As an electrical apprentice, electromobility is not on top of your priority list. Thinking, however, that one size fits all when it comes to motors, means you are definitely on the wrong track. This is what Lucy is about to learn today in another Q & A talk with her colleague Jacob.
Lucy: Oh Jacob, I’m so glad to see you here in the apprentice workshop. You must be heaven-sent!
Jacob: Hi Lucy, sounds more like a serious problem to me and not just flattery. But I think the way to an electrician’s heart is not through his stomach but by asking challenging questions about our favourite subject.
Lucy: Oh yes, there might be some truth behind it. I need to have a closer look at different types of motors, mainly the induction motor or are they engines?
Jacob: Well, these terms are used interchangeably. Motors, however, run on electricity and engines run on combustion. The motor transforms electrical energy into mechanical energy, whereas the engine converts different forms of fuel into mechanical force.
Lucy: I see, so it makes a lot of sense to call road vehicles motor vehicles. (Chuckles)
Jacob: That’s a bit unfortunate, indeed. It would make more sense to simply talk about petrol and electric cars. In petrol cars, the engine produces combustion and moves the pistons. The rotational motion of these pistons is transmitted to the transmission and then converted into the energy to drive the wheels. In an electric car, the motor’s power source is a battery pack. The energy goes through the regulator and then to the motor that turns the wheels.
Lucy: I realize, you’ve found your favourite subject, indeed, which comes as no surprise from a man. But what can you tell me now about induction motors?
Jacob: They are electric motors that use alternating current (AC) and are propelled by a magnetic field that rotates. There’s a rotor, a stator and coils that convert electrical energy into mechanical energy by electromagnetic induction. The stator is the outer stationary chamber in which the motor spins. It consists of a ring of electromagnets that are arranged in such a way that they create a rotating magnetic field inside the stator. The rotor is housed inside the stator and contains conductors which could be copper windings or copper bars, all connected through short-circuit rings. By the way, the bars are connected in the shape of a cage, which is why this type of motor is also called a squirrel cage motor.
Lucy: Why would you need a cage for a squirrel? That’s a wild animal!
Jacob: Haven’t got the foggiest notion who coined the term. But that’s not essential for understanding all this anyway.
Lucy: So how exactly does the rotating magnetic field cause the wire to rotate?
Jacob: Don’t forget that the rotor inside the magnetic field is an electrical conductor and since this magnetic field is constantly changing due to the rotation, it induces an electric current inside the rotor. Simply imagine the rotor frantically trying to catch up with the rotating magnetic field in order to eliminate the difference in motion between them and to create a steady state. This is why a motor keeps spinning and is called an induction motor. The rotor speed is always less than the speed of the rotating field. Therefore, induction motors are asynchronous motors. So, what do you think a synchronous motor is?
Lucy: Well, I guess its rotor speed and the speed of the stator magnetic field are equal.
Jacob: Clever girl! But there’s more to know regarding induction motor categories. You also have single-phase and three-phase induction motors. As the names suggest, they either operate on single-phase AC supply or three-phase AC supply.
Lucy: Wonderful, Jacob, and before you keep on flooding me with even more details, just give me some examples of what appliances they’re used in.
Jacob: Oops! Seems I’ve tired you out again with too much technology. But that’s fine with me, I’ve got to run now anyway. So, to wrap it up, you can say that single-phase induction motors are more economical and are mainly used for domestic purposes. They’re simple in construction and easy to repair and maintain. Examples are small fans, mixers, toys, electric shavers, and drilling machines. The disadvantage, however, is that they’re not self-starting. We always need to provide some extra starting mechanism. That’s different with three-phase induction motors. They can be found in lifts, cranes, hoists, oil-extracting mills, and commercial electric and hybrid vehicles. The starting torque of such a motor is really high and its maintenance is difficult but the motor has a high efficiency, of course, which is a must in industry.
Lucy: Thanks a million, buddy. That’s a wrap now!
Jacob: Pleasure as always! And let me tell you, there’s way more to discuss regarding motors. So, we’ll catch up on that pretty soon, I guess. See you!
Motion and Movement
Do you know the difference between ’motion’ and ’movement’? Both are translated as »Bewegung« in German.
Motion is the general term in kinematics, the study of motion. It says nothing about the purpose of a motion, or its origin and destination. Something just happens to change place.
- Act of moving – The universe is constantly in motion.
- Operation – To set the mechanism in motion you just must press the green button.
- Gesture – She made a motion telling us we were running out of time.
Movement includes some purpose, some origin and destination. A movement is a complete motion, from beginning to end. Movement would be preferred in the arts and social sciences and motion in the natural sciences.
- The act or process of moving, especially a change of place or position or posture – They are studying the movement of planets.
- A particular manner of moving – The audience was fascinated by her graceful movements
- Traffic – There is always a lot of movement of people, cars, and buses in the city centre.
- Finance – Movement in the market is becoming less unstable as a result of economic recovery.
Physics studies motion. Transportation studies movement. They may both speak about something changing position but there is a different perspective.
So much for today. I would like to conclude my »Motor Mania« article with a quote by Dr. No who you might know from the first James Bond movie »Dr. No«: »All the greatest men are maniacs. They are possessed by a mania which drives them forward towards their goal. The great scientists, the philosophers, the religious leaders – all maniacs. What else but blind singleness of purpose (Zielstrebigkeit) could have given focus to their genius, would have kept them in the groove of purpose? Mania is as priceless as genius«.
May such mania always be to our benefit. So stay tuned!