Delta Electronics ASDA-A2 Series User Manual page 35

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If the load inertia is N × motor inertia, the regenerative power will be (N+1) x E0 when
servo motor brakes from 3000r/min to 0. Then, the regenerative resistor can dissipate:
(N+1) x E0 - Ec (joule). If the time of repeat operation cycle is T sec, then the regenerative
power = 2 x ((N+1) x E0 - Ec) / T. The calculating procedure is as follows:
Step
1
2
3
4
5
6
7
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-A2
series servo drives 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, AL005 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.
2-16
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Procedure
Set the capacity of
regenerative resistor to the
maximum
Set the operation cycle T
Set motor speed Wr
Set load/motor inertia ratio N
Calculate the max.
regenerative power Eo
Set the regenerative power Ec
that can be absorbed
Calculate the required
regenerative power capacity
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Equation and Setting Method
Change the value of P1-53 to maximum
Input by the users
Input by the users or read via P0-02 Drive State
Display
Input by the users or read via P0-02 Drive State
Display
Eo = J x wr /182
2
Refer to the table above
2 x (N+1) x Eo－Ec）/ T
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Chapter 2 Installation and Storage
Revision January 2011
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