1 00:00:01,389 --> 00:00:20,750 Well, we are going to study today electric machines. It's a very complicated issue, so you can study deeply in other courses. 2 00:00:20,750 --> 00:00:31,649 But in this one, we are going to understand the main important things of these machines. 3 00:00:31,649 --> 00:00:43,649 We can define a machine as a device which can transform energy into work. 4 00:00:43,649 --> 00:00:56,649 And the machines can be classified, taking into consideration the energy that they need. 5 00:00:56,649 --> 00:01:04,650 So one of these categories is obviously electrical machines. 6 00:01:04,650 --> 00:01:33,650 And it's a very important type of machine because we know that energy can transfer but it also degrades, which means that the effectiveness of a machine is less than 100%. 7 00:01:34,650 --> 00:02:00,150 And for electrical machines, the effectiveness is very, very close to the 100%. And it is the main reason why they are very important in industry and for our daily life. 8 00:02:00,150 --> 00:02:21,129 We can study, we are going to study firstly the classification, after that the transformer, alternator, dynamo and motors, motors of engines, the translator. 9 00:02:21,129 --> 00:02:41,469 Well, we can classify the electric machine into two main types, which are statics and rotary. In statics, as the name, as you can imagine, is something that hasn't any movement. 10 00:02:41,469 --> 00:02:48,469 And the only example of this kind of machine is transformer. 11 00:02:48,469 --> 00:02:55,469 We very often use rotary machines. 12 00:02:55,469 --> 00:03:04,469 In this kind of machines there are always stator and rotor. 13 00:03:04,469 --> 00:03:08,469 And they are the main parts of this kind of machines. 14 00:03:08,469 --> 00:03:16,650 chains but they will be they could be generators or motor oil engines a 15 00:03:16,650 --> 00:03:30,110 generators could be also a direct current such as in Amos or alternative 16 00:03:30,110 --> 00:03:39,710 currents such as alternator. And NGs also can be direct-direct current 17 00:03:39,710 --> 00:03:46,789 which are going to study this type, just only this type, 18 00:03:46,789 --> 00:03:56,629 and alternative current that could be tri-phase or single phase or triple 19 00:03:56,629 --> 00:04:09,909 phase single phase and a triple phase well so let's move on to the first kind 20 00:04:09,909 --> 00:04:17,910 of machine of this kind of machine which is transformer transformers let us to 21 00:04:17,910 --> 00:04:26,569 convert the alternative current from the primary to the secondary there are 22 00:04:26,569 --> 00:04:40,790 mainly a to two circuits with different numbers of a of rings and the result is 23 00:04:40,790 --> 00:04:51,470 that the the current is proportional to the voltage of the current is 24 00:04:51,470 --> 00:04:58,910 proportional to the number of rings in each circuit. Transformer just only can 25 00:04:58,910 --> 00:05:10,029 work in alternative circuit because they are based on the effects of the 26 00:05:10,029 --> 00:05:16,709 different flux magnetic. It is something that depends on magnetism. So we need 27 00:05:16,709 --> 00:05:24,129 that the flux evaluation in the flux of magnetic and magnetic flows and it just 28 00:05:24,129 --> 00:05:32,870 only can be possible if the current is as alternative so it's a good so we 29 00:05:32,870 --> 00:05:41,629 usually use this kind of device to transfer the voltage of the current in 30 00:05:41,629 --> 00:06:01,629 in the state of transport this current from the central engine which is produced and generated to our homes. 31 00:06:01,629 --> 00:06:13,800 Alternator is the machine which can generate electric energy. 32 00:06:13,800 --> 00:06:27,800 As it's known shows the kind of electricity is alternative electricity, it's changing the polarity in the time. 33 00:06:27,800 --> 00:06:39,800 To understand the way it works we need to know two effects. 34 00:06:39,800 --> 00:06:58,360 Firstly, when we have a current, an electric current, the churches are in movement, so they generate always magnetic fields. 35 00:06:58,360 --> 00:07:25,040 In addition to this, when a magnetic flux can change with time, then an alternative current is generated and this effect is usually called Faraday's Length Loss. 36 00:07:25,040 --> 00:07:47,220 So, taking this into consideration, in our machine, in our alternator, we are going to have a magnetic field in the stator, which can be generated with a current. 37 00:07:47,220 --> 00:08:05,740 It can be generated with the current and we also can have some kind of rings of copper 38 00:08:05,740 --> 00:08:20,819 or so on, which can be in movement because of water or because of the wind or so on. 39 00:08:20,819 --> 00:08:38,440 So in the rotor we have just only a ring of a conductor, but it is spinning so the magnetic 40 00:08:38,440 --> 00:08:42,860 flux is changing in the time. 41 00:08:42,860 --> 00:08:52,620 And this is the main reason why it generates electric alternative current. 42 00:08:52,620 --> 00:09:01,519 Well it depends the number of magnetic fields we have in the stator. 43 00:09:01,519 --> 00:09:12,500 This current could be a single phase or three. 44 00:09:12,500 --> 00:09:30,000 We can change in the rotor, we can change the polarity by using some rings, which usually 45 00:09:30,000 --> 00:09:31,740 called friction rings. 46 00:09:31,740 --> 00:09:40,559 The rings can change the polarity at the same time as it changes its polarity. 47 00:09:40,559 --> 00:09:55,899 So that happens in a dynamo and the result of this is a directed current more or less. 48 00:09:55,899 --> 00:10:02,700 It's not exactly a directed current but it's very similar to a directed current. 49 00:10:02,700 --> 00:10:09,120 So it's other kind of generator. 50 00:10:09,120 --> 00:10:21,559 And finally, rotor. If I have understood how the alternative and the dynamic work, 51 00:10:21,559 --> 00:10:33,879 it's very easy to understand the motor. The motor as alternative has a stator in which 52 00:10:33,879 --> 00:10:44,200 there is a magnetic field and a rotor. The magnetic field in the stator can be generated 53 00:10:44,200 --> 00:10:57,149 by using electric current or a natural material such as iron. And in the rotor we have a lot of 54 00:10:57,149 --> 00:11:21,149 If I feed the coils with a current, in the rotor is generated a magnetic field, and the magnetic field of the rotor interacts with the magnetic field in the stator. 55 00:11:21,149 --> 00:11:42,750 As consequence of this interaction, a moment, a force moment is generated and it makes that the rotor spins. 56 00:11:42,750 --> 00:12:00,169 But, if the rotor spins, the magnetic flux changes with the time, so an alternative current 57 00:12:00,169 --> 00:12:13,370 is generated and this current is usually called as an electromotive force, and it is the reason 58 00:12:13,370 --> 00:12:27,860 why the motor, the electric motor, needs more electric energy to move things. 59 00:12:27,860 --> 00:12:56,580 And finally, obviously, when the rotor moves and it has rotated 180 more or less, the direction 60 00:12:56,580 --> 00:13:10,559 they could change the polarity so change the direction of the rotation it could be it could 61 00:13:10,559 --> 00:13:30,279 case at the end that the rotation in rotor couldn't be complete. 62 00:13:30,279 --> 00:13:46,649 To complete this rotation we use again the Rubin rings, which change the polarity in 63 00:13:46,649 --> 00:13:48,389 the rotor. 64 00:13:48,389 --> 00:14:02,470 And now the rotor can rotate 360 degrees and a continuous rotation. 65 00:14:02,470 --> 00:14:09,009 With this we have finished electrical method. 66 00:14:09,009 --> 00:14:12,450 I hope it can be useful for you.