Drivecon XT Series - 5 Motor control modes; Open loop; Open loop vector control; Closed loop

5
Owner's Manual
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Motor control modes
Open loop
XT Drives have a built-in motor model, which calculates - one thousand times in a second - the
values of the real motor. The input data needed for the calculation is the instantaneous value of the
motor voltage from the ASIC and the measured motor current. Motor magnetic flux and shaft torque
are calculated in the motor model based on the nameplate data of the motor.
Open loop
vector control
Speed
ref
InverterAsic
Current
Vector
calculation
Speed
Control
Torque
Flux
ref
M
3
~
Frequency control
Open loop (mode 0)
In frequency control mode of Open Loop, the motor frequency follows the
frequency reference signal. The actual rotating speed depends on load and is
equal to the slip below or above the output frequency. Even with frequency control,
the vector calculation is used to keep the magnetization at a correct level.
Current control
Open Loop (mode 1)
In current control mode of Open Loop, the motor follows the frequency reference
signal. The motor is current controlled in small frequencies (typically <10Hz) and in
higher frequencies the motor is voltage controlled. The current control ensures that
in small frequencies the speed of the motor is almost independent of the load.
Closed loop
The closed loop vector control also includes a motor model, which has even a more simple
configuration than the open loop vector control. This is because an additional input data, as the
signal from the incremental encoder is available. This measurement of the function of the actual
motor is used as feedback to the motor model calculation and allows possibilities for additional
checking of the motor control.
Closed loop vector
control
Speed
ref
InverterAsic
Current
Vector
calculation
Speed
Control
Torque
Flux
ref
Speed
G
M
3
~
Speed control
Closed loop (mode 3)
In speed control mode of Closed Loop, the motor speed follows the speed
reference signal.
XT Drive
adjusts the motor frequency and with this function
compensate the load-dependent slip. The slip compensation keeps the actual
shaft speed constant and independent of loading conditions. With the closed loop
speed control it is even possible to reach zero speed with full torque.
Torque control
Closed loop (mode 4)
In torque control mode, the shaft torque is kept equal to the reference signal. The
motor speed depends very much on loading conditions - for example, an
unloaded motor would run at full speed all the time. For safety reasons, the speed
is limited between adjustable minimum and maximum speeds.