Delta ASDA-A3 Series User Manual page 77

Installation
Calculation of the regenerative energy when there is external torque and the motor does
(b)
the negative work.
2
Usually, when the motor does positive work, the motor's torque direction is identical to the
rotation direction. However, in some instances, the motor's torque direction is opposite to the
rotation direction. This is when the motor is doing negative work and the external energy is
applied to the servo drive through the motor. For instance, if the external force direction is
identical to the rotation direction (such as downward motion of the vertically-mounted machine),
the servo system outputs more power to counterbalance the excessive external force (the
weight of vertically-mounted machine) in order to keep up with the specified target speed. In this
case, considerable energy returns to the servo drive. When the DC Bus is full and cannot store
more energy, this energy is absorbed by the regenerative resistor.
Example:
For a 400 W motor (ECM-A3L-CY0604RS1), when the torque of the external load is +70% of
the rated torque (1.27 N-m) with rotation speed up to 3,000 rpm, the required external
regenerative resistor is:
2 × (0.7 × 1.27) × (
needed.
2-32
(1) Moving direction of the object; (2) Direction of torque; (3) Regenerative energy
3000 × 2 × π
) = 558 W. Therefore, a regenerative resistor of 560 W and 60 Ω is
60
ASDA-A3