How servo motors work
Release Date:
2024-04-03
The working principle of a servo motor is relatively simple, but its efficiency is relatively high. The servo circuit is built into the motor unit, which uses a flexible shaft usually equipped with gears.
The working principle of servo motors is relatively simple, but their efficiency is relatively high. The servo circuit is built into the motor unit, which uses a flexible shaft usually equipped with gears. Electrical signals control the motor and also determine the amount of shaft movement. The internal setup of a servo motor is simple: a small DC motor, a control circuit, and a potentiometer. The DC motor is connected to a control wheel via gears, and as the motor rotates, the resistance of the potentiometer changes, allowing the control circuit to precisely adjust movement and direction.
When the shaft is in the correct (desired) position, the motor stops powering. If the shaft does not stop at the target position, the motor will continue to run until it enters the correct direction. The target position is transmitted via a signal line using electrical pulses. Therefore, the motor speed is proportional to the actual and desired positions. When the motor approaches the desired position, it starts to rotate slowly, but it rotates quickly when it turns further away. In other words, servo motors only need to complete their work as quickly as possible, which makes them efficient devices.
When an AC servo motor has no control voltage, there is only a pulsating magnetic field generated by the excitation winding in the air gap, and the rotor remains stationary with no starting torque. When there is a control voltage and the control winding current and excitation winding current are in different phases, a rotating magnetic field is generated in the air gap, and an electromagnetic torque is produced to make the rotor rotate in the direction of the rotating magnetic field. However, servo motors require not only starting under the action of control voltage, but also that the motor should be able to stop immediately after the voltage disappears. If the control voltage of a servo motor disappears and it continues to rotate like a general single-phase asynchronous motor, then an out-of-control phenomenon occurs. We call this phenomenon, caused by uncontrolled self-rotation, the "self-rotation phenomenon".
The basic working principle of traditional DC servo motors is completely the same as that of ordinary DC motors. They rely on the action of armature current and air gap flux to generate electromagnetic torque, causing the servo motor to rotate. Armature control is usually adopted, which means that while keeping the excitation voltage constant, the speed is adjusted by changing the armature voltage. The smaller the armature voltage, the lower the speed; when the armature voltage is zero, the motor stops. Since the armature voltage is zero, the armature current is also zero, and the motor does not generate electromagnetic torque, thus there will be no "self-rotation" phenomenon.
Recommended News
Analysis of Causes for AC Servo Motor Failure
Three-phase AC servo motors are widely used, but through long-term operation, various faults may occur. Timely identification of the fault cause and corresponding treatment are important tasks to prevent the fault from expanding and ensure the normal operation of the equipment.
The working principle of a servo motor is relatively simple, but its efficiency is relatively high. The servo circuit is built into the motor unit, which uses a flexible shaft usually equipped with gears.
Single-layer winding three-phase asynchronous motor
A single-layer winding is one where only one active side of a coil is embedded in each stator slot, so the total number of coils is only half of the total number of motor slots.
Starting of three-phase asynchronous motor
However, when a three-phase asynchronous motor starts directly, the current can reach 6-7 times the rated current, which has a significant impact on the power grid, especially for high-power motors.
Striped appearance on the outer surface of motor housing extruded profiles
Hollow aluminum alloy profiles are produced using the flat flow split combination die extrusion process. This process presents a relatively increased difficulty in profile production, as the metal goes through a diversion and welding joint process, therefore, hollow profiles have weld lines.
The motor casing is a main component of the electric submersible pump motor.
The motor casing is a main component of the electric submersible pump motor, and its machining accuracy directly affects the quality of the electric submersible pump. Due to the motor casing's thickness being greater than its radius during turning with clamping holes, it is prone to oval deformation. The deformation generally ranges from 0.03 to 0.10 millimeters, which cannot meet user requirements. If this problem is not resolved, it will lead to significant economic losses in producing qualified products.