Lin Catalog 2006 - Lin Engineering - #9

2 PHASE vs. 5 PHASE

MEASURING STEP ACCURACY

How does step accuracy work? Step error is measured in arc minutes. Arc minutes are:

2-PHASE VS. 5-PHASE

STEP ACCURACY COMPARISON

To compare these two mechanically different step motors, we were able to run both motors at a step resolution such that each microstep was the equivalent of 0.018°.

2-Phase: 0.9° Motor / 50x microstepping = 0.018° 5-Phase: 0.72° Motor / 40x microstepping = 0.018°

SPECIFICATIONS OF BOTH MOTORS

Input Voltage of 24VDC

Output Current set to motor's rated current

2- Phase: 0.6 Amps/Phase

5- Phase: 0.75 Amps/Phase

conversion factor : 1 degree = 60 arc minutes

1 degree

0.017°

1 arc minute x (

60 arc minutes

Tj = True position (theoretical reading)

Mj = Measured position (measured reading from encoder)

Position ^ CDCD CD CD ... CD

t ¹

■ Step Error

Example: Run a 64 microstep accuracy test on a 0.9° motor. (0.9°/64) x i = T; M; - T; = Step Error

Lin's 0.9° Stepper

0.72° Stepper

- Error + Error

Error

+ Error

ADDED BENEFIT OF 2 PHASE OVER 5 PHASE: MORE TORQUE

Not only are 0.9° 2-Phase step motors more accurate than 0.72° 5-Phase step motors, they also produce more torque as well. In a 0.72° 5-Phase step motor, there are 50 rotor teeth. A rotor and stator must be offset from each other; therefore, the maximum number of stator teeth must be less than 50 in order to

create the offset spacing. Since 5-Phase steppers contain

2 Phase vs Comparable 5 Phase (Step Motors)

24vDC, 0.75 Amp Peak

10 poles, the maximum number of teeth per pole is 4 which will result in 40 stator teeth.

However, on a typical 0.9° 2-Phase step motor, there are f 100 rotor teeth and 16 stator poles. Therefore, the |

maximum number of teeth allowable on each pole is 5, resulting in a total of 80 teeth on the stator. The more stator teeth, the more output torque.

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Speed (rps)