Hello,

How to set acceleration / deceleration time for the variable frequency ac drive, what's the requirements and how they affect the whole system operation?

The ac drive acceleration time is the time required of output frequency from 0 Hertz to the maximum frequency, the deceleration time is from maximum frequency decrease to 0 Hz. Usually use the frequency setting signal rise and fall to determine the acc/dec time. You need to restrict the rise rate of the frequency setting in acceleration period of the electric motor in order to prevent over-current, and prevent over voltage with the limitation of descent rate in deceleration period.

Acceleration time setting requirement: limit the acceleration current under the over-current capacity of the variable frequency ac drive, to avoid VFD drive tripped in speed loss of over current; Deceleration time set point: avoid excessive voltage of the smoothing circuit, prevent ac drive tripped from regeneration over voltage. Acceleration and deceleration time can be calculated according to the load, in debugging, usually take long acc/dec time at the first, to observe if there is over current, over voltage alarms in start/stop period; Then shorten the acceleration/deceleration time gradually, follow the principle of operation with no alarm, repeat the operation steps by several times, you can determine the best acceleration and deceleration time.

Generally consider the two aspects for the variable frequency drive acc/dec time setting: the first one is the VFD won't be overload in acceleration and DC over voltage in deceleration, means the ac drive starting torque and braking capabilities to meet the requirements or not. The other factor is whether the acceleration and deceleration time can meet the mechanical control start and stop requirements.

Acceleration:

Each time you press the touch screen "accelerate" button, the VFD output frequency will rise 1Hz. Need to pay attention, the variable frequency drive must in VVVF running to make this button work. In addition, you can also directly set the P50 is to achieve the frequency value. Specific method: press the "set" button on the touch screen, pop-up parameter setting frame, the P parameter number field, enter 50 in the P parameters passed by value: enter the pre-set frequency value, and then press the P parameters under the button to determine.

Deceleration:

Press the the touchscreen "deceleration" button, the ac drive output frequency will drop. The step has been set to 1Hz. Note: the VFD must in VVVF running status to make this button work. In addition, you can also directly set P50 to achieve the set frequency value, the specific method you can refer to the "accelerated" part in above.