Rockwell Automation 1391 USER MNL/DIGITAL AC SERVO DR User Manual
Page 86
Chapter 9
1326 AC Servomotors
9-2
Tc – rated torque of motor with windings at rated temperature and an
ambient of 40
°
C. The drive is operating in a rated ambient of 60
°
C.
Tp – the peak torque that can be produced by the motor/drive combination
with both at rated temperature and the motor in a 40
°
C ambient and the
drive in a 60
°
C ambient. Higher peak torques are permissible where RMS
torque is less than or equal to the rated torque (Tc). 1391-DES operation is
shown in the outer envelope and will show higher speed and 300% torque
capability.
Rated Speed – the operating speed of the drive and motor combination at
which a minimum of 70% of continuous rated torque (Tc) can be
developed. This point is defined with the motor at 25
°
C and drive
operating in a 60
°
C ambient.
Rated Operation Area – boundary of speed-torque curve where the motor
and drive combination may operate on a servo basis without exceeding the
RMS rating of either.
Duty Cycle Profile
Decelerate
(Tpd)
Accelerate
(Tpa)
Repeat
Move Cycle
RPM
Steady
Speed
(Tss)
Rest
(Tr)
Total Cycle Time
t
1
t
2
t
3
t
4
where:
Trms
The motors RMS or average torque over the duty cycle. (Expressed in lb.-in. or
lb.-ft. The same units must be used throughout the formula.)
Tpa
Motor peak torque to accelerate to maximum speed. (Expressed in lb.-in. or lb.-ft.
The same units must be used throughout the formula.)
Tss
Motor torque present at the motor shaft during constant speed segment.
(Expressed in lb.-in. or lb.-ft. The same units must be used throughout the
formula.)
Tpd
Motor peak torque to decelerate to zero speed. (Expressed in lb.-in. or lb.-ft. The
same units must be used throughout the formula.)
Tr
Torque when motor is at zero speed.
t
1
, t
2
, t
3
, t
4
Time for each portion of the duty cycle in seconds.
Tpa
2
x t
1
+ Tss
2
x t
2
+ Tpd
2
x t
3
+ Tr
2
x t
4
t
1
+ t
2
+ t
3
+ t
4
Trms =
Intermittent Operation Area – Boundary of speed-torque curve where
the motor and drive combination may operate in acceleration-deceleration
mode without exceeding peak rating of either, provided that the duty cycle
RMS continuous torque limit is not exceeded.