Functions
8.24 Open-loop and closed-loop control
Control Units CU240S
Operating Instructions, 11/2006, A5E00766042B AA
8-169
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Figure 8-87 Imax controller
Note
The inverter load is only reduced when the frequency is reduced if the load decreases at
lower speeds (e.g. square-law torque –speed characteristic of the motor load).
8.24.2 Vector control
Description
Field-orientated Vector control (known as: Vector control) significantly improves torque
control when compared to V/f control. The Vector control principle is based on the fact that
for a specific load situation or required torque, the required motor current is impressed with
respect to the motor flux so that the appropriate torque is obtained. If the stator current is
emulated in a circulating coordinate system, linked with the rotor flux Φ, then it can be
broken-down into the flux-generating current component i
d
in-line with the rotor flux and into
a torque-generating current component i
q
, vertical to the rotor flux. These components are
corrected to track their setpoints in the current controller using their own dedicated PI
controllers and are equal quantities in steady-state operation.
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