JPH05219755A - Malfunction detector for inverter main circuit - Google Patents

Abstract

PURPOSE:To prevent damage on an inverter element by detecting a malfunction of the element to be switched at a high speed by comparing whether a potential difference between the elements such as power semiconductor elements, etc., to be switched in phase in parallel with its rated value or more or not. CONSTITUTION:Voltages of potential points A1, A2, B1 and B2 of pairs of inverter elements to be switched in phase and connected in parallel are voltage-divided by resistors R1 and R2, R3 and R4, R5 and R6, and R7 and R8, These divided voltages and a reference voltage V1 are input to comparators C1, C2, C3 and C4. If a potential difference of its rated value or more is detected, it is compared with a reference potential V2 by a comparator C5 or C6, and then a malfunction signal is output from a photodiode 15. An AND clamper 13 inputs the same pulse signal as that for driving the elements is input to comparators C7, C8. The divided voltages are clamped to a low potential during OFF time of the pulse signal, and an erroneous defection due to a quasi-potential is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting circuit for an inverter main circuit.

[0002]

2. Description of the Related Art Generally, an inverter element (such as a power semiconductor element) used in an inverter has a small tolerance against an overcurrent and an overvoltage. Therefore, a fuse or the like has been conventionally used to prevent malfunction or damage of the inverter element. Anomaly detection was protected by.

[0003]

However, in the case of an inverter element that switches at high speed, the speed at which an abnormality is detected and protected (for example, the fuse blowing speed) is slower than the switching speed. Therefore, it is difficult to prevent damage to the inverter element.

Particularly, in the operation of an inverter in which a large number of inverter elements connected in parallel are switched in the same phase, if any one of the inverter elements fails, the entire system becomes unbalanced and the operation of other inverter elements is adversely affected. There was a problem to exert.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an abnormality detecting circuit for an inverter main circuit which solves the above-mentioned conventional problems.

[0006]

In order to achieve the above-mentioned object, an abnormality detection circuit of an inverter main circuit is provided with a potential difference between the inverter elements of an inverter main circuit composed of inverter elements connected in parallel and switched in the same phase. ,
It is provided with a comparator for detecting an abnormality.

Further, an AND-and-clamp circuit is added to prevent the comparator from malfunctioning due to a pseudo potential generated when commutation of the inverter element of the voltage source inverter.

[0008]

The comparator main circuit detects an abnormality in the inverter main circuit by comparing whether or not the potential difference between the inverter elements switched in parallel and in phase is equal to or greater than a specified value.
Since the abnormality is detected by the electric signal, it is possible to reliably detect the abnormality and prevent the inverter element from being damaged even with the inverter element switching at high speed.

The AND clamp circuit enables the comparator to operate only during the on-time of the pulse signal for driving the inverter element, and prevents the comparator from erroneously detecting the potential difference of the pseudo potential during the off-time.

[0010]

The present invention will be described in detail below with reference to the illustrated embodiments.

In FIG. 1, 1 is a converter circuit 2,
An inverter including a smoothing circuit 3 and an inverter circuit 4 configured to detect an abnormality such as a malfunction occurring in the inverter circuit 4 by an abnormality detection circuit 5 and output an abnormality signal to stop the inverter 1.

FIG. 2 shows an example of a circuit diagram of the voltage-type inverter 1. The converter circuit 2 has terminals 2a ...
AC power supplied from a three-phase AC power supply (not shown) is converted into a DC power supply by the rectifying diodes 6 ... Connected to the three-phase bridge and smoothed by the capacitor 7 of the smoothing circuit 3.

Further, the smoothed DC power supply is converted into an AC power supply by the inverter circuit 4 in parallel with the full bridge 2,
It flows through the series resonance circuit of the parallel balancing capacitors 8 ... And the load coil 9.

The inverter circuit 4 includes inverter elements Q ₁ , Q ₂ , Q ₃ , Q ₄ , such as bipolar transistors.
An inverter main circuit 10 including Q ₅ , Q ₆ , Q ₇ , and Q ₈ is provided. 11 ... is a freewheel diode connected in anti-parallel with the inverter element.

The inverter elements Q ₁ , Q ₂ , Q ₃ , Q ₄ and the inverter elements Q ₅ , Q ₆ , Q ₇ , Q ₈ are alternately switched and smoothed by a pulse signal having a phase difference of 180 °. The DC power source smoothed by the circuit 3 is converted into a two-phase AC power source.

[0016] A _1, A ₂ is a potential point of the inverter element Q _1, Q ₂ that is switched by being connected in parallel in phase (or inverter element Q _7, Q _8), the potential point A _1, A
_The voltage obtained from ₂ is the resistance R ₁ , R ₂ and the resistance R ₃ ,
It is divided by R ₄ .

B ₁ and B ₂ are also potential points of the inverter elements Q ₃ and Q ₄ (or inverter elements Q ₅ and Q ₆ ) that are switched in parallel and in phase, and are obtained from the potential points B ₁ and B ₂ . The voltage is divided by resistors R ₅ , R ₆ and resistors R ₇ , R ₈ .

FIG. 3 shows an abnormality detecting circuit 5. This abnormality detecting circuit 5 includes resistors R ₁ and R ₂ and resistors R ₃ and R _4.
The comparator circuit 12 and the AND clamp circuit 13 are connected between the resistors R ₅ and R _{6 and} between the resistors R ₇ and R ₈ .

The comparison circuit 12 comprises resistors, diodes, capacitors, comparators C ₁ , C ₂ , C ₃ , C ₄ , C ₅ , C ₆ , a variable resistor 14 and a photodiode 15.

The AND-clamp circuit 13 is composed of a resistor, a diode, a capacitor, a photodiode, a phototransistor and comparators C ₇ and C ₈ . Further, a voltage source (not shown) is connected to each terminal K ...

Then, as shown in FIGS. 2 and 3, when a malfunction occurs in any one of the inverter elements Q ₁ and Q ₂ or the inverter elements Q ₇ and Q ₈ , the inverter element Q ₁ , Q ₂ or between the inverter elements Q ₇ , Q ₈ (that is, at the potential points A ₁ , A ₂ ), the inverter elements Q ₁ , Q
_The abnormality detection circuit 5 detects an abnormality in the inverter main circuit 10 by utilizing the fact that a potential difference larger than the variation in the characteristics of ₂ , Q ₇ , and Q ₈ occurs.

That is, as described above, the voltage (at the potential points A ₁ and A ₂ ) divided by the resistors R ₁ and R ₂ and the resistors R ₃ and R ₄ is obtained via the variable resistor 14. the reference voltages V ₁ is input to the comparator C _1, C _2, at the comparator C _1, C _2, (the inverter device for each of the divided voltage Q _1, Q _2, Q ₇ , including variations in the characteristics of Q ₈₎
When a potential difference of a specified value or more is detected, it is compared with the reference voltage V ₂ by the comparator C ₅ , and then the photodiode 15
An abnormality signal is output from the inverter, and the abnormality of the inverter main circuit 10 is detected.

An abnormal signal from the photodiode 15 is latched by a circuit (not shown), and the abnormal output signal immediately stops the inverter 1 (see FIG. 1). In addition,
Comparator C without using the photodiode 15 for noise removal
₅ and the holding circuit may be directly connected.

The reference voltage V ₁ is the inverter elements Q ₁ and Q _2.
Since the variable resistor 14 can be adjusted in accordance with the variation in the characteristics of ..., Due to the variation in the characteristics, the comparators C ₁ , C ₂
Can be prevented from malfunctioning.

Further, the resistors R ₅ , R ₆ and the resistors R ₇ , R ₈
The voltage divided at (potential points B ₁ and B ₂ ) is also compared by the comparators C ₃ and C _{4 in the same} manner as described above.
Inverter elements Q ₃ , Q _{4 of} the inverter main circuit 10,
Q _5, it is the abnormality detection of Q _6.

[0026] AND clamp circuit 13, in the case of the voltage source inverter, the off-time of the inverter element Q _1, Q ₂ ... pulse signal for driving the inverter element Q _1,
Potential points A ₁ , A ₂ , B ₁ , due to commutation of Q ₂ ... (that is, due to the current flowing through the freewheel diode 11)
The potential difference of the pseudo potential generated in B ₂ is calculated by the comparator C ₁ ,
Prevents C ₂ , C ₃ and C _{4 from} being erroneously detected.

Specifically, the inverter elements Q ₁ , Q ₂ ...
Pulse signal that is the same as the pulse signal that drives the terminals H, J
Is input from the comparators C ₇ and C ₈ to the reference voltage V ₂ and compared with the resistors R ₁ and R only during the off time of the pulse signal.
_{2, R 3, R 4,} R 5, divided voltage at R _6, R _7, R ₈ is clamped to a low potential, the comparator C _1, C _2, C
₃ and C ₄ are not activated.

Therefore, only during the on-time of the pulse signal,
The comparators C ₁ , C ₂ , C ₃ , C ₄ become operable, and the potential difference of the pseudo potentials of the potential points A ₁ , A ₂ , B ₁ , B ₂ is calculated during the off time by the comparators C ₁ , C ₂ , It is possible to prevent erroneous detection of C ₃ and C ₄ .

The present invention is not limited to the above-mentioned embodiments, and the design can be freely changed without departing from the gist of the present invention. For example, the abnormality detection circuit 5 can be applied even if the inverter 1 is a current type, and the abnormality detection circuit 5 can be applied even if the inverter circuit 4 has two or more parallel circuits. It is also applicable to connected ones.

Further, as the inverter elements Q ₁ , Q _2, ..., In addition to bipolar transistors, IGBTs (insulated gate bipolar mode transistors), MOSFETs (metal oxide semiconductor field effect transistors), SITs (static induction transistors), and other various power sources are used. The abnormality detection circuit 5 can be applied to the inverter main circuit 10 using the semiconductor device for use.

[0031]

Since the present invention is constructed as described above, it has the following great effects.

Even when an inverter element that switches at high speed is used, the abnormal operation and failure of each inverter element can be surely detected early without being affected by the pseudo potential and the inverter main circuit 10 can be protected. In particular, in the operation of the full-bridge parallel inverter, it is extremely useful because it has an excellent effect of detecting abnormality.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of an inverter.

FIG. 3 is a circuit diagram of an abnormality detection circuit.

[Explanation of symbols]

 10 Inverter main circuit 13 And clamp circuit C comparator

Claims (2)

[Claims] 1. An abnormality of an inverter main circuit, comprising a comparator for detecting an abnormality based on a potential difference between the inverter elements of an inverter main circuit 10 formed of inverter elements connected in parallel and switched in the same phase. Detection circuit. 2. An abnormality detection circuit for an inverter main circuit according to claim 1, further comprising an AND clamp circuit 13 for preventing the comparator from operating due to a pseudo-potential generated when commutating the inverter element of the voltage source inverter.