Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 25)

DESCRIPTION OF OPERATION 5-7
1557-UM050F-EN-P –June 2013
Speed Ramp
The function of the speed ramp is to control the rate of change of the drive speed reference. Independent
four section ramps are provided for acceleration and deceleration. Each ramp is defined by four speed
points which are specified by parameters Ramp Speed 1 to 4 which are the same for both accelerating
and decelerating, and four time intervals which are specified by parameters Acceleration Time 1 to 4 and
Deceleration Time 1 to 4. The input to the speed ramp is the speed command from the skip speed block.
The drive control selects the appropriate acceleration or deceleration rate based on the present value of
the ramp output and whether it is increasing or decreasing. The output of the speed ramp is the speed
reference, which is the input to the speed control block. If the motor is coasting and speed feedback is
available, the speed reference is set equal to the motor speed.