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Fast Rotating Restart
Shown below is an actual X/Y oscillogram showing the stator flux vector
startup spiral of a pre-spinning induction motor.
Initially the motor is spinning, and CogniSim has no knowledge of the state
of the induction motor. The stator flux in the machine is zero. (the center of
the diagram)
Within microseconds, CogniSim detects current trajectories, and the motor
electromagnetic state resulting in the stator flux being established, and sensed
in the motor without any current transients.
Since CogniSim determines the electromagnetic state of the machine, this
"fast" rotating restart capability is not affected by varying system inertia, or
other system variables.
This results in an extremely reliable and robust rotating restart function.
Fast rotating restart into a pre-spinning motor (forward or backward) is
important in HVAC applications where flowing air can actually require starting
the drive in a reverse spinning motor.
In aerospace, the need to emergency start turbines that are spinning due to
wind-stream propulsion with a sensorless motor is a critical task. Some of these
machines rotate so quickly, the option of using a shaft mounted position or
speed sensor is not acceptable. In these applications, the CogniSim reliable
rotating restart performance is a valuable attribute.
Similarly, in wind power generating applications a sensorless rotating
restart capability is the key to allowing the wind power industry to exploit the
low cost, reliable, and rugged attributes of the induction motor.
Special Notes:
CogniSim motor drives do not measure the terminal voltage of the motor
to determine the stator flux.
As a result, motor drives using CogniSim are simpler because they require no
motor line voltage sensing hardware and are therefore more immune to external
Radio Frequency Interference (RFI) an important attribute in military
applications.
For the same reason, CogniSim motor control easily offers opportunity as Grid
Connect power systems in single or three phase systems.
The advantage here is that since CogniSim does not use the line voltage
to establish the synchronization, there are no need for phase-lock-loops, or
special filters typically used to block noise that corrupt reliable behavior.
The simplest way to view this attribute is that CogniSim views the
line-energy source as a large induction generator....this means that during
synchronization and operation it is inherently unaffected by noise on the line,
and for that matter it is also immune to line frequency variation of the line.
For this reason, the CogniSim controller for active front-ends, and
grid-connect operation can realize power generation systems that work very well
in poorly regulated, noisy and soft-grid distribution systems, a very important
attribute.
This aspect also makes the CogniSim grid connect system, naturally world
compatible to all possible frequencies, voltages and power quality environments.
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