Common Mode Toroidal Inductor 47UH

Common Mode Toroidal Inductor 47UH

If the tester is cautious, the saturation characteristics of a common mode choke can be tested with a device similar to the one in MIL-STD-461. The application of this principle is as follows: Two current probes are used in the test, the low frequency probe monitors the line current, and the high frequency probe only measures the common mode emission current. The line current monitor acts as the trigger source. However, one of the pitfalls of using current probes is that differential mode current attenuation is a function of the symmetry of the winding wires in the tube core. If the winding layout is carefully and reasonably arranged, the differential mode current attenuation of about 30dB can be obtained. Even if this attenuation value is reached, the measured differential mode component may exceed the expected common mode component value. Two techniques can be used to solve this problem: First, a high-order high-pass filter with a 6kHz turning frequency is connected to the oscilloscope in series (note that the terminal impedance of 50 is matched). Second, a wire is connected between each 10μF capacitor and the power bus. To measure common-mode radiation, the current probe should be clamped near these wires carrying minimal line currents.

For a quick and superficial introduction to the role of a common-mode choke, consider the following statement: "The magnetic fields on both sides of the common mode choke core cancel each other out, so there is no magnetic flux to saturate the core." Although this argument concretized the intuitive account of the action of a common-mode choke, it was not in essence.