I made a few toroid inductors and i learned that the color coded toroid type (yellow white, yellow green etc.) has relation to frequency. Also a person told me that copper thickness has effect too.

By my tries, if wind same turns in same two toroids with different copper thicknesses they have exactly the same inductance. I do not know about freq. response.

1) Does the copper thickness have any effect on the frequency. If so how?

2)In addition to question 2 should i only consider copper thickness in the case of how many amps the inductor will handle.

3)How the toroid type affecting the frequency. If i have a toroid that has a freq range around 10MHz to 50MHz, can't i use it for filtering my dc power line spikes with LC filter in lower frequencies.

  • \$\begingroup\$ What are your design specs? DC max, Noise BW, Impedance @ f , load Capacitance and ESR? More copper reduces losses with same n turns. \$\endgroup\$ – Sunnyskyguy EE75 Nov 11 '17 at 19:44
  • \$\begingroup\$ 3rd question can be treated separately since i wonder if copper thickness and toroid has any affect on frequency. On the other hand the LC filter is just LC low pass filter on the VCC GND line of the lipo to prevent voltage spikes happening on the brushless motor switches. If no LC filter, 16V DC goes to 40V and with LC it stay more the same. \$\endgroup\$ – ssdflash01 Nov 11 '17 at 20:24

1) The copper thickness does not affect the inductance. It will have an effect on the DC resistance, due to its cross section, and on the RF resistance, due to its surface area.

2) There are at least two limitations on maximum inductor current, the heating effect in the copper, and the maximum field that the core will handle. Above a certain field, the permeability of the core plummets as it goes into saturation. This means the inductance drops by one or even several orders of magnitude.

3) If you use a toroid rated for 50MHz to do low frequency filtering, it will work, but it will not have as high a permeability as one rated (for example) only 1MHz.

  • \$\begingroup\$ Hi, can i ask one more thing. When we have low permeability in lower frequency (if i use high freq toroid), will this decrease the inductance so the filtering characteristic will change. Is this correct. \$\endgroup\$ – ssdflash01 Nov 11 '17 at 21:15
  • \$\begingroup\$ If you have two toroids that are the same size and shape, and wound with the same number of turns, then the inductance will vary as the permeability. As the inductance also varies as the number of turns squared, you can compensate to some extent, although increasing the number of turns will increase the resistance, and decrease the resonant frequency (useful frequency range) of the inductor. \$\endgroup\$ – Neil_UK Nov 12 '17 at 6:40

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