KR20010070924A - Surge protector for power source - Google Patents

Abstract

PURPOSE: A surge protector for a power supply is provided which increases resistance for surge to reduce surge current using characteristics of surge of high voltage, large current and impulse, to stabilize power supply voltage below safety voltage. CONSTITUTION: A surge protecting circuit is constructed in a manner that coils(L1,L2) wound by the same number of times of winding are combined with each other using a low frequency iron core to compose a reactor, and varistors(V1,V5) are connected in crossed form between line terminals(T1,T2) and device terminals(T3,T4) to cancel and disperse surge current. The reactor eliminates reactance for power supply current but makes large reactance for surge current.

Description

Surge protector for power source

The present invention relates to a surge protection device, and prevents accidents caused by a lightning strike or a ground fault of a transmission and distribution line, an arc or induced electric power, or an impact voltage caused by an increase in the ground potential when lightning strikes a nearby structure (such as a steel tower) or a lightning rod. This is to prevent secondary damage of the equipment using AC power as well as the communication equipment connected to such equipment.

Conventional surge protection device absorbs and discharges the entire amount of surge current by using discharge tube, varistor, etc. in order to reduce the device's safety voltage when the impact voltage is inflowed due to lightning, ground, etc. to prevent damage. There is no problem in weak surge as a method of reducing the voltage. However, when the surge current is large, there is a limit in the capacity of the discharge element itself because the voltage rises across the element and burns out in proportion to the current. There is a technical problem due to the impedance of the wire specification and the earth wire surge.

Therefore, there is a defect that the performance depends on the installation technology and the installation environment as well as the manufacture of the protective device. As a large current flows in a moment to discharge to the earth written between the line and the ground, the rise of the ground potential is inevitable. Therefore, the potential rises in proportion to the discharge current, thereby causing a second damage.

For example, even though the surge introduced into the power source is completely protected on the power supply side, the grounding resistance and the whole device become the same potential as the surge voltage due to the grounding resistance, so this current flows to the outside through the conductor such as the communication line. Therefore, not only the damage of the communication circuit but also the short distance devices connected by the wires are damaged. In addition, there is a case where the ground potential rises due to lightning strikes and ground faults of nearby structures such as lightning rods.For example, when lightning strike resistance is 2Ω when lightning strike occurs, lightning current 3,000A flows, The potential of the telecommunication equipment has risen to 6,000V.

Therefore, this current flows 3,000A through the electric and communication lines connected to the outside of the device, so this damage is primarily caused by the weakness of the connected part of the device. Even though it is protected by, the current flows through the line, causing secondary damage to other facilities located in close proximity to the conductor.

Therefore, as in the prior art, all of the surge current is discharged through the varistor, which is a problem even in the limit of capacity specification, installation environment condition, and secondary disaster.

The desired surge protector requires a protection device that eliminates only the surge current regardless of the intended supply current and minimizes the discharge current so that there is no second damage caused by the rise of the ground potential.

The present invention has been made in view of the above-mentioned problems, using the characteristics of high voltage, high current, and impulse of a very short time to increase the comprehensive resistance to surge without disturbing the flow of power to the device to be protected. It is a method of stabilizing below the safety voltage after decreasing.

A method of canceling and dispersing the current flowing through the coils L1 and L2 applied between the lines and the current flowing through the varistors V1 and V5 and reducing the surge current by the reactance value of the surge coil applied between the line and the ground. When you configure the circuit of

First, low cost and low capacity varistors enable stable operation and long life.

Second, it is possible to prevent the rise of the ground potential, so that it does not cause secondary damage to other facilities in the short distance connected by wires.

Third, stable operation is possible even if the ground potential rises due to surrounding factors, and a surge protection circuit that does not cause secondary damage is provided.

1 is a basic circuit diagram for explaining the present invention,

2 is a perspective view for explaining the present invention.

<Description of Major Codes in Drawings>

T1, T2: Line input terminal.

T3, T4: Output terminal for device.

G: ground terminal.

L1, L2: control coil.

V1, V2, V3, V4, V5: Two-way varistor.

C1, C2, C3: condenser.

The surge protection circuit of the present invention for achieving the above object is a coil (L1, L2) that does not flow the surge frequency well, the varistor (V1, V5) and the controlled surge voltage to cancel the current flowing through the coil It is composed of varistors (V2, V3, V4), and condensers (C1, C2, C3) to stabilize below a safety voltage, and the construction and operation of the basic circuit of the present invention will be described in detail with reference to the accompanying drawings.

1) The common mode low frequency choke coil is combined with the low frequency iron core core so that the circuit terminals T1 and T2 are in phase with the two coils wound with the same number of times to resist the flow of surge current.

When the low-frequency AC power flows from the line side to the device side, the current flowing from T1 to T3 and the current flowing from T2 to T4 have the same amount of reverse phase current, so the low frequency iron core core cancels the magnetic flux of the coils L1 and L2. Since the reactance of the coil is 0Ω, the flow of AC power is only affected by the DC resistance of the coil. In other words, the reactance value of the AC power supply is lost by the low frequency core.

2) It is controlled by the combined value of the reactance of two coils (L1, L2) and varistors (V1, V5) applied between the line and ground.The coil's current phase is delayed by 90 °, so the varistor (V1 , The current flowing through V5) and the current flowing through the coils L1 and L2 are distributed, and the instantaneous value of the surge current is decreased. The surge voltage corresponding to this current is applied between the circuit side and the device side of the circuit, and the attenuated current is the varistor (V3). , V4) and capacitors C2 and C3 flow to ground (G).

3) When the low-frequency power current flows through the coils L1 and L2, the reactance becomes 0 같이 as described above. However, when the surge current, which is a high-frequency impulse with a sharp waveform, flows, the low-frequency iron core core has a comprehensive magnetic characteristic such as magnetoresistance. Due to the fact that the core does not play its role, in the large surge current flow, two coils L1 and L2 operate respectively, and most of the surge voltages are applied to both ends of the coil.

4) This voltage crosses the voltage canceling varistors V1 and V5 so that the current flowing through the coils L1 and L2 and the current flowing through the varistor cancel each other. Since the current flows 90 ° late, the current flows in a distributed manner.

The principle of offsetting is explained in detail. When the surge resistance value of the coils L1 and L2 and the surge resistance values of the varistors V1 and V5 are the same, when the surge flows into the line-side terminals T1 and T2, the voltage of T3 and T4 becomes It should be 0V. However, due to the characteristics of the material and the phase relationship, the voltage is not 0V, but the surge voltage across the terminals T3 and T4 is mostly reduced, so that the surge current flowing through the varistor V2 and the capacitor C1 is extremely weak. A stable voltage on the side can be expected. The varistors V1 and V5 also have the purpose of preventing overvoltage rise between both ends of the line-side terminals T1 and T2 and the ground G to prevent burnout or fire due to an arc.

5) C1, V2 stabilizes the output voltage by absorbing the residual surge and the leakage current leaked between the coil windings and the varistors (V1, V5). , And V3, V4 cause the surge applied between line and ground to flow to ground to reduce the reduced surge current through V1, L1 or L2, V5 below the safety voltage.

The surge protection circuit of the present invention configured and operated as described above reduces the discharge current of the surge by only resisting the surge current without loss of normal power supply, while using a low-cost varistor, which is inexpensive, as well as safer protection from surge, and rise of the ground potential. It is a useful invention that prevents secondary damage while preventing the secondary damage even when the earthquake rises due to external factors.

Claims (2)

The coils L1 and L2 wound in the same number of times are combined with a low frequency iron core core to form a reactor such that the reactance is not applied to the power supply current intended for use and the reactance is largely applied to the surge current, and the coils L1 and L2. A surge protection circuit characterized by canceling and distributing surge current by connecting the varistors (V1, V5) to the line-side terminals (T1, T2) and the device-side terminals (T3, T4) in a cross shape. 2. The surge current controlled from the coils L1 and L2 and the varistors V1 and V5 is secured by connecting the varistor V2 and the capacitor C1 in parallel with the terminals to the device-side terminals T3 and T4. It stabilizes below voltage and connects varistor (V3), condenser (C2), varistor (V4) and condenser (C3) to ground terminal (G) from the terminal (T3, T4) to ground terminal (G) side, respectively. So that the controlled surge current between the device side terminals (T3, T4) and ground (G) is stabilized below a safety voltage.