Altivar® 58 TRX AC Drives
Fault Management Parameters
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Automatic Catch of a Spinning Load (Catch-on-the-fly)
This function, also termed a “flying start,” is active by def ault (a lthoug h it is au tomati cally disab l ed if the
Brake Sequence function is configured). It allows the motor to be restarted without a speed surge after
one of these events:
• Mains power break or simple switch off.
• Fault reset or automatic restart.
• Freewheel stop or DC injection stop with logic input.
• Momentary loss of power downstream of drive con troller.
On restart, the controller searche s f or the effective speed of the motor in order to restart on a ramp from
this speed and return to the reference speed. The speed search time can reach 1 s depending on the
initial difference.
This function is often used for applications where the motor speed of a machine does not drop rapidly
after a mains power break (machines with high inertia) as well as fans and pumps driven by residual flux.
Controlled Stop on Power Loss
This function can be used to determine how the drive controller will react to a loss of power. Three
configurations are possible:
• Disabled.
The drive controller immediately faults in response to an input phase loss. This is the f a ctory settin g.
• Follow the programmed deceleration ramp until motor stops or undervoltage fault appears.
Use this configuration if a consistent deceleration ramp is more important than maximizing power
loss ride through.
• Maintain DC bus voltage.
With this configuration, DC bus voltage is maintained as long as possible. The ATV58 TRX drive is
designed to ride through power sags and to provide degraded ope ration do wn to 60% o f nominal lin e
voltage for 500 ms. Longer ride through is possible if there is sufficient kinetic energy generated by
the connected motor load inertia. An undervoltage fault appears after the voltage drops below 60%
of nominal line voltage. This configuration should be used to maximize the ride through time of the
drive controller and to minimize nuisance tripping.