Some Facts About Stepper Motors
Stepper motors are a form of synchronous motors which are brushless and use digital pulses to generate mechanical motion. They are widely used in commercial and industrial applications because of their rugged construction, low cost and high reliability.
Working Principle of Stepper Motors
The stepper motor completes a revolution as a series of consecutive steps. Each pulse received by the motor results in one step. A typical stepper motor contains about 200 steps, which translates to about 1.8 degrees per step. Since the step size and the number of steps a stepper motor will take are predetermined, it can be precisely controlled without using a feedback mechanism. As the motor’s speed is dependent on the pulse frequency, an increase in the pulse frequency will increase the speed of the motor.
Advantages of Using a Stepper Motor
- Stepper motors are inexpensive.
- They are simpler due to the open loop control they use.
- Stepper motors can be precisely controlled with predictable performance.
- The speed of the motor can easily be controlled by varying the frequency of the input pulses.
- Well constructed stepper motors have high accuracy, and any error is non-cumulative in nature.
- The motor has an excellent response to any change in put.
- Energized windings give the motor complete torque when at standstill. Very low speed synchronization can be achieved by directly coupling the load to the motor.
- Being a brushless motor, stepper motors benefit from a comparatively higher mean time between failures (MTBF).
Different types of Stepper Motors
Stepper motors are broadly classified as permanent magnet motors, variable reluctance motors and hybrid motors. Hybrid motors integrate the best features of both the aforementioned types of motors, and are made using a rotor consisting of a permanent magnet and toothed stator poles. Standard hybrid motors consist of 200 rotor teeth which translate to 1.8 degrees in every step of a rotation. They are widely used in a large number of applications due to high static/dynamic torque and the high step rates at which they can operate. Common applications where they are utilized include machine tools, computer disk drives, pick & place machines, printers & plotters, wire bonding machines and automated wire cutting.
Different Modes of Operation
Stepper motors can operate in full step mode, half step mode and microstep mode. The design and make of the driver determines the operating mode of the stepper motor.
1. Full Step Mode
The full-step mode is achieved in a stepper motor by reversing the current alternately and energizing both the windings. Each pulse delivered by the driver results in a single step. In this mode, a complete revolution consists of 200 steps.
2. Half Step Mode
It the half step mode, a stepper motor completes 400 steps in one complete revolution. The windings are energized alternately to cause the rotor to travel half the standard distance. While the half step mode results in a smoother rotation, it can generate lower torque (by about 30%) compared to the full step mode.
3. Microstep Mode
Microstepping drives can divide a standard step into 256 microsteps resulting in a total of 51,200 steps to complete a single revolution. At just 0.007 degrees per step, the microstep mode results in an extremely smooth motion with a considerable range of speeds and improved precision.
If your business requires custom micro motion solutions using stepper motors or other DC electric motors, visit Micromo at Micromo.com!
Processing your request, Please wait....
