Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,688
My inverter came prewired with 4/0 cable from the + and - bars to the inverter + and - connections. Came with two round magnets to go over each 4/0 cable I believe. I'm guessing they didn't install them because they would bounce around during shipping.
Is one of those ferrites big enough to fit over two 4/0 cables at once?
Or can it only fit over a single cable?
Here's an example of a common-mode choke - two wires wrapped around one ferrite core:
744821240 Würth Elektronik | Filters | DigiKey
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So long as current goes through the two windings in opposite directions, it cancels. Only common-mode noise sees inductance from this choke and is attenuated.
If only one winding is used, or if current is run through the two windings in same direction, at just a few percent of normal current flow the core becomes magnetically saturated, and any further current (e.g. high frequency noise) doesn't increase magnetization so doesn't see any impedance, is not attenuated.
Most vendors didn't publish specs for differential mode use. One did, showing it saturated at a couple percent of what it could carry wired for common mode.
I used a network analyzer to measure a sample of one a colleague was using in a design, and biased the second winding with DC current. I confirmed the very low saturation level.
Go ahead and install them, but if each goes on a single wire I doubt they accomplish anything.