12 Appendix
12.1.3 Calculating the Required Capacity of Regenerative Resistors
12-10
(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 (min
-1
)
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.
If the energy consumed by load loss (in step 2 above) is unknown, then perform the calculation using E
L
= 0.
When the operation period in regeneration mode is continuous, add the following items to the above calcula-
tion procedure in order to find the required capacity (W) for the regenerative resistor.
• Energy for continuous regeneration mode operation period: E
G
(joules)
• Energy consumed by regenerative resistor: E
K
= E
S
- (E
L
+ E
M
+ E
C
) + E
G
• Required capacity of regenerative resistor: W
K
= E
K
/ (0.2 × T)
Here, E
G
= (2π/60) N
MG
T
G
t
G
• t
G
: Same operation period (s) as above
• T
G
: Servomotor’s generated torque (N·m) in continuous regeneration mode operation period
• N
MG
: Servomotor rotation speed (min
-1
) for same operation period as above
Step Item Symbol Equation
1
Calculate the rotational energy of the servo-
motor.
E
S
E
S
= JN
M
2
/182
2
Calculate 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 “(b) Servo-
motor Winding Resistance Loss”
diagrams) × t
D
4
Calculate the SERVOPACK energy that can
be absorbed.
E
C
Calculate from “(3) SERVO-
PACK’s Absorbable Energy” dia-
grams.
5
Calculate the energy consumed by the regen-
erative resistor.
E
K
E
K
= E
S
− (E
L
+E
M
+E
C
)
6
Calculate the required regenerative resistor
capacity (W).
W
K
W
K
= E
K
/ (0.2 × T)
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