Siemens A1 User Manual
Simple Applications
International English
26
MICROMASTER Applications Handbook
5.8.5
Start on the Fly
Normally if the inverter attempts to start a motor that is already rotating it will
current limit, stall or slow the motor down. If Start on the Fly is selected it will
sense the speed of the motor and ramp the motor from that speed back to the set
point. This is useful if the motor is already turning for some reason, such as
following a short input supply break.
current limit, stall or slow the motor down. If Start on the Fly is selected it will
sense the speed of the motor and ramp the motor from that speed back to the set
point. This is useful if the motor is already turning for some reason, such as
following a short input supply break.
Start on the fly can operate when the load is rotating in the reverse direction, for
instance when a fan is rotating due to reverse pressure. In this case, the motor
direction is tested at low torque in forward and reverse directions. This can have
the undesirable effect that the motor rotates in both directions at start up.
instance when a fan is rotating due to reverse pressure. In this case, the motor
direction is tested at low torque in forward and reverse directions. This can have
the undesirable effect that the motor rotates in both directions at start up.
5.8.6
Electro-Mechanical Brake Control
The relays can be programmed to control a separate brake and a delay set (using
appropriate parameters) so the motor can be energized prior to relay release.
During the time set in the delay parameters, the inverter runs at its minimum
frequency while the brake is energized, so that when the brake is released the
motor will move immediately.
appropriate parameters) so the motor can be energized prior to relay release.
During the time set in the delay parameters, the inverter runs at its minimum
frequency while the brake is energized, so that when the brake is released the
motor will move immediately.
Time
Output
Frequency
Frequency
Minimum
Frequency
Frequency
Relay can be used to control
external brake during these tmes
external brake during these tmes
Figure 5-5
Possible control cycle using brake control relay and times