Mitsubishi Electric FR-D720-008 Instruction Manual page 83

(4) Setting of stall prevention operation in high frequency range (Pr. 22, Pr. 23, Pr. 66)
Pr. 22
When Pr. 23 = 9999
When Pr. 23 = "9999", the stall prevention
operation level is as set in Pr. 22 to 400Hz.
Pr. 66
During high-speed operation above the rated motor frequency, acceleration may not be made because 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 protective function (OL) is not executed even if the motor is at a stop.
To improve the operating characteristics of the motor in this case, the stall prevention level can be reduced in the high
frequency range. This function is effective for performing operation up to the high-speed range on a centrifugal separator,
etc. Normally, set 60Hz in Pr. 66 and 100% in Pr. 23.
Formula for stall prevention operation level
Stall prevention operation level
in high frequency range (%)
Pr. 66
However, A =
Output frequency (Hz)
By setting "9999" (initial value) in Pr. 23
prevention operation level is constant at the Pr. 22 setting up to 400Hz.
(5) Set two types of stall prevention operation levels (Pr. 48)
Turning RT signal ON makes Pr. 48
For the terminal used for RT signal input, set "3" in any of Pr. 178 to Pr. 182 (input terminal function selection) to assign the
function.
NOTE
Changing the terminal assignment using Pr. 178 to Pr. 182 (input terminal function selection) may affect the other
functions. Make setting after confirming the function of each terminal.
The RT signal acts as the second function selection signal and makes the other second functions valid.
(Refer to page 114)
Adjust the output torque (current) of the motor
Stall prevention operation level
as set in Pr. 23
400Hz
Output frequency (Hz)
Pr. 22 -
× [
= A + B
Pr. 22
× Pr. 22
(Hz) (%)
, B =
Stall prevention operation level compensation factor at double speed
Second stall prevention operation current
(Pr. 22 = 150%, Pr. 23 = 100%, Pr. 66 = 60Hz)
Setting example
150
90
60
45
30
22.5
0 60 100
A Pr. 23 - 100
] × [
]
- B 100
× Pr. 22
( Hz ) ( % )
Pr. 66
400Hz
valid.
150 200 300 400
Output frequency (Hz)
, the stall
4
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