JPS626825Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a surge voltage absorber, and it is based on the fact that a constant or stable ceramic varistor can be used for the purpose of absorbing surges, regardless of the primary side AC circuit voltage, depending on the transformer turns ratio. This is what we provide.

Ceramic varistors, such as ZnO varistors, have extremely good nonlinear coefficients, and for voltages below the varistor voltage (rise voltage), they almost act as insulators and do not conduct current. However, in the case of a voltage that far exceeds the varistor voltage, such as a surge voltage, the resistance value suddenly decreases to an extremely low value, allowing the surge current to flow, absorbing the energy, and constantly suppressing both ends of the varistor to a low limiting voltage. For this reason, the varistor voltage is set to a voltage slightly higher than the circuit voltage, and it is often used as a surge absorber. An example of this is shown in FIG. 1, and FIG. 2 shows the voltage-current characteristics of the varistor. In FIG. 1, 1 is a power supply line, 2 is a ceramic varistor, 3 is a protected device, and 4 is a surge voltage. In Figure 2, A is the voltage-current characteristic, B is the varistor voltage, and C is the normal commercial frequency voltage applied to the varistor.

Now, from a manufacturing perspective, ceramic varistors such as ZnO varistors are easy to make and have a range of element diameters and thicknesses with excellent characteristics, but there are cases where it may not be possible to obtain sufficient characteristics with special shapes. . For example, even if the same surge energy is absorbed, if the varistor voltage is 220V, it is okay, but if the same element diameter is 56V, it may not be able to withstand it. In this example, if the circuit voltage of the device to be protected is around 30V AC, of course it is possible to use a varistor with a voltage of 220V, but the limiting voltage would be high and it would be impractical. In addition, since one varistor voltage of 56V cannot withstand it, it is impossible to apply 56V, so parallel connection is considered, but there are restrictions on the selection of varistor voltage tolerance. FIG. 3 shows the relationship between the varistor voltage and the surge energy withstand capacity of the element at a constant element diameter.

The present invention has been devised in view of the above-mentioned points, and one embodiment thereof will be described below with reference to FIG. 4.

In FIG. 4, 5 is the primary winding of the transformer, 6 is the secondary winding of the transformer, and the number of turns is set to be greater than the number of turns of the primary winding 5. 7 is a ceramic varistor such as a ZnO varistor connected between the lines on the secondary winding 6 side, and 8 is a terminal on the primary winding 5 side connected to the protected equipment. FIG. 5 shows an example of application of FIG. 4, where 9 is a power line and 10 is a protected device.

The invention will be explained with reference to the example given above. now,
If the turns ratio of the transformer is selected to be 1:3.5, for example, the voltage on the primary winding 5 side will be AC30V, and the voltage on the secondary winding 6 side will be AC105V. In this state, if a ceramic varistor 7 with a varistor voltage of 220V is applied between the terminals on the secondary winding 6 side of the transformer, the surge energy on the primary winding 5 side will be converted by the transformer and will be transferred to the secondary winding 6.
side and is absorbed by the 220V varistor 7. As mentioned above, the varistor 7 can withstand energy sufficiently at this time. Also, 1
The limited voltage on the secondary winding 5 side can be considered to be 1/3.5 of the limited voltage on the secondary winding 6 side, and a sufficiently low limited voltage can be obtained. In addition, as an application example, it is possible to have a plurality of secondary windings 6 as shown in Fig. 6 and connect a varistor 7 between each terminal, and due to the effect of the leakage inductance of the transformer,
There are no strict restrictions on the selection of varistor voltage tolerances as there are when directly connecting them in parallel.

The present invention is constructed as described above, and it is possible to provide effective surge countermeasures in terms of surge energy and limited voltage in the field of circuit voltage, which could not be achieved with the performance of conventional varistor elements. In addition, by selecting the turns ratio of the transformer, we can create two varistors that are more advantageous in terms of manufacturing, characteristics, and economics.
It is something that can be brought to the next side as well.

[Brief explanation of the drawing]

Figure 1 is an electrical connection diagram of a conventional surge voltage absorber, Figure 2 is a voltage-current characteristic diagram of a ceramic varistor, Figure 3 is a diagram showing the relationship between varistor voltage and surge energy withstand capacity, and Figure 4. 5 is an electrical wiring diagram showing an example of the surge voltage absorber according to the present invention, FIG. 5 is an electrical wiring diagram showing an example of application of FIG. 4, and FIG. 6 is an electrical wiring diagram showing another example of the present invention. It is a connection diagram. 5...Primary winding, 6...Secondary winding, 7...Ceramic varistor, 10...Protected equipment.

Claims (1)

[Scope of utility model registration request] A ceramic varistor is inserted between the terminals on the secondary winding side of a transformer in which the number of turns on the secondary side is set to be larger than that on the primary side, and the primary winding side of the transformer is connected to the equipment to be protected. A surge voltage absorber that absorbs voltage.