JPH0393425A - Dc power unit - Google Patents

Abstract

PURPOSE:To suppress surge current into a smoothing capacitor, simple operation with simple circuit and small main circuit machine, by inserting the primary winding of a leakage transformer having high leakage reactance between a DC power unit and the capacitor and arranging a resistor and a contact for short-circuiting the resistor on the secondary winding. CONSTITUTION:Primary winding of a leakage transformer 3 having high leakage reactance is connected between a DC power unit 1 and a smoothing capacitor 6. A resistor 4 is connected across the secondary winding of the leakage transformer 3 and a contact 8 for short-circuiting the resistor 4 is also provided. A circuit breaker 2 is closed, under open state of the short circuit contact 8, thus charging the smoothing capacitor 6. When a voltage detecting relay 5 detects that the voltage across the smoothing capacitor 6 has increased upto a predetermined level, the short circuit contact 8 is closed. The leakage transformer 3 functions as a reactor. By such arrangement, surge current can be suppressed and the main circuit machine can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC power supply device that suppresses inrush current when charging a smoothing capacitor. [Prior Art] Electronic devices such as computers and inverters that input direct current and convert it to alternating current require smooth direct current with extremely little pulsation. Such smoothed direct current can be obtained, for example, by a direct current power supply device including a direct current power source such as a rectifier, and a direct current reactor and a smoothing capacitor on the output side of the direct current power source. However, when starting such a DC power supply, a large charging current rushes into the smoothing capacitor from the DC power supply, potentially damaging the equipment, so it is necessary to suppress this rush current. Figure 5 is a circuit diagram showing the first conventional example of reconfiguring a DC power supply to suppress inrush current to a smoothing capacitor. This figure 5 is called the manual preliminary charging method,
By pressing the push button switch 14 while the circuit breaker 2 is open,
Since the charging current from the DC power supply 1 to the smoothing capacitor 6 flows while being restricted by the resistor 13, when the voltage of the smoothing capacitor 6 rises to the voltage determined by the resistance value of the resistor 13,
Alternatively, circuit breaker 2 is closed after a predetermined period of time has elapsed. When the circuit breaker 2 is turned on, the DC power charges the smoothing capacitor 6 to the charging completion state via the circuit breaker 2 and the DC reactor l2, and a charging completion signal is sent from the auxiliary contact of the circuit breaker 2 to the inverter 7 as a load. is sent to the inverter 7, so that the inverter 7 is ready for operation at any time. Figure 6 is a circuit diagram showing a second conventional example of a DC power supply that suppresses inrush current to a smoothing capacitor. This FIG. 6 is called a motor breaker starting method, and according to the operation command signal from the operation command contact l8,
The starting sequence circuit 17 sends a closing signal to the contact 19.
This contact 19 corresponds to the press switch 14 in the first conventional circuit shown in FIG. Charge 6. When the voltage detector 16 detects that the voltage of the smoothing capacitor 6 has increased to a predetermined voltage, the startup sequence circuit 17 sends a closing signal to the motor breaker 15, a circuit signal to the contact 19, and a signal to the inverter 7 that charging is completed. Each signal is sent out, and the inverter 7 is ready to operate at any time. Figure 7 is a circuit diagram showing a third conventional example of a DC power supply that suppresses inrush current to a smoothing capacitor. This figure 7 is called the contactor starting method, and charging of the smoothing capacitor 6 is started by closing the circuit breaker 2. At this time, since the contactor contact 20 is open, the DC power source l DC power from resistor l3
While charging current is limited by DC reactor 12
It flows into the smoothing capacitor 6 through the . When the voltage detector l6 detects that the voltage of the smoothing capacitor 6 has reached a predetermined level, the contactor contact 20 closes in response to a command from the startup sequence circuit l7, shorting the resistor l3 and at the same time, charging the inverter 7 is completed. I am trying to send a signal. In the third conventional circuit shown in FIG. 7, there is also a method of using a semiconductor switching element, such as a thyristor, in place of the contactor contact 20 to make the main circuit contactless. [Problems to be Solved by the Invention] As mentioned above, various methods have been conventionally used to suppress excessive inrush current from flowing when charging a smoothing capacitor in a DC power supply device. However,
Each has drawbacks. That is, although the first conventional circuit shown in FIG. 5 has a simple circuit structure, it is manually operated and requires time and effort. And if the circuit breaker 2 is turned on before the voltage of the smoothing capacitor 6 reaches a predetermined value,
At that moment, excessive charging current may flow, causing a problem that may cause circuit breaker 2 to trip. In addition, the second embodiment circuit shown in FIG.
A separate power supply is required to trip the motor breaker 15 in the event of a power outage, and this has the disadvantage of complicating the circuit.
Furthermore, in the third conventional circuit shown in FIG. 7, since the resistor l3 is short-circuited with a contactor, there is no need to prepare a separate power supply for tripping in the event of a DC power failure, but the contactor contact 20 allows the main circuit current to pass through. However, there are disadvantages in that the device becomes large due to the main circuit equipment, such as the need to provide a circuit breaker 2 for rapid overcurrent disconnection. Therefore, the purpose of this invention is to suppress the inrush current to the smoothing capacitor while keeping the operation simple, the circuit simple, and the main circuit equipment small. (Means for Solving the Problems) In order to achieve the above object, the DC power supply device of the present invention includes a capacitor connected to the output side of the DC power supply, and a capacitor inserted between the capacitor and the DC power supply. When reconfiguring a DC power supply with a DC reactor, the primary winding of a leaky transformer with a large leakage reactance is inserted between the DC power supply and the capacitor instead of the DC reactor. It shall be provided with a resistor that short-circuits the secondary winding of the leaky transformer, and a contact that short-circuits this resistor in response to the voltage of the capacitor. [Operation] This invention connects the primary side of a leaky transformer with a large leakage reactance instead of a DC reactor installed between a DC power source and a smoothing capacitor, and connects a leaky transformer with a secondary side to the secondary side of the leaky transformer. , a resistor that short-circuits this secondary winding, and a contact that short-circuits this resistor. FIG. 3 is a circuit diagram showing a leaky transformer and a load resistor connected to it. , resistance value R. This shows the case where a load resistor 9 is connected. Figure 4 is an equivalent circuit diagram of the leaky transformer and load resistor shown in Figure 3. As can be seen from this equivalent circuit, the primary current port of the leakage transformer 3. is shown by the following formula (1). If the resistance value RL of the load resistor 9 connected to the secondary side is increased, the next current !1 becomes smaller.Also, if the load resistor 9 is shorted,
That is, if RL-0 is set, equation (1) becomes equation (2) below. R na j−X Here, if the leakage transformer 3 is designed so that R(X),
Equation (2) can be approximated by equation (3) below. If you short-circuit the secondary winding of the leaky transformer 3 (J-X, that is, R(X), the leaky transformer 3 will act as a reactor. Therefore, when charging the smoothing capacitor 6, the leaky transformer It is sufficient to connect a resistor of an appropriate value to the secondary side of the device 3 to limit the charging current, and then short-circuit this resistor. [Embodiment] Figure 1 shows an embodiment of the present invention. 1, DC power from a DC power supply 1 is applied to a smoothing capacitor 6 via a circuit breaker 2 to charge it.
The operation of the inverter 7, which is the load, is started after charging is completed, as in the case of each of the conventional circuits described above. In the present invention, instead of the DC reactor l2, the primary winding of the leaky transformer 3 having a large leakage reactance is connected between the DC power supply 1 and the smoothing capacitor 6. A resistor 4 is connected to the secondary winding, and a shorting contact 8 is provided to short-circuit the resistor 4. When starting up the DC power supply shown in FIG. 1, when the circuit breaker 2 is turned on with the short-circuit contact 8 open and the smoothing capacitor 6 is charged, the charging current is as shown in equation (1). is limited by resistor 4, so there is no risk of excessive inrush current flowing. When the voltage detection relay 5 detects that the voltage of the smoothing capacitor 6 increases due to this charging and current and reaches a predetermined voltage, the short circuit contact 8 linked to the operation of the voltage detection relay 5 closes. i.e. resistance 4
is short-circuited, so according to equation (3) mentioned above, this leaky transformer 3 acts as a reactor. FIG. 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in FIG. 1, in which FIG. 2 shows changes in input voltage V, FIG. (C) each represents the change in the input current ■.As shown in Fig. 2, when the circuit breaker 2 is closed at time T, the voltage of the smoothing capacitor 6 is equal to the capacitance of this capacitor and the leakage transformer. The input current I increases according to a time constant determined by the resistance value converted to the primary side of the capacitor 3, but the maximum value of the input current I at this time is suppressed.This capacitor voltage vc is detected at the time of T-hiro. When the set voltage of the relay 5 is reached, the short-circuit contact 8 closes, and at that moment the input current ■ increases rapidly, but there is no risk that its value will become excessive.
Charging is completed immediately and the inverter 7 can be operated. When circuit breaker 2 is opened at time T, capacitor voltage vc
When the voltage decreases to just the voltage setting at T4, the short-circuit contact 8 opens and returns to the original state. T$ is the point at which the circuit breaker 2 is closed, and the smoothing capacitor 6 is recharged by repeating the above-described operation. [Effects of the Invention] According to this invention, the primary winding of the leaky transformer is inserted between the DC power source and the smoothing capacitor. If a resistor is connected to the secondary winding of this leaky transformer, the primary current can be suppressed, and if the resistor is shorted, it acts as an actor, so this can be used to charge the smoothing capacitor. It can be used as a glue actor to control the current and remove ripple after the capacitor is fully charged.
This has the effect of simplifying the equipment used in the main circuit.
Furthermore, since the resistor for suppressing the t-current and the contact for shorting the resistor are installed on the secondary side of the leakage transformer, their current capacity can be small, which is effective in downsizing the device.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in Fig. 1, and Fig. 3 is a leakage transformer and a load resistor connected to it. Figure 4 is an equivalent circuit diagram of the leaky transformer and load resistor shown in Figure 3, and Figure 5 is a circuit diagram of the DC power supply that suppresses the rush current to the smoothing capacitor. 1. A circuit diagram showing a conventional example. Fig. 6 is a circuit diagram showing a 2nd conventional example of a DC power supply device that suppresses inrush current to a smoothing capacitor. Fig. 7 shows a circuit diagram that suppresses inrush current to a smoothing capacitor. FIG. 2 is a circuit diagram showing a third conventional example of a direct current power supply device. 1...DC power supply, 2...breaker, 3...leakage transformer! L4. l3...Resistance, 5...Voltage detection relay 6
...Smoothing capacitor, 7.Inverter as load, 8.Short contact, 9.Load resistance, 12..
DC reactor, 14...Push button switch, 15...
Motor breaker, 16... Voltage detector, l7... Starting sequence circuit, 18... Operation command contact, l9...
・Contact, 20... Contactor contact. Atsushi 2 Figure 6 3 Atsushi 4 Figure

Claims (1)

[Claims] 1) In a DC power supply system consisting of a capacitor connected to the output side of a DC power supply and a DC reactor inserted between this capacitor and the DC power supply, the primary winding of a leaky transformer with large leakage reactance A wire is inserted between the DC power source and the capacitor in place of the DC reactor, and a resistor is inserted to short-circuit the secondary winding of the leaky transformer, and this resistor is short-circuited in accordance with the voltage of the capacitor. A direct current power supply device characterized by comprising a contact point.