55
5.3.9 Acceleration & Deceleration Time
The acceleration time is the time needed to ramp up the frequency from 0Hz to reference frequency, as
shown in Figure 5-27. The deceleration time is the time needed to ramp down the frequency from reference
frequency to 0Hz, see Figure 5-28.
5.3.8 Start Frequency and Minimum Frequency
Start frequency is the initial output frequency, the relationship between the start frequency and VFD running
frequency as shown in Figure 5-26. The minimum frequency is decided by the site condition and load
characteristics, it’s the lowest frequency for stable running. When the set reference is lower than the minimum, it’s
clamped to the minimum limit. The minimum is usually set a little higher than the start frequency.
Figure 5-26 Start Frequency
Attention
！
● If start frequency is set too big, may lead over current of VFD when start;
● Minimum frequency set value is related to the application , it is necessary to confirm with the users;
● The minimum frequency set value normally will be bigger than the start frequency
Figure 5-27 Time Sequence of Acceleration Time Figure 5-28 Time Sequence of Deceleration Time
Time (s)
Time (s)
Reference frequency
(Hz)
0
Acceleration time setting
Standard frequency
Reference frequency
（
Hz
）
0
Deceleration time setting
Standard frequency
Attention
！
●
If the acceleration time is set too short, this could lead over current of VFD.
●
If the deceleration time is set too short, this could lead over voltage of power cell.
●
The setting of the current limiting gain will affect the deceleration time.
