Servo and step motor compare

Item

Step motor

Servo motor

Control accuracy

Two-phase hybrid step motor’s step angle is generally 1.8° and 0.9°, and five-phase hybrid step motor’s is generally0.72° and 0.36°.

AC servo motor’s control accuracy is guaranteed by the rotary encoder in the rear end of the motor shaft.

Low frequency characteristic

Stepper motormay have low frequency vibration phenomena at low speeds

AC servo motor can run very smoothly, even at low speeds vibration phenomenon does not appear

Torque - Frequency Characteristics

Stepper motor’s output torque increases when the speed drops, and will greatly decline at high speed, so its maximum operating speed is generally at 300 ~ 600rpm.

AC servo motor has constant torque output, That’s in its rated speed (typically 2000rpm or 3000rpm), its output is rated torque, and above the rated speed, its output is constant power output.

Overload capacity

Generally, step motor can’t overload.

AC servo motor has good overload capacity.(3 times in general)

Operating performance

Stepper motor is open-loop control

AC servo motor is closed-loop control

Speed response performance

Accelerating from standstill to operating speed (typically a few hundred revolutions per minute) , step motor needs 200 to 400 ms

AC servo motor, accelerates from zero to its rated speed 3000rpm only a few milliseconds