Delta Electronics AC Servo Drive ASDA-B User Manual

Page 149

Chapter 6 Control Modes of Operation|ASDA-B Series

6-34

Revision February 2008, Doc. Name: 2006PDD23000009

If the load inertia is N

× motor inertia, the regenerative power will be (N+1) × E0 when servo motor

brakes from 3000rpm to 0. Then, the regenerative resistor can dissipate: (N+1)

× E0 - Ec (joule). If the

time of repeat operation cycle is T sec, then the regenerative power = 2

× ((N+1) × E0 - Ec) / T. The

calculating procedure is as follows:

Step

Procedure

Equation and Setting Method

Set the capacity of regenerative
resistor to the maximum

Change the value of P1-53 to maximum

Set the operation cycle T

Input by the users

Set motor speed wr

Input by the users or read via P0-02 Drive State Display

Set load/motor inertia ratio N

Input by the users or read via P0-02 Drive State Display

Calculate the max. regenerative
power Eo

Eo= J * wr

/182

Set the regenerative power Ec that
can be absorbed

Refer to the table 6.I above

Calculate the required regenerative
power capacity

2 × (N+1) × Eo－Ec）/ T

Table 6.J

For example:

If we use 750W servo drive, the time of repeat operation cycle is T = 0.4 sec, max. motor speed is

3000rpm, the load inertia = 4

× motor inertia, then the necessary the power of regenerative resistor = 2

Ч ( (4+1) Ч 5.36 – 11.07) / 0.75 = 41.9W. 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-B 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 figure on next page 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 on next page 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.