Delta Electronics AC Servo Drive ASDA-AB User Manual page 141

Chapter 6 Control Modes of Operation|ASDA-AB Series
For example:
If we use 400W servo drive, the time of repeat operation cycle is T = 0.4 sec, max. motor speed is
3000r/min, the load inertia = 7 × motor inertia, then the necessary the power of regenerative resistor =
2 x ( (7+1) × 1.68 - 8) / 0.4 = 27.2W. If the calculation result is smaller than regenerative power, we
recommend the users to use the built-in 60W regenerative resistor. Usually the built-in regenerative
resistor provided by ASDA-AB series can meet the requirement of general application when the external
load inertia is not excessive.
The users 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. The following figure shows the actual operation of regenerative resistor.
(2) With Load
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 6.21 below is an example.
The users 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.
External load torque in reverse direction: TL x Wr
For the safety, we strongly recommend the users should select the proper resistance value according to
the load.
6-38
Reverse
Forward
Rotation
Rotation
Motor Rotation Speed
External Load Torque
Motor Output Torque
Reverse
Rotation
TL : External load torque
Forward
Rotation
Revision January 2009