Emerson unidrive m200 - Open-Loop Mode

Open loop current control
In open loop mode it is possible to control the motor frequency or the motor torque. When the frequency of the motor is controlled
(TorqueModeSelector (04.011) = 0) the PostRampReference (02.001) is defined by the ramp system unless the current limits are active. The
PostRampReference (02.001) can directly define the output frequency of the drive or this can be modified to compensate for motor slip. If the current
limits are active (Currentlimitactive (10.009) = 1) the ramp system remains active, but the output of the current controller is added to the ramp output so
that the frequency applied to the motor is modified to try and reduce the torque producing current in the motor. For example, if the
PostRampReference (02.001) is positive (i.e. motor is running forwards) and the motor is overloaded with a motoring load a positive
TorqueProducingCurrent (04.002) is generated that will exceed the FinalCurrentLimit (04.018). This gives a negative error which attempts to reduce
the ramp output causing the motor to slow down.
When motor torque is being controlled (TorqueModeSelector (04.011) = 1) The FinalTorqueReference (04.003) is converted to a current reference
(flux compensation) and the current limits are applied giving the FinalCurrentReference (04.004). This is used as the reference input to the PI
controller that regulates the torque producing current in the motor. The output of the PI controller is the PostRampReference (02.001), and so the
torque is controlled by increasing or decreasing the motor frequency. This system gives only moderate dynamic performance. For better torque control
in a system without position feedback, closed loop current control should be used.
It is possible to disable the flux compensation by setting FluxControlCompensationDisable (05.028) to 1.
CurrentControllerKpGain (04.013) and CurrentControllerKiGain (04.014) are the proportional and integral gains of the current controller. As already
mentioned the current controller either provides current limits or closed-loop torque control by modifying the PostRampReference (02.001). The control
loop is also used in its torque mode during supply loss, or when the standard ramp control mode is active and the drive is decelerating, to regulate the
flow of current into the drive. Although the default settings have been chosen to give suitable gains for less demanding applications it may be necessary
Unidrive M200 Parameter Reference Guide
Issue: 01.05.00.10
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