JP2007028792A - converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter having a simple configuration capable of suppressing an inrush current at power-on without using a circuit breaker (relay) having a large current capacity and sufficiently ensuring operation reliability.
A rectifier that rectifies and converts DC power into DC, a capacitor that is connected in parallel to an output terminal of DC power and stores DC power rectified by the rectifier, and an input side or an output side of the rectifier It is provided with a current limiting resistor that limits the power supplied to the capacitor and a plurality of circuit breakers having a current capacity smaller than the rated output current capacity, and the total sum of the current capacity exceeds the rated output current capacity. A circuit breaker provided in parallel and electrically driven in a state where the capacitor is charged to short-circuit the current limiting resistor, and further, a contact contact resistance and / or the current limiting resistance of each of these circuit breakers is monitored. And a monitoring means.
[Selection] Figure 1

Description

  The present invention relates to a capacitor input type converter in which a capacitor is connected in parallel to an output terminal of DC power, and more particularly to a converter having a simple configuration having a function of preventing an inrush current when power is turned on.

  In a capacitor input type converter comprising a rectifier that rectifies and converts DC power into DC and a capacitor that is connected in parallel to the DC power output terminal and stores DC power rectified by the rectifier, when the power is turned on, Inrush current that reaches 3 to 5 times the rated current flows into the capacitor. Therefore, a converter having a large rated current uses a power switch or a circuit breaker (relay) having a contact with a current capacity that allows for the inrush current.

In order to suppress this type of inrush current, a current limiting resistor is provided in parallel with the power switch or circuit breaker, and after charging the capacitor to some extent through the current limiting resistor, the power switch or circuit breaker is turned on (conduction) ) Is proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-164058

  However, as described above, even if a current limiting resistor is provided to suppress the inrush current, if the rated current of the converter is large, a large (high current type) power switch or circuit breaker with a contact with a current capacity corresponding to the rated current Must be used. In particular, in a converter incorporated in a large current switching power supply device or inverter device used as a power supply unit of a power device or the like, for example, a current capacity of 100 A or more is required, so the structure of the circuit breaker (relay) itself is considerably enlarged, There is no denying that the price of the parts will increase. In addition, since a large current flows through the contact point of the circuit breaker (relay), the amount of heat generated due to the contact resistance at the contact point increases, resulting in problems such as failure of the circuit breaker.

  The present invention has been made in consideration of such circumstances, and its purpose is to effectively suppress inrush current at power-on without using a large and expensive circuit breaker (relay) having a large current capacity. It is another object of the present invention to provide a converter having a simple configuration that can ensure sufficient operation reliability.

In order to achieve the above-described object, a converter according to the present invention includes a rectifier that rectifies AC power and converts it into DC, a capacitor that is connected in parallel to an output terminal of DC power and stores DC power rectified by the rectifier. A capacitor input type that supplies DC power to a load with
A current limiting resistor provided on the input side or output side of the rectifier for limiting the power supplied to the capacitor, and a plurality of circuit breakers having a current capacity smaller than the rated output current capacity. Circuit breakers that are provided in parallel in a number exceeding the rated output current capacity and are electrically connected in a state where the capacitor is charged to short-circuit the current limiting resistor, and contact resistances of these circuit breakers and / or Or it has the monitoring means which monitors the said current limiting resistance, respectively, It is characterized by the above-mentioned.

  Preferably, each circuit breaker is driven by the driving means after the capacitor is charged through the current limiting resistor when the power is turned on, and the charging voltage of the capacitor is turned off when the power is turned off. The shut-off control is performed in a state where is maintained. Incidentally, the circuit breaker driving means is configured to monitor the charging voltage of the capacitor as described in claim 3 to control conduction / breaking of each circuit breaker, or as described in claim 4. Each circuit breaker is turned on after a predetermined time has elapsed since the power was turned on, and each circuit breaker is cut off after a predetermined time has elapsed since the power supply to the load connected to the output terminal is stopped when the power is turned off. . Further, as described in claim 5, the current limiting resistor is provided as being connected in parallel to each of the circuit breakers, for example.

  Moreover, as for the preferable aspect of this invention, it is desirable to provide the current sensor which measures the amount of electric current which flows through the said circuit breaker or the said current limiting resistor, as described in Claim 6. Furthermore, as described in claim 7, it is also desirable to have a function of diagnosing the fault of the current limiting resistor by monitoring a charging time constant and / or a charging current for the capacitor.

  According to the converter having the above-described configuration, a plurality of circuit breakers having a current capacity smaller than the rated output current capacity are provided in parallel, and each of these circuit breakers is conductively driven in a state where the capacitor is charged, and the current limiting is performed. Since the resistors are short-circuited, even when the rated current capacity is large, the heat generated by the contact resistance at the contacts of each circuit breaker can be suppressed by distributing the current to multiple circuit breakers. Operation reliability can be ensured. Moreover, since the converter is operated while monitoring the contact contact resistance at each of these circuit breakers, if the contact contact resistance at the circuit breaker increases, this will be detected quickly and the contact will fail before an abnormal situation occurs. It is possible to take measures such as replacing a circuit breaker that may cause a fault.

  In addition, even if a circuit breaker whose contact contact resistance has increased or is increasing, the amount of current reduced by this can be covered by another circuit breaker provided in parallel with the circuit breaker. The rated current capacity of the converter itself can be effectively maintained, and its operation reliability can be sufficiently ensured. Furthermore, each circuit breaker itself has a small current capacity, and since only a small capacity of current flows through the contact point, even if contact floating occurs due to unforeseen circumstances, all circuit breaker contacts float simultaneously. Therefore, there is no concern that arc discharge will occur due to this. In addition, the circuit breaker for large current can be reduced in size and greatly reduced in cost, and the operation reliability itself can be easily increased, so that the practical advantage is tremendous.

  Further, as described above, a current sensor and a means for detecting a voltage between terminals of each circuit breaker are provided, and further, a function for monitoring a charging time constant to the capacitor is provided. Since it is possible to monitor deterioration of characteristics, deterioration of current limiting resistance, and the like, it is possible to quickly detect a sign of a malfunction and cope with it.

Hereinafter, a converter according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a converter according to this embodiment. Reference numeral 1 denotes a rectifier that rectifies AC power supplied from an AC power supply 2 to obtain DC power, specifically, a diode bridge. The DC power rectified by the diode bridge (rectifier) 1 is supplied to the load RL via the output terminals 3a and 3b. The load RL is composed of, for example, an inverter circuit that drives a power motor. In particular, in this converter, a capacitor 4 for smoothing the DC power is connected in parallel to the DC power output terminals 3a and 3b, thereby forming a so-called capacitor input type converter.

  Further, between the diode bridge (rectifier) 1 and the output terminals 3a and 3b of this converter, in particular, between the positive output terminal (+) of the diode bridge (rectifier) 1 and the positive output terminal 3a. A plurality of connected current limiting resistors 5a, 5b, .about.5n are inserted, and a small current capacity circuit breaker (relay) 6a, 6b, .about.6n is connected to each of these current limiting resistors 5a, 5b, .about.5n. Are connected in parallel. The current limiting resistors 5a, 5b, .about.5n serve to limit the current of the DC power supplied to the capacitor 4 and charged, and the circuit breakers (relays) 6a, 6b, .about.6n. Plays a role of individually short-circuiting these current limiting resistors 5a, 5b, to 5n. In particular, each of the circuit breakers (relays) 6a, 6b, .about.6n and the current limiting resistors 5a, 5b, .about.5n are controlled in conduction by the relay drive circuit 7 to suppress the inrush current when the converter is turned on. Is building.

  Incidentally, as each of the circuit breakers (relays) 6a, 6b, to 6n, for example, when the rated output current capacity of the converter is 100A, the contact current capacity of about 10A is generally small and has a small power capacity. About a unit is connected in parallel, and the sum of the allowable current capacities of these circuit breakers (relays) 6a, 6b, to 6n is used so as to exceed the rated output current capacity. Further, the current limiting resistors 5a, 5b, .about.5n allow the current flowing into the capacitor through the current limiting resistors 5a, 5b, .about.5n when the converter power is turned on to give a margin to the allowable ripple current of the capacitor. A resistor having a resistance value capable of limiting the current so as to be equal to or less than the current value is used.

  Further, the relay drive circuit 7 is used after the capacitor 4 is charged while being current-limited through the current-limiting resistors 5a, 5b, .about.5n after a predetermined delay time from the time of turning on the power of the converter, or an output voltage described later. The circuit breakers (relays) 6a, 6b, to 6n are configured to be turned on (turned on) when the charging voltage of the capacitor 4 detected by the monitoring circuit 15 exceeds a preset management voltage value. Is done. Further, the relay drive circuit 7 stops the power supply to the load RL when the converter power is shut off, and then replenishes the capacitor 4 and the charge voltage exceeds the management voltage value. The circuit breakers (relays) 6a, 6b,... Regarding the breaker control of the circuit breakers (relays) 6a, 6b, to 6n, for example, after a predetermined delay time has elapsed since the off command (operation stop command) for the load RL is issued, or the capacitor 4 is charged. This is done by monitoring the voltage.

  The circuit breakers (relays) 6a, 6b, and 6n are connected to the relays 6a, 6b, and 6n by the conduction drive (on) and the break control (off) of the circuit breakers (relays) 6a, 6b, and 6n. Each is turned on / off without excessive voltage applied between the contacts. Moreover, the DC current with a small amount of current distributed to each of the circuit breakers (relays) 6a, 6b, to 6n is turned on / off. As a result, there is no risk of arc discharge occurring between the relay contacts when the circuit breakers (relays) 6a, 6b, .about.6n are turned on and off, and the circuit breakers (relays) 6a, 6b,. Since the amount of current flowing through each of them is small, there is almost no possibility that the relay contacts generate heat. Therefore, there is an advantage that it is possible to guarantee a stable operation of each of the circuit breakers (relays) 6a, 6b, to 6n.

  Further, when the contact contact resistance of a specific circuit breaker (relay) 6k increases and current becomes difficult to flow through the circuit breaker (relay) 6k, the current that has become difficult to flow becomes another remaining circuit breaker (relay). Therefore, it can be said that these circuit breakers (relays) 6a, 6b, to 6n back up their functions. Therefore, even if a failure occurs in a specific circuit breaker (relay) 6k, the converter itself does not go down, so that the operation reliability is sufficiently secured and the supply of DC power to the load RL is stable. Can be performed.

  In this converter, current sensors 8a, 8b, and 8n are provided in the current paths of the current limiting resistors 5a, 5b, and 5n, respectively, in which the circuit breakers (relays) 6a, 6b, and 6n are connected in parallel. The amount of current supplied to the output terminal 3a (capacitor 4) is detected via the current limiting resistors 5a, 5b, ˜5n or the circuit breakers (relays) 6a, 6b, ˜6n, respectively. Yes. These current sensors 8a, 8b, to 8n may be so-called shunt resistors or current transformers (CT).

  The current detection circuit 11 calculates the charging current amount for the capacitor 4 from the current amounts detected through the current sensors 8a, 8b, to 8n, and the load RL via the output terminals 3a and 3b during steady operation of the converter. The amount of current supplied to is obtained and monitored. The inter-contact voltage detection circuit 12 detects the voltage applied to the relay contacts of the circuit breakers 6a, 6b, and 6n by detecting the voltage at the output side terminals of the circuit breakers (relays) 6a, 6b, and 6n. Detected. Then, the contact contact resistance calculation circuit 13 determines the relay of each of the circuit breakers 6a, 6b, .about.6n from the energizing current amount of each of the circuit breakers 6a, 6b, .about.6n and the voltage between the relay contacts detected as described above. The contact resistance of the contact is obtained, and for example, it is monitored whether or not it is equal to or less than a preset resistance value. When a circuit breaker with increased contact contact resistance is detected, the alarm display circuit 14 is driven as an “absence of abnormality occurrence” to notify that fact.

  Further, the output voltage monitoring circuit 15 monitors the charging voltage of the capacitor 4 and thus the output voltage between the output terminals 3a and 3b, and also monitors the charging time constant of the capacitor 4 when the power is turned on. Incidentally, the charging time constant of the capacitor 4 is measured as an elapsed time from when the power source of the converter is turned on until the charging voltage of the capacitor 4 reaches a preset voltage. From the charging time constant of the capacitor 4 thus measured, resistance value deterioration of the current limiting resistors 5a, 5b, .about.5n, generally short-circuiting or short-circuiting (opening) due to seizure is detected, and the current is detected. It is detected that the inrush current suppressing function via the limiting resistors 5a, 5b, to 5n has deteriorated.

  Even if the specific current limiting resistor is deteriorated in this way, the function of suppressing the inrush current by another current limiting resistor works, so that a large inrush current does not occur suddenly. However, when any one of the current limiting resistors 5a, 5b, .about.5n is detected, it is preferable to perform maintenance such as stopping the start of the converter and replacing the current limiting resistor at that time. Further, as described above, it is desirable to promptly prompt maintenance when a malfunction of any of the circuit breakers 6a, 6b, to 6n is detected.

  As described above, in the converter according to the present invention, a plurality of circuit breakers 6a, 6b, .about.6n having a small size and a low current capacity are used in parallel to prevent the occurrence of an inrush current when the power is turned on. Therefore, the operation reliability can be sufficiently enhanced as compared with the case where a large-sized and large current capacity circuit breaker is used. In addition, since the converter is operated while monitoring the contact contact resistance of each of the circuit breakers 6a, 6b, .about.6n, when a contact failure occurs in a certain circuit breaker, the failure occurs before the converter system is brought down. Can be dealt with promptly. In addition, even if a contact breaker occurs in a certain circuit breaker, the entire function of the converter is not impaired by this, so that it is possible to cope with the failure while minimizing the influence on the load RL. An enormous effect can be achieved.

  In addition, circuit breakers (relays) with a small current capacity with an allowable current capacity of about 10A are many types compared to 100A class special circuit breakers (relays), and are generally inexpensive and compact as general-purpose products. Although it is necessary to use a plurality of devices in parallel as described above, it is suitable for incorporation in this type of high power converter. Furthermore, by increasing the number of circuit breakers (relays) connected in parallel, a great practical effect is achieved, such as a circuit design with a margin in power supply capacity.

  The present invention is not limited to the embodiment described above. For example, as shown in FIG. 2, the same configuration can be applied to the case where the current limiting resistor 5 and the circuit breaker 6 are provided in the previous stage (input side) of the diode bridge (rectifier). In FIG. 2, the current sensor or the like is omitted, but the current flowing through each of the plurality of current limiting resistors 5a to 5n is monitored and each of the circuit breakers 6a, 6b,. What is necessary is just to monitor 6n contact contact resistance and / or the said current limiting resistance. In this case, it is desirable to provide a diode bridge corresponding to each of the plurality of current limiting resistors 5 and the circuit breaker 6. Further, the number of inrush current prevention circuits composed of the current limiting resistor 5 and the circuit breaker 6 can be set with a predetermined margin in accordance with the rated current capacity required for the converter and the allowable current capacity of the circuit breaker 6. It is enough. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The schematic block diagram of the converter which concerns on one Embodiment of this invention. The principal part schematic block diagram of the converter which concerns on another embodiment of this invention.

Explanation of symbols

1 Diode bridge (rectifier)
3a, 3b Output terminal 4 Capacitor 5a, 5b, ~ 5n Current limiting resistor 6a, 6b, ~ 6n Breaker (relay)
7 Relay drive circuit 8a, 8b, -8n Current sensor 11 Current detection circuit 12 Contact voltage detection circuit 13 Contact contact resistance calculation circuit 14 Alarm display circuit 15 Output voltage monitoring circuit RL Load

Claims (7)

A rectifier that rectifies AC power and converts it into DC,
A capacitor connected in parallel to the output terminal of the DC power and storing the DC power rectified by the rectifier;
A current limiting resistor provided on the input side or output side of the rectifier to limit the power supplied to the capacitor;
It consists of a plurality of circuit breakers with a smaller current capacity than the rated output current capacity, and is provided in parallel so that the sum of the current capacities exceeds the rated output current capacity. A circuit breaker for short-circuiting the current limiting resistor;
A converter comprising: a contact means for monitoring the contact contact resistance of each of the circuit breakers and / or the current limiting resistance.   The circuit breaker is driven by the driving means after the capacitor is charged through the current limiting resistor when the power is turned on, and is controlled to be cut off while the charged voltage of the capacitor is maintained when the power is shut off. The converter according to claim 1, wherein   The converter according to claim 2, wherein the circuit breaker driving means monitors the charging voltage of the capacitor to control conduction / breaking of the circuit breakers.   The circuit breaker driving means causes the circuit breakers to conduct after a predetermined time has elapsed since the power was turned on, and when the power was interrupted, the circuit breakers were operated after the predetermined time had elapsed since the power supply to the load connected to the output terminal was stopped. The converter according to claim 2, wherein the converter is cut off.   The converter according to claim 1, wherein the current limiting resistor is connected to each of the circuit breakers in parallel. The converter of claim 1,
Furthermore, the converter provided with the current sensor which measures the electric current amount which flows through the said circuit breaker or the said current limiting resistance. The converter of claim 1,
A converter comprising a function of diagnosing a fault of the current limiting resistor by monitoring a charging time constant and / or a charging current for the capacitor.

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