JPH01107686A - Inverter device - Google Patents

Abstract

PURPOSE:To detect the lowering of the decelerating capacity of an inverter device due to the trouble of a brake circuit quickly by counting the time until a brake resistor is conducted after a command time when the brake resistor is conducted and deciding the abnormality of the brake circuit. CONSTITUTION:When the voltage value of a DC bus-bar detected by a bus voltage detector 5 extends over a fixed voltage value or more, a comparator 11 for a brake circuit turns a brake transistor 8 for the brake circuit 6 ON through an amplifier 12. A counter 16 counts time difference until the voltage of a brake resistor 7 is detected by a resistance voltage detector 10 and the brake resistor 7 is conducted actually after a command time when the comparator 11 for the brake circuit turns the brake transistor 8 ON. When the counting value of the counter 16 extends over a fixed value or more, an abnormal signal is output from a third comparator 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an inverter device that arbitrarily controls the voltage and frequency of a power source.

[Prior Art] Fig. 4 is a circuit configuration diagram showing an outline of a conventional inverter device. In the figure, (1) is a rectifier circuit connected to a power supply S, (2) is a main circuit smoothing capacitor, and (3) ) is an inverter circuit, (4) is an induction motor to be controlled connected to the output side of the inverter circuit (3), and (5) is for detecting the voltage of the DC bus g on the input side of the inverter circuit (3). bus voltage detector, (6) is the positive and negative P, N of the DC bus g.
The brake circuit is connected between the two and consists of a brake resistor (7) for consuming excess power and a brake transistor connected in series with the brake resistor (7). (9) is a control circuit that controls the inverter device.

A conventional inverter device is configured as described above. For example, when the power source S is first turned on, the power source S is connected to the rectifier circuit (1).
The voltage is then rectified by the main circuit smoothing capacitor (2), resulting in a smooth DC voltage. Hereinafter, this voltage will be referred to as the voltage of the DC bus g, and the positive side is P1 and the negative side is N1, and the voltage value is vPN. Then, based on the command from the control circuit (9), a voltage waveform of an arbitrary voltage and frequency is output from the inverter circuit (3), and the induction motor <4) that is the object to be controlled is operated.

On the other hand, the bus voltage detector (5) detects the voltage VP of the DC bus g.
Although N is constantly detected, for example, when the induction motor (4) is decelerated, the voltage vPN of the DC bus g increases due to regenerative power. In such a case, the control circuit (9) makes the brake transistor (8) conductive and consumes the surplus power of the DC bus g by the brake resistor (7), so that the DC bus voltage vPN exceeds the limit of the inverter device. Make sure it doesn't get too expensive. In addition, if the deceleration time is too short and the rise in the voltage vPN of the DC bus g cannot be suppressed, the rise in the voltage vPN of the DC bus g is stopped by cutting off the output of the inverter circuit (3). (This operation will be referred to as an overvoltage trip.) In this case, the motor is in a free running state.

[Problems to be solved by the invention] In the conventional inverter device as described above, the rectifier circuit (1
) is connected to the output side of the brake circuit (6) consisting of a brake resistor (7) and a brake transistor (8) connected in series, and the linear bus g is controlled by the regenerative power generated when the induction motor (4) is decelerated. When the voltage VPN rises, the control circuit (9) operates to make the brake transistor (8) conductive so that the brake resistor (7) consumes the surplus power of the DC bus Ω, but the brake circuit ( 6) fails, an overvoltage trip is performed because the surplus power of the DC bus g cannot be consumed, but when this overvoltage trip is performed, there is a risk that the deceleration ability of the inverter device will be judged to have exceeded its limit. There was a problem.

The present invention has been made to solve this problem, and an object of the present invention is to provide an inverter device that can promptly detect an abnormality when the brake circuit breaks down and the deceleration ability of the inverter device decreases.

[Means for Solving the Problems] An inverter device according to the present invention includes a bus voltage detector that detects the voltage of a DC bus on the input side of an inverter circuit, and a bus voltage detector that is connected between the positive and negative sides of the DC bus, and is connected between a brake resistor and a brake. A brake circuit in which the switching element is connected in series, a brake circuit comparator that turns on the brake switching element of the brake circuit when the voltage value of the DC bus detected by the bus voltage detector is equal to or higher than a predetermined voltage value, and a brake circuit comparator for the brake circuit. Counts the time difference from when the brake switching element of the comparator is commanded to turn on and make the brake resistor conductive until the brake resistor voltage is detected and the brake resistor actually becomes conductive, and when the count value is greater than a predetermined value and a third comparator for determining that there is an abnormality in the brake circuit.

[Function] In this invention, when the voltage of the DC bus increases due to regenerative power of the load, the bus voltage detector detects the voltage increase, and when the detected voltage value is equal to or higher than a predetermined voltage value, the brake circuit comparator detects the voltage increase. turns on the brake switching element. Turn on this brake switching element
The voltage of the brake resistor is detected from the time of command to operate and make the brake resistor conductive, and the time until the brake resistor actually becomes conductive is counted. When the count value exceeds a predetermined value, an abnormality occurs in the brake circuit. This is determined by the abnormality occurrence determination circuit.

[Embodiment] FIG. 1 is a circuit configuration diagram showing a main part of an embodiment of the present invention.
FIG. 2 is a circuit diagram schematically showing the same embodiment. In the figure, components that are the same as those of the conventional example are given the same reference numerals, and explanations of duplicated components will be omitted.

(8) is a control circuit, (10) is a resistance voltage detector that detects the voltage of the brake resistor (7) of the brake circuit (6), (
11) is a brake circuit comparator that operates the brake transistor (8) which is a brake switching element of the brake circuit (6), and (I2) is a brake circuit comparator (
The output signal of the brake transistor (8) is amplified and the output signal of the brake transistor (8) is amplified.
), (13) is the brake circuit (
(6) is an abnormality occurrence determination circuit that determines whether an abnormality has occurred in (14), which is a circuit that determines whether an abnormality has occurred in
) and outputs a brake resistance voltage detection signal, (15) is a brake circuit comparator (1
A second comparator (1B) that compares the brake switching element ON command signal of 1) and a brake resistance voltage detection signal of the first comparator (14) counts according to the output of the second comparator (1B). The counter, (17) is the brake circuit (
6) is the third comparator that determines the abnormality. The abnormality generation circuit (13) includes a resistance voltage detector (lO) and a first comparator (14).
),! It consists of two comparators (15), a counter (16) and a third comparator (17).

The control circuit (8) also includes a brake circuit comparator (11).
, amplifier (13), first to third amplifiers (14), (1
5), (17) and a counter (16).

Next, the operation of the above embodiment will be explained with reference to FIGS. 1 to 3.

First, a case where the brake circuit is operating normally will be described.

When the voltage vPN of the linear bus g increases due to regenerative power from the induction motor (4), which is a load, the bus voltage detector (5), which constantly detects the voltage vPN' of the DC bus g, detects the increase in voltage vpHl. The detected value is input to the brake circuit comparator (11).

This comparator (11) generates a brake switching element ON command signal as shown in (a) of FIG. A brake transistor ON command signal is output, and this signal is amplified by an amplifier (12) to turn on the brake transistor (8). Then, the DC bus p
The voltage vPN is applied to the brake resistor (7), and the brake resistor (7) consumes the surplus power of the linear bus g to increase the voltage
PN is lowered. This is the case when the brake circuit (7) is operating normally.

On the other hand, the resistance voltage detector (10) constantly detects the voltage across the brake resistor (7), and the detected value is input to the first comparator (12). The detected value of the bus voltage detection 1 (5) is also input to this first comparator (12), and the voltage V of the DC bus ml is compared with the voltage between both ends of the brake resistor (7). When are equal, Figure 2 (a)
As shown in (b), a 1B brake resistance voltage signal is output, and when the two voltage values are not equal, 11 L I
Outputs the brake resistance voltage signal of T. A certain period of time is required until the brake resistance voltage signal of 'H' is output. In this way, the first comparator (14) compares the voltage across the brake resistance (7) with the voltage of the DC bus p. This means that when both voltage values are equal, the brake transistor (8) is in a conductive state, and when both voltage values are not equal, the brake transistor (8) is in a conductive state. OFF or ON opp 5O
This means that it is a transitional state from FF to ON.

Next, the second comparator (15) is a brake circuit comparator (1
The brake transistor ON command signal output from 1) is compared with the brake resistance detection signal output from the first comparator (14), and the brake transistor ON command signal is determined.
It operates by outputting an "H" signal only when the brake resistance voltage detection signal is in the state, and outputting an "L" signal in other cases. To explain this using the waveform of (c) in FIG. 3(a), the brake circuit comparator (11) outputs the brake transistor ON command signal and the brake transistor (8)
) is turned ON, the voltage vPN of the linear bus p is applied to the brake resistor (7), and it takes a certain period of time until the voltage across the brake resistor (7) becomes equal to the voltage vPN. It is necessary for a certain period of time to elapse until the comparator (14) outputs an "H" brake resistance voltage signal, and before that certain period of time elapses, the second comparator (5) A brake resistance voltage detection signal of "L" is sent from (14). Therefore, at this stage, the condition of brake transistor ON command signal>brake resistance voltage detection signal is satisfied, and the second comparator (15) outputs a "Ho" signal.Then, after a certain period of time has elapsed, the first comparator ( 14
) outputs a brake resistance voltage signal of "H" from a brake resistance voltage signal of "L", the above condition is not satisfied and the second comparator (15) outputs a signal of "L". That is, the voltage vPN of the DC bus g and the brake resistance (
The voltage between both terminals of the brake circuit (6) becomes equal and the brake circuit (6) becomes equal.
) would have worked normally.

Furthermore, the counter (1B) counts as time passes when the output of the second comparator (■5) is "H", and
If it is "L", the count value is reset.Therefore, in the third comparator (17), the upper limit value of the counter (IB) is set in advance as a reference value, and the count value of the counter (16) is set in advance. Detects whether the value exceeds a reference value.This reference value is set to a time slightly longer than the time required from when the brake transistor ON command signal is output until the brake transistor (8) actually becomes conductive. Therefore, when the brake circuit (6) operates normally, the count value of the counter (16) stops counting within the reference value as shown in (d) of FIG. 2(a). Therefore, the third comparator (17) determines that the brake circuit (6) is operating normally and does not output an abnormality detection signal.

Next, the operation when there is an abnormality in the brake circuit will be explained.

The operation until the voltage vPN of the linear bus g rises due to regenerative power etc. and the brake circuit comparator (11) outputs the brake transistor ON command signal as shown in (a) of FIG. 3(b) is as follows. This is the same as the operation explained above. However, even if the brake circuit comparator (11) outputs a brake transistor ON command signal to turn on the brake transistor (8), the brake transistor (8) malfunctions or the brake resistor (7) malfunctions. When the brake circuit (6) does not operate normally, the voltage across the brake resistor (7) is not detected by the resistance voltage detector (lO). Therefore, Fig. 3 (b
As shown in (b) of ), the first comparator (14)
'' continues to output the brake resistance voltage signal.
Comparator (15) is also a brake transistor ON command signal>
The conditions of the brake resistance voltage detection signal continue as shown in Fig. 3(b).
) continues to output an "H" signal as shown in (c). Therefore, the counter (1G) continues counting while the "H" signal is being output, and since the count value exceeds the reference value, the third comparator (17) indicates that the brake circuit (6) is abnormal. It determines that there is an abnormality and outputs an abnormality detection signal. Therefore, the output of the third comparator (17) causes the brake circuit (6
), when an overcurrent trip is performed based on an abnormality, there is no risk that it will be determined that the deceleration ability of the inverter device has exceeded its limit.

In the above embodiment, the conduction state of the brake resistor (7) was detected by detecting the voltage between both ends of the brake resistor (7).
) The same operation and effect can be obtained even if a current detector is used instead of the brake resistor (7) to detect the conduction state of the brake resistor (7).

In addition, the voltage detector (10) is connected to the brake transistor (8).
), and the first comparator (14
Of course, the same effect can be obtained even if the logical output of ) is reversed.

[Effects of the Invention] As explained above, in this invention, when the voltage of the DC bus increases due to regenerative power of the load, the bus voltage detector detects the voltage increase, and when the detected voltage value exceeds a predetermined value, the brake circuit The comparator turns on the brake switching element and counts the time from when the brake resistor is commanded to conduct to detect whether or not the brake resistor is conductive until the brake resistor actually conducts, and when the count value is a predetermined value. The abnormality detection circuit detects that an abnormality has occurred in the brake circuit when the voltage exceeds If the abnormality is caused by a failure, the occurrence of the abnormality can be immediately known, and there is no possibility that the deceleration ability of the inverter device will be judged to have exceeded its limit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the main parts of an embodiment of the present invention;
FIG. 2 is a circuit configuration diagram showing the outline of the same embodiment, and FIG. 3 is a time chart showing the operation of the inverter device.
Figure 3 (a) shows the operation of the brake circuit under normal conditions;
b) shows the operation of the brake circuit in an abnormal state, and FIG. 4 is a circuit configuration diagram schematically showing a conventional inverter device. In the figure, (3) is the inverter circuit, (B) is the brake circuit, (7) is the brake resistor, (8) is the brake transistor (brake switching element), (9) is the control circuit, and (10) is the resistance voltage detection. (1"1) is a comparator for the brake circuit, (13) is an abnormality occurrence judgment circuit, and p is a DC bus. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In an inverter device that includes a rectifier circuit, a smoothing capacitor, and an inverter circuit and arbitrarily controls the voltage and frequency of a power supply, a bus voltage detector that detects the voltage of a DC bus on the input side of the inverter circuit; A brake circuit is connected between the positive and negative sides of a DC bus, and a brake resistor and a brake switching element are connected in series.When the voltage value of the DC bus detected by a bus voltage detector is equal to or higher than a predetermined voltage value, the brake switching element of the brake circuit is connected between the positive and negative sides of a DC bus. From the time when the brake circuit comparator turns on the brake circuit comparator and the brake switching element of the brake circuit comparator is commanded to turn on and make the brake resistor conductive, until the voltage of the brake resistor is detected and the brake resistor actually conducts. 1. An inverter device comprising: an abnormality occurrence determination circuit that counts a time difference between and determines that an abnormality has occurred in a brake circuit when the count value exceeds a predetermined value. (2) The abnormality occurrence determination circuit uses a resistance voltage detector that detects the voltage of the brake resistor in the brake circuit, and compares the voltage of the DC bus detected by the bus voltage detector with the voltage of the brake resistor detected by the resistance voltage detector. The first comparator outputs the difference as a brake resistance voltage detection signal, and the brake switching element ON output from the brake circuit comparator.
Compares the command signal with the brake resistance voltage detection signal output from the first comparator, and outputs an H signal when the output value of the brake switching element ON command signal is larger than the output value of the brake resistance voltage detection signal; Other than that, there is a second comparator that outputs an L signal, a counter that counts over time when the output of the second comparator is an H signal, and resets the count value when the output is an L signal, and a counter that outputs a count value of the counter. 2. The inverter device according to claim 1, further comprising a third comparator that determines that there is an abnormality in the brake circuit when is greater than a predetermined value.