JPH0322823A - Rush current suppressor for cvcf - Google Patents

Abstract

PURPOSE:To limit rush current perfectly by shortcircuiting current limiting impedances, connected to the source side of a transformer in a constant voltage constant frequency power supply provided with the transformer at the input side, upon elapse of transient variation of flux in the transformer. CONSTITUTION:An AC power source 1 is connected through an NFB 2 and a contactor 14 to the primary of a transformer 3. A thyristor bridge 4 is connected to the secondary of the transformer 3 in order to feed a load (not shown) with constant voltage constant frequency power. Current limiting impedances 13a-13c are connected between input and output of the contactor 14 which is opened previously. Upon throw-in of the NFB 2, current is fed at first to the primary of the transformer 3 through the current limit impedances 13a-13c. Upon elapse of transient variation of flux in the transformer 3, output from the ternary winding of the transformer 3 is stabilized and the coil 15 in the contactor functions to shortcircuit the contactor 14 thus shortcircuiting the current limiting impedances 13a-13c. By such arrangement, rush current is limited perfectly resulting in reduction of the size and the weight.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention is directed to a CVCF (constant voltage constant frequency power supply device) installed in a place with relatively high power supply impedance, such as a building or office. ) and UPS (uninterruptible power supply), etc.

(Prior Art) An example of a conventional UPS circuit is shown in FIG. AC'Fia
From l to NFB2 (no-fuse breaker), the voltage is optimized and multi-phased with a transformer, the DC voltage is adjusted with a silice bridge 4, smoothed with a reactor 5 and a capacitor 6, and the battery 7 to floating charge. The inverter bridge 8 converts the DC voltage to AC, the transformer 9 performs voltage conversion and insulation, and the capacitor lOa . fob. After removing high frequency components by the filter effect of lOc, power is supplied to the load via NFBII.

UPSs of medium and small capacity are generally installed in buildings and offices, and other OA equipment 12 is often connected in parallel to the AC power supply 1.

(Problem to be solved by the invention) AC power supplies in buildings and offices generally have long wiring lengths. There are many places with high impedance. Therefore, when the NFB 2 is turned on, if the inrush current of the transformer 3 is large, the power supply voltage of OA equipment (such as a personal computer) connected in parallel to the power supply 1 will momentarily drop and malfunction. To prevent this, the inrush current of transformer 3 should be 500 to 500% of the rated current.
It was necessary to limit it to B00% or less. For this reason, conventionally, the magnetic flux density of the transformer was set to 60 to 70
%, the transformer was large in both weight and size. This made the CVCF large and heavy, which was a big problem in places like Japan where the price per unit area of a building is extremely high. In addition, since the price of CVCF is high, smaller, lighter, and more economical
Furthermore, a CVCF with an input current of 100% to 200% or less has been desired.

[Structure of the invention]

(Means for solving the problem) A current limiting impedance is connected in series to the primary side of the input transformer of the CVCF, and a switch is driven by the voltage of the secondary or tertiary winding of the transformer to limit the current. Configure to short impedance.

(Function) When the power is turned on, even if the transformer 3 is saturated, the power supply current is limited by the current limiting impedance. During the period when the transformer is saturated, the secondary or tertiary winding of the transformer has sufficient voltage. does not occur, the voltage applied to the switch coil is low, the magnetic flux of the transformer stabilizes, and the transformer becomes unsaturated, the switch coil voltage reaches its rated value, the switch contacts close, and current is limited. It operates by shorting the impedance and then delivering power from the transformer to the load.

(Example) FIG. 1 shows an example of the present invention. Parts that are the same as those in FIG. 5 are designated by the same numerals, and description thereof will be omitted.

On the load side of NFB2, current limiting resistors 13a, 13b,
13c to the primary side of the transformer 3, and the secondary side of the transformer 3 is connected to the Cyrisk bridge 4 to supply power to the inverter bridge. A coil l5 of a contactor is connected to the tertiary winding of the transformer 3, and the current limiting resistors 13a, 13b . 13c is shorted. After the contact 14 is closed, the silice bridge 4 is controlled to supply power from the transformer 3 to the load side.

Figure 2(a) shows the B-H curve of the transformer core.

Since the phase at which the power is turned on is unstable, when the power is turned on with a polarity voltage that increases the magnetic flux density again at the point of residual magnetic flux density B1, the iron core is saturated and the human power current i increases rapidly, and the second
As shown in Figure (b), an inrush current of about 10 to 15 times the rated current flows.

In the embodiment shown in FIG. 1, even if the transformer 3 is saturated after the power is turned on by the current limiting resistors 13a to 13c, the current j is 100 to 20
Limited to 0% or less. Therefore, as shown in Fig. 3, the AC voltage e1 has a solid line waveform immediately after the power-on time to, but when the transformer 3 is saturated, the tertiary winding voltage e2 of the transformer becomes like a broken line and the voltage value decreases. So the contact point 14 of the contactor
The contactor will not close or the operation delay will be large and the transformer force (when released from saturation, there will be a contactor operation delay (generally 40 to 60
as) Contact l4 closes at t1. At this time, the input power supply i increases slightly, but the magnetic flux of the iron core has passed the transient state, so the rate of increase is extremely small.

As explained above, according to this embodiment, the inrush current of the transformer is limited by the current limiting resistor, the current limiting resistor is inserted during the period when the saturation of the transformer is large, and when the saturation of the transformer is reduced, the Since the current limiting resistor is short-circuited, the input current when turning on is 100%.
Since a current limiting resistor is inserted while the transformer is saturated, the magnetic flux density of the transformer core can be utilized to the maximum, and the transformer can be reduced by about 30 to 40%. , smaller size, and lighter weight. In addition, AC power supply
It is possible to make the beadance higher than before, and the CV
It is possible to reduce the size, weight, and cost of the CF, resulting in extremely economical CVCF power supply equipment.

Another embodiment according to the invention is shown in FIG.

The circuit in figure (a) is for the case where the coil l5 of the contactor is taken from the primary side of the transformer 3, and during the period when the transformer is saturated, a voltage reduced by the current limiting resistor is applied to the coil l5. Ru.

In the figure (b), when the capacity of the contactor is large, the delay in operation of the contactor is large, so even if the contactor is connected to the power supply side, the purpose can be sufficiently achieved.

FIG. 4(c) is an example in which the on-delay time of the contactor is lengthened via the time relay 25 when the contactor operates too quickly in the circuit of FIG. 2(b).

Furthermore, the same effect can be achieved by removing the coil 15 of the contactor from the load side of the transformer 3, as shown in FIG. 3(d).

Incidentally, the cyrisk bridge 4 in FIG.
Since the ignition is controlled after the is closed, the starting circuit is interlocked and controlled by the contact linked to the contact 14.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to limit the inrush current of the transformer to 100% or more, and the bus capacity of the power supply can be designed to be small without affecting other equipment connected to the AC power supply. At the same time, since the magnetic flux density of the transformer can be utilized to the maximum, the transformer becomes smaller, making it possible to construct a small, economical, and lightweight CVCF, which reduces the input current of the CVCF, making it extremely economical and stable as a power supply facility. equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a diagram showing one embodiment of the present invention, Figs. 2 and 3 are diagrams explaining its operation, Fig. 4 is a diagram of another embodiment of the present invention, and Fig. 5 is a configuration diagram of a conventional CVCF device. be. 1... AC power R 2, 11... NFB3...
・Transformer W4...Sirisk Bridge 5...Reactor 6...Capacitor 7...Battery 8.
...Inverter bridge 9...Transformer 10.
... Capacitor l2... OA equipment 13... Current limiting resistor l4... Contact of contactor l5... Coil of contactor 25... Time relay

Claims (2)

[Claims] (1) In a CVCF (constant voltage constant frequency) power supply device equipped with a transformer on the input side, an AC voltage is applied to the transformer via a current limiting impedance, and after the transient state of magnetic flux change of the transformer has passed, A CVCF input current suppressing device, characterized in that the current limiting impedance is short-circuited. (2) In the item described in paragraph 1 above, 2 of the transformer
A CVCF closing current suppressing device characterized in that a coil of a switch is excited by a voltage of a secondary winding or a tertiary winding, and the current limiting impedance is short-circuited by a contact of the switch.