User`s manual

6-107
6
Open Loop and Closed Loop Vector Control
In Open Loop and Closed Loop Vector control, the slip frequency is controlled so that motor efficiency is
maximized.
• Taking the motor rated slip for the base frequency as optimum slip, the inverter calculates the slip for the
optimal motor efficiency depending on the output frequency.
• Before using energy saving always perform autotuning.
• If hunting occurs reduce the set value in b8-02 (Energy-saving Gain), or increase the set value in b8-03
(Energy-saving Filter Time Constant).
 Field Weakening
The field weakening function is used to lower the output voltage when the motor load changes to a low level
(no load). Thereby energy can be saved and motor audible noise is reduced.
Note that this function is designed for the usage with one low load condition that does not change. If the low
load condition changes, the field weakening function can not be optimized. In this case the energy saving
function should be preferred.
The function can be activated using a multifunction input. Therefore set one of the parameters H1-01 to H1-05
to 63.
Field weakening can be used in the V/f control modes only.
Related Parameters
Multi-function Digital Inputs (H1-01 to H1-05)
Setting the Field Weakening Level (d6-01)
To set the field weakening level run the motor under low load condition and activate the field weakening func-
tion using a multifunction input. Monitor the output current and raise or lower the field weakening level until
the output current reaches it’s minimum value.
Observe the following:
• Parameter d6-01 can not be changed during operation (i.e. a RUN command is input).
• If the field weakening level is set too low, the motor may stall.
Activating Field Weakening
If one of the parameters H1-01 to H1-05 is set to “63”, the field weakening function can be activated switching
the regarding terminal input to ON.
Parameter
No.
Name
Factory
Setting
Change
during
Opera-
tion
Control Methods
V/f
V/f with
PG
Open
Loop
Vector
Closed
Loop
Vector
d6-01 Field weakening level 80% No A A No No
d6-02 Field weakening frequency limit 0.0 Hz No A A No No
Set Value Function
Control Methods
V/f
V/f
with
PG
Open
Loop
Vector
Closed
Loop
Vector
63 Field Weakening Yes Yes No No