Installation manual

System Operation 08/04 Danaher Motion Kollmorgen
72 M-SS-001-01 Rev. T SERVOSTAR S Installation
7.4.2 MOTOR FOLDBACK
This FoldBack algorithm is designed to provide motor protection in
cases where the drive’s continuous current rating is above the
motor’s continuous rating. This combination is often desired in
applications where maximum peak motor torques is required. The
possibility exists, however, that the drive could source current on a
continuous basis indefinitely to the motor and would force it beyond
its thermal capability. Unlike the drive FoldBack, you have complete
configurability over this feature (MFOLD, MFOLDD, MFOLDDIS,
MFOLDR, MFOLDT).
7.5 Encoder Simulation
The encoder simulation signal is generally generated in the A-quad-
B format. The addition of ENCOUTMOD enables you to change this
format to a pulse up/down signal.
7.6 Encoder Initialization
In brushless 3-phase motors the torque generated by the motor
depends on the three-phase currents and motor position. In order
to properly control the motor and extract maximum torque out of the
available motor and power stage, the controller must be provided
with the current motor position. In encoder-based systems, the
initial position for commutation initialization is found using hall
sensor switching, index finding, or an appropriate commutation-lock
algorithm (or a combination of the three methods). Encoder
initialization without motion uses a commutation-lock algorithm.
On power up, since the absolute motor position is unknown, two
methods may be implemented:
− Applying a forced commutation to move the motor to a
predetermined position where the torque generated is zero and
updating controller variables accordingly.
− Using a motion control algorithm that brings the commutation
angle of the motor from the initial, unknown position to the
current motor position (instead of moving the motor).
The first method is currently implemented on the SERVO
STAR S.
The disadvantage of this method is that it requires the motor to be
moved. This produces a jumpy motion that may not be tolerable in
some cases (such as linear motors applications).
The second method is designed to solve this problem by
implementing a closed loop commutation-lock algorithm that
adjusts the commutation angle to the motor position rather than
moving the motor to a predetermined place. The motor moves very
slightly. Motion of at least ±4 electrical degrees is expected.