Mitsubishi Electric fr-e700 series, Instruction Manual

Page: 202 / 608

Adjust the output torque (current) of the motor Parameter
6 - 48
Setting of stall prevention operation in high frequency range (Pr. 22, Pr. 23, Pr. 66)
During high-speed operation above the rated motor frequency, acceleration may not be made be-
cause the motor current does not increase. If operation is performed in a high frequency range, the
current at motor lockup becomes smaller than the rated output current of the inverter, and the pro-
tective function (OL) is not executed if the motor is at a stop.
To improve the operating characteristics of the motor in this case, the stall prevention level can be re-
duced in the high frequency region. This function is effective for performing operation up to the high-
speed range on a centrifugal separator etc.
Pr. 23 sets the change in the current limiting in the frequency range starting at the frequency set by
Pr. 66. For example, if Pr. 66 is set to 75 Hz the motor stall prevention operation level at an output fre-
quency of 150 Hz will be reduced to 75% when Pr. 23 is set to 100%, and to 66% when Pr. 23 is set to
50% (see the formula below). Generally Pr. 66 is set to 50 Hz and Pr. 23 to 100%.
Formula for stall prevention operation level:
When Pr. 23 "Stall prevention operation level compensation factor at double speed" = 9999 (initial val-
ue), the stall prevention operation level is kept constant at the Pr. 22 setting up to 400 Hz.
I001900E
Fig. 6-8: Stall prevention operation level
Fig. 6-9:
Stall prevention operation level when
Pr. 22 = 150%, Pr. 23 = 100% and Pr. 66 = 50 Hz
I001545C
Pr. 23 = 9999
Output frequency [Hz]
C
u
rr
ent [%]
Current limiting if the current limit was set at higher
frequency (Pr. 23).
Output frequency [Hz]
C
u
rr
en
t [%]
Setting example
Pr. 22 = 150%
Pr. 23 = 100%
Pr. 66 = 50Hz
Stall prevention operation level [%] A B
Pr. 22 A –
Pr. 22 B
–
-------------------------
Pr. 23 100 –
100
------------------------------- + =
where A
Pr. 66 [Hz] Pr. 22 [%]
Output frequency [Hz]
------------------------------------------------------------ B
Pr. 66 [Hz] Pr. 22 [%]
400Hz
--------------------------------------------------------- = , =