Advantages & Disadvantages of Stepper motors & DC servo motors
Top Ten Stepper motor Advantages:
- Stable. Can drive a wide range of frictional and inertial loads.
- Needs no feedback. The motor is also the position transducer.
- Inexpensive relative to other motion control systems.
- Standardized frame size and performance.
- Plug and play. Easy to setup and use.
- Safe. If anything breaks, the motor stops.
- Long life. Bearings are the only wear-out mechanism.
- Excellent low speed torque. Can drive many loads without gearing.
- Excellent repeatability. Returns to the same location accurately.
- Overload safe. Motor cannot be damaged by mechanical overload.
Top Ten DC Servo motor Advantages:
- High output power relative to motor size and weight.
- Encoder determines accuracy and resolution.
- High efficiency. It can approach 90% at light loads.
- High torque to inertia ratio. It can rapidly accelerate loads.
- Has "reserve" power. 2-3 times continuous power for short periods.
- Has "reserve" torque. 5-10 times rated torque for short periods.
- Motor stays cool. Current draw proportional to load.
- Usable high speed torque. Maintains rated torque to 90% of NL RPM
- Audibly quiet at high speeds.
- Resonance and vibration free operation.
Top Ten Stepper Disadvantages:
- Low efficiency. Motor draws substantial power regardless of load.
- Torque drops rapidly with speed (torque is the inverse of speed).
- Low accuracy. 1:200 at full load, 1:2000 at light loads.
- Prone to resonances. Requires microstepping to move smoothly.
- No feedback to indicate missed steps.
- Low torque to inertia ratio. Cannot accelerate loads very rapidly.
- Motor gets very hot in high performance configurations.
- Motor will not "pick up" after momentary overload.
- Motor is audibly very noisy at moderate to high speeds.
- Low output power for size and weight.
Top Ten DC Servo Disadvantages:
- Requires "tuning" to stabilize feedback loop.
- Motor "runs away" when something breaks. Safety circuits are required.
- Complex. Requires encoder.
- Brush wear out limits life to 2,000 hrs. Service is then required.
- Peak torque is limited to a 1% duty cycle.
- Motor can be damaged by sustained overload.
- Bewildering choice of motors, encoders, and servodrives.
- Power supply current 10 times average to use peak torque. See (5).
- Motor develops peak power at higher speeds. Gearing often required.
- Poor motor cooling. Ventilated motors are easily contaminated.
Author: Mariss from Gecko Drive- www.GeckoDrive.com
Thanks for the article