supply is restored at time u+l t , the capacitor charging current flows through the current suppressing resistor χ) When the input power supply is restored, an excessive capacitor charging current can be suppressed. At time iQ t 1, a signal is sent from the microprocessor (12), the control circuit (11) excites the electromagnetic contactor (4), and the a contact (3) becomes idle, returning to the normal mode.

〔Effect of the invention〕

As described above, according to the present invention, when the human power voltage of the inverter device fluctuates, instantaneous power outage, instantaneous drop, etc. occurs, the degree of DC voltage drop in the converter section is calculated and the electromagnetic contactor (4) is deenergized. Since the capacitor (6) is configured to be charged through the current suppression resistor (5) when the power is restored, excessive charging current can be suppressed when electricity near the undervoltage level is generated, preventing damage to the converter or damage to the converter. It is possible to prevent deterioration of the A contact (3) of the electromagnetic contactor (4), and to prevent fluctuations in input voltage.
This has the effect of providing an inverter device that is resistant to momentary power outages and brownouts.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing circuit waveforms, and FIG. 3 is a block diagram showing a conventional embodiment.

Claims (1)

[Claims] It includes a converter section that converts alternating current into direct current, a capacitor that smoothes the direct current converted by this converter section, and an inverter section that converts the direct current smoothed by this capacitor into alternating current. A method for controlling an inverter device comprising: providing a contact point of an electromagnetic contactor that is energized and deenergized depending on the level of DC voltage of the converter section between the converter section and the converter section, and connecting a current suppressing resistor in parallel with this contact point. Control of an inverter device, characterized in that the degree of level change of the DC voltage in the converter section is constantly monitored, and when the input voltage is momentarily interrupted or dropped and the power is restored, charging of the capacitor is controlled through the current suppression resistor. Method.