NFO
Drives
AB
2021
201013
‐
2
Operating
and
Installation
Manual
29
If the inverter follows a slowly varying setpoint (e.g. analogue setpoint 0
–
10V) and the setpoint enters the bypass
window, the inverter will keep the actual speed (at bypass window start) until the input setpoint has reached a point
outside the bypass window. Then the inverter will use fastest possible acceleration (or deceleration) until the rotor
speed has reached the new setpoint.
Example: Acceleration from 0 to 50 Hz
Accel
= 5,00s,
Bypass-fr
= 25,0Hz,
Bypass-BW
= 10,0Hz
This gives a setspeed curve as shown in Fig. 12.
Fig. 12. Acceleration with frequency bypass
5.8.10 Increased start current (current boost)
It’s possible to set a temporary increased current limit at startup. This can be achieved using a NFO Sinus inverter
with a nominal power that is higher than the motor’s nominal power, e.g. a 2.2kW inverter used with a 1.5kW motor.
After installation, when the motor parameters have been entered and Autotuning has been performed, the NFO
Sinus will set current limit to 120% of motors nominal current. If an oversized inverter has been chosen, there will
be some extra current available up to inverter’s max current limit. Use the parameters
Boost time
to set the time
after start (in seconds) and Boost Level (0-100% of exceeding current capacity) to set the increased current limit
during boost time period.
5.8.11 Control Mode
With
Control Mode
parameter set to
Frequency
, the inverter uses frequency in Hz for setpoint and regulation of
motor rotation. When set to
Speed
, the inverter uses values in rpm for setpoint and regulation of rotor speed. This
mode has a more accurate speed estimation and it compensates for load variations. See sections 5.9 and 5.10.
5.8.12 Autostart
With
AutoStart
parameter =
ON
, the motor will start as soon as power is applied, provided the digital input signal
RUN at the terminal (DIN1) is active. This parameter also controls whether the inverter will attempt to restart after a
fault, see section 5.16.
With
AutoStart
parameter =
OFF
(default setting), when power is applied the inverter will wait for a transition on the
digital input signal RUN at the terminal (DIN1). When the signal goes from inactive to active, the motor will start.
AutoStart
=
OFF
is also the recommended setting if the inverter shall be controlled via the serial channel.
WARNING: use the Auto Start function with caution, and not in combination with control over the
serial channel or field bus. The motor may start automatically after an involuntary power failure.
3006469-2022-04
