In a variable frequency drive (VFD), a flying start is a feature that allows the motor to be ramped up to full operating speed very quickly, without coming to a complete stop. This is especially useful in applications where fast acceleration is required, such as conveyor systems or machine tool operations.
Flying Start – Catching a Spinning Motor
Flying start: When the motor is already spinning, the VFD connects and ramps up from the current speed. The motor never stops!
To perform a flying start, the VFD first detects the current speed and direction of the motor, then rapidly synchronizes its output frequency to match the spinning motor, smoothly ramping up to the target speed. All of this is handled automatically, often via a control interface like a keypad or display—no need for manual intervention.
Using flying start significantly improves system efficiency and reliability, while also reducing the risk of high inrush currents or equipment damage. By synchronizing the output to the motor’s current frequency, amplitude, and phase, the transition is smooth and stress-free for both the motor and the drive.
Flying start is ideal for scenarios where the motor must resume operation after a brief power interruption or an emergency stop—there’s no need to wait for the motor to fully stop before restarting. This saves both time and energy, and protects the entire system.
In the field, flying start can make or break a continuous process line. Without it, every restart means unnecessary downtime and potential mechanical stress—something no plant manager wants.
A lot of technicians overlook this feature when configuring a VFD. In reality, activating flying start extends the life of relays, contactors, and even cables by avoiding high inrush currents.
If you skip flying start, a spinning motor can cause the drive to trip or the supply transformer to overload during restart—especially on high-power installations. It’s not just a “nice to have”; it’s critical for robust automation.
In summary, a well-tuned flying start means less downtime, fewer electrical faults, and longer equipment lifespan. Once you set it up properly, you’ll wonder how you ever ran a plant without it.
