JPS62277081A - Inverter system - Google Patents

Abstract

PURPOSE:To prevent a braking resistor from overheating due to the defect of a braking transistor element by limiting the heat generating action of the resistor due to regenerative power to a certain value. CONSTITUTION:When a motor 14 normally operates, a switch element 21 is closed to connect a braking resistor 15 in series with a transistor 16, and the transistor 16 is turned OFF by the output of a comparator 17. When the motor 14 is decelerated so that regenerative power rises a voltage across a smoothing condenser 12, the transistor 16 is driven by a pulselike voltage. When the transistor 16 is always turned ON due to the defect of the transistor 16, a current larger than a rated value flows to the resistor 15 to raise its temperature. Thus, a switch contact 21 is releasted by a temperature responsive element 20 disposed near the resistor 16 to break the series line of the resistor 15.

Description

Detailed Description of the Invention 6. Detailed Description of the Invention [Field of Professional Application] This invention relates to an inverter device that supplies energizing power to an induction motor, and particularly to an inverter device that supports a regenerative power consumption circuit in an induction motor. This article relates to good inverters and devices.

[Conventional technology]

FIG. 2 is a schematic circuit diagram showing a conventional device. In the figure, Q (1 is the input AC power supply, α power is a rectifier circuit including diode elements, (6) is a smoothing capacitor, αJ is an inverter circuit including transistor elements, α power is an induction motor. α power is for braking. The resistor, α force is the braking transistor element connected in series with the braking resistor (to), and α force is the voltage across the smoothing capacitor αa ("'o) or its fraction voltage and the threshold value of the reference wire α Enoki. A comparison circuit is used to compare the voltage (Vh).

Next, the operation will be explained using the waveform diagrams of (4), (B) and (C'l) in FIG.
The signal of the input AC power supply (1 (J) is converted into a DC voltage (VO) by the rectifier circuit α and the smoothing capacitor α (see Figure 3A), and then passed through the inverter circuit α1 to generate a signal with a predetermined frequency. The output AC is inversely converted into AC output, and power is supplied to the electric motor Cl41.On the other hand, as shown in FIG. 6(C),
The vertical axis indicates the rotation speed N of the motor), and when the motor (1→ decelerates at time (1,), the regenerated power from the motor (14) is passed through the inverter circuit (6) to the smoothing capacitor (
2), and its terminal voltage (Vo) increases. When the voltage of this regenerated power exceeds the threshold voltage (vh) of the reference power supply (to) at time (1,), the output of the comparator circuit α turns on the transistor element αQ (Fig. 6BB
(see). As a result, this regenerated power is consumed by the braking resistor α→, and the rise in its voltage (VO) is suppressed. When the voltage (vo) becomes equal to or less than the threshold voltage (vh) at time (tl), the transistor element αQ is turned off.

In this way, the braking resistor @ is connected between the DC buses (1) and (2) only when the motor α→ is braking and the voltage of the regenerated power is higher than the threshold voltage. The rated capacity of the resistor (14) is selected according to the usage conditions of the load including the motor (14).

Specifically, this braking resistor ( A rated capacity value of 1υ is selected.

[Problem that the invention seeks to solve]

As mentioned above, the braking resistor 0υ of the conventional device is directly connected between the DC buses (1) and (2) through a transistor element, so the braking resistor (g) is prevented from abnormally overheating due to regenerated power. It has a large capacity to avoid this. Further, when the braking transistor element α→ becomes short-circuited due to a failure or the like, the braking resistor 09 is always in a conductive state, and as a result, there is a possibility that a fire may occur due to the heat generated by the braking resistor.

This invention was made to solve the above-mentioned problems. A switching element is connected in series with a braking resistor and a transistor element, and the opening and closing operations of this switching element are controlled by the braking resistor. This is done using a temperature sensitive element installed nearby, and the purpose is to detect abnormal heat generation in the braking resistor and interrupt the series line shown in @, thereby preventing fires due to abnormal heat generation in the braking resistor. .

[Means for solving problems]

In the inverter device according to the present invention, a temperature sensitive element is arranged close to a braking resistor connected to a DC bus, and a switch controlled by the temperature sensitive element is connected in series with the braking resistor and a transistor element. This is what I did.

[Effect]

The temperature sensitive element according to the present invention opens its switch in the event of an abnormality to cut off the line to the braking resistor connected to the DC bus, thereby preventing abnormal heat generation.

, [Embodiment of the Invention] A device according to an embodiment of the invention will be explained below with reference to the circuit diagram shown in FIG. In addition, in the 1st ward, 0)
, (2) and 0Q~0→ are the same as those in FIG. 1 is a bimetal-like temperature sensitive element placed close to the braking resistor r15, and Q is this temperature sensitive element (7).
) is a switch contact whose opening and closing operations are controlled by
This switch contact Q1) is connected in series with a braking resistor q9 and a transistor element (IQ).

The operation of the apparatus having the above configuration will be described next. First, during normal operation of the motor α→, the switching element → is closed, and the braking resistor (19) and transistor element 00 are connected in series, and this transistor element 00 is turned off by the comparison circuit a. At this time, the motor Q4 is decelerated at time (1,), and the regenerated power increases the voltage across the smoothing capacitor a, causing the υ transistor element Ql to produce a pulsed voltage as shown in FIG. 6(B). As mentioned above, it is driven by the brake resistor (19). However, if it is constantly turned on due to a failure of the transistor element ◇ increases. Therefore, 14 υ switch contacts (c) are made by the temperature sensitive element wire placed close to this braking resistor α→, and the series line of the braking resistor (to) is cut off. .

Note that the above configuration assumes that the bimetal element serves as the temperature sensitive element for the opening and closing operation of the switch contact (g), but this switch contact (c) is released due to heat generation of the bimetal element. This is a so-called self-holding type switch, but instead of a bimetal element, an alloy element may be used.

〔Effect of the invention〕

As described above, according to the present invention, the heating effect of the braking resistor due to regenerated electric power is limited to a certain value, which has the effect of preventing the braking resistor from overheating due to failure of the braking transistor element. .

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram of a device according to an embodiment of the present invention;
FIG. 2 is a circuit diagram of a conventional device, and FIG. 6(A). (B) and (C) are waveform diagrams for explaining the operation. In the figure, αQ is the input AC power supply, α■ is the rectifier circuit, a is the smoothing capacitor element, (1→ is the inverter circuit, α◆ is the induction motor, α→ is the braking resistor, and αQ is the braking transistor element. , αη is the comparison circuit, 0→ is the reference power supply, (4)
is a temperature sensitive element and Ql) is a switch contact. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] It consists of a converter circuit that converts input AC to DC, an inverter circuit that converts this DC to AC output, and a series circuit of a braking resistor and transistor element that is connected between the DC bus bars and consumes the regenerated power of the motor. In an inverter device, a temperature sensitive element is disposed close to a braking resistor, and the temperature sensitive element disconnects a series circuit between the braking resistor and a transistor element in response to a rise in temperature of the braking resistor. An inverter device featuring: