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Servo Motors

Servo Motors

Servo Motors are used for various applications. A Servo Motor is a rotary or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. All Servo Motors require a controller,

Servo Motors are relatively small but very powerful and very energy-efficient. When the shaft of the motor is at the desired position, the power supply to the motor is stopped. If not, the motor is turned in the appropriate direction. The desired position is sent via electrical pulses through the signal wire. The motor's speed is proportional to the difference between its actual position and desired position. So if the motor is near the desired position, it will turn slowly, otherwise it will turn fast. This is called proportional control. This means the motor will only run as hard as necessary to accomplish the task at hand, resulting in an extremely efficient setup.

Yaskawa Servo Pack

Types of Servo Motor


There are two types of servo motors - AC and DC. AC Servo can handle higher current surges and tend to be used in industrial machinery. DC Servos are not designed for high current surges and are usually better suited for smaller applications.

DC motors tend to be less less expensive than their AC counterparts. These Servo Motors have been built specifically for continuous rotation, making it an easy way to get your appliance moving. They feature two ball bearings on the output shaft for reduced friction and easy access to the rest-point adjustment potentiometer.

How is a Servo Motor Controlled?


Servos are controlled by sending an electrical pulse of variable width, or pulse width modulation (PWM), through the control wire. There is a minimum pulse, a maximum pulse, and a repetition rate. A servo motor can usually only turn 90° in either direction for a total of 180° movement. The motor's neutral position is defined as the position where the servo has the same amount of potential rotation in the both the clockwise or counter-clockwise direction.

The PWM sent to the motor determines position of the shaft, and based on the duration of the pulse sent via the control wire; the rotor will turn to the desired position. The servo motor expects to see a pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns. For example, a 1.5ms pulse will make the motor turn to the 90° position. Shorter than 1.5ms moves it in the counter clockwise direction toward the 0° position, and any longer than 1.5ms will turn the servo in a clockwise direction toward the 180° position.

Yaskawa Drives

Need Assistance Working Out Which Servo Motor You Require?

If you need specialist components or just a hand to work out which servo motor would suit what you need then give us a call on 01905 887 667. Our staff are available during office hours and will be happy to help you with any questions.

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