Mitsubishi Electric FR-A700 Technical Manual page 266

(2) Operation
Torque control is exercised to develop torque as set
in the torque command.
The motor speed becomes constant when the motor
output torque and load torque are balanced.
For torque control, therefore, the speed is
determined by the load.
For torque control, the motor gains speed as the
motor output torque becomes greater than the motor
load. To prevent overspeed, set the speed limit value
so that the motor speed does not increase too high.
(Speed control is exercised during speed limit and
torque control is disabled.)
When speed limit is not set, the speed limit value
setting is regarded as 0Hz to disable torque control.
When the actual speed reaches or exceeds the
speed limit value, torque control is switched to speed
control to prevent overspeed.
the operation panel during speed limit operation and
the OL signal is output.
When speed limit operation starts, speed control is
enabled internal torque limit ([Pr. 22 Stall prevention
operation level]) (initial value). In such a case, speed
control may not return to torque control. To prevent
this, set torque limit to the setting same as torque
command.
For example, when torque command is analog input
to terminal 1, torque limit be set to external torque
limit (terminal 1, 4). (Refer to page 283)
Undervoltage avoidance function ([Pr. 261 = 11, 12])
of power-failure deceleration stop function becomes
invalid under torque control. When [Pr. 261 = 11 (12)],
the inverter operates in the same manner as when
[Pr. 261 = 1 (2)]. (Refer to page 373)
Set linear acceleration/deceleration ([Pr. 29 = 0 (initial
value)) when torque control is performed. When
acceleration/deceleration patterns other than the
linear acceleration/deceleration are selected, the
protective function of the inverter may function.
(Refer to page 234)
Performing pre-excitation (LX signal and X13 signal)
under torque control (Real sensorless vector control,
vector control) may start the motor running at a low
speed even when the start command (STF or STR) is
not input. The motor may run also at a low speed
when the speed limit value = 0 with a start command
input. Perform pre-excitation after making sure that
there will be no problem in safety if the motor runs.
Speed limit value is
increased up to preset
value according to the
[Pr.7 Acceleration time]
setting.
Torque control
Speed
Speed limit
Start signal
Output
torque
Speed control is performed during
speed limit.
(Thus, torque according to the
commanded is not developed.)
(SL) appears on
Speed limit Speed limit value is
value decreased down to
zero according to the
[Pr.8 Deceleration time]
setting.
Speed limit
Output torque is provided
according to the terminal 1 setting.
[Example] When [Pr. 804 = 0]
Torque control is enabled if the actual speed is less
than the speed limit value.
When the actual speed reaches or exceeds the
speed limit value, speed limit operation starts, torque
control is stopped, and speed control (proportional
control) starts.
The following shows the operations in response to
the analog input command from terminal 1.
Speed
[Pr. 7]
*
Speed
STF
(Forward rotation
command)
Speed limit
operation
(Speed control)
OL
ON
*When the speed limit activates, torque according to the commanded is not developed.
1) When STF signal is turned ON, the speed limit
value is increased according to the time set in [Pr.
7].
2) Speed control operation is performed if the actual
speed rises to or above the speed limit value.
3) When the STF signal is turned OFF, the speed
limit value is decreased according to the time set
in [Pr. 8].
4) For torque control, the actual speed becomes
constant when the torque command and load
torque are balanced.
5) The motor
determined by the combination of the torque
command input polarity and start signal as
indicated in the following table.
Torque
Command
STF signal ON
Polarity
Forward rotation
Positive
torque (forward rotation
command driving/reverse rotation
regeneration)
Reverse rotation
Negative
torque (forward rotation
command regeneration/reverse
rotation driving)
(3) Concept of torque control gains
Normally, it is not necessary to change [Pr. 824, 834
Torque control P gain], [Pr. 825, 835 Torque control
integral time]. Refer to page 306 to make adjustment.
1) Torque control P (proportional) gain
During vector control, [Pr. 824 = 100%] is
equivalent to 2000rad/s.
During Real sensorless vector control, [Pr. 824 =
100%] is equivalent to 1000rad/s.
2) Torque control integral time
[Pr. 825 = 5ms] is equivalent to 200rad/s.
300
PARAMETER
Speed limit value
*
Torque control operation Speed limit Torque
operation control
(Speed control) operation
ON
torque developing
Torque Developing Direction
STR signal ON
Reverse rotation
direction direction
(forward rotation
regeneration/reverse
rotation driving)
Forward rotation
direction direction
(forward rotation
driving/reverse rotation
regeneration)
[Pr. 8]
*
Time
Speed limit
operation
(Speed control)
ON
direction is