Plecto
Full Member level 5
Hi. I'm using two 22uH inductors in parallel as a filter on the output of a class D amplifier. The signal is a 40kHz sine and the RMS current through the inductors is about 3A. Their parallel DC resistance is 17.8mOhm which should lead to about 3^2*0,0178=160mW of heat loss, but I'm getting something close to 2W of heat. I know that the losses increase as frequency increases due to eddy currents and hysteresis losses, but how can they be that great at only 40kHz? The switching frequency of the amplifier is 350kHz, but it's S/N ratio is about 40dB which means that the RMS current of the switching frequency is 30mA.
Inductors: https://no.farnell.com/coilcraft/mss1278-223mld/inductor-pwr-22uh-4a-20-11mhz/dp/2288504RL
Inductors: https://no.farnell.com/coilcraft/mss1278-223mld/inductor-pwr-22uh-4a-20-11mhz/dp/2288504RL