1 00:00:13,260 --> 00:00:18,100 DC and AC motors, basically they do the same thing, take electrical energy and 2 00:00:19,940 --> 00:00:22,780 turn it into rotational energy. 3 00:00:22,780 --> 00:00:28,740 Thanks to having what's called an EMF electromagnetic force, each motor uses 4 00:00:28,740 --> 00:00:30,140 that slightly differently. 5 00:00:30,580 --> 00:00:32,660 And we'll start with the AC motor. 6 00:00:34,980 --> 00:00:39,740 Electrical power comes in here, AC alternating current. 7 00:00:41,180 --> 00:00:44,420 Now, inside the motor itself, we have a rotor. 8 00:00:45,340 --> 00:00:49,580 Now this rotor is on a main shaft carried by two bearings. 9 00:00:50,340 --> 00:00:52,180 These here are magnets. 10 00:00:53,180 --> 00:00:54,420 They're angled for a reason. 11 00:00:55,700 --> 00:01:01,900 If you actually have a look inside the motor itself, you will see copper 12 00:01:01,900 --> 00:01:06,460 windings we'll come to that further on with a DC motor. 13 00:01:06,460 --> 00:01:11,380 But basically what this does is the electricity comes in, it's three phase, it 14 00:01:12,500 --> 00:01:17,020 goes through the wires, and as the electricity flows through the wires 15 00:01:17,580 --> 00:01:23,820 according to Fleming's left and right hand rule, current flows, you get a force 16 00:01:24,140 --> 00:01:26,180 created, which equals motion. 17 00:01:26,780 --> 00:01:35,140 Now, the magnets on these obviously are north, south, north, south, as this 18 00:01:35,140 --> 00:01:43,460 magnetic field within the motor itself on the stator as opposed to the rotor; 19 00:01:44,420 --> 00:01:54,300 rotates, it pushes against the opposing magnetic pole on the rotor held by two 20 00:01:54,300 --> 00:01:59,260 bearings as I've said. Now, these are very, very good for being really, really 21 00:01:59,260 --> 00:02:01,220 accurate for speed differential. 22 00:02:01,260 --> 00:02:04,420 So if you want something to be turned up and turned down the speed to increase 23 00:02:04,420 --> 00:02:07,540 or decrease, very, very, very good very controllable. 24 00:02:08,820 --> 00:02:11,100 They're not very quick start up. 25 00:02:11,140 --> 00:02:14,860 So they have to work their way up to an operating speed slowly. 26 00:02:15,260 --> 00:02:20,020 Now, I'll leave that there because you will be able to see the difference now. 27 00:02:20,620 --> 00:02:24,660 Now, this is a DC motor - direct current motor where the actual electricity 28 00:02:24,660 --> 00:02:27,580 just flows in one direction as opposed to alternating current, which goes 29 00:02:27,580 --> 00:02:33,700 backwards and forwards. The difference between the DC and the AC motor, the DC 30 00:02:33,700 --> 00:02:37,700 in the AC motor we have here carbon brushes. 31 00:02:38,140 --> 00:02:44,380 They carry electrical current to the commutator which actually spins, therefore 32 00:02:45,660 --> 00:02:51,300 making and braking circuit on the rotor, which has 33 00:03:01,060 --> 00:03:10,940 now, if we look at this, the difference is what we have on the rotor itself is 34 00:03:10,940 --> 00:03:18,060 the same as what we have on the actual windings, on he AC motor. 35 00:03:18,220 --> 00:03:24,860 So therefore we get an EMF on here as opposed to around the outside of the 36 00:03:24,860 --> 00:03:26,380 magnet on an AC motor. 37 00:03:27,220 --> 00:03:35,340 So if we look inside all we have is magnets, there are windings there because 38 00:03:35,340 --> 00:03:40,900 that then increases the magnetism within those magnets, which forces this 39 00:03:40,900 --> 00:03:48,500 obviously, again, according to Flemming's rules, the opposing magnetic poles 40 00:03:49,060 --> 00:03:55,260 cause it to spin. Both the rotors obviously carry a fan for cooling; these 41 00:03:55,260 --> 00:04:02,780 types of motor are very, very good for high speed, long period use such as 42 00:04:03,020 --> 00:04:09,700 vacuum cleaners, ceiling fan units, anything where you need a continual steady 43 00:04:09,700 --> 00:04:17,140 speed. The one disadvantage to a DC motor is here and here. 44 00:04:18,700 --> 00:04:21,620 The brushes and the commutator are consumable. 45 00:04:22,060 --> 00:04:27,420 Therefore they need regular maintenance and replacing, as you can see on this 46 00:04:27,420 --> 00:04:32,060 commutator, that should be nice and bright and copper like; it's not is called 47 00:04:32,060 --> 00:04:37,020 in deposits of graphite and carbon where the miniature sparks as it makes and 48 00:04:37,020 --> 00:04:40,220 breaks the circuit. Now that needs regular maintenance. 49 00:04:40,220 --> 00:04:48,700 On here as you will see, there is no physical contact between that rotor 50 00:04:50,140 --> 00:04:52,460 and the windings inside an AC motor. 51 00:04:52,500 --> 00:04:55,020 Therefore, it is very, very low maintenance. 52 00:04:55,500 --> 00:04:57,140 Each has its place in industry. 53 00:04:58,660 --> 00:05:01,140 DC motors now have taken many, many steps further. 54 00:05:01,180 --> 00:05:07,020 We have what's called a brushless motor that are so, so far ahead of these now 55 00:05:07,260 --> 00:05:11,100 . They will be coming in and they will be used. 56 00:05:11,100 --> 00:05:12,500 They do not have a commutator. 57 00:05:12,620 --> 00:05:17,220 So therefore they operate very similarly to an AC motor where there is no 58 00:05:17,220 --> 00:05:21,540 direct contact between anything on the rotor and anything on the wind. 59 00:05:21,940 --> 00:05:30,100 Although on appearance it would show that this has got magnets like these. 60 00:05:30,100 --> 00:05:35,100 They're not the electromagnets as they are energized they become magnetized. 61 00:05:35,100 --> 00:05:38,060 They are not magnetized as they are, these are. 62 00:05:38,060 --> 00:05:45,620 So two completely different animals, two completely different purposes of use, 63 00:05:46,660 --> 00:05:48,660 but both have their place in industry.