DA98A AC Servo Drive Unit
User Manual
67
CHAPTER 9 ORDER GUIDE
9.1 Capacity selection
This servo drive unit capacity is involved with load inertia, load torque, desired positioning
precision and max. speed, it is recommended to consider it by the following steps:
1) To calculate the load inertia and torque
To calculate load inertia, load torque, acceleration/deceleration torque, and effective
torque by the relevant data to make it the base for the next selection.
2) To determine preliminary mechanical gear ratio
Calculate the max. mechanical deceleration ratio by the required highest speed and
highest speed of motor and compare it to the minimum position unit with this ratio and the
motor min. rotation unit. If the position precision requirement is very high, increase the
mechanical deceleration ratio (the actual highest speed is lowered) or choose a faster
motor.
3) To check the inertia and torque
Convert the load inertia and torque to the motor shaft by mechanical deceleration ratio,
the inertia converted should be less than the quintuple of the motor rotor inertia. And the
load torque and effective torque converted should be less than the rated torque of motor.
If the requirement above can’t be met, increment of mechanical deceleration ratio (the
actual max. speed is lowered) or a high capacity motor may be used.
9.2 Electronic gear ratio
Refer to Chapter 4 (Table 4.2 Parameter function), Chapter 6 (6.3 Parameter setting), Chapter
7 (7.3 Debugging) for the significance and adjustment of the electronic gear ratio G:
Under the position control mode, the actual loading speed is:
Instruction pulse speed×G ×mechanical deceleration ratio
Under the position control mode, the actual min. displacement of loading is:
Min. instruction pulse travel×G ×mechanical deceleration ratio
〖Note〗 If the electronic gear ratio G is not 1, there might be a compliment in a gear ratio division
operation, which may lead to position error. And the max. error is the motor min. rotation
amount (min. resolution).
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