Standard programposi features 77
DC magnetization
DC magnetization can be applied to the motor to lock the rotor at or near zero speed.
Pre-magnetization
Pre-magnetization refers to DC magnetization of the motor before start. Depending
on the selected start mode (21.01 Start mode), pre-magnetization is applied to
guarantee the highest possible breakaway torque, up to 200% of the nominal torque
of the motor. By adjusting the pre-magnetization time (21.02 Magnetization time), it is
possible to synchronize the motor start.
DC hold
The function makes it possible to lock the rotor at or near zero speed in the middle of
normal operation. DC hold is activated by parameter 21.08 DC current control. When
both the reference and motor speed drop below a certain level (parameter 21.09 DC
hold speed), the drive stops generating sinusoidal current and start to inject DC into
the motor. The current is set by parameter 21.10 DC current reference. When the
reference exceeds parameter 21.09 DC hold speed, normal drive operation
continues.
Note:
• DC hold is only available in speed control.
• The function applies the DC current to one phase only, depending on the position
of the rotor. The return current will be shared between the other phases.
Post-magnetization
This feature keeps the motor magnetized for a certain period (parameter 21.11 Post
magnetization time) after stopping to prevent the machinery from moving under load.
Post-magnetization is activated by parameter 21.08 DC current control. The
magnetization current is set by parameter 21.10 DC current reference.
Reference
Motor speed
DC hold
21.09 DC hold speed
t
t
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