WEBVTT 00:00.000 --> 00:06.150 Welcome to this introduction to our EMC courses Electromagnetic compatibility 00:06.150 --> 00:14.169 To approach in a practical way this technique not so mysterious ... 00:14.169 --> 00:24.805 Interferers: MLI dimmer, contactor, relay ... 00:24.805 --> 00:33.344 For measurements: 4 decks: loop, contiguous, twisted and shielded 00:33.344 --> 00:39.361 Since the shielding is deliberately degraded, we will correct it 00:39.361 --> 00:45.590 We will implement: ground planes, equipotentiality, braids and armored boxes 00:45.590 --> 00:51.876 We will see shielded cable glands and other solutions 00:51.876 --> 01:00.503 Display on oscilloscope spectrum analyzer on tablet and LCD model 01:00.503 --> 01:11.891 We will also use shielded filters, sine for MLI (PWM), sector ... 01:11.891 --> 01:15.435 As well as shielded power cables 01:15.435 --> 01:24.032 Thus treated, the CEM will become a simple technique like the others! 01:24.032 --> 01:30.518 In preamble: forget the rules of direct current and 50 Hz! 01:30.518 --> 01:37.768 Because of the electronics and its high RF frequencies 01:37.768 --> 01:51.855 The masses including the structure form parasitic capacitances 01:51.855 --> 01:59.662 And in HF, the capacitors have an impedance, inversely proportional to the frequency 01:59.662 --> 02:05.371 In contrast the wires will also offer an impedance! 02:05.371 --> 02:12.729 This unit measures the inductance X! But what is it ? 02:12.729 --> 02:18.519 It is used in impedance mode Z, here it is concrete! U = Z * I! 02:18.519 --> 02:27.095 I have adjusted my device to the PWM frequency of pulse width modulation 02:27.095 --> 02:33.207 This it wound to the old to let the slack 6 Ohm! 02:33.207 --> 02:41.687 This other thread seems identical ... 02:41.687 --> 02:52.532 This thread nevertheless opposes 0.6 ohm! 10 times less! Why ? 02:52.532 --> 03:03.802 It is folded before being wound causing opposite fields: differential 03:03.802 --> 03:18.472 The same length folded wire = 0.56 ohm 03:18.472 --> 03:28.703 If it forms a loop one obtains the double ... 03:28.703 --> 03:37.147 With the loops: the triple! 03:37.147 --> 03:45.892 Never forget: any wire opposes an impedance> to R because of its inductance 03:45.892 --> 03:52.034 HF only circulates in the periphery: pellicular effect also known as 'skin' 03:52.034 --> 04:01.152 In the courses we will see that the braids in + being flat (perimeter>) are multi-strand 04:01.152 --> 04:04.118 Oops: I have the arm too short :-)