YASKAWA SGDS Sigma III Series, User Manual

Page: 325 / 376

11 Appendix
11.1.3 Calculating the Required Capacity of Regenerative Resistors
11-8
• n = J
L
/J
M
• J
M
: Servomotor rotor moment of inertia (kg·m
2
)
• J
L
: Load converted to shaft moment of inertia (kg·m
2
)
(2) Calculating the Regenerative Energy
This section shows the procedure for calculating the regenerative resistor capacity when acceleration and
deceleration operation is as shown in the following diagram.
(a) Calculation Procedure
The procedure for calculating the regenerative capacity is as follows:
Note: 1. The “0.2” in the equation for calculating W
K
is the value for when the regenerative
resistor’s utilized load ratio is 20%.
2. The units for the various symbols are as follows:
E
S
to E
K
: Energy joules (J)
T
L
: Load torque (N·m)
W
K
:
Regenerative resistor required capacity (W)
t
D
: Deceleration stopping time (s)
J :( = J
M
+ J
L
)( kg·m
2
)
T : Servomotor repeat operation period (s)
N
M
: Servomotor rotation speed (RPM)
If the above calculation determines that the amount of regenerative power (Wk) processed by the built-in
resistor is not exceeded, then an external regenerative resistor is not required.
If the amount of regenerative power that can be processed by the built-in resistor is exceeded, then install an
external regenerative resistor for the capacity obtained from the above calculation.
Rotation speed
Motor torque
T
L
:
Load torque
t
D
0
0
Regenerative
torque
N
M
: Motor rotation speed
T
Step Item Symbol Equation
1
Find the rotational energy of the servomotor.
E
S
E
S
= JN
M
2
/182
2
Find the energy consumed by load loss
during the deceleration period.
E
L
E
L
= (
π
/60) N
M
T
L
t
D
3
Calculate the energy lost from servomotor
winding resistance.
E
M
(Value calculated from
“Servomotor Winding Resistance
Loss” diagrams)
×
t
D
4
Calculate the SERVOPACK energy that can
be absorbed.
E
C
Calculate from the “Absorbable
SERVOPACK Energy” diagrams.
5
Find the energy consumed by the
regenerative resistor.
E
K
E
K
= E
S
- (E
L
+E
M
+E
C
)
6
Calculate the required regenerative resistor
capacity.
W
K
W
K
= E
K
/ (0.2
×
T)