WEBVTT 00:00.000 --> 00:13.223 1 Tore with 2 identical windings red and blue 00:13.223 --> 00:20.791 Finally a copper winding connected to black bananas: this will be the secondary 00:20.791 --> 00:29.055 The magnetic fields from the 2 primary red and blue will mutually cancel each other 00:29.055 --> 00:34.034 No intensity in the secondary as long as the primaries remain identical 00:34.034 --> 00:44.873 If the intensity of one of the 2 primary is higher, the copper coil will be fed 00:44.873 --> 01:01.920 Currently red and blue wire carry the same intensity to power the bulb 01:01.920 --> 01:08.490 The ammeter connected to the secondary coil displays 0 01:08.490 --> 01:22.701 This toroid acts as a differential transformer. secondary intensity = primary difference 01:22.701 --> 01:37.029 If the second bulb uses the right path, there is still no intensity in the secondary 01:37.029 --> 01:46.759 I assure this time a direct return to the generator, by its 'land' ... 01:46.759 --> 01:55.073 Now 1.06 mA! A fault current is generated! 01:55.073 --> 02:01.269 Here is the simplified principle of the AC Alternative DDR Differential 02:01.269 --> 02:06.069 We will measure the trigger of a true 30 mA DDR 02:06.069 --> 02:20.487 The bulb feeds red / blue. The rope wire is connected to the potentiometer available in green 02:20.487 --> 02:30.011 Its setting changes the resistance between phase (red) and earth (green): the leakage current! 02:30.011 --> 02:38.125 Here is the test setup with a commercially available DDR 30 mA differential 02:38.125 --> 02:43.948 The use of 24 V does not cause any concern because it measures I and not U! Except for test button 02:43.948 --> 03:00.378 The test button produces only 3 mA (1/10 °) at 24 V (1/10 ° of 230 ~ 240 V) 03:00.378 --> 03:09.932 A DDR triggers between I / 2 and nominal I; therefore between 15 mA and 30 mA for this model 03:09.932 --> 03:20.521 The ammeter is connected to the 'ground' return of the generator and ... 03:20.521 --> 03:28.272 ... And to the leakage terminal controlled by the potentiometer 03:28.272 --> 03:49.980 It triggered just above 21 mA 03:49.980 --> 04:16.295 It triggers instantly for 22 mA, 22 is between 15 and 30: it works! 04:16.295 --> 04:37.845 Real test under 230 V ~ 50 then 60 Hz to check the test button!