35 • Control Keypad
4.7.4.1 Soft Stop Parameters
The ASTAT-XT incorporates 5 stopping curves that enable you to select the suitable torque curve
Soft Stop Curve 0
– Standard Curve (Default) – voltage is linearly reduced from nominal to zero.
The most stable and suitable curve for preventing prolonged stopping and motor overheating.
Soft Stop Curves 1, 2, 3 Pump Control
– In some pump applications, when pumping to higher elevation a
considerable part of the torque is constant and does not decrease with speed.
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.
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