7.7 CONTROL CONSTANTS
Cn- .
(Cont’d)
(6) Speed search deactivation current level
(Cn-38)
When inverter output current immediately after power recovery is larger than the set
value of Cn-38, speed search operation is started. When inverter output current is
smaller than the set value of Cn-38, the frequency is interpreted as a speed
synchronization point and acceleration or deceleration is performed again up to a
specified frequency.
(7) Speed search decel time
(Cn-39)
Set deceleration time during speed search in units of 0.1 second. A setting of 0.0
second causes no speed search.
(8) Minimum baseblock time
(Cn-40)
On detecting momentary power loss, the inverter shuts OFF output and maintains the
baseblock state for a given time. Set a time in Cn-40 when residual voltage is
expected to be almost zero.
When momentary power loss time is longer than the minimum baseblock time,
speed search operation is started immediately after power recovery.
WHEN MIN.
BASEBLOCK TIME IS
LONGER THAN
MOMENTARY POWER
WHEN MIN.
BASEBLOCK TIME IS
SHORTER THAN
MOMENTARY POWER
MOMENTA
RY POWER
LOSS TIME
MIN.
BASEBLOC
K TIME
INVERTER
BASEBLOC
K TIME
MOMENTA
RY POWER
LOSS TIME
MIN.
BASEBLOC
K TIME
INVERTER
BASEBLOC
K TIME
(9) V/f during speed search
(Cn-41)
To ensure that a fault such as OC does not occur during speed search operation, V/f
must be reduced during speed search operation, as compared with that during normal
operation. Set V/f during speed search as follows by the set value of Cn-41:
V/f during speed search = V/f at normal operation × Cn-41
(10) Voltage recovery time
(Cn-42)
Set in Cn-42 the time between completion of speed search operation and return to
V/f at normal operation. The setting of voltage recovery time is set as follows:
230V class: Time required to raise voltage from 0 to 230V
460V class: Time required to raise voltage from 0 to 460V
─
118
─
