About Adaptive Acceleration Control

Adaptive Acceleration Control measures the motor's operating characteristics throughout each start, and creates two reference points: motor characteristics at zero speed and motor characteristics at maximum efficiency. Throughout each start and stop, the starter compares the motor's performance characteristics with these reference points and estimates the motor's speed as a series of values between zero and 100%. To program it the user simply selects the profile that best matches the load type and the soft starter automatically ensures the smoothest possible acceleration for the load.

During each start, Adaptive Acceleration Control measures the motor's characteristics at zero speed and when the motor is operating at maximum efficiency. In subsequent starts and stops, AAC uses the motor's performance characteristics to estimate the present speed.

AAC start and stop profiles

Depending on your application requirements you can select between early, constant or late acceleration/deceleration. ACC's motor control algorithm defines three starting and stopping profiles, which relate motor speed to elapsed time. During a start or stop, the starter compares the estimated motor speed with the present point in the profile and adjusts its behaviour accordingly. If the estimated speed is lower than the profile, more power is applied to the motor. If the estimated speed is higher than the profile, less power is applied to the motor.

Water transients solved

Gradual and shock free acceleration can benefit all motor applications, but many situations need a more precise control over acceleration and/or deceleration. Historically pumping can present a number of scenarios that require specialist attention to reduce transients such as water hammer. With Adaptive Acceleration Control the starter stops the motor with either an early, constant or late deceleration profile. This is best illustrated with a series of examples.

Pump stop with high head

(Click image above for working example)

In a scenario with high back pressure (such as high head), the soft starter can stop damaging shock waves caused by non-return valves. A late deceleration stop will have very slow control of motor deceleration of the flow/no flow transition followed by a rapid deceleration mitigating reversal of the pump.

Pump stop with low head

(Click image above for working example)

When stopping a pump scenario with low head and a high flow rate, the fluid momentum creates a low pressure state behind the pump. The non-return valve is slammed shut and shock waves are sent out as low pressure state is equalised. By selecting a long uniform deceleration fluid momentum will naturally dissipate.

Pump stop with open outlet

(Click image above for working example)

The third scenario is an open system, specifically a pump lifting water from a lake to a channel via a pipe system with no non-return valve. On stopping, water drains back through the pump causing it to spin in reverse. A quick, then slow deceleration stops water being pumped but still keeps the pump rotating in a forward direction while water remaining in the pipe work drains back through leaving the pump primed for the next start.

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