ABB ACS 800 Series, Firmware Manual

Page: 123 / 340

Program features
123
Load speed control
This function is used for running the motor above the base speed if the motor is able
to provide a sufficient torque with respect to the load condition. The function allows
you to run the motor at a higher speed above the base speed according to the motor
current at the base speed with the load. It is assumed that the load at which the
motor crosses the base speed remains constant until the motor stops, and then a
new Start command is given.
The user defines a set of current (A) and speed (rpm) parameters, which specify the
curve to be used to calculate the motor speed limit according to the current at the
base speed Par.
77.20 . The motor current at the base speed Par. 77.20 is checked
for a predefined time period of Par. 77.03 HOLD RAMP, so that the motor current
would have settled down to a less oscillating value.
Parameter 77.01 LOAD SPD CTRL SEL defines the activation command for the
Load speed control function. Parameter 77.03 HOLD RAMP defines the time period
after which the motor has crossed the base speed to check for the motor current.
This motor current after this time period delay is regarded by the function as the
base speed current for the particular load used. Parameters
77.04 … 77.19 plot the
base speed versus current graph in both the forward and reverse direction and are
further used to limit the speed according to the base speed current.
If parameters 77.04 … 77.19 are not configured properly in the correct sequence, the
speed is always limited to Par. 77.20 BASE SPEED, and the error bit (signal 03.32
bit 10) is set to 1. Parameters 77.04 … 77.19 are to be configured as follows:
• The current values for the forward direction to be entered in parameters 77.04 ,
77.06 , 77.08 and 77.10 have to be entered in the increasing order.
• The speed limit values for the forward direction to be entered in parameters
77.05 , 77.07 , 77.09 and 77.11 have to be entered in the decreasing order.
• The current values for the reverse direction to be entered in parameters 77.12 ,
77.14 , 77.16 and 77.18 have to be entered in the increasing order.
• The speed limit values for the reverse direction to be entered in parameters
77.13 , 77.15 , 77.17 and 77.19 have to be entered in the decreasing order.