JPH0417517A - Inrush current suppression power throw-in circuit - Google Patents

Abstract

PURPOSE:To obtain an inrush current suppressing circuit, which can be controlled at TTL level without requiring external timing signal, by charging a smoothing capacitor through a charging/rectifying circuit and throwing power into a main rectifying circuit at the time point when charging of the smoothing capacitor is detected. CONSTITUTION:A command section 1 provides an ON command, PONL, at TTL level to turn an optically isolated SSR 25 ON and an AC current is fed from R-S phases to a charging/rectifying circuit 23 which then produces a DC current for charging a smoothing capacitor 11 while being limited by a resistor 33. A photocoupler 29 is turned ON when the charging voltage of the smoothing capacitor 11 reaches a threshold set by a Zener diode 27. Consequently, an SSR 31 is turned ON to excite a magnetic contactor 7 thereby making the contacts and throwing a 200V AC power supply in a main rectifying circuit, i.e., a three-phase diode bridge 9.

Description

[Detailed Description of the Invention] Purpose of the Invention; (Industrial Application Field) The present invention relates to a power-on circuit for a rectified DC power supply,
In particular, it relates to a power-on circuit that extends the life of magnetic contactors and switch contacts in the input section, and suppresses deterioration of smoothing capacitors due to inrush current.

(Prior Art) A circuit of a power-on section of a conventional rectified DC power supply is configured as shown in FIG. 2 or 3. FIG. 2 shows the case where there is no inrush current suppression circuit. In-rush current is the extremely small impedance of the circuit wiring that occurs when voltage is applied directly to the input section of a rectified DC power supply (because the impedance of the smoothing capacitor is zero at the moment the power is turned on). It refers to a large current that flows instantaneously and is determined by .In Fig. 2, 1 is a command unit such as a sequencer, 3 is a relay, and 5 is a relay sequence power source (ex.

7 is a magnetic contactor, 9 is a three-phase rectifier diode bridge, 11 is a smoothing capacitor, 13 is a load such as an inverter, and R, S, and T are 2
Represents the input of 00V 3-phase power supply. In the figure, when the ON command ON is output from the command unit 1, the relay 3 (MC2> is turned on, and the sequence DC power supply 5 turns on the magnetic contactor 7 (MCI>), and the 3-phase rectifier diode bridge 9 is connected to the AC power is turned on. At the moment when the magnetic contactor 7 is turned on, the impedance of the smoothing capacitor 11 is almost 0 [Ω] transiently.
Therefore, a large current momentarily flows through the path (■).

FIG. 3 shows an example in which an inrush current suppressing resistor and an inrush current suppressing resistor current bypass contact are provided. In FIG. 3, an inrush current suppressing resistor 15, a bypass circuit 21, and relays 17 and 19 for selecting the bypass circuit 21 are provided in the circuit of FIG. 2. In Fig. 3, when the ON command ONI is output from the command unit 1, the relay 3 (MC2> is turned on, the magnetic contactor 7 (MCI) is turned on by the sequence DC power supply 5, and 200V is applied to the three-phase rectifier diode bridge 9. AC power is turned on. At this time, relay 17 (MC3)
Since the contacts are open, the three-phase rectifier diode bridge 9
The current rectified by the inrush current suppression resistor 1
5, the smoothing capacitor 1 is gradually connected to the route of ■.
Charge 1. After the time required to complete charging of the smoothing capacitor 11 has elapsed, the command unit 1 outputs an ON command ON2. Relay 19 (MC4) due to ON command ON2
is turned on and relay 17 (
MC3) is turned on. From this point on, relay 17 (MC
Since the contact point 3) is closed, the load current of the load 13 such as an inverter more actively flows through the path ``■'' than the path ``■'' in the figure.

Figure 4 shows the smoothing capacitor 1 in the case of Figure 3.
1 charging voltage and magnetic contactor 7 (MCI>
The relationship between the timing of turning on the relay 17 (MC3) is also shown.

(Problems to be Solved by the Invention) In the case of the prior art shown in FIG. 2, (a) sparks are generated at the contacts of the magnetic contactor 7 (MC1) due to inrush current, shortening the life of the contacts. (b) In selecting the current capacity of the rectifier 9, it is necessary to consider not only the rated load current but also the inrush current, and in the worst case, there is a problem that the current capacity of the rectifier 9 needs to be upgraded. , in the case shown in Fig. 3 to solve the problem in Fig. 2,
(c) The contacts of the relay 17 (MC3) for short-circuiting the inrush current suppression resistor 15 require a contact capacity commensurate with the rated load current, making the contacts large; ) in the case of relay 17 (MC3)
When using a large magnetic contactor, it requires only TTL level output (requires an additional power source such as 24 VDC), (e) Turn on relay 3 (MC2> and then turn on relay 4 (MC4> There have been problems such as the need to input timing using the command unit 1 in order to do so.

This invention was made in order to solve the above problems, and the object of this invention is to be compact even for a large-capacity power input section, to be controllable at TTL level, and to be able to control external timing. To provide a power-on circuit capable of suppressing inrush current without requiring a signal.

(Means for Solving the Problems) The inrush current suppression type power supply circuit of the present invention has a contactor for supplying AC power on the input side and a smoothing capacitor on the output side. a charging rectifier circuit that is a power supply circuit for a rectifier circuit and supplies a DC voltage for charging the capacitor;
A switch circuit for supplying power to the charging rectifier circuit, a circuit for detecting that the capacitor is charged to a certain charging voltage, and a circuit for turning on the contactor based on the output from the detection circuit. It was characterized by having the following.

(Function) In the in-rush current suppression type power-on circuit of the present invention, power is turned on to the main rectifier circuit by inputting a command output from the command unit to the charging rectifier circuit to supply the AC power to be rectified by the main rectifier circuit. This is done by charging the smoothing capacitor with the direct current output from the charging rectifier circuit, and energizing the magnetic contactor when the detection circuit detects that the smoothing capacitor is charged.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a circuit diagram showing one embodiment of the inrush current suppressing power-on circuit of the present invention. In the figure, parts with the same reference numerals as in FIGS. 2 and 3 indicate similar parts, and reference numeral 23 is composed of a single-phase diode for charging the smoothing capacitor 11. A charging rectifier circuit, 25 an optically isolated 5SR (solid state relay) forming a switch circuit for supplying power to the charging rectifier circuit, 27 a Zener diode, 2
9 is a fort coupler (a charging voltage detection part is composed of a zener diode 27 and a fort coupler 29), 3
Reference numeral 1 denotes an optically insulated type 5SR 133, which constitutes a switch circuit for turning on the power to excite the magnetic contactor 7 (MCI), and represents a resistance.

In the circuit shown in FIG.
ONL (Power On Low) is input at TTL level, the optical isolation type 5SR25 is turned on, and R
The alternating current input from the −3 phase to the charging rectifier circuit #123 is rectified and a direct current is output, which charges the smoothing capacitor 11 while being current limited by the resistor 33. When the charging voltage of the smoothing capacitor 11 reaches a threshold value set by the Zener diode 27, the fort coupler 29 is turned on.

When the fort coupler 29 is turned on, the 5SR31 is turned on, the magnetic contactor 7 (MCI> is energized, the contacts are connected, and a 200μ AC power is supplied to the three-phase rectifier diode bridge 9, which is the main rectifier circuit). Injected.

Effects of the invention: As described above, according to the inrush current suppressing power-on circuit of the present invention, (a) the large current bypass contact is replaced with a small SSR and a single-phase rectifier diode bridge, so the circuit is miniaturized. be able to.

(b) Since an optically insulated SSR is used, control from the TTL level is possible, eliminating the need for an additional power source for relay excitation.

(C) Since the timing for turning on the power to the main rectifier circuit is generated within the circuit itself, there is no need for an external timing input circuit.

The following effects can be achieved.

[Brief explanation of drawings]

Figure 1 shows an inrush current suppression type power-on circuit of the present invention, Figure 2 shows a conventional power-on circuit that does not take measures against inrush current, and Figure 3 shows a conventional power supply that takes measures against inrush current. Closing Circuit FIG. 4 is a diagram showing the relationship between the charging voltage of the smoothing capacitor and the timing of turning on the magnetic contactor and relay in the case of FIG. 3. 1... Command unit, 7... Magnetic contactor
9... Main rectifier circuit, 11... Smoothing capacitor 13... Load, 25.31... Optical isolation type 5SR
517...Charging rectifier circuit, 29...Fort coupler.

Claims (2)

[Claims] (1) A power supply circuit for a main rectifier circuit that converts alternating current into direct current, which has a contactor for supplying alternating current power on the input side and a smoothing capacitor on the output side, and has a contactor for supplying alternating current power on the input side and a smoothing capacitor on the output side. A charging rectifier circuit to supply, a switch circuit to turn on power to the charging rectifier circuit, a circuit to detect that the capacitor has been charged to a certain charging voltage, and a charging circuit based on the output from the detection circuit. An in-rush current suppression type power-on circuit comprising: a circuit for turning on the contactor. (2) The in-rush current suppressing power-on circuit according to claim (1), wherein an optically insulated SSR (solid state relay) is used as a switch circuit for turning on power to the charging rectifier circuit.