Chapter 6 Control Modes of Operation
ASDA-A User Manual
4th Edition 2005/11/30, HE03
© DELTA ELECTRONICS, INC. ALL RIGHTS RESERVED
6-42
For example:
If we use 400W servo drive, the time of repeat operation cycle is T = 0.4 sec, max. rotation speed is
3000rpm, the load inertia = 7
ͪ
motor inertia, then the necessary the power of regenerative resistor = 2
ͪ
( (7+1)
ͪ
1.68
Ё
8) / 0.4=27.2W. If the regenerative power is very small, we recommend user to use the
built-in 60W regenerative resistor. Generally speaking, the built-in regenerative resistor provided by
ASDA-A series can meet the requirement of general application when the external load inertia is not
excessive.
The following figure shows the actual operation of regenerative resistor. You can see when the capacity
of regenerative resistor is too small, the accumulated power will be larger and the temperature will also
increase. The fault, ALE05 may occur if the temperature is over high.
(b) When there is an external load torque, servo motor is in reverse rotation when external load greater than
motor torque. Servo motor is usually in forward rotation and the motor torque output direction is the same
as the rotation direction. However, there is still some special condition. If the motor output torque is in the
reverse direction of rotation, the servo motor is also in the reverse direction of rotation. The external
power is input into the servo drive through servo motor. The figure below is an example. You can see the
motor is in forward rotation at constant speed when a sudden external load torque change and great
power is transmitted to regenerative resistor rapidly.
Motor Rotation Speed
External Load Torque
Motor Output Torque
Reverse
Rotation
Reverse
Rotation
Forward
Rotation
Forward
Rotation
External load torque in reverse direction: TL* Wr TL : External load torque
For the safety, we strongly recommend users should select the proper resistance value according to the
load.