JPS5863032A - Power source circuit - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit, and more particularly to a power supply circuit that supplies direct current to an inverter that drives an alternating current motor. Recent alternating current motors have a feature in which the frequency of alternating current output from the inverter is variable. This type of inverter is supplied with DC power, which is usually obtained by rectifying a three-phase AC commercial power source.

On the other hand, in AC motors such as AC spindle motors, which have large load fluctuations, the load current changes greatly each time the load changes.
However, this type of rectifier circuit uses a capacitor input type smoothing circuit that simply connects a capacitor to the output side of a semiconductor rectifier, so there are many ripples and voltage fluctuations are large.
In addition to adversely affecting the speed control of the AC motor, the current flowing through the rectifier itself not only fluctuates, but also causes a shocking current to flow, so a large rectifying element that can withstand these types of current must be used in advance. There are many disadvantages in this invention.The present invention is an invention that improves the conventional disadvantages as mentioned above.
The purpose is to improve the DC output ripple rate in a power supply circuit that supplies DC to an inverter that drives an AC motor, and to provide a power supply circuit that prevents a dangerous current from flowing through the rectifying element. 0 Next, a practical example of the present invention will be explained in detail using the drawings. 0 The figure shows a speed control device that controls the speed of a three-phase induction motor using an inverter, where 1 is a three-phase induction motor, and 2 is a three-phase induction motor. A speedometer generator that detects its rotation speed, 3Fi fermentation electric motor outline 1
A regeneration circuit that regenerates the power generated during deceleration of the 4Fi sieve taa・1 in the direction of the three-phase power supply, 5
ij 71J con rectifier element.

This is a three-phase rectifier circuit in which the circuits D6 and D6 are bridge-connected, and AC reactors RL, SL, and TL are inserted in series between terminals A, B, and C on the input side and phases of the power supply R, 8, and T.

6 is a speed control circuit, and although it is not clearly shown in the figure, there is a transistor TR constituting the inverter 3 inside.
, -TR6, transistors TR, ITR, and thyristors TH1 to TH6 that constitute the pace circuit and regeneration circuit 4.
It has a gate circuit that controls the gate circuit of the speed meter, and sends a signal to the transistor of the inverter 5 according to the speed command signal V CMD commanded from the outside to rotate the three-phase induction motor a1, and the three-phase motor generated from the speedometer generator ia2. Checking the rotational speed VB of the induction motor 1, the rotational speed is determined by the speed command signal V.
Control is performed to match the speed given by CMD, and when the three-phase conductive IEl1111 decelerates, the inverter 5 and regeneration circuit 4 are driven to regenerate the generated power in the three-phase power supply R, 8, and T directions. This applies a braking force to the three-phase conductive motor 1, but since these effects are common knowledge, no further explanation will be given.

By the way, in the present invention, for example, the three-phase induction motor 11
1K When a load is suddenly applied and the DC current flowing into the inverter 6 tries to rise sharply, the current flowing through the three-phase rectifier circuit 5 and the current flowing through the R, S, and T phases also try to increase. Since the reactors RL, 8L, and TL work to suppress the current flowing through each phase, the current flowing through the three-phase rectifier circuit 5 does not become steep but flat. Also, when power is applied to the three-phase rectifier circuit 5, even if a charging current is forced to flow into the capacitor C', as mentioned above, the AC reactors RL, SL, and TL are three-phase!
In order to suppress the sudden inflow of current into the Iff circuit 5, this is used as a protective film. ◎ :1 As explained in detail above, the present invention inserts an AC reactor between the input side terminal of the rectifier circuit and the AC power supply. Therefore, even if the flowing current changes significantly due to sudden changes in the load on the output side of the rectifier, the AC reactor inserted at the input side of the rectifier circuit acts to suppress the sudden change. Therefore, in addition to stabilizing the DC voltage applied to the inverter, it also has many advantages, such as the need for a smaller surge container for the rectifier elements that make up the rectifier circuit.

[Brief explanation of drawings]

The figure is a circuit diagram showing one embodiment of the present invention. 1...Induction motor, 2...Speedometer generator, 6...
Inverter, 4... Regeneration circuit, 5... Three-phase rectifier circuit, 6... Speed control circuit, [,, SL, TL... AC actor. Patent applicant: Fujitsu Fanuc Co., Ltd. Agent: Sou Sou, a patent attorney (2 persons)

Claims (1)

[Claims] (1) A power supply circuit that obtains direct current by rectifying alternating current on the input side with a rectifying element, characterized in that an AC reactor is inserted between the input side terminal of the rectifying circuit made of the rectifying element and the AC power terminal. . (21$7) The power supply circuit according to claim (1), wherein the load of the current path is an inverter for driving an AC motor.