FAQ
Frequently Asked Questions
What certifications does VOOHU Electronics hold?
VOOHU Electronics holds ISO 9001:2015 international quality management system certification, ISO 14001:2015 environmental certification, RoHS environmental certification, REACH certification, and CE certification.
How can I quickly find the right product for my project?
On the VOOHU official website, you can quickly select products online by product category or by parameter filters (such as data rate, package, operating temperature, current, etc.). You can also visit the "ソリューション" page to view recommended solutions matching your needs. For further support, contact our technical support team directly with your application scenario, and we will recommend the optimal solution for you.
What is a common mode choke for power line, and what does it do?
A power line common mode choke (CMC) consists of a pair (or multiple pairs) of coils wound on the same magnetic core, connected in series with the power input/output lines. It presents high impedance to common mode noise while remaining nearly "transparent" to the differential mode operating current. It is mainly used to suppress common mode EMI on power lines, helping equipment pass conducted emission (CE) and other EMC certifications.
What are the key parameters when selecting a power line common mode choke?
Core parameters include common mode inductance, rated current, DC resistance (DCR), rated voltage and withstand voltage. As a general rule, the rated current should exceed the maximum operating current of the line with some margin, while the inductance is determined by the noise frequency band to be suppressed - choose high inductance for low-frequency noise, or lower inductance combined with filter capacitors for high-frequency noise.
Does higher inductance always mean better filtering?
Not necessarily. Higher inductance means more turns, which increases the parasitic capacitance between windings and lowers the self-resonant frequency (SRF). Above the SRF, the impedance becomes capacitive and high-frequency suppression actually deteriorates, while DCR and temperature rise increase. The correct approach is to first identify the dominant noise frequency, then select the part with the highest impedance in that band; if necessary, cascade two stages with high and low inductance to cover a wide frequency range.
How do you evaluate saturation and temperature rise of a common mode choke under high current?
In theory, the differential mode magnetic flux in a common mode choke cancels out, so the core does not saturate easily. In practice, however, leakage inductance corresponds to a differential mode component, and high current can still cause local core saturation, leading to inductance drop and loss of noise suppression. When evaluating, pay attention to the manufacturer's inductance derating curve at rated current and the temperature rise data (usually limited to a 40 K rise); in high-temperature environments, also consider derating with respect to the core's Curie temperature.
