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4-37
4-4 Regenerative Energy Absorption
OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
4
System Design
4-4 Regenerative Energy Absorption
The Servo Drives have internal regeneration process circuitry, which absorbs the regenerative
energy produced during motor deceleration and prevents the DC voltage from increasing. An
overvoltage error occurs, however, if the amount of regenerative energy from the motor is too
large. If this occurs, remedies must be taken to reduce the regenerative energy by changing
operating patterns, or to increase the regeneration process capacity by connecting an External
Regeneration Unit.
Calculating the Regenerative Energy
Horizontal Axis
Œ
In the output torque graph, acceleration in the forward direction is shown as positive, and
acceleration in the reverse direction is shown as negative.
Œ
The regenerative energy values in each region can be derived from the following equations.
Note. Due to the loss of motor winding resistance and PWM, the actual regenerative energy will be
approx. 90% of the values derived from these equations.
Œ
For driver models with internal capacitors used for absorbing regenerative energy (i.e., models of
400 W or less), the values for both Eg
1
or Eg
2
(unit: J) must be lower than the driver's regeneration
absorption capacity. (The capacity depends on the model.For details, refer to the next section.)
Œ
For driver models with an Internal Regeneration Resistor used for absorbing regenerative energy (i.e., models of 500
W or more), the average amount of regeneration Pr (unit: W) must be calculated, and this value must be lower than the
driver's regeneration absorption capacity. (The capacity depends on the model.For details, refer to the next section.)
The average regeneration power (Pr) is the regeneration power produced in 1 cycle of operation [W].
Motor operation
Motor output torque
+
N
1
−
N
2
T
D1
T
D2
t
1
t
2
T
E
g1
E
g1
E
g2
E
g2
N
1
, N
2
: Rotation speed at start of deceleration [r/min]
: Deceleration torque [N·m]
: Deceleration time [s]
T
D1
, T
D2
t
1
, t
2
2
E
g 1
E
g
=
P
r
( + ) / T[W]
T: Operation cycle [s]