JPS60180476A - Inverter device - Google Patents

Abstract

PURPOSE:To set discharge resistors of inverters in response to the loads of the inverters by providing a connector for disconnecting the inverters from a common power source, and further providing a rectifier in parallel with its contactor. CONSTITUTION:A contactor 9 is closed at the normal operation time. Power can be supplied to inverters 2 from a common power source, and power can be supplied from the inverter 2 of regenerative mode to the inverter 2 of power drive mode in this state. When a motor IM is stopped, the contactor 9 of the inverter 2 is opened, and the frequency reference is then reduced. The current flowed by the regenerative current to the inverter 2 is charged in a smoothing capacitor 3, and a DC voltage rises. Thus, a Zener diode 7 is conducted, a transistor 5 is turned ON, and regenerative energy is consumed at a discharge resistor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention is directed to inverter devices, and particularly to common 'voltage type inverter devices'. :Related.

[Technical background of the invention and its problems]

An example of a conventional common source type voltage source inverter device is shown in FIG. 1 and will be described. In the figure, 1 is a rectifier circuit and 6
A plurality of inverter devices 2 are connected to the output thereof, and the AC motor 8 is driven by the AC output of each inverter. The configuration of the inverter device 2 is as follows: 3 is a smoothing capacitor, 4 is an inverter, 5 is a transistor as a switching element, 6 is a discharge resistor connected through the transistor 5, and 7 is a transistor 50 base circuit v
A Zener diode is connected as a voltage level detector, and its operation is such that when it is in power mode, the output from the rectifier 1 is smoothed by a smoothing capacitor 3, and the inverter 4 converts direct current to alternating current to drive the induction motor 8. During regeneration, the smoothing capacitor 3 stores the regenerated energy, and when the terminal voltage of the smoothing capacitor rises to a certain value, the Zener diode 7
The water becomes conductive, the transistor 5 turns on, and the regenerated energy is consumed by the discharge resistor 6.

In the inverter device having the above-mentioned structure, during normal operation, there are sections that operate in the power mode and sections that operate in the regeneration mode, but the total is in the power mode, so the discharge resistor does not operate. However, when regenerative braking is used to stop multiple sections or a single section, if the regenerative energy becomes larger than the regenerative energy of other sections, the regenerative energy that cannot be consumed as regenerative energy will be lost to the smoothing capacitor 3. The transistor 5 is charged to O.
At this time, even if the Zener diode 70' voltage detection levels are all set to the same level, it is not known which transistor will turn on first due to variations in each element. Further, when all sections are to be regenerated and stopped, even if the total resistance is -1 ONl, the motor stop time is different, so the ON time of the eccentric resistor is determined by the maximum load stop time. For these reasons, the discharge resistance must be selected according to the maximum load, which is uneconomical.

[Purpose of the invention]

An object of the present invention is to provide an inverter device that is provided with a circuit that does not cause a capacity shortage even when each inverter circuit is provided with a discharge resistor according to each load.

[Summary of the invention]

That is, the present invention provides an inverter circuit of a common power source type voltage source inverter in which the inverter circuit of the QL old unit is connected to one rectifier circuit, a contactor for disconnecting the inverter circuit from the common power source, and a contactor connected in parallel to the contactor. The inverter device is provided with a rectifier to prevent one section from supplying excessive regenerative energy to another section.

[Embodiments of the invention]

The present invention will be explained with reference to an embodiment in FIG.

In the figure, the same numbers as in FIG. 1 indicate the same parts, 9 is a contactor for separating the common power supply section and the inverter circuit, and 10 is a rectifier connected in parallel with the contactor 9.

In a device with such a configuration, the contactor 9 is closed during normal operation, and in this state, power is supplied from the common power supply to each inverter circuit, and power is supplied from the inverter circuit in regeneration mode. Power can be supplied to the inverter circuit in row mode. On the other hand, if it is desired to stop a certain motor, the frequency reference is lowered after opening the contactor 9 of the inverter circuit. In this state, when a regenerative current flows through the inverter circuit, the smoothing capacitor 3 is charged by this current, and the DC voltage increases. When this voltage exceeds a certain value, the Zener diode 7 in the base circuit of the transistor 50 is tied off, the transistor 5 is turned on, and the regenerated energy is consumed by the eccentric resistor 6. At this time, the rectifier 10 is initially in the OFF state because the common power source voltage is the DC voltage on the inverter side, and of course there is no effect on other sections. As the rotational speed of the motor gradually decreases and the regenerated power decreases, the DC' voltage of the capacitor 3 drops by 1, and as the common voltage and voltage also decreases, the rectifier 1
0, power required for excitation is supplied to the inverter circuit from the ONL common power supply section.

By providing this circuit in this way, it is only necessary to attach a discharge resistance corresponding to the load capacity to each inverter circuit.
Furthermore, it is possible to secure an excitation current to apply sufficient braking force to the motor until the motor stops. Furthermore, during normal operation, the regenerated electric power can be used to power other sections.

〔Effect of the invention〕

According to the present invention, the discharge resistance of each inverter circuit can be set according to the load of each circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional common power source type voltage source inverter device, and FIG. 2 is a diagram showing an embodiment of the present invention. 1... Rectifier circuit 2... Inverter circuit 3... Capacitor 4... Inverter 5... Switching transistor 6... Discharge resistor 7... Zener diode 8... AC motor 9...
・Contactor 10... Rectifier

Claims (1)

[Claims] In a common power source type voltage source inverter in which multiple inverter circuits are connected to one rectifier, the inverter circuit includes a contactor for disconnecting each inverter circuit from the common power source, and a rectifier connected in parallel to the contactor. An inverter device characterized by being provided with.