The principle of three-phase servo motors is something many users want to understand, but not all users can grasp its essence. Furthermore, those interested in physics also wish to understand the principle of three-phase servo motors. In short, the principle of three-phase servo motors is not difficult to understand. The content is as follows.
(Servo motor)
Three-phase servo motor principle
1. The three-phase AC servo motor is a three-phase squirrel-cage asynchronous motor, and its control method is the same as that of a regular three-phase motor. For synchronous motors, a single-phase reactive synchronous motor should be used. If a three-phase synchronous motor is unavailable, and if the starting torque must be controlled by a frequency converter, a stepper motor is preferable. Using a three-phase motor as a servo motor is simple and convenient, therefore a stepper motor is used.
2. Some three-phase AC servo motors are not ordinary asynchronous motors, but synchronous motors. Their rotors are made of permanent magnet materials, and the stator has symmetrical three-phase windings embedded in it; therefore, it is essentially a permanent magnet AC synchronous motor. If a servo driver is needed for control, the driver can change the power supply frequency and control the motor speed as needed; therefore, the driver can be considered a frequency converter. Furthermore, the motor is connected to the driver via an encoder, forming a closed-loop control system, thereby achieving high-precision adjustment.
3. Servo motors are typical closed-loop feedback systems. The terminals (outputs) of the reduction gear set driven by the motor drive a linear proportional potentiometer to detect the position, convert the angular coordinates into proportional voltages and feed them back to the control board. The control board compares the voltages with the input control pulse signals, generates the correct pulses, and drives the motor to rotate forward or backward, so that the output position of the gear set matches the expected value. When the correct pulses approach zero, the servo motor achieves precise positioning.
4. The working principles of AC service motors and single-phase induction motors are not fundamentally different. However, AC service motors must be able to overcome their inherent "self-rotation" characteristic, meaning they should not rotate without a control signal, especially when they are already rotating. If the control signal disappears, they should be able to stop rotating immediately. When a regular induction motor is rotating, it will continue to rotate normally if the control signal disappears.
5. Working principle of AC servo motors: A servo system generally consists of a servo amplifier and a servo motor. The rotor in the servo motor is controlled by a permanent magnet and the servo amplifier. An electromagnetic field is generated by the U/N/W three-phase electricity, and the rotor rotates under the influence of this magnetic field. Simultaneously, based on the feedback value and the target value, the encoder feedback signal from the motor is compared with the driver, and the rotor rotation angle is adjusted. The accuracy of the servo motor determines the encoder resolution.
6. The rotor in a servo motor is a permanent magnet. The driver controls the UN/W phase current to create an electromagnetic field, under which the rotor rotates. Then, the encoder feedback signal from the motor compares the driver with the target value and adjusts the rotor's rotation angle. The accuracy of a servo motor depends on the accuracy (number of lines) of the encoder. A servo motor, also called an actuator motor, converts received signals into angular displacement or angular velocity output on the motor shaft in an automatic control system, and is divided into DC and AC servo motors. Its main characteristic is that there is no rotation when the signal voltage is low.
Many types of servo motors exhibit a decrease in torque as it increases. Besides three-phase servo motors, common servo motors also include single-phase servo motors, which can be further categorized into synchronous and asynchronous servo motors. The appropriate servo motor should be selected based on your specific needs. Generally, the application of different motors depends on the actual environment.
