What are the differences between Servo Motors and Stepper Mo

time:2019-06-11 Browse:

  Difference 1: Different control methods

  The stepper motor controls the angle of rotation by the number of control pulses, and one pulse corresponds to one step angle. The servo motor controls the angle of rotation by controlling the length of the pulse time.
 

  Difference 2: The required work equipment and workflow are different

  

The picture of Stepper Motor
The picture of Stepper Motor

  The power required for the stepper motor (the required voltage is given by the drive parameters), the pulse generator (mainly with the strip), the stepper motor and the driver (the drive sets the step angle, such as setting the step angle to 0.45°). A pulse is given at this time and the motor is 0.45°. The working process requires two stepper motor pulses: signal pulse and direction pulse.

  The power required for the servo motor is a switch (relay switch or relay board), servo motor; its working process is the power connection switch, and then connected to the servo motor.
 

  Difference 3: Different low frequency characteristics

  Stepper motors are prone to low frequency vibrations at low speeds. The vibration frequency is related to the load conditions and the performance of the drive. The vibration frequency is generally considered to be half the takeoff frequency of the motor's no-load. This low-frequency vibration phenomenon is determined by the working principle of the stepper motor, which is very unfavorable for the normal operation of the machine.

  When stepper motors are operated at low speeds, damping techniques should often be used to overcome low frequency vibrations, such as adding dampers or subdivision drivers to the motor. The AC servo motor runs very smoothly and does not vibrate even at low speeds. The AC servo system has a resonance suppression function that covers the rigidity of the machine and has a frequency analysis function (FFT) inside the system to detect the resonance point of the machine and facilitate system adjustment.
 

  Difference 4: Different torque frequency characteristics

  The output torque of a stepper motor decreases with increasing speed and drops sharply at higher speeds, so the maximum operating speed is typically 300-600 r / min.

  The AC servo motor is a constant torque output that outputs rated torque at rated speed (typically 2000 or 3000 rpm) and is a constant power output above the rated speed.
 

  Difference 5: Different overload capabilities

  Stepper motors are usually not overloaded.

  AC servo motors have a powerful overload capability. Take the Panasonic AC servo system as an example, it has speed overload and torque overload capability. Its maximum torque is three times the front torque and can be used to overcome the moment of inertia of the inertial load at start-up. (Because of the lack of such overload capability, stepper motors usually need to choose a motor with high torque to overcome this moment of inertia, and the machine does not need such a large torque during normal operation. Torque waste)
 

  Difference 6: Different speed response performance

  It takes between 200 and 400 milliseconds for the stepper motor to accelerate from standstill to the working speed (usually a few hundred revolutions per minute). The AC servo system has better acceleration performance. Take the Panasonic MSMA400W AC servo motor as an example. It accelerates from standstill to a rated speed of 3000 rpm. It takes only a few milliseconds to be used for control situations that require a quick start and stop.

  To put it bluntly, the number of poles is large, the speed is slow, the angle of control, the power line pins are mostly stepper motors, and the power is usually very low. High precision and high speed can be applied to speed, position and torque control. The power cords are all UVW three wires, usually servo motors. In addition, the number of pole pairs is usually no more than 5, and the power is from tens of watts to tens of kilowatts.

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