High Voltage Common Mode Choke

Figure 9 4b shows the physical form of an actual choke.

High voltage common mode choke.

The common mode voltage noise terminal voltage was measured for one line with respect to ground using an artificial mains network amn. Impedance of an inductor is usually specified as a minimum in ohms at the desired frequency. 1250 vrms one minute isolation between windings. The common mode currents i1 and i2 flowing in the same direction through each of the choke windings creates equal and in phase magnetic fields which add together.

Common mode noise will be neutralized when it passes through a commom mode choke. Current ratings as high as 15 amps. The we cmbnc is a vde certified series of common mode chokes with a highly permeable nanocrystalline core material. A typical common mode choke configuration.

Dielectric withstanding voltage as high as 4 750 volts to comply with international safety standards. Low profile and high voltage ratings can also be realized by the common mode chokes of the we cmb family. Our extensive inductance values as low as 0 075 uh to 142 mh and low leakage inductance common mode choke designs gives our customers a wide variety to choose from. Figure 9 4 shows a common mode choke that is useful for emi up to about 30 mhz or so.

Highest common mode impedance over the widest frequency range. Common mode choke inductor design the common mode choke is one of the many types of inductors. Figure 9 4a shows the schematic symbol. Ul1446 class b 130 c insulation system ul file e83628.

Despite the small size it delivers oustanding broadband attenuation performance high rated currents and low dc resistance values. In this video we explain how a common mode choke works and how the leakage inductance of a common mode choke can help us filter differential mode noise. Inductance values up to 125 mh. Only current electro magnetic flux through its coupling ferrite core are cancelled out in the common mode choke 1 1 current transformer.

This results in the choke presenting a high impedance to the common mode signal. There is no heating or power dissipation since its only current and the voltage across the winding is zero thus the power is zero. This is done either by paralleling the wires or by twisting them together prior to winding. The turns of the common mode choke are wound in the bifilar manner i e they are wound together.

In general common mode chokes may introduce signal integrity issues and other unexpected results in the can network. When the noise terminal voltage is measured under the initial conditions we can see that a noise spectrum occurs at multiples frequency is converted to n multiples of the 500 khz switching frequency.