ABB ACS880 Series Firmware Manual page 65

Pre-magnetization
Pre-magnetization refers to DC magnetization of the motor before start. Depending
on the selected start mode
magnetization can be 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
example, the release of a mechanical brake.
DC hold
The function makes it possible to lock the rotor at (near) zero speed in the middle of
normal operation. DC hold is activated by parameter
both the reference and motor speed drop below a certain level (parameter
hold speed), the drive will stop generating sinusoidal current and start to inject DC
into the motor. The current is set by parameter
reference exceeds parameter
continues.
Motor speed
Reference
21.09 DC hold speed
Notes:
• DC hold is only available in speed control in DTC motor control mode (see page
22).
• 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
magnetization time) after stopping. This is to prevent the machinery from moving
under load, for example before a mechanical brake can be applied. Post-
(21.01 Start mode
time), it is possible to synchronize the motor start and, for
21.09 DC hold
Program features 65
or 21.19 Scalar start
21.08 DC current
21.10 DC current
speed, normal drive operation
DC hold
mode), pre-
control. When
21.09 DC
reference. When the
t
t
21.11 Post