Delta ASDA-B2-F Series User Manual page 26

ASDA-B2-F
Take the motor (400 W with frame size 60) as the example, the cycle of back and forth operation
is T = 0.4 sec, the maximum speed is 3000 r/min and the load inertia is 7 times to the motor
inertia. Then, the needful power of regenerative resistor is 2 × ((7+1) × 1.37 – 8) / 0.4 = 14.8 W. If
it is smaller than the built-in capacity of regenerative resistor, the built-in 60W regenerative
resistor will do. Generally speaking, when the need of the external load inertia is not much, the
built-in regenerative is enough. The diagram below describes the actual operation. The smaller
power of the regenerative resistor it is, the more energy it accumulates and the higher
temperature it will be. When the temperature is higher than a specific value, AL005 occurs.
(b) If the external load torque exists, the motor is in reverse rotation.
Usually, the motor is in forward rotation, which means the torque output direction of the
motor is the same as the rotation direction. However, in some applications, the direction of
torque output is different from the rotation. In this situation, the motor is in reverse rotation.
The external energy goes into the servo drive through the motor. The diagram below is one
example. When the external force direction is the same as the moving direction, the servo
system has to use the force of the opposite direction to keep the speed and stability. Huge
amount of energy will return to the servo drive at the moment. When DC-BUS is full and
unable to store the regenerative energy, the energy will be leaded to regenerative resistor
and consumed.
Negative torque: TL × Wr
For safety reasons, please calculate it by considering the safest situation.
For example, when the external load torque is +70% rated torque and the rotation reaches
3000 r/min, then take 400W (the rated torque is 1.27 Nt-m) as the example, users have to
connect the regenerative resistor which is 2 × (0.7× 1.27) × (3000 × 2 × π／60) = 560 W, 60
.
September, 2015
Motor Speed
External Load Torque
Motor Output Torque
Negative
Positive
Torque
Torque
TL: external load torque
Positive
Negative Torque
Torque
Installation
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