Specifications

11– 7
11
11.SELECTION
Command pulse frequency Servo motor speed
Servo motor torque
[pps][r/min]
f
0
0
Nofo
Time
Time
Command
Servo motor
speed
Tpsa Tpsd
T Ma
T Md
T 1
T 2
T L
Ta
Td
T1 = TMa + Ta + TL .......................................................................................................................................................................... (11-11)
T2 = TL .................................................................................................................................................................................................... (11-12)
T3 = TMd = - Td + TL .................................................................................................................... (11-13)
Note: In the regenerative mode, the value found by Equation 11-13 is negative.
(4) Continuous effective load torque
If the torque required for the servo motor changes with time, the continuous effective load torque
should be lower than the rated torque of the servo motor. There may be a servo motor torque
delay at the start of acceleration or deceleration due to a delay in the control system. To simplify
the calculation, however, it is assumed that constant acceleration and deceleration torques are
applied during Tpsa and Tpsd. The following equation is used to calculate the continuous effective
load torque in the following operation pattern:
Servo motor speedTime
Servo motor torque
N
[r/min]
0
Time
0
Time
Tpsa tc Tpsd Tr
Tf (1 cycle)
T Ma
T Md
Td
Ta
T
L
T LH
Trms =
T
Ma • Tpsa + TL • tc + TMd • Tpsd + TLH • tR
tf
222
......................................................... (11-14)
Note: TLH indicates the torque applied during a servo motor stop. A large torque may be applied
especially during a stop in vertical motion applications, and this must be fully taken into
consideration. During vertical drive, the unbalanced torque TU will become TLH.