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Working Principle of DC Generator [ Electrical Machine ]

Working Principle of DC Generator



Hii.. and welcome back to my website have you ever wondered how DC Have you ever wondered how DC generator works? and what are basic parts of DC generator?

This website gives you answers to these questions. We will start with basic parts of elementary DC generator.... As you can see configuration of DC generator is pretty simple. The stator is fixed part of the DC generator. Stator consists of permanent magnets, two of them (north and south pole), which is placed to fit around the rotor. Main function of stator is to provide the magnetic fields, through which, rotor or armature coil is rotated.



DC GENERATOR



Armature loop are generally placed in slots of armature core. Armature coil is formed by connecting several loops in the series. Armature winding is formed by connecting several coils in series. Armature loop cuts the magnetic field, due to which an electro motive force (EMF) is induced in it. The split ring is a movable device used for reversing the polarity of the current.

It is made of copper. The ring is divided thru middle into two parts. We must use split ring to achieve single direction of current. The brushes are made of carbon. These are rectangular block shaped. The only function of these carbon brushes of DC generator is to collect current from commutator segments. Galvanometer is an analogue electro mechanical actuator that produces a rotary deflection of some type of pointer in response to electric current. So, how does DC generator works?... Firstly we don't want that current direction to change, we want it to remain the same all the times.



GENERATOR CONSTRUCTION


Let's say in this direction, so,  how do we do that? Now, to make sure that the current direction remains the same, what we require is that these brushes constantly keep changing contacts between these wires for each half of rotation.

So, if the current flows in this way, in this position, this brush must be connected to this wire, so current flows like this and comes out. current flows like this and comes out But when coil rotates, you can see that, when coil comes to this position, the direction of the current changes.

If we want to keep the current in the same direction, we must this brush, to be in contact with this wire, right. And than again, when coil comes to this position, again the direction of the current changes, and again, we want that this brush to come in contact with this wire, right... Probably you already learn that, for every half rotation we must change contacts between brushes and wires How to make that this process happen automatically?

We can automate the process by adding split rings... Split rings as the name suggests, is a ring that is split in between, giving two half rings with some gap in between. Now, let's see how split rings automatically changes contact for every half a rotation. So, right now, this brush is in contact with this half part of split ring, violet color.

When coil rotates and comes to this position, the direction of the current changes, and this brush, now, is in contact with other half part of the split ring, pink color. This arrangement provides that current flows in the same direction... Again, as the coil comes to this position, finishing another half a rotation... You can see that is only changed contact... Brush is in contact, again, with violet color half part of split ring. In this way the DC generator is built where the current only flows in one direction through any external circuit, and this arrangement, with brushes and split rings, which helps us to automatically change contacts, we call them as commutators. So, split rings act like commutators.

Next thing we must mention, that is really important for working principle of DC generator, is how can we determine direction of the current, magnetic field and force. To determine all this we must use Fleming's right-hand rule. So, we will Explained how can we use Fleming's right-hand rule. As you can see, rotation of the coil is clockwise, and force acting on part of the coil A-B pushing that part of the coil upwards. So, to know direction of induced current we apply the Fleming's right-hand rule...How do we that? We place our right hand so that thumb points up, showing direction of the force, indexed finger or for finger pointing in direction of the magnetic field (from north to south pole), and middle finger will point in the direction of the induced current, which is, in our case from A to B.

Similarly, to find induced current in a part of the coil C-D, we again use Fleming's right-hand rule. So rotation of the coil is clockwise and force acting on part of the coil C-D pushing that part of the coil downwards. Thumb points down, indicating direction of the force, indexed finger or for finger pointing in direction of the magnetic field (from north to south pole), and middle finger will point in the direction of the induced current, which is, in this case from C to D. So, to conclude induced current follow path ABCD of the coil.

The effect of the split ring commutator in DC generators is to ensure that induced EMF is always in one direction, we can see that in this graph...where V represent amount of induced EMF and t represent time. You will notice in graph, how sin wave changes with rotational speed of the coil. Coil in this case has clockwise rotation. Increased rotational speed of the coil increases amount of induced EMF. Induced EMF has positive sign. Also, you see example how sin wave changes with rotational speed of the coil, when coil is rotating counter clockwise. Again, Increased rotational speed of the coil increases amount of induced EMF.

In this case induced EMF has negative sign. To conclude...DC generator has many advantages like: Design is simple, Simple operation, Highly reliable, Constant voltage can be achieved, Speed control is easy. Also, DC generator is added in many applications like: boosters, in welding equipment, to charge batteries in solar systems, in an emergency at house and offices... I hope that you now know everything about DC generators? Don"t forget to FOLLOW, LIKE and share this Website, watch  rest of my website from my engineering tech site. Please consider to support me on engineering tech. Thanks very much, see you on next post. 

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