Stepper Motor Drive Configurations

Stepper motors typically come in two motor winding configurations. Before selecting which configuration is appropriate for your application, you should understand the basic difference between the two. This choice will be important when selecting how to drive the motor. The first configuration type is a unipolar motor. Unipolar stepper motor have a winding with a center tap per phase (see Figure 1) which makes them particularly easy to control. The center tap of each winding can be common to both phases. The outer two ends for each winding can be controlled with a single transistor. For the simplest unipolar driver, only four transistors are required for bi-directional motion. The easiest way to identify a unipolar motor is they typically have five or six leads depending on whether the center tap has been internally connected or not. A downside is that half of each phase is de-energized during each step. This means that unipolar motors are typically larger and weigh more compared to a bipolar motor. Unipolar-vs-Bipolar-ConfigurationFigure 1: Unipolar Vs Bipolar Configuration The most popular configuration is a bipolar motor. Bipolar stepper motor have a single winding per phase (see Figure 1). The current in a winding needs to be reversed in order to reverse the direction of motion. In order to achieve bi-directional motion, a full H bridge per phase is required in order to drive a bipolar motor. The real benefit to using a bipolar stepper motor is their improved efficiency compared to the unipolar motor. The entire winding is energized during motion which translates into smaller and lighter motors that can produce a surprising amount of torque. The easiest way to identify a bipolar stepper motor is that it will have four leads, two per phase and none are common. Pro Tip: You can use a unipolar motor as a bipolar motor if you ignore the center tap. This can come in handy if a particular design of motor is only available in a unipolar configuration. See more:china stepper motor for sale online