3 Excitation Modes of Stepper Motor

There are three excitation modes that are commonly used with the stepper motor. These stepper motor modes are the full‐step, half‐step‐ and microstep.

Stepper Motor ‐ Full‐Step

In full‐step operation, the stepper motor steps through the normal step angle, e.g. 200 step/revolution motors take 1.8 steps, while in half‐step operation 0.9 steps are taken. There are two kinds of full‐step modes. Single phase full‐step excitation is where the stepper motor is operated with only one phase energized at a time. This mode should only be used in applications where torque and speed performance are not important, wherein the motor is operated at a fixed speed and load conditions are well defined. Typically stepper motors are used in full‐step mode as replacements in existing motion systems, and not used in new developments. Problems with resonance can prohibit operation at some speeds. This type of mode requires the least amount of power from the drive power supply of any of the excitation modes. Dual phase full‐step excitation is where the stepper motor is operated with two phases energized at a time. This mode provides good torque and speed performance with a minimum of resonance problems.

Note: Dual excitation, provides about 30 to 40 percent more torque than single excitation, but does require twice the power from the drive power supply. Many of ATO microstep drivers can be set at full‐Step mode if needed.

Stepper Motor ‐ Half‐Step

Stepper motor half‐step excitation is alternate single and dual phase operation resulting in steps one half the normal step size. Therefore, this mode provides twice the resolution. While the motor torque output varies on alternate steps, this is more than offset by the need to step through only half the angle.
This mode had become the predominately used mode by ATO beginning in the 1970’s, because it offers almost complete freedom from resonance problems. The stepper motor can be operated over a wide range of speeds and used to drive almost any load commonly encountered. Although half‐step drivers are still a popular and affordable choice, many newer microstep drivers are a cost‐effective alternative. ATO stepper motor driver series is a very popular driver and is suitable for a wide range of stepper motors.

Stepper Motor ‐ Microstep

In the stepper motor microstep mode, a stepper motor’s natural step angle can be divided into much smaller angles. For example, a standard 1.8 degree motor has 200 steps/revolution. If the motor is microstepped with a ‘divide‐by‐10’, then each microstep moves the motor 0.18 degrees, which is 2,000 steps/revolution. The microsteps are produced by proportioning the current in the two windings according to sine and cosine functions. This mode is only used where smoother motion or more resolution is required. Typically, microstep modes range from divide‐by‐10 to divide‐by‐256 (51,200 steps/rev for a 1.8 degree motor). Some microstep drivers have a fixed divisor, while the more expensive microstep drivers provide for selectable divisors. For cost‐effective microstep drivers, see
ATO stepper driver series.

Note: In general, the larger the microstep divisor provided, the more costly the stepper motor driver. Should you prefer, ATO also manufactures a series of integrated stepper motor/Driver, meaning the stepper motor and driver are in one unit. This design approach takes the guesswork out of motor and driver compatibility.

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