Allen-Bradley PowerFlex 70 Reference Manual

2-98 Flying Start
Rated Flux Reached
Flying Start The Flying Start feature is used to start into a rotating motor, as quick as
possible, and resume normal operation with a minimal impact on load or
speed.
When a drive is started in its normal mode it initially applies a frequency of
0 Hz and ramps to the desired frequency. If the drive is started in this mode
with the motor already spinning, large currents will be generated. An
overcurrent trip may result if the current limiter cannot react quickly
enough. The likelihood of an overcurrent trip is further increased if there is
a residual flux (back emf) on the spinning motor when the drive starts. Even
if the current limiter is fast enough to prevent an overcurrent trip, it will take
an unacceptable amount of time for synchronization to occur and for the
motor to reach its desired frequency. In addition, larger mechanical stress is
placed on the application, increasing downtime and repair costs while
decreasing productivity.
In Flying Start mode, the drive’s response to a start command will be to
identify the motor’s speed and apply a voltage that is synchronized in
frequency, amplitude and phase to the back emf of the spinning motor. The
motor will then accelerate to the desired frequency. This process will
prevent an overcurrent trip and significantly reduce the time for the motor to
reach its desired frequency. Since the motor is “picked up “smoothly at its
rotating speed and ramped to the proper speed, little or no mechanical stress
is present.
Configuration
Flying Start is activated by setting the [Flying Start En] parameter to
“Enable”
The gain can be adjusted to increase responsiveness. Increasing the value in
[Flying StartGain] increases the responsiveness of the Flaying Start Feature
Time
Ir Voltage - SVC
Greater of IR Voltage or
Voltage Boost - V/Hz
Flux Up
Normal
Operation
Flux Up
Voltage
Motor Flux
Stator Voltage
Rotor Speed
Motor Flux
Stator Freq
169 [Flying Start En]
Enables/disables the function which
reconnects to a spinning motor at actual
RPM when a start command is issued.
Default:
Options:
0
0
1
“Disabled”
“Disabled”
“Enabled”
170
Restart Modes
170 [Flying StartGain]
Sets the response of the flying start
function.
Default:
Min/Max:
Display:
4000
20/32767
1
169

Allen-Bradley PowerFlex 70 Specifications

General

Brand	Allen-Bradley
Model	PowerFlex 70
Category	Controller
Language	English