Mitsubishi Electric F720PJ-11KF, Manual

Page: 36 / 96

36
When setting parameters, refer to the instruction manual (applied) and understand instructions.
This function monitors the output current and automatically
changes the output frequency to prevent the inverter from coming
to trip due to overcurrent, overvoltage, etc. It can also limit stall
prevention and fast-response current limit operation during
acceleration/deceleration, driving or regeneration.

Stall prevention
If the output current exceeds the limit value, the output frequency of
the inverter is automatically varied to reduce the output current.
 Fast-response current limit
If the current exceeds the limit value, the output of the inverter is
shut off to prevent an overcurrent. (V/F control and General-purpose
magnetic flux vector control)
 For Pr. 22 , set the output current level where the stall prevention is
activated. Set the output current level in ratio to the inverter rated
current (rated IPM motor current under IPM motor control). Normally
set this parameter to120% (initial value).
 When a General-purpose motor is driven at the rated motor
frequency or higher, acceleration may not be possible 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
region. This function is effective for performing operation up to the
high speed region on a centrifugal separator etc. Normally, set 60Hz
in
Pr. 66 and 100% in Pr. 23 .

Setting Pr. 23 Stall prevention operation level compensation factor at
double speed = "9999" (initial value) during General-purpose motor
operation keeps the stall prevention operation level at the Pr. 22
setting until the frequency goes up to 400Hz.

Set Pr.154 = "11" when the overvoltage protective function (E.OV  )
activates during stall prevention operation in an application with
large load inertia. Note that turning OFF the start signal (STF/STR)
or varying the frequency signal during stall prevention operation may
delay the acceleration/deceleration start.
 Stall prevention operation and fast response current restriction
function can be restricted according to the operation condition using
Pr. 156 .
(The fast-response current limit operation is disabled under IPM
motor control.)
You can set the acceleration/deceleration pattern suitable for
application.

When making frequent starts/stops, use the optional brake resistor
to increase the regenerative brake duty.

Use a power regeneration common converter (FR-CV) for
continuous operation in regeneration status.
Use the high power factor converter (FR-HC2) to reduce harmonics,
improve the power factor, or continuously use the regenerative
status.

The brake duty differs according to the capacity.

Available only with FR-F720PJ-3.7K.
22, 23, 48, 66, 154, 156, 157
Stall prevention operation
Pr.22 Stall prevention operation level
Pr.23 Stall prevention operation level compensation factor at double speed
Pr.48 Second stall prevention operation current
Pr.66 Stall prevention operation reduction starting frequency
Pr.154 Voltage reduction selection during stall prevention operation
Pr.156 Stall prevention operation selection Pr.157 OL signal output timer
24 to 27
Refer to the section about Pr.4
V/F V/F V/F
GP
MFVC
GP
MFVC
GP
MFVC
V/F V/F V/F
GP
MFVC
GP
MFVC
GP
MFVC
V/F V/F V/F
GP
MFVC
GP
MFVC
GP
MFVC
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.
29
Acceleration/deceleration pattern
Pr.29 Acceleration/deceleration pattern selection

Linear acceleration/deceleration (setting
"0", initial value)
For the inverter operation, the output
frequency is made to change linearly
(linear acceleration/deceleration) to
prevent the motor and inverter from
getting excessive stress to reach the set
frequency during acceleration,
deceleration, etc. when frequency
changes.
 S-pattern acceleration/deceleration A
(setting "1")
For machine tool spindle applications,
etc.
Use this pattern when acceleration/
deceleration is required in a short time to
a high-speed range higher than
Pr. 3
Base frequency

(fb)

Rated motor frequency under IPM motor
control
(Refer to page 81)

S-pattern acceleration/deceleration B
(setting "2")
For prevention of load shifting in conveyor
and other applications.
Since acceleration/deceleration is
always made in an S shape from current
frequency (f2) to target frequency (f1),
this function eases shock produced at
acceleration/deceleration and is
effective for load collapse prevention,
etc.
30, 70
Selection of regeneration unit
Pr.30 Regenerative function selection Pr.70 Special regenerative brake duty
Pr.30
setting
Pr.70
setting
Regeneration unit
0
(initial
value)

Brake resistor (MRS type, MYS type)
Brake unit (FR-BU2)
Power regeneration common
converter (FR-CV)
High power factor converter (FR-HC2)
1
6%
Brake resistor (MYS type)
(used at 100% torque/6%ED)

10% High-duty brake resistor (FR-ABR)
2 -
High power factor converter (FR-HC2)
(when automatic restart after
instantaneous power failure is
selected)
(Hz)
Time
Setting value "0"
[Linear acceleration/
deceleration]
Output frequency
fb
(Hz)
Setting value "1"
[S-pattern acceleration/
deceleration A]
Output frequency
Time
f1
(Hz)
(Hz)
f2
Set frequency
Output frequency
Time
Setting value "2"
[S-pattern acceleration/
deceleration B]