The speed search is carried out as it controls
the inverter output current during idling
below the Cn.72 (SS Sup-Current)
parameter setting. If the direction of the
idling motor and the direction of operation
command at restart are the same, a stable
speed search function can be performed at
about 10 Hz or lower.
However, if the direction of the idling motor
and the direction of operation command at
restart are different, the speed search does
not produce a satisfactory result because the
direction of idling cannot be established.
The speed search is carried out as it PI
controls the ripple current which is generated
by the counter electromotive force during no-
load rotation. Because this mode establishes
the direction of the idling motor
(forward/reverse), the speed search function
is stable regardless of the direction of the
idling motor and direction of operation
command. However because the ripple
current is used which is generated by the
counter electromotive force at idle (the
counter electromotive force is proportional to
the idle speed), the idle frequency is not
determined accurately and re-acceleration
may start from zero speed when the speed
search is performed for the idling motor at
low speed (about 10–15 Hz, though it
depends on motor characteristics).
Speed search can be selected from the following 4 options. If the top
display segment is on it is enabled (On), and if the bottom segment
is on it is disabled (Off).