GE Industrial Solutions ASTAT BP - Manual (Page 34)

ASTAT BP User Manual
34 GE Industrial Solutions ©2013 GE Company All Rights Reserved
It may happen that during the deceleration process when voltage decreases the motor torque abruptly falls
below load torque (instead of smoothly decreasing speed to zero), thus closing the valve and causing water
hammer.
Soft Stop Curves 1, 2 and 3 eliminate the water hammer phenomenon. In pump applications the
load torque decreases in square relation to the speed, thus correcting control of voltage to reduce torque
adequately and to smooth deceleration to a stop.
Note:
It is recommended that Soft Stop Curve 0 be used for all standard applications (not pumps).
To reduce water hammer, select Soft Stop Curve 1, then 2, then 3 in that order.
Soft Stop Curve 4 - Torque Curve - Provides linear deceleration of the torque. In certain loads, linear
torque deceleration can result in close to linear speed deceleration, thus eliminating stall conditions.
Note:
Always use Soft Stop Curve 0. If the motor stalls quickly instead of slowly decreasing its speed, select
Soft Stop Curve 1, 2, 3 or 4 in that order until the problem is solved.