Jan 21st
Fundamental torque equation
•
Motor drives a
load through a transmission
system.
•
Motor always rotate, load may rotate or undergo
a translational motion.
•
Load speed may be different from that of motor.
•
The basic equation of the motor-load system is
L
T
T
)
(
J
dt
d
dt
dJ
dt
d
J
)
(
•
Drives with constant inertia, (dJ/dt)=0
•
Industrial robots-variable inertia
Fundamental torque equation
)
(
dt
d
J
T
T
L
•
where
T
and
T
L
is motor and load torque respectively in N-
m,
J
is the moment of inertia and
ω
is the angular velocity
in rad/sec.
•
Motor torque is the applied torque and load torque is the
resisting torque.
•
Different states at which an electric drive causing rotational
motion are
(i) T > T
L
(d
ω
/dt >0)
:- The drive will be accelerating, in
particular, picking up speed to reach rated speed.
Dynamic torque and it is present only
during transient operations
(ii)
T
M
< T
L
(d
ω
/dt <0)
:- The drive will be
decelerating and particularly, coming to rest.
(iii)
T
M
=T
L
(d
ω
/dt =0
