nema 17 step motor 3D model

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A stepper motor, also known as a step motor or stepping motor, is a brushless DC electric motor that divides a full rotation into a precise number of equal steps. The motor's position can be commanded to move and hold at one specific step without any need for feedback (an open-loop controller), as long as the motor is carefully sized to the application in terms of torque and speed. Switched reluctance motors are very large stepping motors with a reduced pole count, and generally require closed-loop commutation. Contents 1 Fundamentals of operation 2 Types 3 Two-phase stepper motors 3.1 Unipolar motors 3.2 Bipolar motors 4 Higher-phase count stepper motors 5 Driver circuits 5.1 L/R driver circuits 5.2 Chopper drive circuits 6 Phase current waveforms 6.1 Wave drive (one phase on) 6.2 Full-step drive (two phases on) 6.3 Half-stepping 6.4 Microstepping 7 Theory 7.1 Pull-in torque 7.2 Pull-out torque 7.3 Detent torque 7.4 Ringing and resonance 8 Ratings and specifications 9 Applications 10 Stepper motor system 11 See also 12 References 13 External links Fundamentals of operation A stepper motor A bipolar hybrid stepper motor Brushed DC motors rotate continuously when DC voltage is applied to their terminals. The stepper motor, however, converts a series of input pulses (typically square wave pulses) into a precisely defined increment in the shaft position. Each pulse moves the shaft through a fixed angle. Stepper motors have multiple toothed electromagnets arranged around a central gear-shaped piece of iron. These electromagnets are energized by an external driver circuit or a micro controller. To make the motor shaft turn, first, one electromagnet is given power, which magnetically attracts the gear's teeth. When the gear's teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. This means that when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one. From there, the process is repeated. Each of those rotations is called a step, with an integer number of steps making a full rotation. The circular arrangement of electromagnets is divided into groups, each group called a phase, and there are an equal number of electromagnets per group. The designer chooses the number of groups for the stepper motor. The electromagnets of each group are interleaved with the electromagnets of other groups to form a uniform pattern of arrangement. For example, if the stepper motor has two groups identified as A or B, and ten electromagnets in total, then the grouping pattern would be ABABABABAB. Electromagnets within the same group are all energized together. Because of this, stepper motors with more phases typically have more wires (or leads) to control the motor. Types There are three main types of stepper motors: Permanent magnet stepper Variable reluctance stepper Hybrid synchronous stepper Permanent magnet motors use a permanent magnet in the rotor and operate on the attraction or repulsion between the rotor PM and the stator electromagnets. Pulses move the rotor in discrete steps, clockwise (CW) or counterclockwise (CCW). If left powered at a final step, a strong detent remains at that shaft location. This detent has a predictable spring rate and specified torque limit; slippage occurs if the limit is exceeded. If current is removed, a lesser detent still remains, therefore holding shaft position against spring or other torque influences. Stepping can then be resumed while reliably being synchronized with control electronics. Clarification- Stepper motor detent is analogous to brushless DC motor cogging. In the case of constant speed brushless DC motor, magnetic cogging is a concern for torque ripple effects.