 Hello everyone, welcome to this session. I am Priyanka Bansore and today we are going to see about working of stepper motor. These are the learning outcomes of this video lecture. At the end of this session students will be able to explain construction, principle and operation of stepper motor and students will be able to differentiate the types of stepper motor. These are the contents we will be covering in this session. Now before moving towards pause this video for few seconds and we have to think and give the answer. With the help of this picture do you wonder how does a robotic arm, printer, motion control positioning systems and many more systems work? Yes, the answer is stepper motor. A stepper motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. The stepper motor is a motor that produces rotation through equal angles that is stepped for each digital pulse supplied to its input. The name stepper is used because this motor rotates through a fixed angular step in response to each input current pulse received by its controller. We see the construction of stepper motor. So this is the rotor and there are four stator poles. Rotor is magnetized in the axial direction. For example, if one rotor is polarized with north then another rotor will be polarized with south. Means there is generally a permanent magnet and it is surrounded by the winding of the stator. As we activate the windings step by step in particular order and let current flow through them, they will magnetize the stator and make electromagnetic poles. The stator may be multipolar. Around the poles exciting coils are one. Now we are moving towards the actual working principle of stepper motor. So the principle of stepper motor is based on electromagnetism. It constructs of a rotor that is of permanent magnet and a stator that is of electromagnets. Now when we supply to stator's winding there will be a magnetic field developed in the stator. Now rotor of motor that is made up of permanent magnet will try to move with the revolving magnetic field of stator. So that the electromagnets are energized by an external control circuit. To make the motor shaft turn first one electromagnet is given power. It makes the gears teeth magnetically attracted to the electromagnets teeth. And the point when the gears teeth are thus aligned to the first electromagnet they are slightly offset from the next electromagnet. When the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one and from there the process is repeated. Each of those slight rotations is called a step with an integer number of steps making a full rotation. It doesn't rotate continuously they rotate in steps. There are four coils with 90 degree angle between each other fixed on the stator. The stepper motor connections are determined by the way the coils are interconnected. We will see practically operation of stepper motor. There are different ways of driving the stepper motor. Here you can see in the first figure the top electromagnet is turned on. A motor with four stator poles and one permanent magnet. The rotor will have four steps. We all know that circle is 360 degrees. Consider motor with four poles. So the evolution is calculated by 360 divided by 4 is equal to 90 degrees per step. So motor rotates 90 degrees per step. In the figure 2 the right electromagnet is energised. Then in the next figure the bottom electromagnet is energised. Finally the left electromagnet is enabled. In this way when the next electromagnet is turned on the first is turned off. And the motor rotates again and again in steps. Now we see the types of stepper motor. Stepper motor has three types. First permanent magnet. Then second variable reluctance. And the third is hybrid synchronons. Now let us see one by one. So first is permanent magnet stepper motor. The figure shows the permanent magnet. In this we use the permanent magnet in the rotor. It consists of rotor and stator. It operates on the attraction or repulsion between the rotor. That is the permanent magnet and the stator electromagnets. The electromagnets are excited by giving pearls from the controller. This is the second type of stepper motor that is variable reluctance. Here alternately ground each phase. You can see in the figure. It consists of soft ion, multi-tooth rotor and a wound stator. DC voltage is applied to the stator winding. The poles become magnetized. And if we have to decrease the gap between the rotor and the stator gears. The less the loss of magnetic force. In short, area between the rotor and stator is directly proportional to the loss of magnetic force. In this the number of rotor teeth are always less than the stator poles. Usually two teeth less than the number of stator poles. Now this is the last type of stepper motor. That is hybrid synchronous stepper motor. The figure shows stator windings. And two rotors that are north cup and south cup. From the name we can say that hybrid stepper motor are named. Because they use a combination of PM that is permanent magnet. And we are that is variable reluctance. Techniques to achieve maximum power in a small packet size. Then in second figure, end caps and magnet is shown. The hybrid motor has an actually magnetized rotor. With tooth steel caps. As shown in third figure one end of rotor becomes the north pole. And other end becomes south pole. It provides better performance with respect to stepper evolution torque and speed. Practically we use different types of motor according to applications. So these are the specifications of this specific motor. So the specifications are varying according to motors. Now we see the advantages of stepper motor. So these are the advantages of stepper motor. It has low cost. Then it is simple in construction. We know that the difference between the open loop and the closed loop. So it can operate in an open loop control system. Then it has low maintenance. And mainly it will work in any environment. Now we see the disadvantages of stepper motor. So first it requires a dedicated control circuit. It uses more current than DC motors. And high torque output achieved at low speeds. These are the applications of stepper motor. It is used in printing press, robotics. Then it is used in commercial and industrial applications. Then used in medical equipments like scanners, blood pumps etc. It is used in elevator, liquid level monitoring and many more applications of stepper motor. These are the references of this video lecture. Thank you.