L umanand department of power electronics group, cedt iisc bangalore. Step motors often referred as stepper motors are different from all other types. There are a number of stepper motor designs that run from the most basic to very complex. The shaft or spindle of a stepper motor rotates indiscrete step increments when electrical command pulses are applied to it in the proper sequence. The movement of each step is precise and repeatable. Animation from wikimedia commons what are stepper motors good for. Optical encoders for stepper motors trinamic digikey. Specialpurpose electric machines the machines introduced in this lecture are used in many applications requiring fractional horsepower, or the ability.
Stepper motors are used in a variety of automation applications in which a relatively small amount of torque is needed. Stepper motors rotate at a set speed under different load, provided the rated torque is maintained. The unipolar stepper motor has five or six wires and four coils actually two coils divided by center connections on each coil. It is an incremental drive digital actuator and is driven in fixed angular steps. Lecture 7 stepper motors, permanent magnet dc motors. In a stepper motor, the stator is a set of electromagnets. And the higher steprates needed to turn these motors results in lower torque than a similar size lowstepcount motor at similar speeds. Induction machines 1 introduction the induction machine was invented by nikola tesla in 1888. The introduction is driven by a general trend towards energy and cost efficient stepper motor servos replacing dc or bldc drives, which rely on a gearbox to supply sufficient torque at low speed, where stepper motors have their strength.
The rotor moves in discrete steps as commanded, rather than rotating continuously like a conventional motor. The hybrid stepper motor is more expensive than the pm stepper motor but provides better performance with respect to step resolution, torque and speed. Except for limit switches no other feedback is used in the stepping motor control system. The hybrid stepper motor combines the best features of both the pm and vr type stepper. How to pick the right stepper motor for the job and what. A stepping motor system consists of three basic elements, often combined with some type of user interface such as a host. Part a of this application example provides general information on stepper motors design, areas of application, control, etc.
They cannot be driven by just connecting the positive and negative leads of the power supply. Asds may be referred to by a variety of names, such as variable speed drives, adjustable frequency drives or variable frequency inverters. How to download all of the lectures in pdf for a course in. It is a motor that can rotate in both directions, move in precise angular increments, sustain a holding torque at zero. They are called unipolar steppers because power always comes in. Dedicated integrated circuits have dramatically simplified stepper motor driving. Limited high speed torque in general, stepper motors have less torque at high speeds than at low speeds. A stepper motor or a step motor is a brushless, synchronous motor which divides a full rotation into a number of steps. Basic electrical technology basic electrical technology. You will find all pdfs and also as mp3 file for all video lectures which are in nptel. The stepper motor can be controlled with or without feedback.
Electrical engineering special electromechanical systems nptel. The step motor specialists stepper motor basics page 3 the rotor is connected to the motor shaft, which gives the output rotation and torque of the motor when voltage and current pulses are applied to the motor windings. They draw the most current when they are doing no work at all. Unit 2 stepper motors constructional features principle of. Industrial circuit application note stepper motor and driver selection 0 10 20 30 40 50 60 70 80. Such an operation of stepper motor at highspeed is called slewing.
Stepper motor is a specially designed dc motor that can be driven by giving excitation pulses to the phase windings. Figure 1 illustrates the most basic variable reluctance. So, in the last lecture we were discussing about a 4 pole stator and a 6 pole rotor variable reluctance type stepper motor let us have a look at it once again. Principle operation of stepper motor how variable reluctance stepper motor works. Stepper motor armature, fitting, and socket astepper motor armature, bmachined 38 fitting, c10 mm socket the mounting bracket for the stepper of the y axis, the longer of two axes, was fashioned from the larger mounting bracket. Asd is capable of adjusting both speed and torque from an induction or synchronous motor. The motors rotation has several direct relationships to these. Introduction to brushless permanent magnet motors, stepper motor. A stepper motor is an electric motor that rotates in discrete step increments. Stepper motor driver ic allegro 3977 v max 35v i max 2. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control constant slip control fieldoriented control. The motors position can then be commanded to move and hold at one of these steps without any feedback sensor an openloop controller, as long as the motor is carefully sized to the application in respect to torque and speed. Now in hybrid stepper motor the torque is produced by the combination of variable reluctance torque and the permanent magnet torque. For our purposes, this guide will focus on stepper motors that can be driven with commonly available drivers.
Typical step angles for the hb stepper motor range from 3. Stepper motor basics a stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. Some steppers are optimized for better highspeed performance, but they need to be paired. The series features two motor types with three basic step angles. The center connections of the coils are tied together and used as the power connection.
This video provides all the important concept of stepper motor in detail and also provides some important points to remember for exams and interviews. Hello at first is it possible to control a stepper motor using discrete components. To apply these ics designers need little specific knowledge of motor driving techniques, but an understanding of the basics will help in finding the best solution. Stepper motors are dc motors that move in discrete steps. Stepper motors work on the principle of electromagnetism. Unlike a brushless dc motor which rotates continuously when a fixed dc voltage is applied to it, a step motor rotates in discrete step angles. A 3phase vr motor diagram is shown in figure 7 see page z10. This mean that a digital signal is used to drive the motor and every time it receives a digital pulse it rotates a specific number of degrees in rotation. More important is the fact that a stepper motor can actually be used without any type of feedback loop. When stopped but energized, a stepper short for stepper motor.
The construction of a 3phase vr stepper motor with 6 poles on the stator and 4 pole on the rotor as shown. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. Variable reluctance stepper motor its working circuit. High step count motors topout at lower rpms than similar size. You can find them according to your branch and subject in the below link national mission on education through ict this was initiated by iit madras. Stepper motors stepper motor an electromagnetic actuator. It also checks to see which pairs of wires go to each winding. Industrial circuit application note stepper motor and. Step angle of the stepper motor is defined as the angle traversed by the motor in one step. Stepper motor basics a stepper motor just like any other motor, converts electrical energy into mechanical energy.
This doesnt mean you wouldnt use a feedback loop in some applications. First step movement and next step to move the motor in a clockwise direction from its initial stop position, we need to generate torque in the clockwise direction. Variable reluctance stepper motor jun 2 general 236 views 4 comments on variable reluctance stepper motor it is electromagnetic and electrodynamic equipment. The tradeoff for high resolution is speed and torque. Low efficiency unlike dc motors, stepper motor current consumption is independent of load. A stepper motor is a brushless dc motor whose rotor rotates in discrete angular displacements when its stator windings are energized in a programmed manner. The energization sequence is shown in table v see page z11. Trinamic motion control presents a new family of optical rotary encoders optimized for stepper motor servos.
Nptel video lectures, iit video lectures online, nptel youtube. A stepper motor is a brushless dc electric motor that divides a full rotation into a number of equal steps. Variable reluctance stepper motor the principle of variable reluctance stepper motor is based on the property of the flux lines which capture the low reluctance path. Induction machines guru nanak dev engineering college. They are driven by a stepping sequence which is generated by a controller. They have multiple coils that are organized in groups called phases.
This note explains the basics of stepper motor driving and describes the drive techniques used. A stepper motor is a digital version of the electric motor. How stepper motors work modes of operation types of stepper motors identifying the stepper motor type drive circuits. Oriental motor offers a wide range of motion control products to meet a wide range of applications, select the appropriate application type below. By energizing each phase in sequence, the motor will rotate, one step at a time.
Variable reluctance stepper motor construction and working. More important is the fact that a stepper motor can actually be used without any. An introduction to stepper motors university of arizona. An introduction to stepper motors xinda hu university of arizona college of optical sciences introduction. In applications with low damping, the usable torque from the stepper motor can be drastically reduced by resonances. An822 ds00822apage 2 2002 microchip technology inc. Instead, its a synchronous motor with electronicallyswitched magnetic fields which rotate the armature magnets.
Mounting brackets for each stepper motor were cut down to allow for a better fit to each stepper motor. Stepper motor driver ic lower current capacity uses a minimum of 2 io pins minimal software overhead builtin failure diagnostics. To calculate step angle,simply divide 360 by number of steps a motor takes to complete one revolution. In particular, there are currently no plans for using tachometers. Mukhopadhyay, department of electrical engineering, iit kharagpur. Industrial circuits application note stepper motor basics. Considerations in choosing motors for robotics by bill schweber for mouser electronics robots perform specific, welldefined tasks like assemblyline work, surgical assistance, warehouse. Motor winding 1 is distributed between the top and bottom stator poles, while motor winding 2 is distributed. In this video we explain about how stepper motor works. Right from its inception its ease of manufacture and its robustness have made it a very strong candidate for electromechanical energy conversion. Stepper motor technical tutorial haydon kerk pittman.
There are a many types and variations of stepper types, some of which require very specialized drivers. Stepper motor driving university of texas at austin. The stator and the rotor of the motor are aligned in such a way that the magnetic reluctance is minimum. Basic electrical technology nptel online videos, courses. Since the motor moves in distinct steps as defined by a step angle, we need only count the number of steps to position the motor accordingly.
Tech in electrical engineering iase deemed university. Stepper motor lecture georgia institute of technology. This is a simple test to see if the windings in the motor are good. Fall 2005 ee595s electric drive systems 3 voltsperhertz control. As we have seen that in half mode, the number of steps taken by the motor to complete one revolution gets doubled, so step angle reduces to half. An907 ds00907apage 2 2004 microchip technology inc. Lecture series on industrial automation and control by prof. Positioning since steppers move in precise repeatable steps, they. An electric asd is an electrical system used to control motor speed. Principle of stepper motor a stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. Unlike conventional motors, stepper motors move through steps of 0.
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