Function Application
‑528‑
Figure 3‑31 Flying start
Pre-excitation start
When F6‑00 is set to 2, the AC drive uses the pre‑excitation start mode. This mode is
applicable only to the SVC and FVC control modes of asynchronous motors. In this
mode, the motor is pre‑excited before AC drive startup, which speeds up response of
the motor and reduces the startup current. The timing diagram of this mode is the
same as that of start after DC braking. It is recommended that the pre‑excitation
current be set to 1.5 times the no‑load current (F1‑10), but in no case exceeds the
rated motor current. If the pre‑excitation current equals the no‑load current (F1‑10),
the optimal pre‑excitation time is 3 times the rotor time constant. The rotor time
constant is calculated using the following formula: Mutual inductance (F1‑09) +
Leakage inductance (F1‑08)/Rotor resistance (F1‑07). The unit of mutual inductance
and leakage inductance is L, and the unit of resistance is Ω. If the pre‑excitation
current is greater than the no‑load current, the pre‑excitation time can be reduced
proportionally. If the pre‑excitation current is less than the no‑load current, the pre‑
excitation time can be increased proportionally.
3.1.3.2 Stop Modes
The AC drive supports two stop modes: decelerate to stop and coast to stop. You can
set F6‑10 to select a stop mode as needed.
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