JPS586079A - Protecting circuit for transistor inverter - Google Patents

Abstract

PURPOSE:To protect an inverter by inputting the input and output voltage of the inverter, comparing them by the first to fourth comparators and detecting a shortcircuiting current, an overload current, an abnormally high voltage and an insufficient voltage state. CONSTITUTION:When the output of a transistor inverter B is detected by a curent transformer 5 and an detected current value inputted through a Zener diode D and a resistor R2 of the first comparator 1 exceeds a reference value, the output value is inverted to ''L'' level, a photodiode PD is emitted to detect the shortcircuiting current state. Similarly, when the current detected by the transformer 5 is overloaded current, the second comparator 2 operates, when the input voltage of the inverter B is abnormally high, the third comparator 3 operates, when the input voltage of the inverter B is insufficient, the fourth comparator 4 operates, respective photodiodes are emitted, thereby detecting the respective abnormal states.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection circuit for a transistor inverter.

When driving a single cage-type conductive casting machine, a drive input control bag W is used that converts the frequency of the commercial power source and uses it as the drive input.
It is customary to intervene.

Therefore, the frequency conversion t of such a commercial power source is
Input control fi: Wj, , is A for converting commercial power to DC.
It is composed of two stages: a C-DC conversion circuit and an inverter that converts the DC output of this AC-DC conversion circuit into a desired frequency output.

IIjIIill! Switching elements such as transistors are used as the components of an inverter, but an overload may cause an overcurrent on the load side of the first transistor inverter, or a short-circuit accident may occur in the load all, causing a short-circuit current to flow. In this case, there is a problem in that not only the current is destroyed, but also the current flows through the transistors constituting the inverter and destroys the circuit.

Similarly, if an abnormally high voltage occurs on the input side of the inverter, there is a risk that the inverter's transistor t'' will be destroyed. There is also the problem that one mistake is made.

Therefore, the object of this invention is to reduce the overload current on the load side,
Transistor/inverter protection that can detect short-circuit currents, abnormal high voltages, and voltage drops on the input side and prevent damage to transistors/inverters and circuit malfunctions due to overload currents, high voltages, low voltages, etc. The purpose is to provide circuits.

An embodiment of the invention is shown in FIGS. 1 to 4. In other words, this transistor in/(-) protection circuit is
A converts 3-phase commercial power 1 V3φ to DC as shown in Figure 1.
Each pair of diodes DUIIDυ2-DvIIDv2IDWIIDwsa corresponds to the DC output VDC of the C-DC conversion times %A to each phase of U, V, and W as shown in FIG.
Toto" shifter QUI ・QU2- Qvl-Qva-
A half-bridge type transistor inverter B consisting of QWl and QW2 converts it into predetermined frequency outputs vU, vy, and vw as shown in Fig. 3 (2), however, 1, and is used in a cage type spinning machine M, etc. This is a protection circuit C for the transistor inverter B in a drive 1 input control system designed to supply power to a load, and has a circuit configuration as shown in FIG.

This protection circuit C consists of four comparators l, 2°3.4
Preparation, 1st. Each of the second comparators 1 and 2 has a load current x detected by the current transformer 5 disposed on the output side of the transistor inverter B.
oty'rt rectifier circuit 6, while the manual input terminal of the third comparator 3 and W! , 4 are connected to one input terminal of the comparator 4 to receive the DC output VDC of the 1ile Ac-DC conversion circuit applied to the input side of the transistor inverter B, and the first comparator l is connected to the DC power supply VDC applied to the input side of the transistor inverter B. A reference value that is input to the manual input terminal by dividing the voltage V with a resistor R3 and a variable resistor vR1,
Zener diode ZD detected by said current transformer 5.

Comparing the load current detection value manually input to one input terminal with the voltage dividing circuit of resistor R2, if a short circuit current occurs on the load side and the load current detection value exceeds the reference value, the output value t-
The photodiode PD is inverted from H level to L level.
t-illuminated and similarly @2 comparator 2, resistor R
4. Compare the reference value given by the voltage divider circuit consisting of the variable resistor VR2 and input to the manual input terminal with the detected load current value of the llI switch/distributor 5 to determine if an overload has occurred on the load side. When the detected load current value exceeds the reference value, the output value is inverted from t-H level to L level, and the photodiode PD is illuminated, and in the core parator 3 of sg3, the voltage is applied by resistor R4 and variable resistor 1IVR3. The reference value input to the input terminal is compared with the input DC voltage VDC of the AC-DC conversion circuit A applied to the - input terminal, and the DC voltage VDC on the input side exceeds the reference value. When the voltage becomes high, the output value is inverted from tH level to L level and the 1ItI photodiode PDt- is illuminated, and in the fourth comparator 4, the reference value given by resistor R7 and variable resistor VR is inputted to one input terminal. and the input side DC voltage VDC applied to the manual input terminal, 3
When the input side DC voltage VDC drops below the reference value due to an open phase of the phase commercial power supply v3φ, the output value is set to H.
The photodiode PIII is inverted from the level to the L level.
I'm trying to illuminate it.

IIT#j3 Abnormalities such as load short circuits, overloads, input abnormal Shimada, and power supply phase failures detected by the illumination operation of the photodiode FD are output as current signals by the photodiode FD and the phototransistor PT that constitutes the photocoupler 7.
The control circuit is configured as shown in the block diagram in Figure 1.
The input/output side 1K11M to the AC-DC conversion circuit is cut off via the drive circuit E, and the short-circuit current and overload flow to the transistors constituting the AC-DC conversion circuit At, causing abnormally high voltage and undervoltage. All inputs are blocked to protect transistor inverter B and prevent malfunction.

In the second comparator 2 that compares and determines overload current,
The detected value is received by a charging circuit made up of resistor R5 and capacitor C1, and its input is delayed to avoid detecting overload phenomena such as when the electric current IFIIm starts. In No. 1, direct input is performed without delay, thereby effectively avoiding circuit destruction due to short-circuit current.

Note that the capacitors C2, . . ., connected between the input terminals of each comparator 1, 2, 3, and 4 are noise limiters.

Further, in this embodiment, the first 64 comparators 1.2, 3.41-* are constructed using l-chip quad comparators, thereby simplifying the circuit configuration during mounting.

With this configuration, transistor inverter B
It is possible to prevent overload current and short-circuit current from flowing into the load side and application of abnormally high voltage to the input side.
In order to avoid destruction of QU2-...-QW2, it is necessary to protect the transistor/inverter Bt from destruction caused by these abnormal signals, and to prevent direct current from being applied to the input #J of the transistor/inverter B due to phase loss or other causes in the power supply. It is possible to prevent the circuit 11IF1 from operating when the voltage is insufficient, and to maintain a stable 1IF1 operation.

As described above, the transistor inverter protection circuit of the present invention is an AC-DC converter that converts commercial power into DC power.
In a drive input control system including an f conversion circuit and a transistor inverter that converts the l15& output of this AC-DC conversion circuit into high frequency and supplies it to a load, IIES)-! 7
The first comparator detects an overcurrent on the load side of the transistor inverter and inverts the output.
a second comparator that detects an overvoltage of the DC output of the AC-DC conversion circuit and inverts the output; and a third comparator that detects a decrease in the DC output of the previous eA C-DC conversion circuit and inverts the output. A fourth comparator is provided, and the input of overvoltage and overcurrent to the transistors of the ItI transistor/inverter is prevented by using the inverted outputs of the respective comparators, and the transistors are prevented from being erroneously activated.・Protects the inverter from damage caused by short-circuit currents, overload currents, and abnormally high voltages on the input side that occur on the load side.
- Avoids erroneous operation when the level of DC voltage on the input side is insufficient due to power supply phase loss or other causes, and provides stable operation with zero downtime.
It has the effect of being able to maintain the

[Brief explanation of the drawing]

Figure 2 is a schematic circuit diagram of an inverter that is protected by the transistor-inverter protection circuit of this invention, and Figure 3 or Q is the output waveform of the inverter. 4 are circuit diagrams showing an embodiment of the present invention. A...AC-DC conversion circuit, B...transistor.
Inverter, C... Inverter protection circuit, D... Control circuit, E... Drive circuit, 1, 2.3.4...
Comparator, 5... Current transformer, 6... Rectifier circuit, 7
...Hoto couple

Claims (1)

[Claims] Commercial wll! ! it - AC-DC conversion circuit that converts to DC power supply and DC output of this AC-DC conversion circuit? In a dedicated input control system including a transistor/inverter that converts high frequency and supplies it to a load, a first step is performed to detect an overcurrent on the load side of the transistor/inverter and invert the output.
a second comparator that detects a short-circuit current on the load side of the transistor inverter and operates to invert the output; and a third comparator that detects an overvoltage of the DC output of the AC-DC conversion circuit and inverts the output. , said A
A fourth comparator detects a drop in the DC output of the C-DC conversion circuit and inverts the output, and the inverted output of each of the comparators prevents input of overvoltage/current to the transistors of the III transistor/inverter and W4 #
A protection circuit for a transistor/inverter, which is characterized by preventing operation.