User Constant Settings and Functions
5.6.2 Calculating the Required Capacity of Regenerative Resistors
5 -84
5.6.2 Calculating the Required Capacity of Regenerative Resistors
J
J
By Means of a Simple Calculation
When driving a Servomotor normally with the horizontal axis, check the external regenerative
resistor requirements using the calculation method shown below.
Servopacks with Capacities of 400 W or Less
Servopacks with capacities of 400 W or less do not have built-in regenerative resistors. The en-
ergy that can be charged by capacitors is shown in the following table. If the rotational energy
in the servo system exceeds these values, then connect a regenerative resistor externally.
Voltage
Applicable
Servopacks
Regenerative Energy that
Can be Processed (joules)
Remarks
100 V
SGDH-A3BE
7.8
Value when main cir-
cuit input voltage is
SGDH-A5BE to -02BE
15.7
cuit input voltage is
100 VAC
200 V
SGDH-A3AE, -A5AE
18.5
Value when main cir-
cuit input voltage is
SGDH-01AE to -04AE
37.1
cuit input voltage is
200 VAC
Calculate the rotational energy in the servo system from the following equation:
E
S
= J
¢
(N
M
)
2
/182 (joules)
D
J = J
M
+ J
L
D
J
M
:
Servomotor rotor inertia (kg·m
2
) (oz·in·s
2
)
D
J
L
:
Motor axis conversion load inertia (kg·m
2
) (oz·in·s
2
)
D
N
M
:
Rotation speed used by Servomotor (r/min)
Servopacks with Capacities of 0.5 to 5.0 kW
Servomotorswith capacitiesof 0.5 to 5.0 kW have built-in regenerative resistors. The allowable
frequencies for just the Servomotor in acceleration and deceleration operation, during the rota-
tion speed cycle from 0 to the maximum rotation speed to 0, are summarized in the following
table.
Convertthedata intothe valuesobtained withactual rotationspeed usedand loadinertia todeter-
mine whether an external regenerative resistor is needed.
5
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