Mitsubishi Electric 700 Series, Instruction Manual

Page: 93 / 416

82
Adjustment of the output torque (current) of the motor
(2) Stall prevention operation signal output and output timing adjustment (OL signal, Pr. 157 )
⋅
When the output current exceeds the stall prevention operation level and stall prevention is activated, the stall
prevention operation signal (OL signal) turns ON for longer than 100ms. When the output current falls to or below
the stall prevention operation level, the output signal turns OFF.
⋅
Use Pr. 157 OL signal output timer to set whether the OL signal is output immediately or after a preset period of time.
⋅
This operation is also performed when the regeneration avoidance function (overvoltage stall) is executed.
(3) 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 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 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
⋅
When
Pr. 23 Stall prevention operation level compensation factor at double speed
= "9999" (initial value), the stall
prevention operation level is kept constant at the
Pr. 22
setting up to 400Hz.
Pr. 157
Setting Description
0
(initial value)
Output immediately.
0.1 to 25 Output after the set time (s) has elapsed.
9999 Not output.
REMARKS
⋅
The OL signal is assigned to the terminal OL in the initial setting. The OL signal can also be assigned to the other terminal by
setting "3 (positive logic) or 103 (negative logic)" to any of
Pr. 190 to Pr. 196 (output terminal function selection)
.
CAUTION
· If the frequency has fallen to 0.5Hz by stall prevention operation and remains for 3s, a fault (E.OLT) appears to shutoff the
inverter output.
· Changing the terminal assignment using Pr. 190 to Pr. 196 (output terminal function selection) may affect the other functions.
Please set parameters after confirming the function of each terminal.
Stall prevention operation level in high
frequency range (%)
= A + B
×
[
Pr. 22
- A
]
×
[
Pr. 23
- 100
]
Pr. 22 - B 100
However, A =
Pr. 66
(Hz)
×
Pr. 22
(%)
, B =
Pr. 66
(Hz)
×
Pr. 22
(%)
Output frequency (H) 400Hz
Overload state
(OL operation)
OL output signal
Pr.157
Set time(s)
Output frequency (Hz)
Pr. 22
When
Pr. 23
= 9999
Pr. 66
400Hz
Stall prevention operation level (%)
Stall prevention operation level
as set in
Pr. 23
When
Pr. 23
= "9999", the stall prevention
operation level is as set in
Pr. 22
to 400Hz.
Output frequency (Hz)
Setting example
Stall prevention operation level (%)
Pr.22 =
110%
Pr.23
= 100%
Pr.66
= 60Hz
110
66
33
22
16.5
60 0 100 200 300 400