• Class B insulation, operate at ambient temperatures from -40°C to +65°C (-40°F to +149°F)
• No brushes, ratchets or detents to wear out
• Lubricated-for-life ball bearings

Servomotor Characteristics
• Require complex, expensive control systems
• Position sensing devices needed for feedback to control
• Relatively low torque for size
• Thermally inefficient
• Control system must be “tuned” to load; must be “retuned” if load is changed
•Brushes on DC servomotors subject to wear Superior Electric Step Motor Characteristics
• Relatively inexpensive
• Can be operated “open-loop” (no position feedback required)
• Noncumulative step error
• Simple control electronics can be used
•Brushless construction aids reliability
•Maintenance free
•Will not be damaged if stalled
• High torque for size
• Maintain position when at rest
Technical Notes (Continued)
Stepping Techniques
The terms full-step, half-step and microstep are commonly used in the discussion of step motors.
A standard 1.8° step motor has 200 discrete positions in a full 360°revolution.
Since 360° divided by 200 equals 1.8°, the motor shaft will advance 1.8° each time the motor is given a digital command to take one step.
This is known as a full-step.
The term “half-step” indicates a 0.9° step angle (half of a full 1.8° step).
This is achieved with a switching technique that alternately applies positive current, no current, and negative current to each winding in succession.
The term “microstep” refers to a more sophisticated form of control which goes beyond the simple switching of power between phase A and phase B of the motor windings, and takes control of the amount of current being sent to the individual windings.
Microstepping permits the shaft to be positioned at places other than the 1.8° or 0.9° locations provided by the full-step and half step methods.
Microstepping positions occur between these two angular points in the rotation of the rotor
The most commonly used microstep increments are 1/5,1/10,1/16,1/32, 1/125 and 1/250 of a full step. Microstep increments chosen by Superior Electric simplify control of both US and metric units of measurement, and also allow finer positioning resolution.
While a full step of 1.8° will give a 0.001 inch resolution when the motor is driving through a lead screw which has a 0.2000 inch lead,resolutions of 0.000008 inch or less are possible using microstepping.
A major benefit of microstepping is that it reduces the amplitude of the resonance that occurs when the motor is operated at its natural frequency or at sub-harmonics of that frequency.
The improved step response and reduced amplitude of the natural resonances result from the finer step angle.
