WEIHONG WISE WSDV-6R820PSB - 3.5 Motor Selection Calculations and Torque Formulas; Effective Torque Calculation Formulas; Rotational Speed of Motor; 3.5.2 Example of Motor Selection

Specialized Concentrated Focused
Servo Motor「25」
Driving system
Formula for T
Vertical axis
P
1/n
W
1
W
2
Guide
Ascending
f U F
T +TT 
Decending
2
f U F
-T +T  T
T
F
:Friction torque of moving parts
12
U
W +W
gP
2 
  
（ ）
T
12
F
W +W
gP
2


  
（ ）
T
W
1
:Load mass [kg]
W
2
:Balancing mass [kg]
3) Effective Torque
Effective torque can be figured out according to the formula below, whose value is approximate 80% less
of rated torque of the motor.
2 2 2
a a f b d d
rms
c
T t T t T t
T
t
    

T
a
: Acceleration torque [N•m] t
a
: Acceleration time [s] t
c
: Cycle time [s]
T
f
: Constant torque [N•m] t
b
: Constant speed time [s] (Rotating time + Stopping time)
T
d
: Deceleration torque [N•m] t
d
: Deceleration time [s]
3.5.1.5 Rotational Speed of Motor
Max. rotational speed means the permissible max. rotational speed of the motor in running period,
whose value is approximate less than rated rotational speed. However, when enabling the max.
rotational speed, you should pay special attention to the torque and rising temperature.
max
Movement distance
Acc. time Dec. time
+ +Constant speed time
22
V 
3.5.2 Example of Motor Selection
3.5.2.1 Example of Motor Selection for Ball Screw System
1) Ball Screw Structure
The structure of ball screw is illustrated as follows:
Fig. 3-7 Structure of ball screw
Mass of part W
A
=10[kg] Ball screw length B
L
=0.5[m]