Wednesday, December 29, 2010

【 Weak current College 】 isolation transformers, filter circuit, SPD of concepts, principles and compare 】


1. basic concepts

Isolation transformer: isolation original side and adverse side of the join, to achieve stable voltage, isolation, harmonic and protection of personal safety. In the power and signal transmission with isolating transformer can introduce lightning high effective restrictions function, this is because when the powerful lightning wave input transformer, voltage due to lightning than normal high voltage transformers and many times, making the excitation of magnetic flux density is greater than the core allows for maximum magnetic BM, transformer core saturation, transformer magnetic-electric transform temporarily fail, lightning high voltage cannot be transferred to the side of the transformer, thereby protecting electrical devices.

Filtering circuit: low-frequency high-frequency or resistance is low-frequency high-frequency resistance. In some power lines and high-frequency circuit ingenious design can greatly reduce the energy surge voltage.

SPD: parallel to the line, when the line voltage reaches a critical value of SPD action, the action through the SPD, the lines on the ground to form an instant on-State that limits the transient overvoltage or shunt surge current devices.

Working principle and characteristics

1, isolation Transformers:

Isolation transformer anti-surge of equivalent circuit

1.1 grounding method: side coils electrostatic shielding ground (see Figure 1 for a side EI) in power switch box of 「introduction ground bus 」 (Note: the ground bus is connected in total power neutral and building infrastructure reinforced), must be from the power supply ground bus pulled from the ground up, the power supply from the power outlet of 「introduction neutral 」 received. The remaining ground leads, including the secondary winding of electrostatic shielding ground, shell core Earth grounding, and one with the secondary coil cover ground between the magnetic field, the add-in on a private ground bus, grounding resistance values are best able to control the following effects in 10 Ω.

1.2 characteristics: isolating transformer anti surge voltage level of ability and depends on the value of the pressure resistance, insulation level, and other technical parameters. In General, a phenomenon Thunder instantaneously generate tens or even hundreds of thousands of volts v overvoltage, such excess voltage isolation transformer is the bear. And, a few KHZ within-frequency impulse is not protection.

2. filter circuit

2.1 characteristics: for more than 10-high-frequency common mode 100KHz miscellaneous spread differential-mode clutter to good effect, while suppression can reduce pulse of sharp. As long as the clever calculation arranged capacitor and choke of values, and that the impact of timber (capacitor and resistance to flow ring cores of material) you can reach a very good filter effect, the filter contains three anti-flow ring (Figure 3-common mode choke coil winding diagram).

3, SPD

Surge protector for schematic diagram

3.1 characteristics: absorption of surge capacity can be large, reaction speed quickly, you can prevent various spectrum of surge voltage of invasion; however anti-surge reliability can lower, when after the SPD damage may have an impact on the system to work properly, and the device selection need some experience.

3. use compare

Isolating transformer is often used to give important equipment/computer lab supply, reduce line surge voltage, can be used as power system C/D-level protection. It can also be used for the signal system's anti-surge design circuit, and SPD tie. At the same time have isolated power supply with the load.

Filter circuits are often used for high-grade

Isolating transformer, filter circuit, SPD

1. basic concepts

Isolation transformer: isolation original side and adverse side of the join, to achieve stable voltage, isolation, harmonic and protection of personal safety. In the power and signal transmission with isolating transformer can introduce lightning high effective restrictions function, this is because when the powerful lightning wave input transformer, voltage due to lightning than normal high voltage transformers and many times, making the excitation of magnetic flux density is greater than the core allows for maximum magnetic BM, transformer core saturation, transformer magnetic-electric transform temporarily fail, lightning high voltage cannot be transferred to the side of the transformer, thereby protecting electrical devices.

Filtering circuit: low-frequency high-frequency or resistance is low-frequency high-frequency resistance. In some power lines and high-frequency circuit ingenious design can greatly reduce the energy surge voltage.

SPD: parallel to the line, when the line voltage reaches a critical value of SPD action, the action through the SPD, the lines on the ground to form an instant on-State that limits the transient overvoltage or shunt surge current devices.

Working principle and characteristics

1, isolation Transformers:

Isolation transformer anti-surge of equivalent circuit

1.1 grounding method: side coils electrostatic shielding ground (see Figure 1 for a side EI) in power switch box of 「introduction ground bus 」 (Note: the ground bus is connected in total power neutral and building infrastructure reinforced), must be from the power supply ground bus pulled from the ground up, the power supply from the power outlet of 「introduction neutral 」 received. The remaining ground leads, including the secondary winding of electrostatic shielding ground, shell core Earth grounding, and one with the secondary coil cover ground between the magnetic field, the add-in on a private ground bus, grounding resistance values are best able to control the following effects in 10 Ω.

1.2 characteristics: isolating transformer anti surge voltage level ofability and depends on the value of the pressure resistance, insulation level, and other technical parameters. In General, a phenomenon Thunder instantaneously generate tens or even hundreds of thousands of volts v overvoltage, such excess voltage isolation transformer is the bear. And, a few KHZ within-frequency impulse is not protection.

2And filter circuit

2.1 characteristics: for more than 10-high-frequency common mode 100KHz miscellaneous spread differential-mode clutter to good effect, while suppression can reduce pulse of sharp. As long as the clever calculation arranged capacitor and choke of values, and that the impact of timber (capacitor and resistance to flow ring cores of material) you can reach a very good filter effect, the filter contains three anti-flow ring (Figure 3-common mode choke coil winding diagram).

3, SPD

Surge protector for schematic diagram

3.1 characteristics: absorption of surge capacity can be large, reaction speed quickly, you can prevent various spectrum of surge voltage of invasion; however anti-surge reliability can lower, when after the SPD damage may have an impact on the system to work properly, and the device selection need some experience.

3. use compare

Isolating transformer is often used to give important equipment/computer lab supply, reduce line surge voltage, can be used as power system C/D-level protection. It can also be used for the signal system's anti-surge design circuit, and SPD tie. At the same time have isolated power supply with the load.

Filter circuits are often used for high-grade lighting Sockets/UPS design, reduced from line surge voltage, can be used as power system C/D-level protection. It can also be used for the signal system's anti-surge design circuit, and SPD tie. At the same time reducing the role of surge steepness.

Surge protector can be used for protection from power lines and signal line, the antenna and cable lines, line surge voltage, B, C and D would not be appropriate for all levels of protection, integrated in the system. At the same time with the flow, inhibits voltages lower characteristics.

Isolating transformer, filter circuit, SPD should be used in combination, as shown in Figure 5, the best anti surge.

~ Jack/UPS design, reduced from line surge voltage, can be used as power system C/D-level protection. It can also be used for the signal system's anti-surge design circuit, and SPD tie. At the same time reducing the role of surge steepness.

Surge protector can be used for protection from power lines and signal line, the antenna and cable lines, line surge voltage, B, C and D would not be appropriate for all levels of protection, integrated in the system. At the same time with the flow, inhibits voltages lower characteristics.

Isolating transformer, filter circuit, SPD should be used in combination, as shown in Figure 5, the best anti surge.

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