| Electronics > Beginners |
| Choke differences |
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| Momchilo:
Hi, I look for chokes to smooth the leg currents of a inverter. The inductance should be ~1mH and the maximal current is 5A at 100V. I know that something like this will work: 157D But it's chunky and there are a lot more smaller chokes with similar specifications like this Kemet one. I could use both coils for the positive and negative leg instead of two big chokes. I don't think I could use the Kemet choke, it's built for another purpose, but why wouldn't it work? I know that the voltage in each leg of the inverter isn't sinusoidal. Because of the PWM control, it's more pulse-shaped. So for a very short time the current is more DC likely. That's the whole reason for this choke to get a sinusoidal current. But is that the problem why I can't use the small choke? Thanks for your help. Best regards Momchilo |
| MagicSmoker:
The Hammond choke is more suited to the job and is actually a choke (that is, an inductor expected to withstand a significant DC or low-frequency bias), whereas the Kemet part is commonly (at least in English) called a "common mode choke" and is not actually a choke at all, but a 1:1 transformer which cannot support any net DC bias, really. Common mode chokes are expected to be placed in series with the forward and return conductors of a power supply, etc., so that the magnetic flux from any "normal mode" curren (that is, it goes out on one line and comes back on the other) is cancelled out, while common mode current (that is, having the same phase/magnitude on both lines) sees an inductance that is 4x larger than the single winding inductance, providing significant filtering. For your specific application you want a choke that has a laminated silicon steel core with a "large" air gap (large being a relative term here). The Hammond part most likely fits this description, though it may not necessarily be ideal or the most cost-effective for the job. |
| capt bullshot:
The small one is a "common mode choke", used for EMC purposes. These have two windings on the same core. It's usage requires the current through one winding to return through the other winding, so the sum of currents in the core is zero for the normal operating current. The inductance in this mode is near zero. You may find some better explanations here: https://www.we-online.de/web/en/passive_components_custom_magnetics/blog_pbcm/blog_detail_electronics_in_action_61439.php https://en.wikipedia.org/wiki/Choke_(electronics) Short conclusion: Common mode chokes don't work for your purpose. |
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