Hitachi SJ Series, User Manual

Page: 207 / 786

12-8-2
Chapter 12 Inverter Function
An actual example of setting up the acceleration or
deceleration time
• However short the acceleration or deceleration
time is set, the actual acceleration or deceleration
of the motor cannot be shorter than the minimum
acceleration or deceleration time that is determined
by the moment of inertia J of the mechanical
system and the motor torque. An act of
acceleration or deceleration in a shorter time than
the minimum acceleration or deceleration time may
cause an over current or over voltage trip to
happen.
!
J
L
: Moment of inertia J (kg·m
2
) of the load converted into that of
the motor shaft.
J
M
: Moment of inertia J (kg·m
2
) of the motor.
N
M
: Revolution speed of the motor (r/min)
T
s
: Maximum acceleration torque (N·m) of the motor driven by
the inverter.
T
B
: Maximum deceleration torque (N·m) of the motor driven by the
inverter.
T
L
: required operating torque (N·m)
Acceleration time t
s
Deceleration time t
B
(J
L
＋
J
M
)×N
M
9.55×(T
S
-T
L
)
t
S
＝
(J
L
＋
J
M
)×N
M
9.55×(T
B
+T
L
)
t
B ＝
Output
frequency
Set frequency
Maximum
frequency
[Hb105]/
[Hd105]
Actual
acceleration time
[FA-10]
Actual
deceleration time
[FA-12]
Time