![]() To commutate brushless dc motors, the instantaneous position of the rotor is required. Stepper motors offer superior positional accuracy because they can step by such small angles.īrushless dc motors have a permanent magnet rotor and electromagnet stator and require electronic commutation. The step angle can be reduced by a half-step, quarter-step, and up to a 1/256 step. With an advanced stepper motor driver, this small step angle can be further divided into even smaller angles by implementing microstepping operation. This makes the step angle as small as 1.8° or 0.9°. Most stepper motors on the market have 50 or 100 pole pairs, with 200 or 400 full steps for one full rotor revolution. During full-step operation, the commutation sequence and rotor position follow a particular sequence. (1) Step Angle (in °) = 360/(2 x (n_ROTORTEETH)(n_PHASE))įor each step pulse, the rotor rotates 30° - this stepper is known as a 12 full-step stepper motor. The step angle can be calculated with Equation (1): According to step input pulses, the bipolar stepper driver uses a dual H-bridge circuit to energize the stator poles in a sequence that allows the rotor to rotate by a step angle. Here, the working principles of a BLDC motor and a simplified single pole pair 3-phase BLDC motor (denoted as (a) and (b) in the figure respectively) are shown. The graphics show the simplified working principles of hybrid bipolar stepper motors. ![]() The stator consists of four poles with two phase windings. In this case, these cups are assembled such that they are out of phase by a half-pitch (60°). Each cup has three teeth with a respective magnet pole. Rotors have two cups with permanent magnets: one with north poles, and a second with south poles.Ī simplified stepper motor has a rotor made of two cups of permanent magnets. Most widely used stepper motors are hybrid stepper motors, which consist of permanent magnet rotors and electromagnet stators. The key dimensions of the EZmotion MMS742038-24-R1-1 BLDC motor and a general-purpose stepper motor used in the test setup are shown here. ![]()
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