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The Servo Motor and Stepper Motor

Views:4     Author:Site Editor     Publish Time: 2019-05-22      Origin:Site

The basic difference between the traditional stepper motor and the servo motor lies in the type of motor and its control mode. Stepper motors typically use 50 to 100 extremely brushless motors, while typical servo motors are only 4 to 12 poles.

The pole is an area of the motor in which the Arctic or Antarctic magnetic poles are generated by permanent magnet magnets or coils through the windings through the current. Stepper motors do not require encoders because they can move precisely between multiple poles, while a very small number of servo motors require an encoder to track their position.

When the servo unit reads the difference between the motor encoder and the instruction position [closed loop] and adjusts the current required for movement, the stepper motor moves incrementally using only the pulse [open ring]. Some of the performance differences between the stepper machine and the servo machine are the result of the respective motor design. Stepper motors have more poles than servo motors. The stepper motor rotates a lap and requires more current than the servo motor to pass through the winding. Compared with servo, the design of stepper motor will lead to lower rotational speed. Use a higher drive bus voltage to reduce this effect by reducing the electrical time constant of the winding.

On the contrary, the high pole number has beneficial effect at lower speed, which makes the stepper motor have the torque advantage compared with the servo motor of the same size. Another difference is the way each motor type is controlled. The traditional stepper motor works in open-loop constant current mode. This is cost savings because most positioning applications do not require encoders. However, stepper motor systems running in constant current mode generate a large amount of heat in the motor and drive, which is a consideration for some applications. Servo control solves this problem only by providing the motor current required to move or maintain the load. It can also provide a peak torque, several times higher than the maximum continuous motor torque at acceleration.

However, the stepper motor can also be controlled in full servo closed-loop mode by adding an encoder. Compared with the rudder, the slotting device is easier to debug and maintain. They are cheaper, especially in small motor applications. If you operate within the design limits, they do not lose steps or require an encoder.

The stepper motor remains stable in a stationary state and maintains its position without any fluctuations, especially under dynamic loads. Servo systems are extremely demanding in high-speed applications that require speeds greater than 2,000 rpm, and require high torque or high dynamic response at high speeds. The stepper performance is excellent at speeds below 2000RPM and at low to medium acceleration and high retention torque.


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